This patch implements NCQ command translation and exclusion.  Note
that NCQ commands don't use ata_rwcmd_protocol() to choose ATA
command.  This is because, unlike non-NCQ RW commands, NCQ commands
can only be used for NCQ protocol and FUA handling is done with a flag
rather than separate command.

NCQ enabled device will have queue depth larger than one but no two
non-NCQ commands can be issued simultaneously, neither can a non-NCQ
command and NCQ commands.  This patch makes ata_scsi_translate()
return SCSI_MLQUEUE_DEVICE_BUSY if such exclusion is necessary.  SCSI
midlayer will retry the command later.

As SCSI midlayer always retries once a command completes, this doesn't
incur unnecessary delays and as most commands will be NCQ ones for NCQ
device, so the overhead should be negligible.

Initial implementation is from Jens Axboe and using
SCSI_MLQUEUE_DEVICE_BUSY for exclusion is suggested by Jeff Garzik.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Add ap->qc_active and ap->sactive, mask of all active qcs and libata's
view of the SActive register, respectively.  Also, implement
ata_qc_complete_multiple() which takes new qc_active mask and complete
multiple qcs according to the mask.

These will be used to track NCQ commands and complete them.  The
distinction between ap->qc_active and ap->sactive is also useful for
later PM implementation.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Rename ap->qactive to ap->qc_allocated.  This is to accomodate
addition of ap->qc_active, mask of active qcs.
Signed-off-by: NTejun Heo <htejun@gmail.com>

ata_scsi_translate() will need to return SCSI_ML_QUEUE_DEVICE_BUSY to
achieve exlusion between NCQ and non-NCQ commands or among non-NCQ
commands.  Pass its return value upward to SCSI midlayer.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Add NCQ related ATA/libata constants and macros.
Signed-off-by: NTejun Heo <htejun@gmail.com>

* kill ata_poll_qc_complete() and implement/use ata_hsm_qc_complete()
  which completes qcs in new EH compliant manner from HSM

* don't print error message from ata_hsm_move().  it's responsibility
  of EH.

* kill ATA_FLAG_NOINTR usage in bmdma EH
Signed-off-by: NTejun Heo <htejun@gmail.com>

Conflicts:

	drivers/scsi/libata-core.c
	include/linux/libata.h

Convert sata_sil24 to new EH.

* When port is frozen, IRQ for the port is masked.

* sil24_softreset() doesn't need to mangle with IRQ mask anymore.
  libata ensures that the port is frozen during reset.

* Only turn on interrupts which are handled by interrupt handler and
  EH.  As we don't handle SDB notify yet, turn it off. DEV_XCHG and
  UNK_FIS are handled by EH and thus turned on.

* sil24_softreset() usually fails to recover the port after DEV_XCHG.
  ATA_PORT_HARDRESET is used as recovery action for DEV_XCHG.

* sil24 may be invoked without any active command.  e.g. DEV_XCHG irq
  occuring while no qc in progress still triggers EH and will reset
  the port and revalidate attached device.
Signed-off-by: NTejun Heo <htejun@gmail.com>

During multiblock PIO, multiple PIOS interrupts are generated before
qc compltion.  Current code prints unnecessary message for such cases.
This is exposed when new EH slows down attached device into PIO mode.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Convert AHCI to new EH.  Unfortunately, ICH7 AHCI reacts badly if IRQ
mask is diddled during operation.  So, freezing is implemented by
unconditionally clearing interrupt conditions while frozen.

* Interrupts are categorized according to required action.
  e.g. Connection status or unknown FIS error requires freezing the
  port while TF or HBUS_DATA don't.

* Only CONNECT (reflects SErr.X) interrupt is taken into account not
  PHYRDY (SErr.N), as CONNECT is better cue for starting EH.

* AHCI may be invoked without any active command.  e.g. CONNECT irq
  occuring while no qc in progress still triggers EH and will reset
  the port and revalidate attached device.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Convert sata_sil to new EH.  As these controllers have hardware
interrupt mask and are known to have screaming interrupts issues, use
hardware IRQ masking for freezing.  sil_freeze() masks interrupts for
the port and sil_thaw() unmasks them.  As ports are automatically
frozen before probing reset, there is no need to initialize interrupt
masks sil_init_onde().  Remove related code.

Other than freezing, sata_sil uses stock BMDMA EH routines.
Signed-off-by: NTejun Heo <htejun@gmail.com>

ata_piix can use stock BMDMA EH routines.  Convert to new EH.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Implement stock BMDMA error handling methods.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Implement new EH.  The exported interface is ata_do_eh() which is to
be called from ->error_handler and performs the following steps to
recover the failed port.

ata_eh_autopsy() : analyze SError/TF, determine the cause of failure
		   and required recovery actions and record it in
		   ap->eh_context
ata_eh_report()	 : report the failure to user
ata_eh_recover() : perform recovery actions described in ap->eh_context
ata_eh_finish()	 : finish failed qcs

LLDDs can customize error handling by modifying eh_context before
calling ata_do_eh() or, if necessary, doing so inbetween each major
steps by calling each step explicitly.
Signed-off-by: NTejun Heo <htejun@gmail.com>

struct ata_eh_info serves as the communication channel between
execution path and EH.  Execution path describes detected error
condition in ap->eh_info and EH recovers the port using it.  To avoid
missing error conditions detected during EH, EH makes its own copy of
eh_info and clears it on entry allowing error info to accumulate
during EH.

Most EH states including EH's copy of eh_info are stored in
ap->eh_context (struct ata_eh_context) which is owned by EH and thus
doesn't require any synchronization to access and alter.  This
standardized context makes it easy to integrate various parts of EH
and extend EH to handle multiple links (for PM).
Signed-off-by: NTejun Heo <htejun@gmail.com>

This patch implements ata_ering and uses it to define dev->ering.

ata_ering is a ring buffer which records libata errors - whether a
command was for normar IO request, err_mask and timestamp.  Errors are
recorded per-device in dev->ering.  This will be used by EH to
determine recovery actions.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Add ATA and libata flags to be used by new EH.
Signed-off-by: NTejun Heo <htejun@gmail.com>

SCSI command completion path used to do some part of EH including
printing messages and obtaining sense data.  With new EH, all these
are responsibilities of the EH, update SCSI command completion path to
reflect this.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Update ata_exec_internal() such that it uses new EH framework.
->post_internal_cmd() is always invoked regardless of completion
status.  Also, when ata_exec_internal() detects a timeout condition
and new EH is in place, it freezes the port as timeout for normal
commands would do.

Note that ata_port_flush_task() is called regardless of
wait_for_completion status.  This is necessary as exceptions unrelated
to the qc can abort the qc, in which case PIO task could still be
running after the wait for completion returns.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Update ata_scsi_error() for new EH.  ata_scsi_error() is responsible
for claiming timed out qcs and invoking ->error_handler in safe and
synchronized manner.  As the state of the controller is unknown if a
qc has timed out, the port is frozen in such cases.

Note that ata_scsi_timed_out() isn't used for new EH.  This is because
a timed out qc cannot be claimed by EH without freezing the port and
freezing the port in ata_scsi_timed_out() results in unnecessary
abortion of other active qcs.  ata_scsi_timed_out() can be removed
once all drivers are converted to new EH.

While at it, add 'TODO: kill' comments to old EH functions.
Signed-off-by: NTejun Heo <htejun@gmail.com>

PIO executes without holding host_set lock, so it cannot be
synchronized using the same mechanism as interrupt driven execution.
port_task framework makes sure that EH is not entered until PIO task
is flushed, so PIO task can be sure the qc in progress won't go away
underneath it.  One thing it cannot be sure of is whether the qc has
already been scheduled for EH by another exception condition while
host_set lock was released.

This patch makes ata_poll_qc-complete() handle such conditions
properly and make it freeze the port if HSM violation is detected
during PIO execution.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Freezing is performed atomic w.r.t. host_set->lock and once frozen
LLDD is not allowed to access the port or any qc on it.  Also, libata
makes sure that no new qc gets issued to a frozen port.

A frozen port is thawed after a reset operation completes
successfully, so reset methods must do its job while the port is
frozen.  During initialization all ports get frozen before requesting
IRQ, so reset methods are always invoked on a frozen port.

Optional ->freeze and ->thaw operations notify LLDD that the port is
being frozen and thawed, respectively.  LLDD can disable/enable
hardware interrupt in these callbacks if the controller's IRQ mask can
be changed dynamically.  If the controller doesn't allow such
operation, LLDD can check for frozen state in the interrupt handler
and ack/clear interrupts unconditionally while frozen.
Signed-off-by: NTejun Heo <htejun@gmail.com>

ata_port_schedule_eh() directly schedules EH for @ap without
associated qc.  Once EH scheduled, no further qc is allowed and EH
kicks in as soon as all currently active qc's are drained.

ata_port_abort() schedules all currently active commands for EH by
qc_completing them with ATA_QCFLAG_FAILED set.  If ata_port_abort()
doesn't find any qc to abort, it directly schedule EH using
ata_port_schedule_eh().

These two functions provide ways to invoke EH for conditions which
aren't directly related to any specfic qc.
Signed-off-by: NTejun Heo <htejun@gmail.com>

There are several ways a qc can get schedule for EH in new EH.  This
patch implements one of them - completing a qc with ATA_QCFLAG_FAILED
set or with non-zero qc->err_mask.  ALL such qc's are examined by EH.

New EH schedules a qc for EH from completion iff ->error_handler is
implemented, qc is marked as failed or qc->err_mask is non-zero and
the command is not an internal command (internal cmd is handled via
->post_internal_cmd).  The EH scheduling itself is performed by asking
SCSI midlayer to schedule EH for the specified scmd.

For drivers implementing old-EH, nothing changes.  As this change
makes ata_qc_complete() rather large, it's not inlined anymore and
__ata_qc_complete() is exported to other parts of libata for later
use.
Signed-off-by: NTejun Heo <htejun@gmail.com>

New EH framework has clear distinction about who owns a qc.  Every qc
starts owned by normal execution path - PIO, interrupt or whatever.
When an exception condition occurs which affects the qc, the qc gets
scheduled for EH.  Note that some events (say, link lost and regained,
command timeout) may schedule qc's which are not directly related but
could have been affected for EH too.  Scheduling for EH is atomic
w.r.t. ap->host_set->lock and once schedule for EH, normal execution
path is not allowed to access the qc in whatever way.  (PIO
synchronization acts a bit different and will be dealt with later)

This patch make ata_qc_from_tag() check whether a qc is active and
owned by normal path before returning it.  If conditions don't match,
NULL is returned and thus access to the qc is denied.
__ata_qc_from_tag() is the original ata_qc_from_tag() and is used by
libata core/EH layers to access inactive/failed qc's.

This change is applied only if the associated LLDD implements new EH
as indicated by non-NULL ->error_handler
Signed-off-by: NTejun Heo <htejun@gmail.com>

New EH may issue internal commands to recover from error while failed
qc's are still hanging around.  To allow such usage, reserve tag
ATA_MAX_QUEUE-1 for internal command.  This also makes it easy to tell
whether a qc is for internal command or not.  ata_tag_internal() test
implements this test.

To avoid breaking existing drivers, ata_exec_internal() uses
ATA_TAG_INTERNAL only for drivers which implement ->error_handler.
For drivers using old EH, tag 0 is used.  Note that this makes
ata_tag_internal() test valid only when ->error_handler is
implemented.  This is okay as drivers on old EH should not and does
not have any reason to use ata_tag_internal().
Signed-off-by: NTejun Heo <htejun@gmail.com>

Clear SError in ata_std_postreset().  This is to clear SError bits
which get set during reset.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Add ATA_FLAG_EH_{PENDING|FROZEN}, ATA_ATA_QCFLAG_{FAILED|SENSE_VALID}
and ops->freeze, thaw, error_handler, post_internal_cmd() for new EH.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Use ATA printk helpers.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Implement ata_{port|dev}_printk() which prefixes the message with
proper identification string.  This change is necessary for later PM
support because devices and links should be identified differently
depending on how they are attached.

This also helps unifying device id strings.  Currently, there are two
forms in use (P is the port number D device number) - 'ataP(D):', and
'ataP: dev D '.  These macros also make it harder to forget proper ID
string (e.g. printing only port number when a device is in question).

Debug message handling can be integrated into these printk macros by
passing debug type and level via @lv.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Use dev->ap where possible and eliminate superflous @ap from functions
and structures.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Add dev->ap which points back to the port the device belongs to.  This
makes it unnecessary to pass @ap for silly reasons (e.g. printks).
Also, this change is necessary to accomodate later PM support which
will introduce ATA link inbetween port and device.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Kill now unused scr_{read|write|write_flush}() and sata_dev_present().
Signed-off-by: NTejun Heo <htejun@gmail.com>

Use new SCR and on/offline functions.  Note that for LLDD which know
it implements SCR callbacks, SCR functions are guaranteed to succeed
and ata_port_online() == !ata_port_offline().
Signed-off-by: NTejun Heo <htejun@gmail.com>

Implement ata_scr_{valid|read|write|write_flush}() and
ata_port_{online|offline}().  These functions replace
scr_{read|write}() and sata_dev_present().

Major difference between between the new SCR functions and the old
ones is that the new ones have a way to signal error to the caller.
This makes handling SCR-available and SCR-unavailable cases in the
same path easier.  Also, it eases later PM implementation where SCR
access can fail due to various reasons.

ata_port_{online|offline}() functions return 1 only when they are
affirmitive of the condition.  e.g.  if SCR is unaccessible or
presence cannot be determined for other reasons, these functions
return 0.  So, ata_port_online() != !ata_port_offline().  This
distinction is useful in many exception handling cases.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Init ap->cbl to ATA_CBL_SATA in ata_host_init().  This is necessary
for soon-to-follow SCR handling function changes.  LLDDs are free to
change ap->cbl during probing.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Update TF image (pp->tf) only when necessary.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Add qc->result_tf and ATA_QCFLAG_RESULT_TF.  This moves the
responsibility of loading result TF from post-compltion path to qc
execution path.  qc->result_tf is loaded if explicitly requested or
the qc failsa.  This allows more efficient completion implementation
and correct handling of result TF for controllers which don't have
global TF representation such as sil3124/32.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Make ata_do_reset() deal only with reset.  postreset is now the
responsibility of the caller.  This is simpler and eases later
prereset addition.
Signed-off-by: NTejun Heo <htejun@gmail.com>

Move ->set_mode() handlng into ata_set_mode().
Signed-off-by: NTejun Heo <htejun@gmail.com>