[PATCH] libata-hp: move ata_do_reset() to libata-eh.c

[linux-2.6] / drivers / scsi / libata-eh.c

/*
 *  libata-eh.c - libata error handling
 *
 *  Maintained by:  Jeff Garzik <jgarzik@pobox.com>
 *                  Please ALWAYS copy linux-ide@vger.kernel.org
 *                  on emails.
 *
 *  Copyright 2006 Tejun Heo <htejun@gmail.com>
 *
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License as
 *  published by the Free Software Foundation; either version 2, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139,
 *  USA.
 *
 *
 *  libata documentation is available via 'make {ps|pdf}docs',
 *  as Documentation/DocBook/libata.*
 *
 *  Hardware documentation available from http://www.t13.org/ and
 *  http://www.sata-io.org/
 *
 */

#include <linux/config.h>
#include <linux/kernel.h>
#include <scsi/scsi.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_cmnd.h>
#include "scsi_transport_api.h"

#include <linux/libata.h>

#include "libata.h"

static void __ata_port_freeze(struct ata_port *ap);
static void ata_eh_finish(struct ata_port *ap);

static void ata_ering_record(struct ata_ering *ering, int is_io,
                             unsigned int err_mask)
{
        struct ata_ering_entry *ent;

        WARN_ON(!err_mask);

        ering->cursor++;
        ering->cursor %= ATA_ERING_SIZE;

        ent = &ering->ring[ering->cursor];
        ent->is_io = is_io;
        ent->err_mask = err_mask;
        ent->timestamp = get_jiffies_64();
}

static struct ata_ering_entry * ata_ering_top(struct ata_ering *ering)
{
        struct ata_ering_entry *ent = &ering->ring[ering->cursor];
        if (!ent->err_mask)
                return NULL;
        return ent;
}

static int ata_ering_map(struct ata_ering *ering,
                         int (*map_fn)(struct ata_ering_entry *, void *),
                         void *arg)
{
        int idx, rc = 0;
        struct ata_ering_entry *ent;

        idx = ering->cursor;
        do {
                ent = &ering->ring[idx];
                if (!ent->err_mask)
                        break;
                rc = map_fn(ent, arg);
                if (rc)
                        break;
                idx = (idx - 1 + ATA_ERING_SIZE) % ATA_ERING_SIZE;
        } while (idx != ering->cursor);

        return rc;
}

/**
 *      ata_scsi_timed_out - SCSI layer time out callback
 *      @cmd: timed out SCSI command
 *
 *      Handles SCSI layer timeout.  We race with normal completion of
 *      the qc for @cmd.  If the qc is already gone, we lose and let
 *      the scsi command finish (EH_HANDLED).  Otherwise, the qc has
 *      timed out and EH should be invoked.  Prevent ata_qc_complete()
 *      from finishing it by setting EH_SCHEDULED and return
 *      EH_NOT_HANDLED.
 *
 *      TODO: kill this function once old EH is gone.
 *
 *      LOCKING:
 *      Called from timer context
 *
 *      RETURNS:
 *      EH_HANDLED or EH_NOT_HANDLED
 */
enum scsi_eh_timer_return ata_scsi_timed_out(struct scsi_cmnd *cmd)
{
        struct Scsi_Host *host = cmd->device->host;
        struct ata_port *ap = ata_shost_to_port(host);
        unsigned long flags;
        struct ata_queued_cmd *qc;
        enum scsi_eh_timer_return ret;

        DPRINTK("ENTER\n");

        if (ap->ops->error_handler) {
                ret = EH_NOT_HANDLED;
                goto out;
        }

        ret = EH_HANDLED;
        spin_lock_irqsave(&ap->host_set->lock, flags);
        qc = ata_qc_from_tag(ap, ap->active_tag);
        if (qc) {
                WARN_ON(qc->scsicmd != cmd);
                qc->flags |= ATA_QCFLAG_EH_SCHEDULED;
                qc->err_mask |= AC_ERR_TIMEOUT;
                ret = EH_NOT_HANDLED;
        }
        spin_unlock_irqrestore(&ap->host_set->lock, flags);

 out:
        DPRINTK("EXIT, ret=%d\n", ret);
        return ret;
}

/**
 *      ata_scsi_error - SCSI layer error handler callback
 *      @host: SCSI host on which error occurred
 *
 *      Handles SCSI-layer-thrown error events.
 *
 *      LOCKING:
 *      Inherited from SCSI layer (none, can sleep)
 *
 *      RETURNS:
 *      Zero.
 */
void ata_scsi_error(struct Scsi_Host *host)
{
        struct ata_port *ap = ata_shost_to_port(host);
        spinlock_t *hs_lock = &ap->host_set->lock;
        int i, repeat_cnt = ATA_EH_MAX_REPEAT;
        unsigned long flags;

        DPRINTK("ENTER\n");

        /* synchronize with port task */
        ata_port_flush_task(ap);

        /* synchronize with host_set lock and sort out timeouts */

        /* For new EH, all qcs are finished in one of three ways -
         * normal completion, error completion, and SCSI timeout.
         * Both cmpletions can race against SCSI timeout.  When normal
         * completion wins, the qc never reaches EH.  When error
         * completion wins, the qc has ATA_QCFLAG_FAILED set.
         *
         * When SCSI timeout wins, things are a bit more complex.
         * Normal or error completion can occur after the timeout but
         * before this point.  In such cases, both types of
         * completions are honored.  A scmd is determined to have
         * timed out iff its associated qc is active and not failed.
         */
        if (ap->ops->error_handler) {
                struct scsi_cmnd *scmd, *tmp;
                int nr_timedout = 0;

                spin_lock_irqsave(hs_lock, flags);

                list_for_each_entry_safe(scmd, tmp, &host->eh_cmd_q, eh_entry) {
                        struct ata_queued_cmd *qc;

                        for (i = 0; i < ATA_MAX_QUEUE; i++) {
                                qc = __ata_qc_from_tag(ap, i);
                                if (qc->flags & ATA_QCFLAG_ACTIVE &&
                                    qc->scsicmd == scmd)
                                        break;
                        }

                        if (i < ATA_MAX_QUEUE) {
                                /* the scmd has an associated qc */
                                if (!(qc->flags & ATA_QCFLAG_FAILED)) {
                                        /* which hasn't failed yet, timeout */
                                        qc->err_mask |= AC_ERR_TIMEOUT;
                                        qc->flags |= ATA_QCFLAG_FAILED;
                                        nr_timedout++;
                                }
                        } else {
                                /* Normal completion occurred after
                                 * SCSI timeout but before this point.
                                 * Successfully complete it.
                                 */
                                scmd->retries = scmd->allowed;
                                scsi_eh_finish_cmd(scmd, &ap->eh_done_q);
                        }
                }

                /* If we have timed out qcs.  They belong to EH from
                 * this point but the state of the controller is
                 * unknown.  Freeze the port to make sure the IRQ
                 * handler doesn't diddle with those qcs.  This must
                 * be done atomically w.r.t. setting QCFLAG_FAILED.
                 */
                if (nr_timedout)
                        __ata_port_freeze(ap);

                spin_unlock_irqrestore(hs_lock, flags);
        } else
                spin_unlock_wait(hs_lock);

 repeat:
        /* invoke error handler */
        if (ap->ops->error_handler) {
                /* fetch & clear EH info */
                spin_lock_irqsave(hs_lock, flags);

                memset(&ap->eh_context, 0, sizeof(ap->eh_context));
                ap->eh_context.i = ap->eh_info;
                memset(&ap->eh_info, 0, sizeof(ap->eh_info));

                ap->flags |= ATA_FLAG_EH_IN_PROGRESS;
                ap->flags &= ~ATA_FLAG_EH_PENDING;

                spin_unlock_irqrestore(hs_lock, flags);

                /* invoke EH.  if unloading, just finish failed qcs */
                if (!(ap->flags & ATA_FLAG_UNLOADING))
                        ap->ops->error_handler(ap);
                else
                        ata_eh_finish(ap);

                /* Exception might have happend after ->error_handler
                 * recovered the port but before this point.  Repeat
                 * EH in such case.
                 */
                spin_lock_irqsave(hs_lock, flags);

                if (ap->flags & ATA_FLAG_EH_PENDING) {
                        if (--repeat_cnt) {
                                ata_port_printk(ap, KERN_INFO,
                                        "EH pending after completion, "
                                        "repeating EH (cnt=%d)\n", repeat_cnt);
                                spin_unlock_irqrestore(hs_lock, flags);
                                goto repeat;
                        }
                        ata_port_printk(ap, KERN_ERR, "EH pending after %d "
                                        "tries, giving up\n", ATA_EH_MAX_REPEAT);
                }

                /* this run is complete, make sure EH info is clear */
                memset(&ap->eh_info, 0, sizeof(ap->eh_info));

                /* Clear host_eh_scheduled while holding hs_lock such
                 * that if exception occurs after this point but
                 * before EH completion, SCSI midlayer will
                 * re-initiate EH.
                 */
                host->host_eh_scheduled = 0;

                spin_unlock_irqrestore(hs_lock, flags);
        } else {
                WARN_ON(ata_qc_from_tag(ap, ap->active_tag) == NULL);
                ap->ops->eng_timeout(ap);
        }

        /* finish or retry handled scmd's and clean up */
        WARN_ON(host->host_failed || !list_empty(&host->eh_cmd_q));

        scsi_eh_flush_done_q(&ap->eh_done_q);

        /* clean up */
        spin_lock_irqsave(hs_lock, flags);

        if (ap->flags & ATA_FLAG_LOADING) {
                ap->flags &= ~ATA_FLAG_LOADING;
        } else {
                if (ap->flags & ATA_FLAG_SCSI_HOTPLUG)
                        queue_work(ata_aux_wq, &ap->hotplug_task);
                if (ap->flags & ATA_FLAG_RECOVERED)
                        ata_port_printk(ap, KERN_INFO, "EH complete\n");
        }

        ap->flags &= ~(ATA_FLAG_SCSI_HOTPLUG | ATA_FLAG_RECOVERED);

        /* tell wait_eh that we're done */
        ap->flags &= ~ATA_FLAG_EH_IN_PROGRESS;
        wake_up_all(&ap->eh_wait_q);

        spin_unlock_irqrestore(hs_lock, flags);

        DPRINTK("EXIT\n");
}

/**
 *      ata_port_wait_eh - Wait for the currently pending EH to complete
 *      @ap: Port to wait EH for
 *
 *      Wait until the currently pending EH is complete.
 *
 *      LOCKING:
 *      Kernel thread context (may sleep).
 */
void ata_port_wait_eh(struct ata_port *ap)
{
        unsigned long flags;
        DEFINE_WAIT(wait);

 retry:
        spin_lock_irqsave(&ap->host_set->lock, flags);

        while (ap->flags & (ATA_FLAG_EH_PENDING | ATA_FLAG_EH_IN_PROGRESS)) {
                prepare_to_wait(&ap->eh_wait_q, &wait, TASK_UNINTERRUPTIBLE);
                spin_unlock_irqrestore(&ap->host_set->lock, flags);
                schedule();
                spin_lock_irqsave(&ap->host_set->lock, flags);
        }

        spin_unlock_irqrestore(&ap->host_set->lock, flags);

        /* make sure SCSI EH is complete */
        if (scsi_host_in_recovery(ap->host)) {
                msleep(10);
                goto retry;
        }
}

/**
 *      ata_qc_timeout - Handle timeout of queued command
 *      @qc: Command that timed out
 *
 *      Some part of the kernel (currently, only the SCSI layer)
 *      has noticed that the active command on port @ap has not
 *      completed after a specified length of time.  Handle this
 *      condition by disabling DMA (if necessary) and completing
 *      transactions, with error if necessary.
 *
 *      This also handles the case of the "lost interrupt", where
 *      for some reason (possibly hardware bug, possibly driver bug)
 *      an interrupt was not delivered to the driver, even though the
 *      transaction completed successfully.
 *
 *      TODO: kill this function once old EH is gone.
 *
 *      LOCKING:
 *      Inherited from SCSI layer (none, can sleep)
 */
static void ata_qc_timeout(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        struct ata_host_set *host_set = ap->host_set;
        u8 host_stat = 0, drv_stat;
        unsigned long flags;

        DPRINTK("ENTER\n");

        ap->hsm_task_state = HSM_ST_IDLE;

        spin_lock_irqsave(&host_set->lock, flags);

        switch (qc->tf.protocol) {

        case ATA_PROT_DMA:
        case ATA_PROT_ATAPI_DMA:
                host_stat = ap->ops->bmdma_status(ap);

                /* before we do anything else, clear DMA-Start bit */
                ap->ops->bmdma_stop(qc);

                /* fall through */

        default:
                ata_altstatus(ap);
                drv_stat = ata_chk_status(ap);

                /* ack bmdma irq events */
                ap->ops->irq_clear(ap);

                ata_dev_printk(qc->dev, KERN_ERR, "command 0x%x timeout, "
                               "stat 0x%x host_stat 0x%x\n",
                               qc->tf.command, drv_stat, host_stat);

                /* complete taskfile transaction */
                qc->err_mask |= AC_ERR_TIMEOUT;
                break;
        }

        spin_unlock_irqrestore(&host_set->lock, flags);

        ata_eh_qc_complete(qc);

        DPRINTK("EXIT\n");
}

/**
 *      ata_eng_timeout - Handle timeout of queued command
 *      @ap: Port on which timed-out command is active
 *
 *      Some part of the kernel (currently, only the SCSI layer)
 *      has noticed that the active command on port @ap has not
 *      completed after a specified length of time.  Handle this
 *      condition by disabling DMA (if necessary) and completing
 *      transactions, with error if necessary.
 *
 *      This also handles the case of the "lost interrupt", where
 *      for some reason (possibly hardware bug, possibly driver bug)
 *      an interrupt was not delivered to the driver, even though the
 *      transaction completed successfully.
 *
 *      TODO: kill this function once old EH is gone.
 *
 *      LOCKING:
 *      Inherited from SCSI layer (none, can sleep)
 */
void ata_eng_timeout(struct ata_port *ap)
{
        DPRINTK("ENTER\n");

        ata_qc_timeout(ata_qc_from_tag(ap, ap->active_tag));

        DPRINTK("EXIT\n");
}

/**
 *      ata_qc_schedule_eh - schedule qc for error handling
 *      @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_set lock)
 */
void ata_qc_schedule_eh(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;

        WARN_ON(!ap->ops->error_handler);

        qc->flags |= ATA_QCFLAG_FAILED;
        qc->ap->flags |= ATA_FLAG_EH_PENDING;

        /* The following will fail if timeout has already expired.
         * ata_scsi_error() takes care of such scmds on EH entry.
         * Note that ATA_QCFLAG_FAILED is unconditionally set after
         * this function completes.
         */
        scsi_req_abort_cmd(qc->scsicmd);
}

/**
 *      ata_port_schedule_eh - schedule error handling without a qc
 *      @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_set lock)
 */
void ata_port_schedule_eh(struct ata_port *ap)
{
        WARN_ON(!ap->ops->error_handler);

        ap->flags |= ATA_FLAG_EH_PENDING;
        scsi_schedule_eh(ap->host);

        DPRINTK("port EH scheduled\n");
}

/**
 *      ata_port_abort - abort all qc's on the 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)
 *
 *      RETURNS:
 *      Number of aborted qc's.
 */
int ata_port_abort(struct ata_port *ap)
{
        int tag, nr_aborted = 0;

        WARN_ON(!ap->ops->error_handler);

        for (tag = 0; tag < ATA_MAX_QUEUE; tag++) {
                struct ata_queued_cmd *qc = ata_qc_from_tag(ap, tag);

                if (qc) {
                        qc->flags |= ATA_QCFLAG_FAILED;
                        ata_qc_complete(qc);
                        nr_aborted++;
                }
        }

        if (!nr_aborted)
                ata_port_schedule_eh(ap);

        return nr_aborted;
}

/**
 *      __ata_port_freeze - freeze 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_set lock)
 */
static void __ata_port_freeze(struct ata_port *ap)
{
        WARN_ON(!ap->ops->error_handler);

        if (ap->ops->freeze)
                ap->ops->freeze(ap);

        ap->flags |= ATA_FLAG_FROZEN;

        DPRINTK("ata%u port frozen\n", ap->id);
}

/**
 *      ata_port_freeze - abort & freeze port
 *      @ap: ATA port to freeze
 *
 *      Abort and freeze @ap.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS:
 *      Number of aborted commands.
 */
int ata_port_freeze(struct ata_port *ap)
{
        int nr_aborted;

        WARN_ON(!ap->ops->error_handler);

        nr_aborted = ata_port_abort(ap);
        __ata_port_freeze(ap);

        return nr_aborted;
}

/**
 *      ata_eh_freeze_port - EH helper to freeze port
 *      @ap: ATA port to freeze
 *
 *      Freeze @ap.
 *
 *      LOCKING:
 *      None.
 */
void ata_eh_freeze_port(struct ata_port *ap)
{
        unsigned long flags;

        if (!ap->ops->error_handler)
                return;

        spin_lock_irqsave(&ap->host_set->lock, flags);
        __ata_port_freeze(ap);
        spin_unlock_irqrestore(&ap->host_set->lock, flags);
}

/**
 *      ata_port_thaw_port - EH helper to thaw port
 *      @ap: ATA port to thaw
 *
 *      Thaw frozen port @ap.
 *
 *      LOCKING:
 *      None.
 */
void ata_eh_thaw_port(struct ata_port *ap)
{
        unsigned long flags;

        if (!ap->ops->error_handler)
                return;

        spin_lock_irqsave(&ap->host_set->lock, flags);

        ap->flags &= ~ATA_FLAG_FROZEN;

        if (ap->ops->thaw)
                ap->ops->thaw(ap);

        spin_unlock_irqrestore(&ap->host_set->lock, flags);

        DPRINTK("ata%u port thawed\n", ap->id);
}

static void ata_eh_scsidone(struct scsi_cmnd *scmd)
{
        /* nada */
}

static void __ata_eh_qc_complete(struct ata_queued_cmd *qc)
{
        struct ata_port *ap = qc->ap;
        struct scsi_cmnd *scmd = qc->scsicmd;
        unsigned long flags;

        spin_lock_irqsave(&ap->host_set->lock, flags);
        qc->scsidone = ata_eh_scsidone;
        __ata_qc_complete(qc);
        WARN_ON(ata_tag_valid(qc->tag));
        spin_unlock_irqrestore(&ap->host_set->lock, flags);

        scsi_eh_finish_cmd(scmd, &ap->eh_done_q);
}

/**
 *      ata_eh_qc_complete - Complete an active ATA command from EH
 *      @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_complete(struct ata_queued_cmd *qc)
{
        struct scsi_cmnd *scmd = qc->scsicmd;
        scmd->retries = scmd->allowed;
        __ata_eh_qc_complete(qc);
}

/**
 *      ata_eh_qc_retry - Tell midlayer to retry an ATA command after EH
 *      @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->retries is decremented for commands which get retried
 *      due to unrelated failures (qc->err_mask is zero).
 */
void ata_eh_qc_retry(struct ata_queued_cmd *qc)
{
        struct scsi_cmnd *scmd = qc->scsicmd;
        if (!qc->err_mask && scmd->retries)
                scmd->retries--;
        __ata_eh_qc_complete(qc);
}

/**
 *      ata_eh_detach_dev - detach ATA device
 *      @dev: ATA device to detach
 *
 *      Detach @dev.
 *
 *      LOCKING:
 *      None.
 */
static void ata_eh_detach_dev(struct ata_device *dev)
{
        struct ata_port *ap = dev->ap;
        unsigned long flags;

        ata_dev_disable(dev);

        spin_lock_irqsave(&ap->host_set->lock, flags);

        dev->flags &= ~ATA_DFLAG_DETACH;

        if (ata_scsi_offline_dev(dev)) {
                dev->flags |= ATA_DFLAG_DETACHED;
                ap->flags |= ATA_FLAG_SCSI_HOTPLUG;
        }

        spin_unlock_irqrestore(&ap->host_set->lock, flags);
}

/**
 *      ata_eh_about_to_do - about to perform eh_action
 *      @ap: target ATA port
 *      @action: action about to be performed
 *
 *      Called just before performing EH actions to clear related bits
 *      in @ap->eh_info such that eh actions are not unnecessarily
 *      repeated.
 *
 *      LOCKING:
 *      None.
 */
static void ata_eh_about_to_do(struct ata_port *ap, unsigned int action)
{
        unsigned long flags;

        spin_lock_irqsave(&ap->host_set->lock, flags);
        ap->eh_info.action &= ~action;
        ap->flags |= ATA_FLAG_RECOVERED;
        spin_unlock_irqrestore(&ap->host_set->lock, flags);
}

/**
 *      ata_err_string - convert err_mask to descriptive string
 *      @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.
 *
 *      RETURNS:
 *      Descriptive string for @err_mask
 */
static const char * ata_err_string(unsigned int err_mask)
{
        if (err_mask & AC_ERR_HOST_BUS)
                return "host bus error";
        if (err_mask & AC_ERR_ATA_BUS)
                return "ATA bus error";
        if (err_mask & AC_ERR_TIMEOUT)
                return "timeout";
        if (err_mask & AC_ERR_HSM)
                return "HSM violation";
        if (err_mask & AC_ERR_SYSTEM)
                return "internal error";
        if (err_mask & AC_ERR_MEDIA)
                return "media error";
        if (err_mask & AC_ERR_INVALID)
                return "invalid argument";
        if (err_mask & AC_ERR_DEV)
                return "device error";
        return "unknown error";
}

/**
 *      ata_read_log_page - read a specific log page
 *      @dev: target device
 *      @page: page to read
 *      @buf: buffer to store read page
 *      @sectors: number of sectors to read
 *
 *      Read log page using READ_LOG_EXT command.
 *
 *      LOCKING:
 *      Kernel thread context (may sleep).
 *
 *      RETURNS:
 *      0 on success, AC_ERR_* mask otherwise.
 */
static unsigned int ata_read_log_page(struct ata_device *dev,
                                      u8 page, void *buf, unsigned int sectors)
{
        struct ata_taskfile tf;
        unsigned int err_mask;

        DPRINTK("read log page - page %d\n", page);

        ata_tf_init(dev, &tf);
        tf.command = ATA_CMD_READ_LOG_EXT;
        tf.lbal = page;
        tf.nsect = sectors;
        tf.hob_nsect = sectors >> 8;
        tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_LBA48 | ATA_TFLAG_DEVICE;
        tf.protocol = ATA_PROT_PIO;

        err_mask = ata_exec_internal(dev, &tf, NULL, DMA_FROM_DEVICE,
                                     buf, sectors * ATA_SECT_SIZE);

        DPRINTK("EXIT, err_mask=%x\n", err_mask);
        return err_mask;
}

/**
 *      ata_eh_read_log_10h - Read log page 10h for NCQ error details
 *      @dev: Device to read log page 10h from
 *      @tag: Resulting tag of the failed command
 *      @tf: Resulting taskfile registers of the failed command
 *
 *      Read log page 10h to obtain NCQ error details and clear error
 *      condition.
 *
 *      LOCKING:
 *      Kernel thread context (may sleep).
 *
 *      RETURNS:
 *      0 on success, -errno otherwise.
 */
static int ata_eh_read_log_10h(struct ata_device *dev,
                               int *tag, struct ata_taskfile *tf)
{
        u8 *buf = dev->ap->sector_buf;
        unsigned int err_mask;
        u8 csum;
        int i;

        err_mask = ata_read_log_page(dev, ATA_LOG_SATA_NCQ, buf, 1);
        if (err_mask)
                return -EIO;

        csum = 0;
        for (i = 0; i < ATA_SECT_SIZE; i++)
                csum += buf[i];
        if (csum)
                ata_dev_printk(dev, KERN_WARNING,
                               "invalid checksum 0x%x on log page 10h\n", csum);

        if (buf[0] & 0x80)
                return -ENOENT;

        *tag = buf[0] & 0x1f;

        tf->command = buf[2];
        tf->feature = buf[3];
        tf->lbal = buf[4];
        tf->lbam = buf[5];
        tf->lbah = buf[6];
        tf->device = buf[7];
        tf->hob_lbal = buf[8];
        tf->hob_lbam = buf[9];
        tf->hob_lbah = buf[10];
        tf->nsect = buf[12];
        tf->hob_nsect = buf[13];

        return 0;
}

/**
 *      atapi_eh_request_sense - perform ATAPI REQUEST_SENSE
 *      @dev: device to perform REQUEST_SENSE to
 *      @sense_buf: result sense data buffer (SCSI_SENSE_BUFFERSIZE bytes long)
 *
 *      Perform ATAPI REQUEST_SENSE after the device reported CHECK
 *      SENSE.  This function is EH helper.
 *
 *      LOCKING:
 *      Kernel thread context (may sleep).
 *
 *      RETURNS:
 *      0 on success, AC_ERR_* mask on failure
 */
static unsigned int atapi_eh_request_sense(struct ata_device *dev,
                                           unsigned char *sense_buf)
{
        struct ata_port *ap = dev->ap;
        struct ata_taskfile tf;
        u8 cdb[ATAPI_CDB_LEN];

        DPRINTK("ATAPI request sense\n");

        ata_tf_init(dev, &tf);

        /* FIXME: is this needed? */
        memset(sense_buf, 0, SCSI_SENSE_BUFFERSIZE);

        /* XXX: why tf_read here? */
        ap->ops->tf_read(ap, &tf);

        /* fill these in, for the case where they are -not- overwritten */
        sense_buf[0] = 0x70;
        sense_buf[2] = tf.feature >> 4;

        memset(cdb, 0, ATAPI_CDB_LEN);
        cdb[0] = REQUEST_SENSE;
        cdb[4] = SCSI_SENSE_BUFFERSIZE;

        tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
        tf.command = ATA_CMD_PACKET;

        /* is it pointless to prefer PIO for "safety reasons"? */
        if (ap->flags & ATA_FLAG_PIO_DMA) {
                tf.protocol = ATA_PROT_ATAPI_DMA;
                tf.feature |= ATAPI_PKT_DMA;
        } else {
                tf.protocol = ATA_PROT_ATAPI;
                tf.lbam = (8 * 1024) & 0xff;
                tf.lbah = (8 * 1024) >> 8;
        }

        return ata_exec_internal(dev, &tf, cdb, DMA_FROM_DEVICE,
                                 sense_buf, SCSI_SENSE_BUFFERSIZE);
}

/**
 *      ata_eh_analyze_serror - analyze SError for a failed port
 *      @ap: ATA port to analyze SError for
 *
 *      Analyze SError if available and further determine cause of
 *      failure.
 *
 *      LOCKING:
 *      None.
 */
static void ata_eh_analyze_serror(struct ata_port *ap)
{
        struct ata_eh_context *ehc = &ap->eh_context;
        u32 serror = ehc->i.serror;
        unsigned int err_mask = 0, action = 0;

        if (serror & SERR_PERSISTENT) {
                err_mask |= AC_ERR_ATA_BUS;
                action |= ATA_EH_HARDRESET;
        }
        if (serror &
            (SERR_DATA_RECOVERED | SERR_COMM_RECOVERED | SERR_DATA)) {
                err_mask |= AC_ERR_ATA_BUS;
                action |= ATA_EH_SOFTRESET;
        }
        if (serror & SERR_PROTOCOL) {
                err_mask |= AC_ERR_HSM;
                action |= ATA_EH_SOFTRESET;
        }
        if (serror & SERR_INTERNAL) {
                err_mask |= AC_ERR_SYSTEM;
                action |= ATA_EH_SOFTRESET;
        }
        if (serror & (SERR_PHYRDY_CHG | SERR_DEV_XCHG))
                ata_ehi_hotplugged(&ehc->i);

        ehc->i.err_mask |= err_mask;
        ehc->i.action |= action;
}

/**
 *      ata_eh_analyze_ncq_error - analyze NCQ error
 *      @ap: ATA port to analyze NCQ error for
 *
 *      Read log page 10h, determine the offending qc and acquire
 *      error status TF.  For NCQ device errors, all LLDDs have to do
 *      is setting AC_ERR_DEV in ehi->err_mask.  This function takes
 *      care of the rest.
 *
 *      LOCKING:
 *      Kernel thread context (may sleep).
 */
static void ata_eh_analyze_ncq_error(struct ata_port *ap)
{
        struct ata_eh_context *ehc = &ap->eh_context;
        struct ata_device *dev = ap->device;
        struct ata_queued_cmd *qc;
        struct ata_taskfile tf;
        int tag, rc;

        /* if frozen, we can't do much */
        if (ap->flags & ATA_FLAG_FROZEN)
                return;

        /* is it NCQ device error? */
        if (!ap->sactive || !(ehc->i.err_mask & AC_ERR_DEV))
                return;

        /* has LLDD analyzed already? */
        for (tag = 0; tag < ATA_MAX_QUEUE; tag++) {
                qc = __ata_qc_from_tag(ap, tag);

                if (!(qc->flags & ATA_QCFLAG_FAILED))
                        continue;

                if (qc->err_mask)
                        return;
        }

        /* okay, this error is ours */
        rc = ata_eh_read_log_10h(dev, &tag, &tf);
        if (rc) {
                ata_port_printk(ap, KERN_ERR, "failed to read log page 10h "
                                "(errno=%d)\n", rc);
                return;
        }

        if (!(ap->sactive & (1 << tag))) {
                ata_port_printk(ap, KERN_ERR, "log page 10h reported "
                                "inactive tag %d\n", tag);
                return;
        }

        /* we've got the perpetrator, condemn it */
        qc = __ata_qc_from_tag(ap, tag);
        memcpy(&qc->result_tf, &tf, sizeof(tf));
        qc->err_mask |= AC_ERR_DEV;
        ehc->i.err_mask &= ~AC_ERR_DEV;
}

/**
 *      ata_eh_analyze_tf - analyze taskfile of a failed qc
 *      @qc: qc to analyze
 *      @tf: Taskfile registers to analyze
 *
 *      Analyze taskfile of @qc and further determine cause of
 *      failure.  This function also requests ATAPI sense data if
 *      avaliable.
 *
 *      LOCKING:
 *      Kernel thread context (may sleep).
 *
 *      RETURNS:
 *      Determined recovery action
 */
static unsigned int ata_eh_analyze_tf(struct ata_queued_cmd *qc,
                                      const struct ata_taskfile *tf)
{
        unsigned int tmp, action = 0;
        u8 stat = tf->command, err = tf->feature;

        if ((stat & (ATA_BUSY | ATA_DRQ | ATA_DRDY)) != ATA_DRDY) {
                qc->err_mask |= AC_ERR_HSM;
                return ATA_EH_SOFTRESET;
        }

        if (!(qc->err_mask & AC_ERR_DEV))
                return 0;

        switch (qc->dev->class) {
        case ATA_DEV_ATA:
                if (err & ATA_ICRC)
                        qc->err_mask |= AC_ERR_ATA_BUS;
                if (err & ATA_UNC)
                        qc->err_mask |= AC_ERR_MEDIA;
                if (err & ATA_IDNF)
                        qc->err_mask |= AC_ERR_INVALID;
                break;

        case ATA_DEV_ATAPI:
                tmp = atapi_eh_request_sense(qc->dev,
                                             qc->scsicmd->sense_buffer);
                if (!tmp) {
                        /* ATA_QCFLAG_SENSE_VALID is used to tell
                         * atapi_qc_complete() that sense data is
                         * already valid.
                         *
                         * TODO: interpret sense data and set
                         * appropriate err_mask.
                         */
                        qc->flags |= ATA_QCFLAG_SENSE_VALID;
                } else
                        qc->err_mask |= tmp;
        }

        if (qc->err_mask & (AC_ERR_HSM | AC_ERR_TIMEOUT | AC_ERR_ATA_BUS))
                action |= ATA_EH_SOFTRESET;

        return action;
}

static int ata_eh_categorize_ering_entry(struct ata_ering_entry *ent)
{
        if (ent->err_mask & (AC_ERR_ATA_BUS | AC_ERR_TIMEOUT))
                return 1;

        if (ent->is_io) {
                if (ent->err_mask & AC_ERR_HSM)
                        return 1;
                if ((ent->err_mask &
                     (AC_ERR_DEV|AC_ERR_MEDIA|AC_ERR_INVALID)) == AC_ERR_DEV)
                        return 2;
        }

        return 0;
}

struct speed_down_needed_arg {
        u64 since;
        int nr_errors[3];
};

static int speed_down_needed_cb(struct ata_ering_entry *ent, void *void_arg)
{
        struct speed_down_needed_arg *arg = void_arg;

        if (ent->timestamp < arg->since)
                return -1;

        arg->nr_errors[ata_eh_categorize_ering_entry(ent)]++;
        return 0;
}

/**
 *      ata_eh_speed_down_needed - Determine wheter speed down is necessary
 *      @dev: Device of interest
 *
 *      This function examines error ring of @dev and determines
 *      whether speed down is necessary.  Speed down is necessary if
 *      there have been more than 3 of Cat-1 errors or 10 of Cat-2
 *      errors during last 15 minutes.
 *
 *      Cat-1 errors are ATA_BUS, TIMEOUT for any command and HSM
 *      violation for known supported commands.
 *
 *      Cat-2 errors are unclassified DEV error for known supported
 *      command.
 *
 *      LOCKING:
 *      Inherited from caller.
 *
 *      RETURNS:
 *      1 if speed down is necessary, 0 otherwise
 */
static int ata_eh_speed_down_needed(struct ata_device *dev)
{
        const u64 interval = 15LLU * 60 * HZ;
        static const int err_limits[3] = { -1, 3, 10 };
        struct speed_down_needed_arg arg;
        struct ata_ering_entry *ent;
        int err_cat;
        u64 j64;

        ent = ata_ering_top(&dev->ering);
        if (!ent)
                return 0;

        err_cat = ata_eh_categorize_ering_entry(ent);
        if (err_cat == 0)
                return 0;

        memset(&arg, 0, sizeof(arg));

        j64 = get_jiffies_64();
        if (j64 >= interval)
                arg.since = j64 - interval;
        else
                arg.since = 0;

        ata_ering_map(&dev->ering, speed_down_needed_cb, &arg);

        return arg.nr_errors[err_cat] > err_limits[err_cat];
}

/**
 *      ata_eh_speed_down - record error and speed down if necessary
 *      @dev: Failed device
 *      @is_io: Did the device fail during normal IO?
 *      @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).
 *
 *      RETURNS:
 *      0 on success, -errno otherwise
 */
static int ata_eh_speed_down(struct ata_device *dev, int is_io,
                             unsigned int err_mask)
{
        if (!err_mask)
                return 0;

        /* record error and determine whether speed down is necessary */
        ata_ering_record(&dev->ering, is_io, err_mask);

        if (!ata_eh_speed_down_needed(dev))
                return 0;

        /* speed down SATA link speed if possible */
        if (sata_down_spd_limit(dev->ap) == 0)
                return ATA_EH_HARDRESET;

        /* lower transfer mode */
        if (ata_down_xfermask_limit(dev, 0) == 0)
                return ATA_EH_SOFTRESET;

        ata_dev_printk(dev, KERN_ERR,
                       "speed down requested but no transfer mode left\n");
        return 0;
}

/**
 *      ata_eh_autopsy - analyze error and determine recovery action
 *      @ap: ATA port to perform autopsy on
 *
 *      Analyze why @ap failed and determine which recovery action is
 *      needed.  This function also sets more detailed AC_ERR_* values
 *      and fills sense data for ATAPI CHECK SENSE.
 *
 *      LOCKING:
 *      Kernel thread context (may sleep).
 */
static void ata_eh_autopsy(struct ata_port *ap)
{
        struct ata_eh_context *ehc = &ap->eh_context;
        unsigned int action = ehc->i.action;
        struct ata_device *failed_dev = NULL;
        unsigned int all_err_mask = 0;
        int tag, is_io = 0;
        u32 serror;
        int rc;

        DPRINTK("ENTER\n");

        /* obtain and analyze SError */
        rc = sata_scr_read(ap, SCR_ERROR, &serror);
        if (rc == 0) {
                ehc->i.serror |= serror;
                ata_eh_analyze_serror(ap);
        } else if (rc != -EOPNOTSUPP)
                action |= ATA_EH_HARDRESET;

        /* analyze NCQ failure */
        ata_eh_analyze_ncq_error(ap);

        /* any real error trumps AC_ERR_OTHER */
        if (ehc->i.err_mask & ~AC_ERR_OTHER)
                ehc->i.err_mask &= ~AC_ERR_OTHER;

        all_err_mask |= ehc->i.err_mask;

        for (tag = 0; tag < ATA_MAX_QUEUE; tag++) {
                struct ata_queued_cmd *qc = __ata_qc_from_tag(ap, tag);

                if (!(qc->flags & ATA_QCFLAG_FAILED))
                        continue;

                /* inherit upper level err_mask */
                qc->err_mask |= ehc->i.err_mask;

                /* analyze TF */
                action |= ata_eh_analyze_tf(qc, &qc->result_tf);

                /* DEV errors are probably spurious in case of ATA_BUS error */
                if (qc->err_mask & AC_ERR_ATA_BUS)
                        qc->err_mask &= ~(AC_ERR_DEV | AC_ERR_MEDIA |
                                          AC_ERR_INVALID);

                /* any real error trumps unknown error */
                if (qc->err_mask & ~AC_ERR_OTHER)
                        qc->err_mask &= ~AC_ERR_OTHER;

                /* SENSE_VALID trumps dev/unknown error and revalidation */
                if (qc->flags & ATA_QCFLAG_SENSE_VALID) {
                        qc->err_mask &= ~(AC_ERR_DEV | AC_ERR_OTHER);
                        action &= ~ATA_EH_REVALIDATE;
                }

                /* accumulate error info */
                failed_dev = qc->dev;
                all_err_mask |= qc->err_mask;
                if (qc->flags & ATA_QCFLAG_IO)
                        is_io = 1;
        }

        /* speed down iff command was in progress */
        if (failed_dev)
                action |= ata_eh_speed_down(failed_dev, is_io, all_err_mask);

        /* enforce default EH actions */
        if (ap->flags & ATA_FLAG_FROZEN ||
            all_err_mask & (AC_ERR_HSM | AC_ERR_TIMEOUT))
                action |= ATA_EH_SOFTRESET;
        else if (all_err_mask)
                action |= ATA_EH_REVALIDATE;

        /* record autopsy result */
        ehc->i.dev = failed_dev;
        ehc->i.action = action;

        DPRINTK("EXIT\n");
}

/**
 *      ata_eh_report - report error handling to user
 *      @ap: ATA port EH is going on
 *
 *      Report EH to user.
 *
 *      LOCKING:
 *      None.
 */
static void ata_eh_report(struct ata_port *ap)
{
        struct ata_eh_context *ehc = &ap->eh_context;
        const char *frozen, *desc;
        int tag, nr_failed = 0;

        desc = NULL;
        if (ehc->i.desc[0] != '\0')
                desc = ehc->i.desc;

        for (tag = 0; tag < ATA_MAX_QUEUE; tag++) {
                struct ata_queued_cmd *qc = __ata_qc_from_tag(ap, tag);

                if (!(qc->flags & ATA_QCFLAG_FAILED))
                        continue;
                if (qc->flags & ATA_QCFLAG_SENSE_VALID && !qc->err_mask)
                        continue;

                nr_failed++;
        }

        if (!nr_failed && !ehc->i.err_mask)
                return;

        frozen = "";
        if (ap->flags & ATA_FLAG_FROZEN)
                frozen = " frozen";

        if (ehc->i.dev) {
                ata_dev_printk(ehc->i.dev, KERN_ERR, "exception Emask 0x%x "
                               "SAct 0x%x SErr 0x%x action 0x%x%s\n",
                               ehc->i.err_mask, ap->sactive, ehc->i.serror,
                               ehc->i.action, frozen);
                if (desc)
                        ata_dev_printk(ehc->i.dev, KERN_ERR, "(%s)\n", desc);
        } else {
                ata_port_printk(ap, KERN_ERR, "exception Emask 0x%x "
                                "SAct 0x%x SErr 0x%x action 0x%x%s\n",
                                ehc->i.err_mask, ap->sactive, ehc->i.serror,
                                ehc->i.action, frozen);
                if (desc)
                        ata_port_printk(ap, KERN_ERR, "(%s)\n", desc);
        }

        for (tag = 0; tag < ATA_MAX_QUEUE; tag++) {
                struct ata_queued_cmd *qc = __ata_qc_from_tag(ap, tag);

                if (!(qc->flags & ATA_QCFLAG_FAILED) || !qc->err_mask)
                        continue;

                ata_dev_printk(qc->dev, KERN_ERR, "tag %d cmd 0x%x "
                               "Emask 0x%x stat 0x%x err 0x%x (%s)\n",
                               qc->tag, qc->tf.command, qc->err_mask,
                               qc->result_tf.command, qc->result_tf.feature,
                               ata_err_string(qc->err_mask));
        }
}

static int ata_do_reset(struct ata_port *ap, ata_reset_fn_t reset,
                        unsigned int *classes)
{
        int i, rc;

        for (i = 0; i < ATA_MAX_DEVICES; i++)
                classes[i] = ATA_DEV_UNKNOWN;

        rc = reset(ap, classes);
        if (rc)
                return rc;

        /* If any class isn't ATA_DEV_UNKNOWN, consider classification
         * is complete and convert all ATA_DEV_UNKNOWN to
         * ATA_DEV_NONE.
         */
        for (i = 0; i < ATA_MAX_DEVICES; i++)
                if (classes[i] != ATA_DEV_UNKNOWN)
                        break;

        if (i < ATA_MAX_DEVICES)
                for (i = 0; i < ATA_MAX_DEVICES; i++)
                        if (classes[i] == ATA_DEV_UNKNOWN)
                                classes[i] = ATA_DEV_NONE;

        return 0;
}

static int ata_eh_followup_srst_needed(int rc, int classify,
                                       const unsigned int *classes)
{
        if (rc == -EAGAIN)
                return 1;
        if (rc != 0)
                return 0;
        if (classify && classes[0] == ATA_DEV_UNKNOWN)
                return 1;
        return 0;
}

static int ata_eh_reset(struct ata_port *ap, int classify,
                        ata_prereset_fn_t prereset, ata_reset_fn_t softreset,
                        ata_reset_fn_t hardreset, ata_postreset_fn_t postreset)
{
        struct ata_eh_context *ehc = &ap->eh_context;
        unsigned int *classes = ehc->classes;
        int tries = ATA_EH_RESET_TRIES;
        int verbose = !(ap->flags & ATA_FLAG_LOADING);
        unsigned int action;
        ata_reset_fn_t reset;
        int i, did_followup_srst, rc;

        /* Determine which reset to use and record in ehc->i.action.
         * prereset() may examine and modify it.
         */
        action = ehc->i.action;
        ehc->i.action &= ~ATA_EH_RESET_MASK;
        if (softreset && (!hardreset || (!sata_set_spd_needed(ap) &&
                                         !(action & ATA_EH_HARDRESET))))
                ehc->i.action |= ATA_EH_SOFTRESET;
        else
                ehc->i.action |= ATA_EH_HARDRESET;

        if (prereset) {
                rc = prereset(ap);
                if (rc) {
                        ata_port_printk(ap, KERN_ERR,
                                        "prereset failed (errno=%d)\n", rc);
                        return rc;
                }
        }

        /* prereset() might have modified ehc->i.action */
        if (ehc->i.action & ATA_EH_HARDRESET)
                reset = hardreset;
        else if (ehc->i.action & ATA_EH_SOFTRESET)
                reset = softreset;
        else {
                /* prereset told us not to reset, bang classes and return */
                for (i = 0; i < ATA_MAX_DEVICES; i++)
                        classes[i] = ATA_DEV_NONE;
                return 0;
        }

        /* did prereset() screw up?  if so, fix up to avoid oopsing */
        if (!reset) {
                ata_port_printk(ap, KERN_ERR, "BUG: prereset() requested "
                                "invalid reset type\n");
                if (softreset)
                        reset = softreset;
                else
                        reset = hardreset;
        }

 retry:
        /* shut up during boot probing */
        if (verbose)
                ata_port_printk(ap, KERN_INFO, "%s resetting port\n",
                                reset == softreset ? "soft" : "hard");

        /* reset */
        ata_eh_about_to_do(ap, ATA_EH_RESET_MASK);
        ehc->i.flags |= ATA_EHI_DID_RESET;

        rc = ata_do_reset(ap, reset, classes);

        did_followup_srst = 0;
        if (reset == hardreset &&
            ata_eh_followup_srst_needed(rc, classify, classes)) {
                /* okay, let's do follow-up softreset */
                did_followup_srst = 1;
                reset = softreset;

                if (!reset) {
                        ata_port_printk(ap, KERN_ERR,
                                        "follow-up softreset required "
                                        "but no softreset avaliable\n");
                        return -EINVAL;
                }

                ata_eh_about_to_do(ap, ATA_EH_RESET_MASK);
                rc = ata_do_reset(ap, reset, classes);

                if (rc == 0 && classify &&
                    classes[0] == ATA_DEV_UNKNOWN) {
                        ata_port_printk(ap, KERN_ERR,
                                        "classification failed\n");
                        return -EINVAL;
                }
        }

        if (rc && --tries) {
                const char *type;

                if (reset == softreset) {
                        if (did_followup_srst)
                                type = "follow-up soft";
                        else
                                type = "soft";
                } else
                        type = "hard";

                ata_port_printk(ap, KERN_WARNING,
                                "%sreset failed, retrying in 5 secs\n", type);
                ssleep(5);

                if (reset == hardreset)
                        sata_down_spd_limit(ap);
                if (hardreset)
                        reset = hardreset;
                goto retry;
        }

        if (rc == 0) {
                /* After the reset, the device state is PIO 0 and the
                 * controller state is undefined.  Record the mode.
                 */
                for (i = 0; i < ATA_MAX_DEVICES; i++)
                        ap->device[i].pio_mode = XFER_PIO_0;

                if (postreset)
                        postreset(ap, classes);

                /* reset successful, schedule revalidation */
                ehc->i.dev = NULL;
                ehc->i.action &= ~ATA_EH_RESET_MASK;
                ehc->i.action |= ATA_EH_REVALIDATE;
        }

        return rc;
}

static int ata_eh_revalidate_and_attach(struct ata_port *ap,
                                        struct ata_device **r_failed_dev)
{
        struct ata_eh_context *ehc = &ap->eh_context;
        struct ata_device *dev;
        unsigned long flags;
        int i, rc = 0;

        DPRINTK("ENTER\n");

        for (i = 0; i < ATA_MAX_DEVICES; i++) {
                dev = &ap->device[i];

                if (ehc->i.action & ATA_EH_REVALIDATE && ata_dev_enabled(dev) &&
                    (!ehc->i.dev || ehc->i.dev == dev)) {
                        if (ata_port_offline(ap)) {
                                rc = -EIO;
                                break;
                        }

                        ata_eh_about_to_do(ap, ATA_EH_REVALIDATE);
                        rc = ata_dev_revalidate(dev,
                                        ehc->i.flags & ATA_EHI_DID_RESET);
                        if (rc)
                                break;

                        ehc->i.action &= ~ATA_EH_REVALIDATE;
                } else if (dev->class == ATA_DEV_UNKNOWN &&
                           ehc->tries[dev->devno] &&
                           ata_class_enabled(ehc->classes[dev->devno])) {
                        dev->class = ehc->classes[dev->devno];

                        rc = ata_dev_read_id(dev, &dev->class, 1, dev->id);
                        if (rc == 0)
                                rc = ata_dev_configure(dev, 1);

                        if (rc) {
                                dev->class = ATA_DEV_UNKNOWN;
                                break;
                        }

                        spin_lock_irqsave(&ap->host_set->lock, flags);
                        ap->flags |= ATA_FLAG_SCSI_HOTPLUG;
                        spin_unlock_irqrestore(&ap->host_set->lock, flags);
                }
        }

        if (rc)
                *r_failed_dev = dev;

        DPRINTK("EXIT\n");
        return rc;
}

static int ata_port_nr_enabled(struct ata_port *ap)
{
        int i, cnt = 0;

        for (i = 0; i < ATA_MAX_DEVICES; i++)
                if (ata_dev_enabled(&ap->device[i]))
                        cnt++;
        return cnt;
}

static int ata_port_nr_vacant(struct ata_port *ap)
{
        int i, cnt = 0;

        for (i = 0; i < ATA_MAX_DEVICES; i++)
                if (ap->device[i].class == ATA_DEV_UNKNOWN)
                        cnt++;
        return cnt;
}

static int ata_eh_skip_recovery(struct ata_port *ap)
{
        struct ata_eh_context *ehc = &ap->eh_context;
        int i;

        if (ap->flags & ATA_FLAG_FROZEN || ata_port_nr_enabled(ap))
                return 0;

        /* skip if class codes for all vacant slots are ATA_DEV_NONE */
        for (i = 0; i < ATA_MAX_DEVICES; i++) {
                struct ata_device *dev = &ap->device[i];

                if (dev->class == ATA_DEV_UNKNOWN &&
                    ehc->classes[dev->devno] != ATA_DEV_NONE)
                        return 0;
        }

        return 1;
}

/**
 *      ata_eh_recover - recover host port after error
 *      @ap: host port to recover
 *      @prereset: prereset method (can be NULL)
 *      @softreset: softreset method (can be NULL)
 *      @hardreset: hardreset method (can be NULL)
 *      @postreset: postreset method (can be NULL)
 *
 *      This is the alpha and omega, eum and yang, heart and soul of
 *      libata exception handling.  On entry, actions required to
 *      recover the port and hotplug requests are recorded in
 *      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).
 *
 *      RETURNS:
 *      0 on success, -errno on failure.
 */
static 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_eh_context *ehc = &ap->eh_context;
        struct ata_device *dev;
        int down_xfermask, i, rc;

        DPRINTK("ENTER\n");

        /* prep for recovery */
        for (i = 0; i < ATA_MAX_DEVICES; i++) {
                dev = &ap->device[i];

                ehc->tries[dev->devno] = ATA_EH_DEV_TRIES;

                /* process hotplug request */
                if (dev->flags & ATA_DFLAG_DETACH)
                        ata_eh_detach_dev(dev);

                if (!ata_dev_enabled(dev) &&
                    ((ehc->i.probe_mask & (1 << dev->devno)) &&
                     !(ehc->did_probe_mask & (1 << dev->devno)))) {
                        ata_eh_detach_dev(dev);
                        ata_dev_init(dev);
                        ehc->did_probe_mask |= (1 << dev->devno);
                        ehc->i.action |= ATA_EH_SOFTRESET;
                }
        }

 retry:
        down_xfermask = 0;
        rc = 0;

        /* skip EH if possible. */
        if (ata_eh_skip_recovery(ap))
                ehc->i.action = 0;

        for (i = 0; i < ATA_MAX_DEVICES; i++)
                ehc->classes[i] = ATA_DEV_UNKNOWN;

        /* reset */
        if (ehc->i.action & ATA_EH_RESET_MASK) {
                ata_eh_freeze_port(ap);

                rc = ata_eh_reset(ap, ata_port_nr_vacant(ap), prereset,
                                  softreset, hardreset, postreset);
                if (rc) {
                        ata_port_printk(ap, KERN_ERR,
                                        "reset failed, giving up\n");
                        goto out;
                }

                ata_eh_thaw_port(ap);
        }

        /* revalidate existing devices and attach new ones */
        rc = ata_eh_revalidate_and_attach(ap, &dev);
        if (rc)
                goto dev_fail;

        /* configure transfer mode if the port has been reset */
        if (ehc->i.flags & ATA_EHI_DID_RESET) {
                rc = ata_set_mode(ap, &dev);
                if (rc) {
                        down_xfermask = 1;
                        goto dev_fail;
                }
        }

        goto out;

 dev_fail:
        switch (rc) {
        case -ENODEV:
                /* device missing, schedule probing */
                ehc->i.probe_mask |= (1 << dev->devno);
        case -EINVAL:
                ehc->tries[dev->devno] = 0;
                break;
        case -EIO:
                sata_down_spd_limit(ap);
        default:
                ehc->tries[dev->devno]--;
                if (down_xfermask &&
                    ata_down_xfermask_limit(dev, ehc->tries[dev->devno] == 1))
                        ehc->tries[dev->devno] = 0;
        }

        if (ata_dev_enabled(dev) && !ehc->tries[dev->devno]) {
                /* disable device if it has used up all its chances */
                ata_dev_disable(dev);

                /* detach if offline */
                if (ata_port_offline(ap))
                        ata_eh_detach_dev(dev);

                /* probe if requested */
                if ((ehc->i.probe_mask & (1 << dev->devno)) &&
                    !(ehc->did_probe_mask & (1 << dev->devno))) {
                        ata_eh_detach_dev(dev);
                        ata_dev_init(dev);

                        ehc->tries[dev->devno] = ATA_EH_DEV_TRIES;
                        ehc->did_probe_mask |= (1 << dev->devno);
                        ehc->i.action |= ATA_EH_SOFTRESET;
                }
        } else {
                /* soft didn't work?  be haaaaard */
                if (ehc->i.flags & ATA_EHI_DID_RESET)
                        ehc->i.action |= ATA_EH_HARDRESET;
                else
                        ehc->i.action |= ATA_EH_SOFTRESET;
        }

        if (ata_port_nr_enabled(ap)) {
                ata_port_printk(ap, KERN_WARNING, "failed to recover some "
                                "devices, retrying in 5 secs\n");
                ssleep(5);
        } else {
                /* no device left, repeat fast */
                msleep(500);
        }

        goto retry;

 out:
        if (rc) {
                for (i = 0; i < ATA_MAX_DEVICES; i++)
                        ata_dev_disable(&ap->device[i]);
        }

        DPRINTK("EXIT, rc=%d\n", rc);
        return rc;
}

/**
 *      ata_eh_finish - finish up EH
 *      @ap: host port to finish EH for
 *
 *      Recovery is complete.  Clean up EH states and retry or finish
 *      failed qcs.
 *
 *      LOCKING:
 *      None.
 */
static void ata_eh_finish(struct ata_port *ap)
{
        int tag;

        /* retry or finish qcs */
        for (tag = 0; tag < ATA_MAX_QUEUE; tag++) {
                struct ata_queued_cmd *qc = __ata_qc_from_tag(ap, tag);

                if (!(qc->flags & ATA_QCFLAG_FAILED))
                        continue;

                if (qc->err_mask) {
                        /* FIXME: Once EH migration is complete,
                         * generate sense data in this function,
                         * considering both err_mask and tf.
                         */
                        if (qc->err_mask & AC_ERR_INVALID)
                                ata_eh_qc_complete(qc);
                        else
                                ata_eh_qc_retry(qc);
                } else {
                        if (qc->flags & ATA_QCFLAG_SENSE_VALID) {
                                ata_eh_qc_complete(qc);
                        } else {
                                /* feed zero TF to sense generation */
                                memset(&qc->result_tf, 0, sizeof(qc->result_tf));
                                ata_eh_qc_retry(qc);
                        }
                }
        }
}

/**
 *      ata_do_eh - do standard error handling
 *      @ap: host port to handle error for
 *      @prereset: prereset method (can be NULL)
 *      @softreset: softreset method (can be NULL)
 *      @hardreset: hardreset method (can be NULL)
 *      @postreset: postreset method (can be NULL)
 *
 *      Perform standard error handling sequence.
 *
 *      LOCKING:
 *      Kernel thread context (may sleep).
 */
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)
{
        if (!(ap->flags & ATA_FLAG_LOADING)) {
                ata_eh_autopsy(ap);
                ata_eh_report(ap);
        }

        ata_eh_recover(ap, prereset, softreset, hardreset, postreset);
        ata_eh_finish(ap);
}