libATA Developer’s Guide

Author:

Jeff Garzik

Introduction

libATA is a library used inside the Linux kernel to support ATA host controllers and devices. libATA provides an ATA driver API, class transports for ATA and ATAPI devices, and SCSI<->ATA translation for ATA devices according to the T10 SAT specification.

This Guide documents the libATA driver API, library functions, library internals, and a couple sample ATA low-level drivers.

libata Driver API

struct ata_port_operations is defined for every low-level libata hardware driver, and it controls how the low-level driver interfaces with the ATA and SCSI layers.

FIS-based drivers will hook into the system with ->qc_prep() and ->qc_issue() high-level hooks. Hardware which behaves in a manner similar to PCI IDE hardware may utilize several generic helpers, defining at a bare minimum the bus I/O addresses of the ATA shadow register blocks.

struct ata_port_operations

Post-IDENTIFY device configuration

void (*dev_config) (struct ata_port *, struct ata_device *);

Called after IDENTIFY [PACKET] DEVICE is issued to each device found. Typically used to apply device-specific fixups prior to issue of SET FEATURES - XFER MODE, and prior to operation.

This entry may be specified as NULL in ata_port_operations.

Set PIO/DMA mode

void (*set_piomode) (struct ata_port *, struct ata_device *);
void (*set_dmamode) (struct ata_port *, struct ata_device *);
void (*post_set_mode) (struct ata_port *);
unsigned int (*mode_filter) (struct ata_port *, struct ata_device *, unsigned int);

Hooks called prior to the issue of SET FEATURES - XFER MODE command. The optional ->mode_filter() hook is called when libata has built a mask of the possible modes. This is passed to the ->mode_filter() function which should return a mask of valid modes after filtering those unsuitable due to hardware limits. It is not valid to use this interface to add modes.

dev->pio_mode and dev->dma_mode are guaranteed to be valid when ->set_piomode() and when ->set_dmamode() is called. The timings for any other drive sharing the cable will also be valid at this point. That is the library records the decisions for the modes of each drive on a channel before it attempts to set any of them.

->post_set_mode() is called unconditionally, after the SET FEATURES - XFER MODE command completes successfully.

->set_piomode() is always called (if present), but ->set_dma_mode() is only called if DMA is possible.

Taskfile read/write

void (*sff_tf_load) (struct ata_port *ap, struct ata_taskfile *tf);
void (*sff_tf_read) (struct ata_port *ap, struct ata_taskfile *tf);

->tf_load() is called to load the given taskfile into hardware registers / DMA buffers. ->tf_read() is called to read the hardware registers / DMA buffers, to obtain the current set of taskfile register values. Most drivers for taskfile-based hardware (PIO or MMIO) use ata_sff_tf_load() and ata_sff_tf_read() for these hooks.

PIO data read/write

void (*sff_data_xfer) (struct ata_device *, unsigned char *, unsigned int, int);

All bmdma-style drivers must implement this hook. This is the low-level operation that actually copies the data bytes during a PIO data transfer. Typically the driver will choose one of ata_sff_data_xfer(), or ata_sff_data_xfer32().

ATA command execute

void (*sff_exec_command)(struct ata_port *ap, struct ata_taskfile *tf);

causes an ATA command, previously loaded with ->tf_load(), to be initiated in hardware. Most drivers for taskfile-based hardware use ata_sff_exec_command() for this hook.

Per-cmd ATAPI DMA capabilities filter

int (*check_atapi_dma) (struct ata_queued_cmd *qc);

Allow low-level driver to filter ATA PACKET commands, returning a status indicating whether or not it is OK to use DMA for the supplied PACKET command.

This hook may be specified as NULL, in which case libata will assume that atapi dma can be supported.

Read specific ATA shadow registers

u8   (*sff_check_status)(struct ata_port *ap);
u8   (*sff_check_altstatus)(struct ata_port *ap);

Reads the Status/AltStatus ATA shadow register from hardware. On some hardware, reading the Status register has the side effect of clearing the interrupt condition. Most drivers for taskfile-based hardware use ata_sff_check_status() for this hook.

Write specific ATA shadow register

void (*sff_set_devctl)(struct ata_port *ap, u8 ctl);

Write the device control ATA shadow register to the hardware. Most drivers don’t need to define this.

Select ATA device on bus

void (*sff_dev_select)(struct ata_port *ap, unsigned int device);

Issues the low-level hardware command(s) that causes one of N hardware devices to be considered ‘selected’ (active and available for use) on the ATA bus. This generally has no meaning on FIS-based devices.

Most drivers for taskfile-based hardware use ata_sff_dev_select() for this hook.

Private tuning method

void (*set_mode) (struct ata_port *ap);

By default libata performs drive and controller tuning in accordance with the ATA timing rules and also applies blacklists and cable limits. Some controllers need special handling and have custom tuning rules, typically raid controllers that use ATA commands but do not actually do drive timing.

Warning

This hook should not be used to replace the standard controller tuning logic when a controller has quirks. Replacing the default tuning logic in that case would bypass handling for drive and bridge quirks that may be important to data reliability. If a controller needs to filter the mode selection it should use the mode_filter hook instead.

Control PCI IDE BMDMA engine

void (*bmdma_setup) (struct ata_queued_cmd *qc);
void (*bmdma_start) (struct ata_queued_cmd *qc);
void (*bmdma_stop) (struct ata_port *ap);
u8   (*bmdma_status) (struct ata_port *ap);

When setting up an IDE BMDMA transaction, these hooks arm (->bmdma_setup), fire (->bmdma_start), and halt (->bmdma_stop) the hardware’s DMA engine. ->bmdma_status is used to read the standard PCI IDE DMA Status register.

These hooks are typically either no-ops, or simply not implemented, in FIS-based drivers.

Most legacy IDE drivers use ata_bmdma_setup() for the bmdma_setup() hook. ata_bmdma_setup() will write the pointer to the PRD table to the IDE PRD Table Address register, enable DMA in the DMA Command register, and call exec_command() to begin the transfer.

Most legacy IDE drivers use ata_bmdma_start() for the bmdma_start() hook. ata_bmdma_start() will write the ATA_DMA_START flag to the DMA Command register.

Many legacy IDE drivers use ata_bmdma_stop() for the bmdma_stop() hook. ata_bmdma_stop() clears the ATA_DMA_START flag in the DMA command register.

Many legacy IDE drivers use ata_bmdma_status() as the bmdma_status() hook.

High-level taskfile hooks

enum ata_completion_errors (*qc_prep) (struct ata_queued_cmd *qc);
int (*qc_issue) (struct ata_queued_cmd *qc);

Higher-level hooks, these two hooks can potentially supersede several of the above taskfile/DMA engine hooks. ->qc_prep is called after the buffers have been DMA-mapped, and is typically used to populate the hardware’s DMA scatter-gather table. Some drivers use the standard ata_bmdma_qc_prep() and ata_bmdma_dumb_qc_prep() helper functions, but more advanced drivers roll their own.

->qc_issue is used to make a command active, once the hardware and S/G tables have been prepared. IDE BMDMA drivers use the helper function ata_sff_qc_issue() for taskfile protocol-based dispatch. More advanced drivers implement their own ->qc_issue.

ata_sff_qc_issue() calls ->sff_tf_load(), ->bmdma_setup(), and ->bmdma_start() as necessary to initiate a transfer.

Exception and probe handling (EH)

void (*freeze) (struct ata_port *ap);
void (*thaw) (struct ata_port *ap);

ata_port_freeze() is called when HSM violations or some other condition disrupts normal operation of the port. A frozen port is not allowed to perform any operation until the port is thawed, which usually follows a successful reset.

The optional ->freeze() callback can be used for freezing the port hardware-wise (e.g. mask interrupt and stop DMA engine). If a port cannot be frozen hardware-wise, the interrupt handler must ack and clear interrupts unconditionally while the port is frozen.

The optional ->thaw() callback is called to perform the opposite of ->freeze(): prepare the port for normal operation once again. Unmask interrupts, start DMA engine, etc.

void (*error_handler) (struct ata_port *ap);

->error_handler() is a driver’s hook into probe, hotplug, and recovery and other exceptional conditions. The primary responsibility of an implementation is to call ata_do_eh() or ata_bmdma_drive_eh() with a set of EH hooks as arguments:

‘prereset’ hook (may be NULL) is called during an EH reset, before any other actions are taken.

‘postreset’ hook (may be NULL) is called after the EH reset is performed. Based on existing conditions, severity of the problem, and hardware capabilities,

Either ‘softreset’ (may be NULL) or ‘hardreset’ (may be NULL) will be called to perform the low-level EH reset.

void (*post_internal_cmd) (struct ata_queued_cmd *qc);

Perform any hardware-specific actions necessary to finish processing after executing a probe-time or EH-time command via ata_exec_internal().

Hardware interrupt handling

irqreturn_t (*irq_handler)(int, void *, struct pt_regs *);
void (*irq_clear) (struct ata_port *);

->irq_handler is the interrupt handling routine registered with the system, by libata. ->irq_clear is called during probe just before the interrupt handler is registered, to be sure hardware is quiet.

The second argument, dev_instance, should be cast to a pointer to struct ata_host_set.

Most legacy IDE drivers use ata_sff_interrupt() for the irq_handler hook, which scans all ports in the host_set, determines which queued command was active (if any), and calls ata_sff_host_intr(ap,qc).

Most legacy IDE drivers use ata_sff_irq_clear() for the irq_clear() hook, which simply clears the interrupt and error flags in the DMA status register.

SATA phy read/write

int (*scr_read) (struct ata_port *ap, unsigned int sc_reg,
         u32 *val);
int (*scr_write) (struct ata_port *ap, unsigned int sc_reg,
                   u32 val);

Read and write standard SATA phy registers. sc_reg is one of SCR_STATUS, SCR_CONTROL, SCR_ERROR, or SCR_ACTIVE.

Init and shutdown

int (*port_start) (struct ata_port *ap);
void (*port_stop) (struct ata_port *ap);
void (*host_stop) (struct ata_host_set *host_set);

->port_start() is called just after the data structures for each port are initialized. Typically this is used to alloc per-port DMA buffers / tables / rings, enable DMA engines, and similar tasks. Some drivers also use this entry point as a chance to allocate driver-private memory for ap->private_data.

Many drivers use ata_port_start() as this hook or call it from their own port_start() hooks. ata_port_start() allocates space for a legacy IDE PRD table and returns.

->port_stop() is called after ->host_stop(). Its sole function is to release DMA/memory resources, now that they are no longer actively being used. Many drivers also free driver-private data from port at this time.

->host_stop() is called after all ->port_stop() calls have completed. The hook must finalize hardware shutdown, release DMA and other resources, etc. This hook may be specified as NULL, in which case it is not called.

Error handling

This chapter describes how errors are handled under libata. Readers are advised to read SCSI EH (SCSI EH) and ATA exceptions doc first.

Origins of commands

In libata, a command is represented with struct ata_queued_cmd or qc. qc’s are preallocated during port initialization and repetitively used for command executions. Currently only one qc is allocated per port but yet-to-be-merged NCQ branch allocates one for each tag and maps each qc to NCQ tag 1-to-1.

libata commands can originate from two sources - libata itself and SCSI midlayer. libata internal commands are used for initialization and error handling. All normal blk requests and commands for SCSI emulation are passed as SCSI commands through queuecommand callback of SCSI host template.

How commands are issued

Internal commands

Once allocated qc’s taskfile is initialized for the command to be executed. qc currently has two mechanisms to notify completion. One is via qc->complete_fn() callback and the other is completion qc->waiting. qc->complete_fn() callback is the asynchronous path used by normal SCSI translated commands and qc->waiting is the synchronous (issuer sleeps in process context) path used by internal commands.

Once initialization is complete, host_set lock is acquired and the qc is issued.

SCSI commands

All libata drivers use ata_scsi_queuecmd() as hostt->queuecommand callback. scmds can either be simulated or translated. No qc is involved in processing a simulated scmd. The result is computed right away and the scmd is completed.

qc->complete_fn() callback is used for completion notification. ATA commands use ata_scsi_qc_complete() while ATAPI commands use atapi_qc_complete(). Both functions end up calling qc->scsidone to notify upper layer when the qc is finished. After translation is completed, the qc is issued with ata_qc_issue().

Note that SCSI midlayer invokes hostt->queuecommand while holding host_set lock, so all above occur while holding host_set lock.

How commands are processed

Depending on which protocol and which controller are used, commands are processed differently. For the purpose of discussion, a controller which uses taskfile interface and all standard callbacks is assumed.

Currently 6 ATA command protocols are used. They can be sorted into the following four categories according to how they are processed.

ATA NO DATA or DMA

ATA_PROT_NODATA and ATA_PROT_DMA fall into this category. These types of commands don’t require any software intervention once issued. Device will raise interrupt on completion.

ATA PIO

ATA_PROT_PIO is in this category. libata currently implements PIO with polling. ATA_NIEN bit is set to turn off interrupt and pio_task on ata_wq performs polling and IO.

ATAPI NODATA or DMA

ATA_PROT_ATAPI_NODATA and ATA_PROT_ATAPI_DMA are in this category. packet_task is used to poll BSY bit after issuing PACKET command. Once BSY is turned off by the device, packet_task transfers CDB and hands off processing to interrupt handler.

ATAPI PIO

ATA_PROT_ATAPI is in this category. ATA_NIEN bit is set and, as in ATAPI NODATA or DMA, packet_task submits cdb. However, after submitting cdb, further processing (data transfer) is handed off to pio_task.

How commands are completed

Once issued, all qc’s are either completed with ata_qc_complete() or time out. For commands which are handled by interrupts, ata_host_intr() invokes ata_qc_complete(), and, for PIO tasks, pio_task invokes ata_qc_complete(). In error cases, packet_task may also complete commands.

ata_qc_complete() does the following.

1. DMA memory is unmapped.

2. ATA_QCFLAG_ACTIVE is cleared from qc->flags.

3. qc->complete_fn callback is invoked. If the return value of the callback is not zero. Completion is short circuited and ata_qc_complete() returns.

4. __ata_qc_complete() is called, which does

   1. qc->flags is cleared to zero.

   2. ap->active_tag and qc->tag are poisoned.

   3. qc->waiting is cleared & completed (in that order).

   4. qc is deallocated by clearing appropriate bit in ap->qactive.

So, it basically notifies upper layer and deallocates qc. One exception is short-circuit path in #3 which is used by atapi_qc_complete().

For all non-ATAPI commands, whether it fails or not, almost the same code path is taken and very little error handling takes place. A qc is completed with success status if it succeeded, with failed status otherwise.

However, failed ATAPI commands require more handling as REQUEST SENSE is needed to acquire sense data. If an ATAPI command fails, ata_qc_complete() is invoked with error status, which in turn invokes atapi_qc_complete() via qc->complete_fn() callback.

This makes atapi_qc_complete() set scmd->result to SAM_STAT_CHECK_CONDITION, complete the scmd and return 1. As the sense data is empty but scmd->result is CHECK CONDITION, SCSI midlayer will invoke EH for the scmd, and returning 1 makes ata_qc_complete() to return without deallocating the qc. This leads us to ata_scsi_error() with partially completed qc.

ata_scsi_error()

ata_scsi_error() is the current transportt->eh_strategy_handler() for libata. As discussed above, this will be entered in two cases - timeout and ATAPI error completion. This function will check if a qc is active and has not failed yet. Such a qc will be marked with AC_ERR_TIMEOUT such that EH will know to handle it later. Then it calls low level libata driver’s error_handler() callback.

When the error_handler() callback is invoked it stops BMDMA and completes the qc. Note that as we’re currently in EH, we cannot call scsi_done. As described in SCSI EH doc, a recovered scmd should be either retried with scsi_queue_insert() or finished with scsi_finish_command(). Here, we override qc->scsidone with scsi_finish_command() and calls ata_qc_complete().

If EH is invoked due to a failed ATAPI qc, the qc here is completed but not deallocated. The purpose of this half-completion is to use the qc as place holder to make EH code reach this place. This is a bit hackish, but it works.

Once control reaches here, the qc is deallocated by invoking __ata_qc_complete() explicitly. Then, internal qc for REQUEST SENSE is issued. Once sense data is acquired, scmd is finished by directly invoking scsi_finish_command() on the scmd. Note that as we already have completed and deallocated the qc which was associated with the scmd, we don’t need to/cannot call ata_qc_complete() again.

Problems with the current EH

• Error representation is too crude. Currently any and all error conditions are represented with ATA STATUS and ERROR registers. Errors which aren’t ATA device errors are treated as ATA device errors by setting ATA_ERR bit. Better error descriptor which can properly represent ATA and other errors/exceptions is needed.

• When handling timeouts, no action is taken to make device forget about the timed out command and ready for new commands.

• EH handling via ata_scsi_error() is not properly protected from usual command processing. On EH entrance, the device is not in quiescent state. Timed out commands may succeed or fail any time. pio_task and atapi_task may still be running.

• Too weak error recovery. Devices / controllers causing HSM mismatch errors and other errors quite often require reset to return to known state. Also, advanced error handling is necessary to support features like NCQ and hotplug.

• ATA errors are directly handled in the interrupt handler and PIO errors in pio_task. This is problematic for advanced error handling for the following reasons.

  First, advanced error handling often requires context and internal qc execution.

  Second, even a simple failure (say, CRC error) needs information gathering and could trigger complex error handling (say, resetting & reconfiguring). Having multiple code paths to gather information, enter EH and trigger actions makes life painful.

  Third, scattered EH code makes implementing low level drivers difficult. Low level drivers override libata callbacks. If EH is scattered over several places, each affected callbacks should perform its part of error handling. This can be error prone and painful.

libata Library

struct ata_link *ata_link_next(struct ata_link *link, struct ata_port *ap, enum ata_link_iter_mode mode)

link iteration helper

Parameters

struct ata_link *link

the previous link, NULL to start

struct ata_port *ap

ATA port containing links to iterate

enum ata_link_iter_mode mode

iteration mode, one of ATA_LITER_*

LOCKING: Host lock or EH context.

Return

Pointer to the next link.

struct ata_device *ata_dev_next(struct ata_device *dev, struct ata_link *link, enum ata_dev_iter_mode mode)

device iteration helper

Parameters

struct ata_device *dev

the previous device, NULL to start

struct ata_link *link

ATA link containing devices to iterate

enum ata_dev_iter_mode mode

iteration mode, one of ATA_DITER_*

LOCKING: Host lock or EH context.

Return

Pointer to the next device.

int atapi_cmd_type(u8 opcode)

Determine ATAPI command type from SCSI opcode

Parameters

u8 opcode

SCSI opcode

Determine ATAPI command type from opcode.

LOCKING: None.

Return

ATAPI_{READ|WRITE|READ_CD|PASS_THRU|MISC}

unsigned int ata_pack_xfermask(unsigned int pio_mask, unsigned int mwdma_mask, unsigned int udma_mask)

Pack pio, mwdma and udma masks into xfer_mask

Parameters

unsigned int pio_mask

pio_mask

unsigned int mwdma_mask

mwdma_mask

unsigned int udma_mask

udma_mask

Pack pio_mask, mwdma_mask and udma_mask into a single unsigned int xfer_mask.

LOCKING: None.

Return

Packed xfer_mask.

u8 ata_xfer_mask2mode(unsigned int xfer_mask)

Find matching XFER_* for the given xfer_mask

Parameters

unsigned int xfer_mask

xfer_mask of interest

Return matching XFER_* value for xfer_mask. Only the highest bit of xfer_mask is considered.

LOCKING: None.

Return

Matching XFER_* value, 0xff if no match found.

unsigned int ata_xfer_mode2mask(u8 xfer_mode)

Find matching xfer_mask for XFER_*

Parameters

u8 xfer_mode

XFER_* of interest

Return matching xfer_mask for xfer_mode.

LOCKING: None.

Return

Matching xfer_mask, 0 if no match found.

int ata_xfer_mode2shift(u8 xfer_mode)

Find matching xfer_shift for XFER_*

Parameters

u8 xfer_mode

XFER_* of interest

Return matching xfer_shift for xfer_mode.

LOCKING: None.

Return

Matching xfer_shift, -1 if no match found.

const char *ata_mode_string(unsigned int xfer_mask)

convert xfer_mask to string

Parameters

unsigned int xfer_mask

mask of bits supported; only highest bit counts.

Determine string which represents the highest speed (highest bit in modemask).

LOCKING: None.

Return

Constant C string representing highest speed listed in mode_mask, or the constant C string “<n/a>”.

unsigned int ata_dev_classify(const struct ata_taskfile *tf)

determine device type based on ATA-spec signature

Parameters

const struct ata_taskfile *tf

ATA taskfile register set for device to be identified

Determine from taskfile register contents whether a device is ATA or ATAPI, as per “Signature and persistence” section of ATA/PI spec (volume 1, sect 5.14).

LOCKING: None.

Return

Device type, ATA_DEV_ATA, ATA_DEV_ATAPI, ATA_DEV_PMP, ATA_DEV_ZAC, or ATA_DEV_UNKNOWN the event of failure.

void ata_id_string(const u16 *id, unsigned char *s, unsigned int ofs, unsigned int len)

Convert IDENTIFY DEVICE page into string

Parameters

const u16 *id

IDENTIFY DEVICE results we will examine

unsigned char *s

string into which data is output

unsigned int ofs

offset into identify device page

unsigned int len

length of string to return. must be an even number.

The strings in the IDENTIFY DEVICE page are broken up into 16-bit chunks. Run through the string, and output each 8-bit chunk linearly, regardless of platform.

LOCKING: caller.

void ata_id_c_string(const u16 *id, unsigned char *s, unsigned int ofs, unsigned int len)

Convert IDENTIFY DEVICE page into C string

Parameters

const u16 *id

IDENTIFY DEVICE results we will examine

unsigned char *s

string into which data is output

unsigned int ofs

offset into identify device page

unsigned int len

length of string to return. must be an odd number.

This function is identical to ata_id_string except that it trims trailing spaces and terminates the resulting string with null. len must be actual maximum length (even number) + 1.

LOCKING: caller.

unsigned int ata_id_xfermask(const u16 *id)

Compute xfermask from the given IDENTIFY data

Parameters

const u16 *id

IDENTIFY data to compute xfer mask from

Compute the xfermask for this device. This is not as trivial as it seems if we must consider early devices correctly.

FIXME: pre IDE drive timing (do we care ?).

LOCKING: None.

Return

Computed xfermask

unsigned int ata_pio_need_iordy(const struct ata_device *adev)

check if iordy needed

Parameters

const struct ata_device *adev

ATA device

Check if the current speed of the device requires IORDY. Used by various controllers for chip configuration.

unsigned int ata_do_dev_read_id(struct ata_device *dev, struct ata_taskfile *tf, __le16 *id)

default ID read method

Parameters

struct ata_device *dev

device

struct ata_taskfile *tf

proposed taskfile

__le16 *id

data buffer

Issue the identify taskfile and hand back the buffer containing identify data. For some RAID controllers and for pre ATA devices this function is wrapped or replaced by the driver

int ata_cable_40wire(struct ata_port *ap)

return 40 wire cable type

Parameters

struct ata_port *ap

port

Helper method for drivers which want to hardwire 40 wire cable detection.

int ata_cable_80wire(struct ata_port *ap)

return 80 wire cable type

Parameters

struct ata_port *ap

port

Helper method for drivers which want to hardwire 80 wire cable detection.

int ata_cable_unknown(struct ata_port *ap)

return unknown PATA cable.

Parameters

struct ata_port *ap

port

Helper method for drivers which have no PATA cable detection.

int ata_cable_ignore(struct ata_port *ap)

return ignored PATA cable.

Parameters

struct ata_port *ap

port

Helper method for drivers which don’t use cable type to limit transfer mode.

int ata_cable_sata(struct ata_port *ap)

return SATA cable type

Parameters

struct ata_port *ap

port

Helper method for drivers which have SATA cables

struct ata_device *ata_dev_pair(struct ata_device *adev)

return other device on cable

Parameters

struct ata_device *adev

device

Obtain the other device on the same cable, or if none is present NULL is returned

int ata_do_set_mode(struct ata_link *link, struct ata_device **r_failed_dev)

Program timings and issue SET FEATURES - XFER

Parameters

struct ata_link *link

link on which timings will be programmed

struct ata_device **r_failed_dev

out parameter for failed device

Standard implementation of the function used to tune and set ATA device disk transfer mode (PIO3, UDMA6, etc.). If ata_dev_set_mode() fails, pointer to the failing device is returned in r_failed_dev.

LOCKING: PCI/etc. bus probe sem.

Return

0 on success, negative errno otherwise

int ata_wait_after_reset(struct ata_link *link, unsigned long deadline, int (*check_ready)(struct ata_link *link))

wait for link to become ready after reset

Parameters

struct ata_link *link

link to be waited on

unsigned long deadline

deadline jiffies for the operation

int (*check_ready)(struct ata_link *link)

callback to check link readiness

Wait for link to become ready after reset.

LOCKING: EH context.

Return

0 if link is ready before deadline; otherwise, -errno.

int ata_std_prereset(struct ata_link *link, unsigned long deadline)

prepare for reset

Parameters

struct ata_link *link

ATA link to be reset

unsigned long deadline

deadline jiffies for the operation

link is about to be reset. Initialize it. Failure from prereset makes libata abort whole reset sequence and give up that port, so prereset should be best-effort. It does its best to prepare for reset sequence but if things go wrong, it should just whine, not fail.

LOCKING: Kernel thread context (may sleep)

Return

Always 0.

int sata_std_hardreset(struct ata_link *link, unsigned int *class, unsigned long deadline)

COMRESET w/o waiting or classification

Parameters

struct ata_link *link

link to reset

unsigned int *class

resulting class of attached device

unsigned long deadline

deadline jiffies for the operation

Standard SATA COMRESET w/o waiting or classification.

LOCKING: Kernel thread context (may sleep)

Return

0 if link offline, -EAGAIN if link online, -errno on errors.

void ata_std_postreset(struct ata_link *link, unsigned int *classes)

standard postreset callback

Parameters

struct ata_link *link

the target ata_link

unsigned int *classes

classes of attached devices

This function is invoked after a successful reset. Note that the device might have been reset more than once using different reset methods before postreset is invoked.

LOCKING: Kernel thread context (may sleep)

unsigned int ata_dev_set_feature(struct ata_device *dev, u8 subcmd, u8 action)

Issue SET FEATURES

Parameters

struct ata_device *dev

Device to which command will be sent

u8 subcmd

The SET FEATURES subcommand to be sent

u8 action

The sector count represents a subcommand specific action

Issue SET FEATURES command to device dev on port ap with sector count

LOCKING: PCI/etc. bus probe sem.

Return

0 on success, AC_ERR_* mask otherwise.

int ata_std_qc_defer(struct ata_queued_cmd *qc)

Check whether a qc needs to be deferred

Parameters

struct ata_queued_cmd *qc

ATA command in question

Non-NCQ commands cannot run with any other command, NCQ or not. As upper layer only knows the queue depth, we are responsible for maintaining exclusion. This function checks whether a new command qc can be issued.

LOCKING: spin_lock_irqsave(host lock)

Return

ATA_DEFER_* if deferring is needed, 0 otherwise.

void ata_qc_complete(struct ata_queued_cmd *qc)

Complete an active ATA command

Parameters

struct ata_queued_cmd *qc

Command to complete

Indicate to the mid and upper layers that an ATA command has completed, with either an ok or not-ok status.

Refrain from calling this function multiple times when successfully completing multiple NCQ commands. ata_qc_complete_multiple() should be used instead, which will properly update IRQ expect state.

LOCKING: spin_lock_irqsave(host lock)

u64 ata_qc_get_active(struct ata_port *ap)

get bitmask of active qcs

Parameters

struct ata_port *ap

port in question

LOCKING: spin_lock_irqsave(host lock)

Return

Bitmask of active qcs

bool ata_link_online(struct ata_link *link)

test whether the given link is online

Parameters

struct ata_link *link

ATA link to test

Test whether link is online. This is identical to ata_phys_link_online() when there’s no slave link. When there’s a slave link, this function should only be called on the master link and will return true if any of M/S links is online.

LOCKING: None.

Return

True if the port online status is available and online.

bool ata_link_offline(struct ata_link *link)

test whether the given link is offline

Parameters

struct ata_link *link

ATA link to test

Test whether link is offline. This is identical to ata_phys_link_offline() when there’s no slave link. When there’s a slave link, this function should only be called on the master link and will return true if both M/S links are offline.

LOCKING: None.

Return

True if the port offline status is available and offline.

void ata_host_suspend(struct ata_host *host, pm_message_t mesg)

suspend host

Parameters

struct ata_host *host

host to suspend

pm_message_t mesg

PM message

Suspend host. Actual operation is performed by port suspend.

void ata_host_resume(struct ata_host *host)

resume host

Parameters

struct ata_host *host

host to resume

Resume host. Actual operation is performed by port resume.

struct ata_host *ata_host_alloc(struct device *dev, int max_ports)

allocate and init basic ATA host resources

Parameters

struct device *dev

generic device this host is associated with

int max_ports

maximum number of ATA ports associated with this host

Allocate and initialize basic ATA host resources. LLD calls this function to allocate a host, initializes it fully and attaches it using ata_host_register().

max_ports ports are allocated and host->n_ports is initialized to max_ports. The caller is allowed to decrease host->n_ports before calling ata_host_register(). The unused ports will be automatically freed on registration.

Return

Allocate ATA host on success, NULL on failure.

LOCKING: Inherited from calling layer (may sleep).

struct ata_host *ata_host_alloc_pinfo(struct device *dev, const struct ata_port_info *const *ppi, int n_ports)

alloc host and init with port_info array

Parameters

struct device *dev

generic device this host is associated with

const struct ata_port_info * const * ppi

array of ATA port_info to initialize host with

int n_ports

number of ATA ports attached to this host

Allocate ATA host and initialize with info from ppi. If NULL terminated, ppi may contain fewer entries than n_ports. The last entry will be used for the remaining ports.

Return

Allocate ATA host on success, NULL on failure.

LOCKING: Inherited from calling layer (may sleep).

int ata_host_start(struct ata_host *host)

start and freeze ports of an ATA host

Parameters

struct ata_host *host

ATA host to start ports for

Start and then freeze ports of host. Started status is recorded in host->flags, so this function can be called multiple times. Ports are guaranteed to get started only once. If host->ops is not initialized yet, it is set to the first non-dummy port ops.

LOCKING: Inherited from calling layer (may sleep).

Return

0 if all ports are started successfully, -errno otherwise.

void ata_host_init(struct ata_host *host, struct device *dev, struct ata_port_operations *ops)

Initialize a host struct for sas (ipr, libsas)

Parameters

struct ata_host *host

host to initialize

struct device *dev

device host is attached to

struct ata_port_operations *ops

port_ops

int ata_host_register(struct ata_host *host, const struct scsi_host_template *sht)

register initialized ATA host

Parameters

struct ata_host *host

ATA host to register

const struct scsi_host_template *sht

template for SCSI host

Register initialized ATA host. host is allocated using ata_host_alloc() and fully initialized by LLD. This function starts ports, registers host with ATA and SCSI layers and probe registered devices.

LOCKING: Inherited from calling layer (may sleep).

Return

0 on success, -errno otherwise.

int ata_host_activate(struct ata_host *host, int irq, irq_handler_t irq_handler, unsigned long irq_flags, const struct scsi_host_template *sht)

start host, request IRQ and register it

Parameters

struct ata_host *host

target ATA host

int irq

IRQ to request

irq_handler_t irq_handler

irq_handler used when requesting IRQ

unsigned long irq_flags

irq_flags used when requesting IRQ

const struct scsi_host_template *sht

scsi_host_template to use when registering the host

After allocating an ATA host and initializing it, most libata LLDs perform three steps to activate the host - start host, request IRQ and register it. This helper takes necessary arguments and performs the three steps in one go.

An invalid IRQ skips the IRQ registration and expects the host to have set polling mode on the port. In this case, irq_handler should be NULL.

LOCKING: Inherited from calling layer (may sleep).

Return

0 on success, -errno otherwise.

void ata_host_detach(struct ata_host *host)

Detach all ports of an ATA host

Parameters

struct ata_host *host

Host to detach

Detach all ports of host.

LOCKING: Kernel thread context (may sleep).

void ata_pci_remove_one(struct pci_dev *pdev)

PCI layer callback for device removal

Parameters

struct pci_dev *pdev

PCI device that was removed

PCI layer indicates to libata via this hook that hot-unplug or module unload event has occurred. Detach all ports. Resource release is handled via devres.

LOCKING: Inherited from PCI layer (may sleep).

void ata_platform_remove_one(struct platform_device *pdev)

Platform layer callback for device removal

Parameters

struct platform_device *pdev

Platform device that was removed

Platform layer indicates to libata via this hook that hot-unplug or module unload event has occurred. Detach all ports. Resource release is handled via devres.

LOCKING: Inherited from platform layer (may sleep).

void ata_msleep(struct ata_port *ap, unsigned int msecs)

ATA EH owner aware msleep

Parameters

struct ata_port *ap

ATA port to attribute the sleep to

unsigned int msecs

duration to sleep in milliseconds

Sleeps msecs. If the current task is owner of ap’s EH, the ownership is released before going to sleep and reacquired after the sleep is complete. IOW, other ports sharing the ap->host will be allowed to own the EH while this task is sleeping.

LOCKING: Might sleep.

u32 ata_wait_register(struct ata_port *ap, void __iomem *reg, u32 mask, u32 val, unsigned int interval, unsigned int timeout)

wait until register value changes

Parameters

struct ata_port *ap

ATA port to wait register for, can be NULL

void __iomem *reg

IO-mapped register

u32 mask

Mask to apply to read register value

u32 val

Wait condition

unsigned int interval

polling interval in milliseconds

unsigned int timeout

timeout in milliseconds

Waiting for some bits of register to change is a common operation for ATA controllers. This function reads 32bit LE IO-mapped register reg and tests for the following condition.

(*reg & mask) != val

If the condition is met, it returns; otherwise, the process is repeated after interval_msec until timeout.

LOCKING: Kernel thread context (may sleep)

Return

The final register value.

libata Core Internals

struct ata_link *ata_dev_phys_link(struct ata_device *dev)

find physical link for a device

Parameters

struct ata_device *dev

ATA device to look up physical link for

Look up physical link which dev is attached to. Note that this is different from dev->link only when dev is on slave link. For all other cases, it’s the same as dev->link.

LOCKING: Don’t care.

Return

Pointer to the found physical link.

void ata_force_cbl(struct ata_port *ap)

force cable type according to libata.force

Parameters

struct ata_port *ap

ATA port of interest

Force cable type according to libata.force and whine about it. The last entry which has matching port number is used, so it can be specified as part of device force parameters. For example, both “a:40c,1.00:udma4” and “1.00:40c,udma4” have the same effect.

LOCKING: EH context.

void ata_force_link_limits(struct ata_link *link)

force link limits according to libata.force

Parameters

struct ata_link *link

ATA link of interest

Force link flags and SATA spd limit according to libata.force and whine about it. When only the port part is specified (e.g. 1:), the limit applies to all links connected to both the host link and all fan-out ports connected via PMP. If the device part is specified as 0 (e.g. 1.00:), it specifies the first fan-out link not the host link. Device number 15 always points to the host link whether PMP is attached or not. If the controller has slave link, device number 16 points to it.

LOCKING: EH context.

void ata_force_xfermask(struct ata_device *dev)

force xfermask according to libata.force

Parameters

struct ata_device *dev

ATA device of interest

Force xfer_mask according to libata.force and whine about it. For consistency with link selection, device number 15 selects the first device connected to the host link.

LOCKING: EH context.

void ata_force_horkage(struct ata_device *dev)

force horkage according to libata.force

Parameters

struct ata_device *dev

ATA device of interest

Force horkage according to libata.force and whine about it. For consistency with link selection, device number 15 selects the first device connected to the host link.

LOCKING: EH context.

bool ata_set_rwcmd_protocol(struct ata_device *dev, struct ata_taskfile *tf)

set taskfile r/w command and protocol

Parameters

struct ata_device *dev

target device for the taskfile

struct ata_taskfile *tf

taskfile to examine and configure

Examine the device configuration and tf->flags to determine the proper read/write command and protocol to use for tf.

LOCKING: caller.

u64 ata_tf_read_block(const struct ata_taskfile *tf, struct ata_device *dev)

Read block address from ATA taskfile

Parameters

const struct ata_taskfile *tf

ATA taskfile of interest

struct ata_device *dev

ATA device tf belongs to

LOCKING: None.

Read block address from tf. This function can handle all three address formats - LBA, LBA48 and CHS. tf->protocol and flags select the address format to use.

Return

Block address read from tf.

int ata_build_rw_tf(struct ata_queued_cmd *qc, u64 block, u32 n_block, unsigned int tf_flags, int cdl, int class)

Build ATA taskfile for given read/write request

Parameters

struct ata_queued_cmd *qc

Metadata associated with the taskfile to build

u64 block

Block address

u32 n_block

Number of blocks

unsigned int tf_flags

RW/FUA etc...

int cdl

Command duration limit index

int class

IO priority class

LOCKING: None.

Build ATA taskfile for the command qc for read/write request described by block, n_block, tf_flags and class.

Return

0 on success, -ERANGE if the request is too large for dev, -EINVAL if the request is invalid.

void ata_unpack_xfermask(unsigned int xfer_mask, unsigned int *pio_mask, unsigned int *mwdma_mask, unsigned int *udma_mask)

Unpack xfer_mask into pio, mwdma and udma masks

Parameters

unsigned int xfer_mask

xfer_mask to unpack

unsigned int *pio_mask

resulting pio_mask

unsigned int *mwdma_mask

resulting mwdma_mask

unsigned int *udma_mask

resulting udma_mask

Unpack xfer_mask into pio_mask, mwdma_mask and udma_mask. Any NULL destination masks will be ignored.

int ata_read_native_max_address(struct ata_device *dev, u64 *max_sectors)

Read native max address

Parameters

struct ata_device *dev

target device

u64 *max_sectors

out parameter for the result native max address

Perform an LBA48 or LBA28 native size query upon the device in question.

Return

0 on success, -EACCES if command is aborted by the drive. -EIO on other errors.

int ata_set_max_sectors(struct ata_device *dev, u64 new_sectors)

Set max sectors

Parameters

struct ata_device *dev

target device

u64 new_sectors

new max sectors value to set for the device

Set max sectors of dev to new_sectors.

Return

0 on success, -EACCES if command is aborted or denied (due to previous non-volatile SET_MAX) by the drive. -EIO on other errors.

int ata_hpa_resize(struct ata_device *dev)

Resize a device with an HPA set

Parameters

struct ata_device *dev

Device to resize

Read the size of an LBA28 or LBA48 disk with HPA features and resize it if required to the full size of the media. The caller must check the drive has the HPA feature set enabled.

Return

0 on success, -errno on failure.

void ata_dump_id(struct ata_device *dev, const u16 *id)

IDENTIFY DEVICE info debugging output

Parameters

struct ata_device *dev

device from which the information is fetched

const u16 *id

IDENTIFY DEVICE page to dump

Dump selected 16-bit words from the given IDENTIFY DEVICE page.

LOCKING: caller.

unsigned int ata_exec_internal(struct ata_device *dev, struct ata_taskfile *tf, const u8 *cdb, enum dma_data_direction dma_dir, void *buf, unsigned int buflen, unsigned int timeout)

execute libata internal command

Parameters

struct ata_device *dev

Device to which the command is sent

struct ata_taskfile *tf

Taskfile registers for the command and the result

const u8 *cdb

CDB for packet command

enum dma_data_direction dma_dir

Data transfer direction of the command

void *buf

Data buffer of the command

unsigned int buflen

Length of data buffer

unsigned int timeout

Timeout in msecs (0 for default)

Executes libata internal command with timeout. tf contains the command on entry and the result on return. Timeout and error conditions are reported via the return value. No recovery action is taken after a command times out. It is the caller’s duty to clean up after timeout.

LOCKING: None. Should be called with kernel context, might sleep.

Return

Zero on success, AC_ERR_* mask on failure

u32 ata_pio_mask_no_iordy(const struct ata_device *adev)

Return the non IORDY mask

Parameters

const struct ata_device *adev

ATA device

Compute the highest mode possible if we are not using iordy. Return -1 if no iordy mode is available.

int ata_dev_read_id(struct ata_device *dev, unsigned int *p_class, unsigned int flags, u16 *id)

Read ID data from the specified device

Parameters

struct ata_device *dev

target device

unsigned int *p_class

pointer to class of the target device (may be changed)

unsigned int flags

ATA_READID_* flags

u16 *id

buffer to read IDENTIFY data into

Read ID data from the specified device. ATA_CMD_ID_ATA is performed on ATA devices and ATA_CMD_ID_ATAPI on ATAPI devices. This function also issues ATA_CMD_INIT_DEV_PARAMS for pre-ATA4 drives.

FIXME: ATA_CMD_ID_ATA is optional for early drives and right now we abort if we hit that case.

LOCKING: Kernel thread context (may sleep)

Return

0 on success, -errno otherwise.

void ata_dev_power_set_standby(struct ata_device *dev)

Set a device power mode to standby

Parameters

struct ata_device *dev

target device

Issue a STANDBY IMMEDIATE command to set a device power mode to standby. For an HDD device, this spins down the disks.

LOCKING: Kernel thread context (may sleep).

void ata_dev_power_set_active(struct ata_device *dev)

Set a device power mode to active

Parameters

struct ata_device *dev

target device

Issue a VERIFY command to enter to ensure that the device is in the active power mode. For a spun-down HDD (standby or idle power mode), the VERIFY command will complete after the disk spins up.

LOCKING: Kernel thread context (may sleep).

unsigned int ata_read_log_page(struct ata_device *dev, u8 log, u8 page, void *buf, unsigned int sectors)

read a specific log page

Parameters

struct ata_device *dev

target device

u8 log

log to read

u8 page

page to read

void *buf

buffer to store read page

unsigned int sectors

number of sectors to read

Read log page using READ_LOG_EXT command.

LOCKING: Kernel thread context (may sleep).

Return

0 on success, AC_ERR_* mask otherwise.

int ata_dev_configure(struct ata_device *dev)

Configure the specified ATA/ATAPI device

Parameters

struct ata_device *dev

Target device to configure

Configure dev according to dev->id. Generic and low-level driver specific fixups are also applied.

LOCKING: Kernel thread context (may sleep)

Return

0 on success, -errno otherwise

void sata_print_link_status(struct ata_link *link)

Print SATA link status

Parameters

struct ata_link *link

SATA link to printk link status about

This function prints link speed and status of a SATA link.

LOCKING: None.

int sata_down_spd_limit(struct ata_link *link, u32 spd_limit)

adjust SATA spd limit downward

Parameters

struct ata_link *link

Link to adjust SATA spd limit for

u32 spd_limit

Additional limit

Adjust SATA spd limit of link downward. Note that this function only adjusts the limit. The change must be applied using sata_set_spd().

If spd_limit is non-zero, the speed is limited to equal to or lower than spd_limit if such speed is supported. If spd_limit is slower than any supported speed, only the lowest supported speed is allowed.

LOCKING: Inherited from caller.

Return

0 on success, negative errno on failure

u8 ata_timing_cycle2mode(unsigned int xfer_shift, int cycle)

find xfer mode for the specified cycle duration

Parameters

unsigned int xfer_shift

ATA_SHIFT_* value for transfer type to examine.

int cycle

cycle duration in ns

Return matching xfer mode for cycle. The returned mode is of the transfer type specified by xfer_shift. If cycle is too slow for xfer_shift, 0xff is returned. If cycle is faster than the fastest known mode, the fasted mode is returned.

LOCKING: None.

Return

Matching xfer_mode, 0xff if no match found.

int ata_down_xfermask_limit(struct ata_device *dev, unsigned int sel)

adjust dev xfer masks downward

Parameters

struct ata_device *dev

Device to adjust xfer masks

unsigned int sel

ATA_DNXFER_* selector

Adjust xfer masks of dev downward. Note that this function does not apply the change. Invoking ata_set_mode() afterwards will apply the limit.

LOCKING: Inherited from caller.

Return

0 on success, negative errno on failure

int ata_wait_ready(struct ata_link *link, unsigned long deadline, int (*check_ready)(struct ata_link *link))

wait for link to become ready

Parameters

struct ata_link *link

link to be waited on

unsigned long deadline

deadline jiffies for the operation

int (*check_ready)(struct ata_link *link)

callback to check link readiness

Wait for link to become ready. check_ready should return positive number if link is ready, 0 if it isn’t, -ENODEV if link doesn’t seem to be occupied, other errno for other error conditions.

Transient -ENODEV conditions are allowed for ATA_TMOUT_FF_WAIT.

LOCKING: EH context.

Return

0 if link is ready before deadline; otherwise, -errno.

int ata_dev_same_device(struct ata_device *dev, unsigned int new_class, const u16 *new_id)

Determine whether new ID matches configured device

Parameters

struct ata_device *dev

device to compare against

unsigned int new_class

class of the new device

const u16 *new_id

IDENTIFY page of the new device

Compare new_class and new_id against dev and determine whether dev is the device indicated by new_class and new_id.

LOCKING: None.

Return

1 if dev matches new_class and new_id, 0 otherwise.

int ata_dev_reread_id(struct ata_device *dev, unsigned int readid_flags)

Re-read IDENTIFY data

Parameters

struct ata_device *dev

target ATA device

unsigned int readid_flags

read ID flags

Re-read IDENTIFY page and make sure dev is still attached to the port.

LOCKING: Kernel thread context (may sleep)

Return

0 on success, negative errno otherwise

int ata_dev_revalidate(struct ata_device *dev, unsigned int new_class, unsigned int readid_flags)

Revalidate ATA device

Parameters

struct ata_device *dev

device to revalidate

unsigned int new_class

new class code

unsigned int readid_flags

read ID flags

Re-read IDENTIFY page, make sure dev is still attached to the port and reconfigure it according to the new IDENTIFY page.

LOCKING: Kernel thread context (may sleep)

Return

0 on success, negative errno otherwise

int ata_is_40wire(struct ata_device *dev)

check drive side detection

Parameters

struct ata_device *dev

device

Perform drive side detection decoding, allowing for device vendors who can’t follow the documentation.

int cable_is_40wire(struct ata_port *ap)

40/80/SATA decider

Parameters

struct ata_port *ap

port to consider

This function encapsulates the policy for speed management in one place. At the moment we don’t cache the result but there is a good case for setting ap->cbl to the result when we are called with unknown cables (and figuring out if it impacts hotplug at all).

Return 1 if the cable appears to be 40 wire.

void ata_dev_xfermask(struct ata_device *dev)

Compute supported xfermask of the given device

Parameters

struct ata_device *dev

Device to compute xfermask for

Compute supported xfermask of dev and store it in dev->*_mask. This function is responsible for applying all known limits including host controller limits, device blacklist, etc...

LOCKING: None.

unsigned int ata_dev_set_xfermode(struct ata_device *dev)

Issue SET FEATURES - XFER MODE command

Parameters

struct ata_device *dev

Device to which command will be sent

Issue SET FEATURES - XFER MODE command to device dev on port ap.

LOCKING: PCI/etc. bus probe sem.

Return

0 on success, AC_ERR_* mask otherwise.

unsigned int ata_dev_init_params(struct ata_device *dev, u16 heads, u16 sectors)

Issue INIT DEV PARAMS command

Parameters

struct ata_device *dev

Device to which command will be sent

u16 heads

Number of heads (taskfile parameter)

u16 sectors

Number of sectors (taskfile parameter)

LOCKING: Kernel thread context (may sleep)

Return

0 on success, AC_ERR_* mask otherwise.

int atapi_check_dma(struct ata_queued_cmd *qc)

Check whether ATAPI DMA can be supported

Parameters

struct ata_queued_cmd *qc

Metadata associated with taskfile to check

Allow low-level driver to filter ATA PACKET commands, returning a status indicating whether or not it is OK to use DMA for the supplied PACKET command.

LOCKING: spin_lock_irqsave(host lock)

Return

0 when ATAPI DMA can be used

nonzero otherwise

void ata_sg_init(struct ata_queued_cmd *qc, struct scatterlist *sg, unsigned int n_elem)

Associate command with scatter-gather table.

Parameters

struct ata_queued_cmd *qc

Command to be associated

struct scatterlist *sg

Scatter-gather table.

unsigned int n_elem

Number of elements in s/g table.

Initialize the data-related elements of queued_cmd qc to point to a scatter-gather table sg, containing n_elem elements.

LOCKING: spin_lock_irqsave(host lock)

void ata_sg_clean(struct ata_queued_cmd *qc)

Unmap DMA memory associated with command

Parameters

struct ata_queued_cmd *qc

Command containing DMA memory to be released

Unmap all mapped DMA memory associated with this command.

LOCKING: spin_lock_irqsave(host lock)

int ata_sg_setup(struct ata_queued_cmd *qc)

DMA-map the scatter-gather table associated with a command.

Parameters

struct ata_queued_cmd *qc

Command with scatter-gather table to be mapped.

DMA-map the scatter-gather table associated with queued_cmd qc.

LOCKING: spin_lock_irqsave(host lock)

Return

Zero on success, negative on error.

void swap_buf_le16(u16 *buf, unsigned int buf_words)

swap halves of 16-bit words in place

Parameters

u16 *buf

Buffer to swap

unsigned int buf_words

Number of 16-bit words in buffer.

Swap halves of 16-bit words if needed to convert from little-endian byte order to native cpu byte order, or vice-versa.

LOCKING: Inherited from caller.

void ata_qc_free(struct ata_queued_cmd *qc)

free unused ata_queued_cmd

Parameters

struct ata_queued_cmd *qc

Command to complete

Designed to free unused ata_queued_cmd object in case something prevents using it.

LOCKING: spin_lock_irqsave(host lock)

void ata_qc_issue(struct ata_queued_cmd *qc)

issue taskfile to device

Parameters

struct ata_queued_cmd *qc

command to issue to device

Prepare an ATA command to submission to device. This includes mapping the data into a DMA-able area, filling in the S/G table, and finally writing the taskfile to hardware, starting the command.

LOCKING: spin_lock_irqsave(host lock)

bool ata_phys_link_online(struct ata_link *link)

test whether the given link is online

Parameters

struct ata_link *link

ATA link to test

Test whether link is online. Note that this function returns 0 if online status of link cannot be obtained, so ata_link_online(link) != !ata_link_offline(link).

LOCKING: None.

Return

True if the port online status is available and online.

bool ata_phys_link_offline(struct ata_link *link)

test whether the given link is offline

Parameters

struct ata_link *link

ATA link to test

Test whether link is offline. Note that this function returns 0 if offline status of link cannot be obtained, so ata_link_online(link) != !ata_link_offline(link).

LOCKING: None.

Return

True if the port offline status is available and offline.

void ata_dev_init(struct ata_device *dev)

Initialize an ata_device structure

Parameters

struct ata_device *dev

Device structure to initialize

Initialize dev in preparation for probing.

LOCKING: Inherited from caller.

void ata_link_init(struct ata_port *ap, struct ata_link *link, int pmp)

Initialize an ata_link structure

Parameters

struct ata_port *ap

ATA port link is attached to

struct ata_link *link

Link structure to initialize

int pmp

Port multiplier port number

Initialize link.

LOCKING: Kernel thread context (may sleep)

int sata_link_init_spd(struct ata_link *link)

Initialize link->sata_spd_limit

Parameters

struct ata_link *link

Link to configure sata_spd_limit for

Initialize link->[hw_]sata_spd_limit to the currently configured value.

LOCKING: Kernel thread context (may sleep).

Return

0 on success, -errno on failure.

struct ata_port *ata_port_alloc(struct ata_host *host)

allocate and initialize basic ATA port resources

Parameters

struct ata_host *host

ATA host this allocated port belongs to

Allocate and initialize basic ATA port resources.

Return

Allocate ATA port on success, NULL on failure.

LOCKING: Inherited from calling layer (may sleep).

void ata_finalize_port_ops(struct ata_port_operations *ops)

finalize ata_port_operations

Parameters

struct ata_port_operations *ops

ata_port_operations to finalize

An ata_port_operations can inherit from another ops and that ops can again inherit from another. This can go on as many times as necessary as long as there is no loop in the inheritance chain.

Ops tables are finalized when the host is started. NULL or unspecified entries are inherited from the closet ancestor which has the method and the entry is populated with it. After finalization, the ops table directly points to all the methods and ->inherits is no longer necessary and cleared.

Using ATA_OP_NULL, inheriting ops can force a method to NULL.

LOCKING: None.

void ata_port_detach(struct ata_port *ap)

Detach ATA port in preparation of device removal

Parameters

struct ata_port *ap

ATA port to be detached

Detach all ATA devices and the associated SCSI devices of ap; then, remove the associated SCSI host. ap is guaranteed to be quiescent on return from this function.

LOCKING: Kernel thread context (may sleep).

void __ata_ehi_push_desc(struct ata_eh_info *ehi, const char *fmt, ...)

push error description without adding separator

Parameters

struct ata_eh_info *ehi

target EHI

const char *fmt

printf format string

Format string according to fmt and append it to ehi->desc.

LOCKING: spin_lock_irqsave(host lock)

...

variable arguments

void ata_ehi_push_desc(struct ata_eh_info *ehi, const char *fmt, ...)

push error description with separator

Parameters

struct ata_eh_info *ehi

target EHI

const char *fmt

printf format string

Format string according to fmt and append it to ehi->desc. If ehi->desc is not empty, “, “ is added in-between.

LOCKING: spin_lock_irqsave(host lock)

...

variable arguments

void ata_ehi_clear_desc(struct ata_eh_info *ehi)

clean error description

Parameters

struct ata_eh_info *ehi

target EHI

Clear ehi->desc.

LOCKING: spin_lock_irqsave(host lock)

void ata_port_desc(struct ata_port *ap, const char *fmt, ...)

append port description

Parameters

struct ata_port *ap

target ATA port

const char *fmt

printf format string

Format string according to fmt and append it to port description. If port description is not empty, “ “ is added in-between. This function is to be used while initializing ata_host. The description is printed on host registration.

LOCKING: None.

...

variable arguments

void ata_port_pbar_desc(struct ata_port *ap, int bar, ssize_t offset, const char *name)

append PCI BAR description

Parameters

struct ata_port *ap

target ATA port

int bar

target PCI BAR

ssize_t offset

offset into PCI BAR

const char *name

name of the area

If offset is negative, this function formats a string which contains the name, address, size and type of the BAR and appends it to the port description. If offset is zero or positive, only name and offsetted address is appended.

LOCKING: None.

unsigned int ata_internal_cmd_timeout(struct ata_device *dev, u8 cmd)

determine timeout for an internal command

Parameters

struct ata_device *dev

target device

u8 cmd

internal command to be issued

Determine timeout for internal command cmd for dev.

LOCKING: EH context.

Return

Determined timeout.

void ata_internal_cmd_timed_out(struct ata_device *dev, u8 cmd)

notification for internal command timeout

Parameters

struct ata_device *dev

target device

u8 cmd

internal command which timed out

Notify EH that internal command cmd for dev timed out. This function should be called only for commands whose timeouts are determined using ata_internal_cmd_timeout().

LOCKING: EH context.

void ata_eh_acquire(struct ata_port *ap)

acquire EH ownership

Parameters

struct ata_port *ap

ATA port to acquire EH ownership for

Acquire EH ownership for ap. This is the basic exclusion mechanism for ports sharing a host. Only one port hanging off the same host can claim the ownership of EH.

LOCKING: EH context.

void ata_eh_release(struct ata_port *ap)

release EH ownership

Parameters

struct ata_port *ap

ATA port to release EH ownership for

Release EH ownership for ap if the caller. The caller must have acquired EH ownership using ata_eh_acquire() previously.

LOCKING: EH context.

void ata_scsi_error(struct Scsi_Host *host)

SCSI layer error handler callback

Parameters

struct Scsi_Host *host

SCSI host on which error occurred

Handles SCSI-layer-thrown error events.

LOCKING: Inherited from SCSI layer (none, can sleep)

Return

Zero.

void ata_scsi_cmd_error_handler(struct Scsi_Host *host, struct ata_port *ap, struct list_head *eh_work_q)

error callback for a list of commands

Parameters

struct Scsi_Host *host

scsi host containing the port

struct ata_port *ap

ATA port within the host

struct list_head *eh_work_q

list of commands to process

Description

process the given list of commands and return those finished to the ap->eh_done_q. This function is the first part of the libata error handler which processes a given list of failed commands.

void ata_scsi_port_error_handler(struct Scsi_Host *host, struct ata_port *ap)

recover the port after the commands

Parameters

struct Scsi_Host *host

SCSI host containing the port

struct ata_port *ap

the ATA port

Description

Handle the recovery of the port ap after all the commands have been recovered.

void ata_port_wait_eh(struct ata_port *ap)

Wait for the currently pending EH to complete

Parameters

struct ata_port *ap

Port to wait EH for

Wait until the currently pending EH is complete.

LOCKING: Kernel thread context (may sleep).

void ata_eh_set_pending(struct ata_port *ap, int fastdrain)

set ATA_PFLAG_EH_PENDING and activate fast drain

Parameters

struct ata_port *ap

target ATA port

int fastdrain

activate fast drain

Set ATA_PFLAG_EH_PENDING and activate fast drain if fastdrain is non-zero and EH wasn’t pending before. Fast drain ensures that EH kicks in in timely manner.

LOCKING: spin_lock_irqsave(host lock)

void ata_qc_schedule_eh(struct ata_queued_cmd *qc)

schedule qc for error handling

Parameters

struct ata_queued_cmd *qc

command to schedule error handling for

Schedule error handling for qc. EH will kick in as soon as other commands are drained.

LOCKING: spin_lock_irqsave(host lock)

void ata_std_sched_eh(struct ata_port *ap)

non-libsas ata_ports issue eh with this common routine

Parameters

struct ata_port *ap

ATA port to schedule EH for

LOCKING: inherited from ata_port_schedule_eh spin_lock_irqsave(host lock)

void ata_std_end_eh(struct ata_port *ap)

non-libsas ata_ports complete eh with this common routine

Parameters

struct ata_port *ap

ATA port to end EH for

Description

In the libata object model there is a 1:1 mapping of ata_port to shost, so host fields can be directly manipulated under ap->lock, in the libsas case we need to hold a lock at the ha->level to coordinate these events.

LOCKING: spin_lock_irqsave(host lock)

void ata_port_schedule_eh(struct ata_port *ap)

schedule error handling without a qc

Parameters

struct ata_port *ap

ATA port to schedule EH for

Schedule error handling for ap. EH will kick in as soon as all commands are drained.

LOCKING: spin_lock_irqsave(host lock)

int ata_link_abort(struct ata_link *link)

abort all qc’s on the link

Parameters

struct ata_link *link

ATA link to abort qc’s for

Abort all active qc’s active on link and schedule EH.

LOCKING: spin_lock_irqsave(host lock)

Return

Number of aborted qc’s.

int ata_port_abort(struct ata_port *ap)

abort all qc’s on the port

Parameters

struct ata_port *ap

ATA port to abort qc’s for

Abort all active qc’s of ap and schedule EH.

LOCKING: spin_lock_irqsave(host_set lock)

Return

Number of aborted qc’s.

void __ata_port_freeze(struct ata_port *ap)

freeze port

Parameters

struct ata_port *ap

ATA port to freeze

This function is called when HSM violation or some other condition disrupts normal operation of the port. Frozen port is not allowed to perform any operation until the port is thawed, which usually follows a successful reset.

ap->ops->freeze() callback can be used for freezing the port hardware-wise (e.g. mask interrupt and stop DMA engine). If a port cannot be frozen hardware-wise, the interrupt handler must ack and clear interrupts unconditionally while the port is frozen.

LOCKING: spin_lock_irqsave(host lock)

int ata_port_freeze(struct ata_port *ap)

abort & freeze port

Parameters

struct ata_port *ap

ATA port to freeze

Abort and freeze ap. The freeze operation must be called first, because some hardware requires special operations before the taskfile registers are accessible.

LOCKING: spin_lock_irqsave(host lock)

Return

Number of aborted commands.

void ata_eh_freeze_port(struct ata_port *ap)

EH helper to freeze port

Parameters

struct ata_port *ap

ATA port to freeze

Freeze ap.

LOCKING: None.

void ata_eh_thaw_port(struct ata_port *ap)

EH helper to thaw port

Parameters

struct ata_port *ap

ATA port to thaw

Thaw frozen port ap.

LOCKING: None.

void ata_eh_qc_complete(struct ata_queued_cmd *qc)

Complete an active ATA command from EH

Parameters

struct ata_queued_cmd *qc

Command to complete

Indicate to the mid and upper layers that an ATA command has completed. To be used from EH.

void ata_eh_qc_retry(struct ata_queued_cmd *qc)

Tell midlayer to retry an ATA command after EH

Parameters

struct ata_queued_cmd *qc

Command to retry

Indicate to the mid and upper layers that an ATA command should be retried. To be used from EH.

SCSI midlayer limits the number of retries to scmd->allowed. scmd->allowed is incremented for commands which get retried due to unrelated failures (qc->err_mask is zero).

void ata_dev_disable(struct ata_device *dev)

disable ATA device

Parameters

struct ata_device *dev

ATA device to disable

Disable dev.

Locking: EH context.

void ata_eh_detach_dev(struct ata_device *dev)

detach ATA device

Parameters

struct ata_device *dev

ATA device to detach

Detach dev.

LOCKING: None.

void ata_eh_about_to_do(struct ata_link *link, struct ata_device *dev, unsigned int action)

about to perform eh_action

Parameters

struct ata_link *link

target ATA link

struct ata_device *dev

target ATA dev for per-dev action (can be NULL)

unsigned int action

action about to be performed

Called just before performing EH actions to clear related bits in link->eh_info such that eh actions are not unnecessarily repeated.

LOCKING: None.

void ata_eh_done(struct ata_link *link, struct ata_device *dev, unsigned int action)

EH action complete

Parameters

struct ata_link *link

ATA link for which EH actions are complete

struct ata_device *dev

target ATA dev for per-dev action (can be NULL)

unsigned int action

action just completed

Called right after performing EH actions to clear related bits in link->eh_context.

LOCKING: None.

const char *ata_err_string(unsigned int err_mask)

convert err_mask to descriptive string

Parameters

unsigned int err_mask

error mask to convert to string

Convert err_mask to descriptive string. Errors are prioritized according to severity and only the most severe error is reported.

LOCKING: None.

Return

Descriptive string for err_mask

unsigned int atapi_eh_tur(struct ata_device *dev, u8 *r_sense_key)

perform ATAPI TEST_UNIT_READY

Parameters

struct ata_device *dev

target ATAPI device

u8 *r_sense_key

out parameter for sense_key

Perform ATAPI TEST_UNIT_READY.

LOCKING: EH context (may sleep).

Return

0 on success, AC_ERR_* mask on failure.

bool ata_eh_request_sense(struct ata_queued_cmd *qc)

perform REQUEST_SENSE_DATA_EXT

Parameters

struct ata_queued_cmd *qc

qc to perform REQUEST_SENSE_SENSE_DATA_EXT to

Perform REQUEST_SENSE_DATA_EXT after the device reported CHECK SENSE. This function is an EH helper.

LOCKING: Kernel thread context (may sleep).

Return

true if sense data could be fetched, false otherwise.

unsigned int atapi_eh_request_sense(struct ata_device *dev, u8 *sense_buf, u8 dfl_sense_key)

perform ATAPI REQUEST_SENSE

Parameters

struct ata_device *dev

device to perform REQUEST_SENSE to

u8 *sense_buf

result sense data buffer (SCSI_SENSE_BUFFERSIZE bytes long)

u8 dfl_sense_key

default sense key to use

Perform ATAPI REQUEST_SENSE after the device reported CHECK SENSE. This function is EH helper.

LOCKING: Kernel thread context (may sleep).

Return

0 on success, AC_ERR_* mask on failure

void ata_eh_analyze_serror(struct ata_link *link)

analyze SError for a failed port

Parameters

struct ata_link *link

ATA link to analyze SError for

Analyze SError if available and further determine cause of failure.

LOCKING: None.

unsigned int ata_eh_analyze_tf(struct ata_queued_cmd *qc)

analyze taskfile of a failed qc

Parameters

struct ata_queued_cmd *qc

qc to analyze

Analyze taskfile of qc and further determine cause of failure. This function also requests ATAPI sense data if available.

LOCKING: Kernel thread context (may sleep).

Return

Determined recovery action

unsigned int ata_eh_speed_down_verdict(struct ata_device *dev)

Determine speed down verdict

Parameters

struct ata_device *dev

Device of interest

This function examines error ring of dev and determines whether NCQ needs to be turned off, transfer speed should be stepped down, or falling back to PIO is necessary.

ECAT_ATA_BUS : ATA_BUS error for any command

ECAT_TOUT_HSMTIMEOUT for any command or HSM violation for

IO commands

ECAT_UNK_DEV : Unknown DEV error for IO commands

ECAT_DUBIOUS_*Identical to above three but occurred while

data transfer hasn’t been verified.

Verdicts are

NCQ_OFF : Turn off NCQ.

SPEED_DOWNSpeed down transfer speed but don’t fall back

to PIO.

FALLBACK_TO_PIO : Fall back to PIO.

Even if multiple verdicts are returned, only one action is taken per error. An action triggered by non-DUBIOUS errors clears ering, while one triggered by DUBIOUS_* errors doesn’t. This is to expedite speed down decisions right after device is initially configured.

The following are speed down rules. #1 and #2 deal with DUBIOUS errors.

1. If more than one DUBIOUS_ATA_BUS or DUBIOUS_TOUT_HSM errors occurred during last 5 mins, SPEED_DOWN and FALLBACK_TO_PIO.

2. If more than one DUBIOUS_TOUT_HSM or DUBIOUS_UNK_DEV errors occurred during last 5 mins, NCQ_OFF.

3. If more than 8 ATA_BUS, TOUT_HSM or UNK_DEV errors occurred during last 5 mins, FALLBACK_TO_PIO

4. If more than 3 TOUT_HSM or UNK_DEV errors occurred during last 10 mins, NCQ_OFF.

5. If more than 3 ATA_BUS or TOUT_HSM errors, or more than 6 UNK_DEV errors occurred during last 10 mins, SPEED_DOWN.

LOCKING: Inherited from caller.

Return

OR of ATA_EH_SPDN_* flags.

unsigned int ata_eh_speed_down(struct ata_device *dev, unsigned int eflags, unsigned int err_mask)

record error and speed down if necessary

Parameters

struct ata_device *dev

Failed device

unsigned int eflags

mask of ATA_EFLAG_* flags

unsigned int err_mask

err_mask of the error

Record error and examine error history to determine whether adjusting transmission speed is necessary. It also sets transmission limits appropriately if such adjustment is necessary.

LOCKING: Kernel thread context (may sleep).

Return

Determined recovery action.

int ata_eh_worth_retry(struct ata_queued_cmd *qc)

analyze error and decide whether to retry

Parameters

struct ata_queued_cmd *qc

qc to possibly retry

Look at the cause of the error and decide if a retry might be useful or not. We don’t want to retry media errors because the drive itself has probably already taken 10-30 seconds doing its own internal retries before reporting the failure.

bool ata_eh_quiet(struct ata_queued_cmd *qc)

check if we need to be quiet about a command error

Parameters

struct ata_queued_cmd *qc

qc to check

Look at the qc flags anbd its scsi command request flags to determine if we need to be quiet about the command failure.

void ata_eh_link_autopsy(struct ata_link *link)

analyze error and determine recovery action

Parameters

struct ata_link *link

host link to perform autopsy on

Analyze why link failed and determine which recovery actions are needed. This function also sets more detailed AC_ERR_* values and fills sense data for ATAPI CHECK SENSE.

LOCKING: Kernel thread context (may sleep).

void ata_eh_autopsy(struct ata_port *ap)

analyze error and determine recovery action

Parameters

struct ata_port *ap

host port to perform autopsy on

Analyze all links of ap and determine why they failed and which recovery actions are needed.

LOCKING: Kernel thread context (may sleep).

const char *ata_get_cmd_name(u8 command)

get name for ATA command

Parameters

u8 command

ATA command code to get name for

Return a textual name of the given command or “unknown”

LOCKING: None

void ata_eh_link_report(struct ata_link *link)

report error handling to user

Parameters

struct ata_link *link

ATA link EH is going on

Report EH to user.

LOCKING: None.

void ata_eh_report(struct ata_port *ap)

report error handling to user

Parameters

struct ata_port *ap

ATA port to report EH about

Report EH to user.

LOCKING: None.

int ata_set_mode(struct ata_link *link, struct ata_device **r_failed_dev)

Program timings and issue SET FEATURES - XFER

Parameters

struct ata_link *link

link on which timings will be programmed

struct ata_device **r_failed_dev

out parameter for failed device

Set ATA device disk transfer mode (PIO3, UDMA6, etc.). If ata_set_mode() fails, pointer to the failing device is returned in r_failed_dev.

LOCKING: PCI/etc. bus probe sem.

Return

0 on success, negative errno otherwise

int atapi_eh_clear_ua(struct ata_device *dev)

Clear ATAPI UNIT ATTENTION after reset

Parameters

struct ata_device *dev

ATAPI device to clear UA for

Resets and other operations can make an ATAPI device raise UNIT ATTENTION which causes the next operation to fail. This function clears UA.

LOCKING: EH context (may sleep).

Return

0 on success, -errno on failure.

int ata_eh_maybe_retry_flush(struct ata_device *dev)

Retry FLUSH if necessary

Parameters

struct ata_device *dev

ATA device which may need FLUSH retry

If dev failed FLUSH, it needs to be reported upper layer immediately as it means that dev failed to remap and already lost at least a sector and further FLUSH retrials won’t make any difference to the lost sector. However, if FLUSH failed for other reasons, for example transmission error, FLUSH needs to be retried.

This function determines whether FLUSH failure retry is necessary and performs it if so.

Return

0 if EH can continue, -errno if EH needs to be repeated.

int ata_eh_set_lpm(struct ata_link *link, enum ata_lpm_policy policy, struct ata_device **r_failed_dev)

configure SATA interface power management

Parameters

struct ata_link *link

link to configure power management

enum ata_lpm_policy policy

the link power management policy

struct ata_device **r_failed_dev

out parameter for failed device

Enable SATA Interface power management. This will enable Device Interface Power Management (DIPM) for min_power and medium_power_with_dipm policies, and then call driver specific callbacks for enabling Host Initiated Power management.

LOCKING: EH context.

Return

0 on success, -errno on failure.

int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset, ata_reset_fn_t softreset, ata_reset_fn_t hardreset, ata_postreset_fn_t postreset, struct ata_link **r_failed_link)

recover host port after error

Parameters

struct ata_port *ap

host port to recover

ata_prereset_fn_t prereset

prereset method (can be NULL)

ata_reset_fn_t softreset

softreset method (can be NULL)

ata_reset_fn_t hardreset

hardreset method (can be NULL)

ata_postreset_fn_t postreset

postreset method (can be NULL)

struct ata_link **r_failed_link

out parameter for failed link

This is the alpha and omega, eum and yang, heart and soul of libata exception handling. On entry, actions required to recover each link and hotplug requests are recorded in the link’s eh_context. This function executes all the operations with appropriate retrials and fallbacks to resurrect failed devices, detach goners and greet newcomers.

LOCKING: Kernel thread context (may sleep).

Return

0 on success, -errno on failure.

void ata_eh_finish(struct ata_port *ap)

finish up EH

Parameters

struct ata_port *ap

host port to finish EH for

Recovery is complete. Clean up EH states and retry or finish failed qcs.

LOCKING: None.

void ata_do_eh(struct ata_port *ap, ata_prereset_fn_t prereset, ata_reset_fn_t softreset, ata_reset_fn_t hardreset, ata_postreset_fn_t postreset)

do standard error handling

Parameters

struct ata_port *ap

host port to handle error for

ata_prereset_fn_t prereset

prereset method (can be NULL)

ata_reset_fn_t softreset

softreset method (can be NULL)

ata_reset_fn_t hardreset

hardreset method (can be NULL)

ata_postreset_fn_t postreset

postreset method (can be NULL)

Perform standard error handling sequence.

LOCKING: Kernel thread context (may sleep).

void ata_std_error_handler(struct ata_port *ap)

standard error handler

Parameters

struct ata_port *ap

host port to handle error for

Standard error handler

LOCKING: Kernel thread context (may sleep).

void ata_eh_handle_port_suspend(struct ata_port *ap)

perform port suspend operation

Parameters

struct ata_port *ap

port to suspend

Suspend ap.

LOCKING: Kernel thread context (may sleep).

void ata_eh_handle_port_resume(struct ata_port *ap)

perform port resume operation

Parameters

struct ata_port *ap

port to resume

Resume ap.

LOCKING: Kernel thread context (may sleep).

libata SCSI translation/emulation

int ata_std_bios_param(struct scsi_device *sdev, struct block_device *bdev, sector_t capacity, int geom[])

generic bios head/sector/cylinder calculator used by sd.

Parameters

struct scsi_device *sdev

SCSI device for which BIOS geometry is to be determined

struct block_device *bdev

block device associated with sdev

sector_t capacity

capacity of SCSI device

int geom[]

location to which geometry will be output

Generic bios head/sector/cylinder calculator used by sd. Most BIOSes nowadays expect a XXX/255/16 (CHS) mapping. Some situations may arise where the disk is not bootable if this is not used.

LOCKING: Defined by the SCSI layer. We don’t really care.

Return

Zero.

void ata_scsi_unlock_native_capacity(struct scsi_device *sdev)

unlock native capacity

Parameters

struct scsi_device *sdev

SCSI device to adjust device capacity for

This function is called if a partition on sdev extends beyond the end of the device. It requests EH to unlock HPA.

LOCKING: Defined by the SCSI layer. Might sleep.

bool ata_scsi_dma_need_drain(struct request *rq)

Check whether data transfer may overflow

Parameters

struct request *rq

request to be checked

ATAPI commands which transfer variable length data to host might overflow due to application error or hardware bug. This function checks whether overflow should be drained and ignored for request.

LOCKING: None.

Return

1 if ; otherwise, 0.

int ata_scsi_slave_alloc(struct scsi_device *sdev)

Early setup of SCSI device

Parameters

struct scsi_device *sdev

SCSI device to examine

This is called from scsi_alloc_sdev() when the scsi device associated with an ATA device is scanned on a port.

LOCKING: Defined by SCSI layer. We don’t really care.

int ata_scsi_device_configure(struct scsi_device *sdev, struct queue_limits *lim)

Set SCSI device attributes

Parameters

struct scsi_device *sdev

SCSI device to examine

struct queue_limits *lim

queue limits

This is called before we actually start reading and writing to the device, to configure certain SCSI mid-layer behaviors.

LOCKING: Defined by SCSI layer. We don’t really care.

void ata_scsi_slave_destroy(struct scsi_device *sdev)

SCSI device is about to be destroyed

Parameters

struct scsi_device *sdev

SCSI device to be destroyed

sdev is about to be destroyed for hot/warm unplugging. If this unplugging was initiated by libata as indicated by NULL dev->sdev, this function doesn’t have to do anything. Otherwise, SCSI layer initiated warm-unplug is in progress. Clear dev->sdev, schedule the device for ATA detach and invoke EH.

LOCKING: Defined by SCSI layer. We don’t really care.

int ata_scsi_queuecmd(struct Scsi_Host *shost, struct scsi_cmnd *cmd)

Issue SCSI cdb to libata-managed device

Parameters

struct Scsi_Host *shost

SCSI host of command to be sent

struct scsi_cmnd *cmd

SCSI command to be sent

In some cases, this function translates SCSI commands into ATA taskfiles, and queues the taskfiles to be sent to hardware. In other cases, this function simulates a SCSI device by evaluating and responding to certain SCSI commands. This creates the overall effect of ATA and ATAPI devices appearing as SCSI devices.

LOCKING: ATA host lock

Return

Return value from __ata_scsi_queuecmd() if cmd can be queued, 0 otherwise.

int ata_get_identity(struct ata_port *ap, struct scsi_device *sdev, void __user *arg)

Handler for HDIO_GET_IDENTITY ioctl

Parameters

struct ata_port *ap

target port

struct scsi_device *sdev

SCSI device to get identify data for

void __user *arg

User buffer area for identify data

LOCKING: Defined by the SCSI layer. We don’t really care.

Return

Zero on success, negative errno on error.

int ata_cmd_ioctl(struct scsi_device *scsidev, void __user *arg)

Handler for HDIO_DRIVE_CMD ioctl

Parameters

struct scsi_device *scsidev

Device to which we are issuing command

void __user *arg

User provided data for issuing command

LOCKING: Defined by the SCSI layer. We don’t really care.

Return

Zero on success, negative errno on error.

int ata_task_ioctl(struct scsi_device *scsidev, void __user *arg)

Handler for HDIO_DRIVE_TASK ioctl

Parameters

struct scsi_device *scsidev

Device to which we are issuing command

void __user *arg

User provided data for issuing command

LOCKING: Defined by the SCSI layer. We don’t really care.

Return

Zero on success, negative errno on error.

struct ata_queued_cmd *ata_scsi_qc_new(struct ata_device *dev, struct scsi_cmnd *cmd)

acquire new ata_queued_cmd reference

Parameters

struct ata_device *dev

ATA device to which the new command is attached

struct scsi_cmnd *cmd

SCSI command that originated this ATA command

Obtain a reference to an unused ata_queued_cmd structure, which is the basic libata structure representing a single ATA command sent to the hardware.

If a command was available, fill in the SCSI-specific portions of the structure with information on the current command.

LOCKING: spin_lock_irqsave(host lock)

Return

Command allocated, or NULL if none available.

void ata_to_sense_error(unsigned id, u8 drv_stat, u8 drv_err, u8 *sk, u8 *asc, u8 *ascq)

convert ATA error to SCSI error

Parameters

unsigned id

ATA device number

u8 drv_stat

value contained in ATA status register

u8 drv_err

value contained in ATA error register

u8 *sk

the sense key we’ll fill out

u8 *asc

the additional sense code we’ll fill out

u8 *ascq

the additional sense code qualifier we’ll fill out

Converts an ATA error into a SCSI error. Fill out pointers to SK, ASC, and ASCQ bytes for later use in fixed or descriptor format sense blocks.

LOCKING: spin_lock_irqsave(host lock)

void ata_gen_ata_sense(struct ata_queued_cmd *qc)

generate a SCSI fixed sense block

Parameters

struct ata_queued_cmd *qc

Command that we are erroring out

Generate sense block for a failed ATA command qc. Descriptor format is used to accommodate LBA48 block address.

LOCKING: None.

unsigned int ata_scsi_start_stop_xlat(struct ata_queued_cmd *qc)

Translate SCSI START STOP UNIT command

Parameters

struct ata_queued_cmd *qc

Storage for translated ATA taskfile

Sets up an ATA taskfile to issue STANDBY (to stop) or READ VERIFY (to start). Perhaps these commands should be preceded by CHECK POWER MODE to see what power mode the device is already in. [See SAT revision 5 at www.t10.org]

LOCKING: spin_lock_irqsave(host lock)

Return

Zero on success, non-zero on error.

unsigned int ata_scsi_flush_xlat(struct ata_queued_cmd *qc)

Translate SCSI SYNCHRONIZE CACHE command

Parameters

struct ata_queued_cmd *qc

Storage for translated ATA taskfile

Sets up an ATA taskfile to issue FLUSH CACHE or FLUSH CACHE EXT.

LOCKING: spin_lock_irqsave(host lock)

Return

Zero on success, non-zero on error.

void scsi_6_lba_len(const u8 *cdb, u64 *plba, u32 *plen)

Get LBA and transfer length

Parameters

const u8 *cdb

SCSI command to translate

Calculate LBA and transfer length for 6-byte commands.

u64 *plba

the LBA

u32 *plen

the transfer length

Return

void scsi_10_lba_len(const u8 *cdb, u64 *plba, u32 *plen)

Get LBA and transfer length

Parameters

const u8 *cdb

SCSI command to translate

Calculate LBA and transfer length for 10-byte commands.

u64 *plba

the LBA

u32 *plen

the transfer length

Return

void scsi_16_lba_len(const u8 *cdb, u64 *plba, u32 *plen)

Get LBA and transfer length

Parameters

const u8 *cdb

SCSI command to translate

Calculate LBA and transfer length for 16-byte commands.

u64 *plba

the LBA

u32 *plen

the transfer length

Return

int scsi_dld(const u8 *cdb)

Get duration limit descriptor index

Parameters

const u8 *cdb

SCSI command to translate

Returns the dld bits indicating the index of a command duration limit descriptor.

unsigned int ata_scsi_verify_xlat(struct ata_queued_cmd *qc)

Translate SCSI VERIFY command into an ATA one

Parameters

struct ata_queued_cmd *qc

Storage for translated ATA taskfile

Converts SCSI VERIFY command to an ATA READ VERIFY command.

LOCKING: spin_lock_irqsave(host lock)

Return

Zero on success, non-zero on error.

unsigned int ata_scsi_rw_xlat(struct ata_queued_cmd *qc)

Translate SCSI r/w command into an ATA one

Parameters

struct ata_queued_cmd *qc

Storage for translated ATA taskfile

Converts any of six SCSI read/write commands into the ATA counterpart, including starting sector (LBA), sector count, and taking into account the device’s LBA48 support.

Commands READ_6, READ_10, READ_16, WRITE_6, WRITE_10, and WRITE_16 are currently supported.

LOCKING: spin_lock_irqsave(host lock)

Return

Zero on success, non-zero on error.

int ata_scsi_translate(struct ata_device *dev, struct scsi_cmnd *cmd, ata_xlat_func_t xlat_func)

Translate then issue SCSI command to ATA device

Parameters

struct ata_device *dev

ATA device to which the command is addressed

struct scsi_cmnd *cmd

SCSI command to execute

ata_xlat_func_t xlat_func

Actor which translates cmd to an ATA taskfile

Our ->queuecommand() function has decided that the SCSI command issued can be directly translated into an ATA command, rather than handled internally.

This function sets up an ata_queued_cmd structure for the SCSI command, and sends that ata_queued_cmd to the hardware.

The xlat_func argument (actor) returns 0 if ready to execute ATA command, else 1 to finish translation. If 1 is returned then cmd->result (and possibly cmd->sense_buffer) are assumed to be set reflecting an error condition or clean (early) termination.

LOCKING: spin_lock_irqsave(host lock)

Return

0 on success, SCSI_ML_QUEUE_DEVICE_BUSY if the command needs to be deferred.

void ata_scsi_rbuf_fill(struct ata_scsi_args *args, unsigned int (*actor)(struct ata_scsi_args *args, u8 *rbuf))

wrapper for SCSI command simulators

Parameters

struct ata_scsi_args *args

device IDENTIFY data / SCSI command of interest.

unsigned int (*actor)(struct ata_scsi_args *args, u8 *rbuf)

Callback hook for desired SCSI command simulator

Takes care of the hard work of simulating a SCSI command... Mapping the response buffer, calling the command’s handler, and handling the handler’s return value. This return value indicates whether the handler wishes the SCSI command to be completed successfully (0), or not (in which case cmd->result and sense buffer are assumed to be set).

LOCKING: spin_lock_irqsave(host lock)

unsigned int ata_scsiop_inq_std(struct ata_scsi_args *args, u8 *rbuf)

Simulate INQUIRY command

Parameters

struct ata_scsi_args *args

device IDENTIFY data / SCSI command of interest.

u8 *rbuf

Response buffer, to which simulated SCSI cmd output is sent.

Returns standard device identification data associated with non-VPD INQUIRY command output.

LOCKING: spin_lock_irqsave(host lock)

unsigned int ata_scsiop_inq_00(struct ata_scsi_args *args, u8 *rbuf)

Simulate INQUIRY VPD page 0, list of pages

Parameters

struct ata_scsi_args *args

device IDENTIFY data / SCSI command of interest.

u8 *rbuf

Response buffer, to which simulated SCSI cmd output is sent.

Returns list of inquiry VPD pages available.

LOCKING: spin_lock_irqsave(host lock)

unsigned int ata_scsiop_inq_80(struct ata_scsi_args *args, u8 *rbuf)

Simulate INQUIRY VPD page 80, device serial number

Parameters

struct ata_scsi_args *args

device IDENTIFY data / SCSI command of interest.

u8 *rbuf

Response buffer, to which simulated SCSI cmd output is sent.

Returns ATA device serial number.

LOCKING: spin_lock_irqsave(host lock)

unsigned int ata_scsiop_inq_83(struct ata_scsi_args *args, u8 *rbuf)

Simulate INQUIRY VPD page 83, device identity

Parameters

struct ata_scsi_args *args

device IDENTIFY data / SCSI command of interest.

u8 *rbuf

Response buffer, to which simulated SCSI cmd output is sent.

Yields two logical unit device identification designators:

• vendor specific ASCII containing the ATA serial number

• SAT defined “t10 vendor id based” containing ASCII vendor name (“ATA “), model and serial numbers.

LOCKING: spin_lock_irqsave(host lock)

unsigned int ata_scsiop_inq_89(struct ata_scsi_args *args, u8 *rbuf)

Simulate INQUIRY VPD page 89, ATA info

Parameters

struct ata_scsi_args *args

device IDENTIFY data / SCSI command of interest.

u8 *rbuf

Response buffer, to which simulated SCSI cmd output is sent.

Yields SAT-specified ATA VPD page.

LOCKING: spin_lock_irqsave(host lock)

void modecpy(u8 *dest, const u8 *src, int n, bool changeable)

Prepare response for MODE SENSE

Parameters

u8 *dest

output buffer

const u8 *src

data being copied

int n

length of mode page

bool changeable

whether changeable parameters are requested

Generate a generic MODE SENSE page for either current or changeable parameters.

LOCKING: None.

unsigned int ata_msense_caching(u16 *id, u8 *buf, bool changeable)

Simulate MODE SENSE caching info page

Parameters

u16 *id

device IDENTIFY data

u8 *buf

output buffer

bool changeable

whether changeable parameters are requested

Generate a caching info page, which conditionally indicates write caching to the SCSI layer, depending on device capabilities.

LOCKING: None.

unsigned int ata_msense_control(struct ata_device *dev, u8 *buf, u8 spg, bool changeable)

Simulate MODE SENSE control mode page

Parameters

struct ata_device *dev

ATA device of interest

u8 *buf

output buffer

u8 spg

sub-page code

bool changeable

whether changeable parameters are requested

Generate a generic MODE SENSE control mode page.

LOCKING: None.

unsigned int ata_msense_rw_recovery(u8 *buf, bool changeable)

Simulate MODE SENSE r/w error recovery page

Parameters

u8 *buf

output buffer

bool changeable

whether changeable parameters are requested

Generate a generic MODE SENSE r/w error recovery page.

LOCKING: None.

unsigned int ata_scsiop_mode_sense(struct ata_scsi_args *args, u8 *rbuf)

Simulate MODE SENSE 6, 10 commands

Parameters

struct ata_scsi_args *args

device IDENTIFY data / SCSI command of interest.

u8 *rbuf

Response buffer, to which simulated SCSI cmd output is sent.

Simulate MODE SENSE commands. Assume this is invoked for direct access devices (e.g. disks) only. There should be no block descriptor for other device types.

LOCKING: spin_lock_irqsave(host lock)

unsigned int ata_scsiop_read_cap(struct ata_scsi_args *args, u8 *rbuf)

Simulate READ CAPACITY[ 16] commands

Parameters

struct ata_scsi_args *args

device IDENTIFY data / SCSI command of interest.

u8 *rbuf

Response buffer, to which simulated SCSI cmd output is sent.

Simulate READ CAPACITY commands.

LOCKING: None.

unsigned int ata_scsiop_report_luns(struct ata_scsi_args *args, u8 *rbuf)

Simulate REPORT LUNS command

Parameters

struct ata_scsi_args *args

device IDENTIFY data / SCSI command of interest.

u8 *rbuf

Response buffer, to which simulated SCSI cmd output is sent.

Simulate REPORT LUNS command.

LOCKING: spin_lock_irqsave(host lock)

unsigned int atapi_xlat(struct ata_queued_cmd *qc)

Initialize PACKET taskfile

Parameters

struct ata_queued_cmd *qc

command structure to be initialized

LOCKING: spin_lock_irqsave(host lock)

Return

Zero on success, non-zero on failure.

struct ata_device *ata_scsi_find_dev(struct ata_port *ap, const struct scsi_device *scsidev)

lookup ata_device from scsi_cmnd

Parameters

struct ata_port *ap

ATA port to which the device is attached

const struct scsi_device *scsidev

SCSI device from which we derive the ATA device

Given various information provided in struct scsi_cmnd, map that onto an ATA bus, and using that mapping determine which ata_device is associated with the SCSI command to be sent.

LOCKING: spin_lock_irqsave(host lock)

Return

Associated ATA device, or NULL if not found.

unsigned int ata_scsi_pass_thru(struct ata_queued_cmd *qc)

convert ATA pass-thru CDB to taskfile

Parameters

struct ata_queued_cmd *qc

command structure to be initialized

Handles either 12, 16, or 32-byte versions of the CDB.

Return

Zero on success, non-zero on failure.

size_t ata_format_dsm_trim_descr(struct scsi_cmnd *cmd, u32 trmax, u64 sector, u32 count)

SATL Write Same to DSM Trim

Parameters

struct scsi_cmnd *cmd

SCSI command being translated

u32 trmax

Maximum number of entries that will fit in sector_size bytes.

u64 sector

Starting sector

u32 count

Total Range of request in logical sectors

Description

Rewrite the WRITE SAME descriptor to be a DSM TRIM little-endian formatted descriptor.

Upto 64 entries of the format:

63:48 Range Length 47:0 LBA

Range Length of 0 is ignored. LBA’s should be sorted order and not overlap.

NOTE

this is the same format as ADD LBA(S) TO NV CACHE PINNED SET

Return

Number of bytes copied into sglist.

unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)

SATL Write Same to ATA SCT Write Same

Parameters

struct ata_queued_cmd *qc

Command to be translated

Description

Translate a SCSI WRITE SAME command to be either a DSM TRIM command or an SCT Write Same command. Based on WRITE SAME has the UNMAP flag:

• When set translate to DSM TRIM

• When clear translate to SCT Write Same

unsigned int ata_scsiop_maint_in(struct ata_scsi_args *args, u8 *rbuf)

Simulate a subset of MAINTENANCE_IN

Parameters

struct ata_scsi_args *args

device MAINTENANCE_IN data / SCSI command of interest.

u8 *rbuf

Response buffer, to which simulated SCSI cmd output is sent.

Yields a subset to satisfy scsi_report_opcode()

LOCKING: spin_lock_irqsave(host lock)

void ata_scsi_report_zones_complete(struct ata_queued_cmd *qc)

convert ATA output

Parameters

struct ata_queued_cmd *qc

command structure returning the data

Convert T-13 little-endian field representation into T-10 big-endian field representation. What a mess.

int ata_mselect_caching(struct ata_queued_cmd *qc, const u8 *buf, int len, u16 *fp)

Simulate MODE SELECT for caching info page

Parameters

struct ata_queued_cmd *qc

Storage for translated ATA taskfile

const u8 *buf

input buffer

int len

number of valid bytes in the input buffer

u16 *fp

out parameter for the failed field on error

Prepare a taskfile to modify caching information for the device.

LOCKING: None.

int ata_mselect_control(struct ata_queued_cmd *qc, u8 spg, const u8 *buf, int len, u16 *fp)

Simulate MODE SELECT for control page

Parameters

struct ata_queued_cmd *qc

Storage for translated ATA taskfile

u8 spg

target sub-page of the control page

const u8 *buf

input buffer

int len

number of valid bytes in the input buffer

u16 *fp

out parameter for the failed field on error

Prepare a taskfile to modify caching information for the device.

LOCKING: None.

unsigned int ata_scsi_mode_select_xlat(struct ata_queued_cmd *qc)

Simulate MODE SELECT 6, 10 commands

Parameters

struct ata_queued_cmd *qc

Storage for translated ATA taskfile

Converts a MODE SELECT command to an ATA SET FEATURES taskfile. Assume this is invoked for direct access devices (e.g. disks) only. There should be no block descriptor for other device types.

LOCKING: spin_lock_irqsave(host lock)

unsigned int ata_scsi_var_len_cdb_xlat(struct ata_queued_cmd *qc)

SATL variable length CDB to Handler

Parameters

struct ata_queued_cmd *qc

Command to be translated

Translate a SCSI variable length CDB to specified commands. It checks a service action value in CDB to call corresponding handler.

Return

Zero on success, non-zero on failure

ata_xlat_func_t ata_get_xlat_func(struct ata_device *dev, u8 cmd)

check if SCSI to ATA translation is possible

Parameters

struct ata_device *dev

ATA device

u8 cmd

SCSI command opcode to consider

Look up the SCSI command given, and determine whether the SCSI command is to be translated or simulated.

Return

Pointer to translation function if possible, NULL if not.

void ata_scsi_simulate(struct ata_device *dev, struct scsi_cmnd *cmd)

simulate SCSI command on ATA device

Parameters

struct ata_device *dev

the target device

struct scsi_cmnd *cmd

SCSI command being sent to device.

Interprets and directly executes a select list of SCSI commands that can be handled internally.

LOCKING: spin_lock_irqsave(host lock)

int ata_scsi_offline_dev(struct ata_device *dev)

offline attached SCSI device

Parameters

struct ata_device *dev

ATA device to offline attached SCSI device for

This function is called from ata_eh_hotplug() and responsible for taking the SCSI device attached to dev offline. This function is called with host lock which protects dev->sdev against clearing.

LOCKING: spin_lock_irqsave(host lock)

Return

1 if attached SCSI device exists, 0 otherwise.

void ata_scsi_remove_dev(struct ata_device *dev)

remove attached SCSI device

Parameters

struct ata_device *dev

ATA device to remove attached SCSI device for

This function is called from ata_eh_scsi_hotplug() and responsible for removing the SCSI device attached to dev.

LOCKING: Kernel thread context (may sleep).

void ata_scsi_media_change_notify(struct ata_device *dev)

send media change event

Parameters

struct ata_device *dev

Pointer to the disk device with media change event

Tell the block layer to send a media change notification event.

LOCKING: spin_lock_irqsave(host lock)

void ata_scsi_hotplug(struct work_struct *work)

SCSI part of hotplug

Parameters

struct work_struct *work

Pointer to ATA port to perform SCSI hotplug on

Perform SCSI part of hotplug. It’s executed from a separate workqueue after EH completes. This is necessary because SCSI hot plugging requires working EH and hot unplugging is synchronized with hot plugging with a mutex.

LOCKING: Kernel thread context (may sleep).

int ata_scsi_user_scan(struct Scsi_Host *shost, unsigned int channel, unsigned int id, u64 lun)

indication for user-initiated bus scan

Parameters

struct Scsi_Host *shost

SCSI host to scan

unsigned int channel

Channel to scan

unsigned int id

ID to scan

u64 lun

LUN to scan

This function is called when user explicitly requests bus scan. Set probe pending flag and invoke EH.

LOCKING: SCSI layer (we don’t care)

Return

Zero.

void ata_scsi_dev_rescan(struct work_struct *work)

initiate scsi_rescan_device()

Parameters

struct work_struct *work

Pointer to ATA port to perform scsi_rescan_device()

After ATA pass thru (SAT) commands are executed successfully, libata need to propagate the changes to SCSI layer.

LOCKING: Kernel thread context (may sleep).

ATA errors and exceptions

This chapter tries to identify what error/exception conditions exist for ATA/ATAPI devices and describe how they should be handled in implementation-neutral way.

The term ‘error’ is used to describe conditions where either an explicit error condition is reported from device or a command has timed out.

The term ‘exception’ is either used to describe exceptional conditions which are not errors (say, power or hotplug events), or to describe both errors and non-error exceptional conditions. Where explicit distinction between error and exception is necessary, the term ‘non-error exception’ is used.

Exception categories

Exceptions are described primarily with respect to legacy taskfile + bus master IDE interface. If a controller provides other better mechanism for error reporting, mapping those into categories described below shouldn’t be difficult.

In the following sections, two recovery actions - reset and reconfiguring transport - are mentioned. These are described further in EH recovery actions.

HSM violation

This error is indicated when STATUS value doesn’t match HSM requirement during issuing or execution any ATA/ATAPI command.

• ATA_STATUS doesn’t contain !BSY && DRDY && !DRQ while trying to issue a command.

• !BSY && !DRQ during PIO data transfer.

• DRQ on command completion.

• !BSY && ERR after CDB transfer starts but before the last byte of CDB is transferred. ATA/ATAPI standard states that “The device shall not terminate the PACKET command with an error before the last byte of the command packet has been written” in the error outputs description of PACKET command and the state diagram doesn’t include such transitions.

In these cases, HSM is violated and not much information regarding the error can be acquired from STATUS or ERROR register. IOW, this error can be anything - driver bug, faulty device, controller and/or cable.

As HSM is violated, reset is necessary to restore known state. Reconfiguring transport for lower speed might be helpful too as transmission errors sometimes cause this kind of errors.

ATA/ATAPI device error (non-NCQ / non-CHECK CONDITION)

These are errors detected and reported by ATA/ATAPI devices indicating device problems. For this type of errors, STATUS and ERROR register values are valid and describe error condition. Note that some of ATA bus errors are detected by ATA/ATAPI devices and reported using the same mechanism as device errors. Those cases are described later in this section.

For ATA commands, this type of errors are indicated by !BSY && ERR during command execution and on completion.

For ATAPI commands,

• !BSY && ERR && ABRT right after issuing PACKET indicates that PACKET command is not supported and falls in this category.

• !BSY && ERR(==CHK) && !ABRT after the last byte of CDB is transferred indicates CHECK CONDITION and doesn’t fall in this category.

• !BSY && ERR(==CHK) && ABRT after the last byte of CDB is transferred *probably* indicates CHECK CONDITION and doesn’t fall in this category.

Of errors detected as above, the following are not ATA/ATAPI device errors but ATA bus errors and should be handled according to ATA bus error.

CRC error during data transfer

This is indicated by ICRC bit in the ERROR register and means that corruption occurred during data transfer. Up to ATA/ATAPI-7, the standard specifies that this bit is only applicable to UDMA transfers but ATA/ATAPI-8 draft revision 1f says that the bit may be applicable to multiword DMA and PIO.

ABRT error during data transfer or on completion

Up to ATA/ATAPI-7, the standard specifies that ABRT could be set on ICRC errors and on cases where a device is not able to complete a command. Combined with the fact that MWDMA and PIO transfer errors aren’t allowed to use ICRC bit up to ATA/ATAPI-7, it seems to imply that ABRT bit alone could indicate transfer errors.

However, ATA/ATAPI-8 draft revision 1f removes the part that ICRC errors can turn on ABRT. So, this is kind of gray area. Some heuristics are needed here.

ATA/ATAPI device errors can be further categorized as follows.

Media errors

This is indicated by UNC bit in the ERROR register. ATA devices reports UNC error only after certain number of retries cannot recover the data, so there’s nothing much else to do other than notifying upper layer.

READ and WRITE commands report CHS or LBA of the first failed sector but ATA/ATAPI standard specifies that the amount of transferred data on error completion is indeterminate, so we cannot assume that sectors preceding the failed sector have been transferred and thus cannot complete those sectors successfully as SCSI does.

Media changed / media change requested error

<<TODO: fill here>>

Address error

This is indicated by IDNF bit in the ERROR register. Report to upper layer.

Other errors

This can be invalid command or parameter indicated by ABRT ERROR bit or some other error condition. Note that ABRT bit can indicate a lot of things including ICRC and Address errors. Heuristics needed.

Depending on commands, not all STATUS/ERROR bits are applicable. These non-applicable bits are marked with “na” in the output descriptions but up to ATA/ATAPI-7 no definition of “na” can be found. However, ATA/ATAPI-8 draft revision 1f describes “N/A” as follows.

3.2.3.3a N/A

A keyword the indicates a field has no defined value in this standard and should not be checked by the host or device. N/A fields should be cleared to zero.

So, it seems reasonable to assume that “na” bits are cleared to zero by devices and thus need no explicit masking.

ATAPI device CHECK CONDITION

ATAPI device CHECK CONDITION error is indicated by set CHK bit (ERR bit) in the STATUS register after the last byte of CDB is transferred for a PACKET command. For this kind of errors, sense data should be acquired to gather information regarding the errors. REQUEST SENSE packet command should be used to acquire sense data.

Once sense data is acquired, this type of errors can be handled similarly to other SCSI errors. Note that sense data may indicate ATA bus error (e.g. Sense Key 04h HARDWARE ERROR && ASC/ASCQ 47h/00h SCSI PARITY ERROR). In such cases, the error should be considered as an ATA bus error and handled according to ATA bus error.

ATA device error (NCQ)

NCQ command error is indicated by cleared BSY and set ERR bit during NCQ command phase (one or more NCQ commands outstanding). Although STATUS and ERROR registers will contain valid values describing the error, READ LOG EXT is required to clear the error condition, determine which command has failed and acquire more information.

READ LOG EXT Log Page 10h reports which tag has failed and taskfile register values describing the error. With this information the failed command can be handled as a normal ATA command error as in ATA/ATAPI device error (non-NCQ / non-CHECK CONDITION) and all other in-flight commands must be retried. Note that this retry should not be counted - it’s likely that commands retried this way would have completed normally if it were not for the failed command.

Note that ATA bus errors can be reported as ATA device NCQ errors. This should be handled as described in ATA bus error.

If READ LOG EXT Log Page 10h fails or reports NQ, we’re thoroughly screwed. This condition should be treated according to HSM violation.

ATA bus error

ATA bus error means that data corruption occurred during transmission over ATA bus (SATA or PATA). This type of errors can be indicated by

• ICRC or ABRT error as described in ATA/ATAPI device error (non-NCQ / non-CHECK CONDITION).

• Controller-specific error completion with error information indicating transmission error.

• On some controllers, command timeout. In this case, there may be a mechanism to determine that the timeout is due to transmission error.

• Unknown/random errors, timeouts and all sorts of weirdities.

As described above, transmission errors can cause wide variety of symptoms ranging from device ICRC error to random device lockup, and, for many cases, there is no way to tell if an error condition is due to transmission error or not; therefore, it’s necessary to employ some kind of heuristic when dealing with errors and timeouts. For example, encountering repetitive ABRT errors for known supported command is likely to indicate ATA bus error.

Once it’s determined that ATA bus errors have possibly occurred, lowering ATA bus transmission speed is one of actions which may alleviate the problem. See Reconfigure transport for more information.

PCI bus error

Data corruption or other failures during transmission over PCI (or other system bus). For standard BMDMA, this is indicated by Error bit in the BMDMA Status register. This type of errors must be logged as it indicates something is very wrong with the system. Resetting host controller is recommended.

Late completion

This occurs when timeout occurs and the timeout handler finds out that the timed out command has completed successfully or with error. This is usually caused by lost interrupts. This type of errors must be logged. Resetting host controller is recommended.

Unknown error (timeout)

This is when timeout occurs and the command is still processing or the host and device are in unknown state. When this occurs, HSM could be in any valid or invalid state. To bring the device to known state and make it forget about the timed out command, resetting is necessary. The timed out command may be retried.

Timeouts can also be caused by transmission errors. Refer to ATA bus error for more details.

Hotplug and power management exceptions

<<TODO: fill here>>

EH recovery actions

This section discusses several important recovery actions.

Clearing error condition

Many controllers require its error registers to be cleared by error handler. Different controllers may have different requirements.

For SATA, it’s strongly recommended to clear at least SError register during error handling.

Reset

During EH, resetting is necessary in the following cases.

• HSM is in unknown or invalid state

• HBA is in unknown or invalid state

• EH needs to make HBA/device forget about in-flight commands

• HBA/device behaves weirdly

Resetting during EH might be a good idea regardless of error condition to improve EH robustness. Whether to reset both or either one of HBA and device depends on situation but the following scheme is recommended.

• When it’s known that HBA is in ready state but ATA/ATAPI device is in unknown state, reset only device.

• If HBA is in unknown state, reset both HBA and device.

HBA resetting is implementation specific. For a controller complying to taskfile/BMDMA PCI IDE, stopping active DMA transaction may be sufficient iff BMDMA state is the only HBA context. But even mostly taskfile/BMDMA PCI IDE complying controllers may have implementation specific requirements and mechanism to reset themselves. This must be addressed by specific drivers.

OTOH, ATA/ATAPI standard describes in detail ways to reset ATA/ATAPI devices.

PATA hardware reset

This is hardware initiated device reset signalled with asserted PATA RESET- signal. There is no standard way to initiate hardware reset from software although some hardware provides registers that allow driver to directly tweak the RESET- signal.

Software reset

This is achieved by turning CONTROL SRST bit on for at least 5us. Both PATA and SATA support it but, in case of SATA, this may require controller-specific support as the second Register FIS to clear SRST should be transmitted while BSY bit is still set. Note that on PATA, this resets both master and slave devices on a channel.

EXECUTE DEVICE DIAGNOSTIC command

Although ATA/ATAPI standard doesn’t describe exactly, EDD implies some level of resetting, possibly similar level with software reset. Host-side EDD protocol can be handled with normal command processing and most SATA controllers should be able to handle EDD’s just like other commands. As in software reset, EDD affects both devices on a PATA bus.

Although EDD does reset devices, this doesn’t suit error handling as EDD cannot be issued while BSY is set and it’s unclear how it will act when device is in unknown/weird state.

ATAPI DEVICE RESET command

This is very similar to software reset except that reset can be restricted to the selected device without affecting the other device sharing the cable.

SATA phy reset

This is the preferred way of resetting a SATA device. In effect, it’s identical to PATA hardware reset. Note that this can be done with the standard SCR Control register. As such, it’s usually easier to implement than software reset.

One more thing to consider when resetting devices is that resetting clears certain configuration parameters and they need to be set to their previous or newly adjusted values after reset.

Parameters affected are.

• CHS set up with INITIALIZE DEVICE PARAMETERS (seldom used)

• Parameters set with SET FEATURES including transfer mode setting

• Block count set with SET MULTIPLE MODE

• Other parameters (SET MAX, MEDIA LOCK...)

ATA/ATAPI standard specifies that some parameters must be maintained across hardware or software reset, but doesn’t strictly specify all of them. Always reconfiguring needed parameters after reset is required for robustness. Note that this also applies when resuming from deep sleep (power-off).

Also, ATA/ATAPI standard requires that IDENTIFY DEVICE / IDENTIFY PACKET DEVICE is issued after any configuration parameter is updated or a hardware reset and the result used for further operation. OS driver is required to implement revalidation mechanism to support this.

Reconfigure transport

For both PATA and SATA, a lot of corners are cut for cheap connectors, cables or controllers and it’s quite common to see high transmission error rate. This can be mitigated by lowering transmission speed.

The following is a possible scheme Jeff Garzik suggested.

If more than $N (3?) transmission errors happen in 15 minutes,

• if SATA, decrease SATA PHY speed. if speed cannot be decreased,

• decrease UDMA xfer speed. if at UDMA0, switch to PIO4,

• decrease PIO xfer speed. if at PIO3, complain, but continue

ata_piix Internals

int ich_pata_cable_detect(struct ata_port *ap)

Probe host controller cable detect info

Parameters

struct ata_port *ap

Port for which cable detect info is desired

Read 80c cable indicator from ATA PCI device’s PCI config register. This register is normally set by firmware (BIOS).

LOCKING: None (inherited from caller).

int piix_pata_prereset(struct ata_link *link, unsigned long deadline)

prereset for PATA host controller

Parameters

struct ata_link *link

Target link

unsigned long deadline

deadline jiffies for the operation

LOCKING: None (inherited from caller).

void piix_set_piomode(struct ata_port *ap, struct ata_device *adev)

Initialize host controller PATA PIO timings

Parameters

struct ata_port *ap

Port whose timings we are configuring

struct ata_device *adev

Drive in question

Set PIO mode for device, in host controller PCI config space.

LOCKING: None (inherited from caller).

void do_pata_set_dmamode(struct ata_port *ap, struct ata_device *adev, int isich)

Initialize host controller PATA PIO timings

Parameters

struct ata_port *ap

Port whose timings we are configuring

struct ata_device *adev

Drive in question

int isich

set if the chip is an ICH device

Set UDMA mode for device, in host controller PCI config space.

LOCKING: None (inherited from caller).

void piix_set_dmamode(struct ata_port *ap, struct ata_device *adev)

Initialize host controller PATA DMA timings

Parameters

struct ata_port *ap

Port whose timings we are configuring

struct ata_device *adev

um

Set MW/UDMA mode for device, in host controller PCI config space.

LOCKING: None (inherited from caller).

void ich_set_dmamode(struct ata_port *ap, struct ata_device *adev)

Initialize host controller PATA DMA timings

Parameters

struct ata_port *ap

Port whose timings we are configuring

struct ata_device *adev

um

Set MW/UDMA mode for device, in host controller PCI config space.

LOCKING: None (inherited from caller).

int piix_check_450nx_errata(struct pci_dev *ata_dev)

Check for problem 450NX setup

Parameters

struct pci_dev *ata_dev

the PCI device to check

Check for the present of 450NX errata #19 and errata #25. If they are found return an error code so we can turn off DMA

int piix_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)

Register PIIX ATA PCI device with kernel services

Parameters

struct pci_dev *pdev

PCI device to register

const struct pci_device_id *ent

Entry in piix_pci_tbl matching with pdev

Called from kernel PCI layer. We probe for combined mode (sigh), and then hand over control to libata, for it to do the rest.

LOCKING: Inherited from PCI layer (may sleep).

Return

Zero on success, or -ERRNO value.

sata_sil Internals

int sil_set_mode(struct ata_link *link, struct ata_device **r_failed)

wrap set_mode functions

Parameters

struct ata_link *link

link to set up

struct ata_device **r_failed

returned device when we fail

Wrap the libata method for device setup as after the setup we need to inspect the results and do some configuration work

void sil_dev_config(struct ata_device *dev)

Apply device/host-specific errata fixups

Parameters

struct ata_device *dev

Device to be examined

After the IDENTIFY [PACKET] DEVICE step is complete, and a device is known to be present, this function is called. We apply two errata fixups which are specific to Silicon Image, a Seagate and a Maxtor fixup.

For certain Seagate devices, we must limit the maximum sectors to under 8K.

For certain Maxtor devices, we must not program the drive beyond udma5.

Both fixups are unfairly pessimistic. As soon as I get more information on these errata, I will create a more exhaustive list, and apply the fixups to only the specific devices/hosts/firmwares that need it.

20040111 - Seagate drives affected by the Mod15Write bug are blacklisted The Maxtor quirk is in the blacklist, but I’m keeping the original pessimistic fix for the following reasons... - There seems to be less info on it, only one device gleaned off the Windows driver, maybe only one is affected. More info would be greatly appreciated. - But then again UDMA5 is hardly anything to complain about

Thanks

The bulk of the ATA knowledge comes thanks to long conversations with Andre Hedrick (www.linux-ide.org), and long hours pondering the ATA and SCSI specifications.

Thanks to Alan Cox for pointing out similarities between SATA and SCSI, and in general for motivation to hack on libata.

libata’s device detection method, ata_pio_devchk, and in general all the early probing was based on extensive study of Hale Landis’s probe/reset code in his ATADRVR driver (www.ata-atapi.com).