Commits · 66db383439b51b1aa920f3579da644fb5fdb2b7c · Kirill Smelkov / linux

15 Jun, 2015 5 commits

ACPI / EC: Fix a code coverity issue when QR_EC transactions are failed. · 66db3834

Lv Zheng authored Jun 11, 2015

When the QR_EC transaction fails, the EC_FLAGS_QUERY_PENDING flag prevents
the event handling work queue from being scheduled again.

Though there shouldn't be failed QR_EC transactions, and this gap was
efficiently used for catching and learning the SCI_EVT clearing timing
compliance issues, we need to fix this as we are not fully compatible
with all platforms/Windows to handle SCI_EVT clearing timing correctly.
Fixing this gives the EC driver the chances to recover from a state machine
failure.

So this patch fixes this issue. When nr_pending_queries drops to 0, it
clears EC_FLAGS_QUERY_PENDING at the proper position for different modes in
order to ensure that the SCI_EVT handling can proceed.

In order to be clearer for future ec_event_clearing modes, all checks in
this patch are written in the inclusive style, not the exclusive style.

Cc: 3.16+ <stable@vger.kernel.org> # 3.16+
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

66db3834

ACPI / EC: Fix EC_FLAGS_QUERY_HANDSHAKE platforms using new event clearing timing. · 3cb02aeb

Lv Zheng authored Jun 11, 2015

It is reported that on several platforms, EC firmware will not respond
non-expected QR_EC (see EC_FLAGS_QUERY_HANDSHAKE, only write QR_EC when
SCI_EVT is set).

Unfortunately, ACPI specification doesn't define when the SCI_EVT should be
cleared by the firmware, thus the original implementation queued up second
QR_EC right after writing QR_EC command and before reading the returned
event value as at that time the SCI_EVT is ensured not cleared. This
behavior is also based on the assumption that the firmware should be able
to return 0x00 to indicate "no outstanding event". This behavior did fix
issues on Samsung platforms where the spurious query value of 0x00 is
supported and didn't break platforms in my test queue.

But recently, specific Acer, Asus, Lenovo platforms keep on blaming this
change.

This patch changes the behavior to re-check the SCI_EVT a bit later and
removes EC_FLAGS_QUERY_HANDSHAKE quirks, hoping this is the Windows
compliant EC driver behavior.

In order to be robust to the possible regressions, instead of removing the
quirk directly, this patch keeps the quirk code, removes the quirk users
and keeps old behavior for Samsung platforms.

Cc: 3.16+ <stable@vger.kernel.org> # 3.16+
Link: https://bugzilla.kernel.org/show_bug.cgi?id=94411
Link: https://bugzilla.kernel.org/show_bug.cgi?id=97381
Link: https://bugzilla.kernel.org/show_bug.cgi?id=98111Reported-and-tested-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Reported-and-tested-by: Tigran Gabrielyan <tigrangab@gmail.com>
Reported-and-tested-by: Adrien D <ghbdtn@openmailbox.org>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

3cb02aeb

ACPI / EC: Add event clearing variation support. · 1d68d261

Lv Zheng authored Jun 11, 2015

We've been suffering from the uncertainty of the SCI_EVT clearing timing.
This patch implements 3 of 4 possible modes to handle SCI_EVT clearing
variations. The old behavior is kept in this patch.

Status: QR_EC is re-checked as early as possible after checking previous
SCI_EVT. This always leads to 2 QR_EC transactions per SCI_EVT
indication and the target may implement event queue which returns
0x00 indicating "no outstanding event".
This is proven to be a conflict against Windows behavior, but is
still kept in this patch to make the EC driver robust to the
possible regressions that may occur on Samsung platforms.
Query: QR_EC is re-checked after the target has handled the QR_EC query
request command pushed by the host.
Event: QR_EC is re-checked after the target has noticed the query event
response data pulled by the host.
This timing is not determined by any IRQs, so we may need to use a
guard period in this mode, which may explain the existence of the
ec_guard() code used by the old EC driver where the re-check timing
is implemented in the similar way as this mode.
Method: QR_EC is re-checked as late as possible after completing the _Qxx
evaluation. The target may implement SCI_EVT like a level triggered
interrupt.
It is proven on kernel bugzilla 94411 that, Windows will have all
_Qxx evaluations parallelized. Thus unless required by further
evidences, we needn't implement this mode as it is a conflict of
the _Qxx parallelism requirement.

Note that, according to the reports, there are platforms that cannot be
handled using the "Status" mode without enabling the
EC_FLAGS_QUERY_HANDSHAKE quirk. But they can be handled with the other
modes according to the tests (kernel bugzilla 97381).

The following log entry can be used to confirm the differences of the 3
modes as it should appear at the different positions for the 3 modes:
Command(QR_EC) unblocked
Status: appearing after
EC_SC(W) = 0x84
Query: appearing after
EC_DATA(R) = 0xXX
where XX is the event number used to determine _QXX
Event: appearing after first
EC_SC(R) = 0xX0 SCI_EVT=x BURST=0 CMD=0 IBF=0 OBF=0
that is next to the following log entry:
Command(QR_EC) completed by hardware

Link: https://bugzilla.kernel.org/show_bug.cgi?id=94411
Link: https://bugzilla.kernel.org/show_bug.cgi?id=97381
Link: https://bugzilla.kernel.org/show_bug.cgi?id=98111Reported-and-tested-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Reported-and-tested-by: Tigran Gabrielyan <tigrangab@gmail.com>
Reported-and-tested-by: Adrien D <ghbdtn@openmailbox.org>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1d68d261

ACPI / EC: Convert event handling work queue into loop style. · 9d8993be

Lv Zheng authored Jun 11, 2015

During the period that a work queue is scheduled (queued up for run) but
hasn't been run, second schedule_work() could fail. This may not lead to
the loss of queries because QR_EC is always ensured to be submitted after
the work queue has been in the running state.

The event handling work queue can be changed into the loop style to allow
us to control the code in a more flexible way:
1. Makes it possible to add event=0x00 termination condition in the loop.
2. Increases the thoughput of the QR_EC transactions as the 2nd+ QR_EC
   transactions may be handled in the same work item used for the 1st QR_EC
   transaction, thus the delay caused by the 2nd+ work item scheduling can
   be eliminated.

Except the logging message changes and the throughput improvement, this
patch is just a funcitonal no-op.
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Tested-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Tested-by: Tigran Gabrielyan <tigrangab@gmail.com>
Tested-by: Adrien D <ghbdtn@openmailbox.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

9d8993be

ACPI / EC: Cleanup transaction state transition. · f8b8eb71

Lv Zheng authored Jun 11, 2015

This patch collects transaction state transition code into one function. We
then could have a single function to maintain transaction transition
related behaviors. No functional changes.
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Tested-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Tested-by: Tigran Gabrielyan <tigrangab@gmail.com>
Tested-by: Adrien D <ghbdtn@openmailbox.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

f8b8eb71

15 May, 2015 6 commits

ACPI / EC: Remove non-root-caused busy polling quirks. · 3174abcf