Failure handling of the boot EC code is not tidy. This patch cleans
them up with acpi_ec_alloc().

This patch also changes acpi_ec_dsdt_probe(), always switches the
boot EC from the ECDT one to the DSDT one in this function.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

According to the Windows probing result, during the table loading, the EC
device described in the ECDT should be used. And the ECDT EC is also
effective during the period the namespace objects are initialized (we can
see a separate process executing _STA/_INI on Windows before executing
other device specific control methods, for example, EC._REG). During the
device enumration, the EC device described in the DSDT should be used. But
there are differences between Linux and Windows around the device probing
order. Thus in Linux, we should enable the DSDT EC as early as possible
before enumerating devices in order not to trigger issues related to the
device enumeration order differences.

This patch thus converts acpi_boot_ec_enable() into acpi_ec_dsdt_probe() to
fix the gap. This also fixes a user reported regression triggered after we
switched the "table loading"/"ECDT support" to be ACPI spec 2.0 compliant.

Fixes: 59f0aa94 (ACPI 2.0 / ECDT: Remove early namespace reference from EC)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=119261Reported-and-tested-by: NGabriele Mazzotta <gabriele.mzt@gmail.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

All operation region accesses are allowed by AML interpreter when AML is
executed, so actually BIOSen are responsible to avoid the operation region
accesses in AML before OSPM has prepared an operation region driver. This
is done via _REG control method. So AML code normally sets a global named
object REGC to 1 when _REG(3, 1) is evaluated.

Then what is ECDT? Quoting from ACPI spec 6.0, 5.2.15 Embedded Controller
Boot Resources Table (ECDT):
 "The presence of this table allows OSPM to provide Embedded Controller
  operation region space access before the namespace has been evaluated."
Spec also suggests a compatible mean to indicate the early EC access
availability:
 Device (EC)
 {
     Name (REGC, Ones)
     Method (_REG, 2)
     {
         If (LEqual (Arg0, 3))
         {
             Store (Arg1, REGC)
         }
     }
     Method (ECAV)
     {
         If (LEqual (REGC, Ones))
         {
             If (LGreaterEqual (_REV, 2))
             {
                 Return (One)
             }
             Else
             {
                 Return (Zero)
             }
         }
         Else
         {
             Return (REGC)
         }
     }
 }
In this way, it allows EC accesses to happen before EC._REG(3, 1) is
invoked.

But ECAV is not the only way practical BIOSen using to indicate the early
EC access availibility, the known variations include:
1. Setting REGC to One in \_SB._INI when _REV >= 2. Since \_SB._INI is the
   first control method evaluated by OSPM during the enumeration, this
   allows EC accesses to happen for the entire enumeration process before
   the namespace EC is enumerated.
2. Initialize REGC to One by default, this even allows EC accesses to
   happen during the table loading.

Linux is now broken around ECDT support during the long term bug fixing
work because it has merged many wrong ECDT bug fixes (see details below).
Linux currently uses namespace EC's settings instead of ECDT settings when
ECDT is detected. This apparently will result in namespace walk and
_CRS/_GPE/_REG evaluations. Such stuffs could only happen after namespace
is ready, while ECDT is purposely to be used before namespace is ready.

The wrong bug fixing story is:
1. Link 1:
   At Linux ACPI early stages, "no _Lxx/_Exx/_Qxx evaluation can happen
   before the namespace is ready" are not ensured by ACPICA core and Linux.
   This is currently ensured by deferred enabling of GPE and defered
   registering of EC query methods (acpi_ec_register_query_methods).
2. Link 2:
   Reporters reported buggy ECDTs, expecting quirks for the platform.
   Originally, the quirk is simple, only doing things with ECDT.
   Bug 9399 and 12461 are platforms (Asus L4R, Asus M6R, MSI MS-171F)
   reported to have wrong ECDT IO port addresses, the port addresses are
   reversed.
   Bug 11880 is a platform (Asus X50GL) reported to have 0 valued port
   addresses, we can see that all EC accesses are protected by ECAV on
   this platform, so actually no early EC accesses is required by this
   platform.
3. Link 3:
   But when the bug fixing developer was requested to provide a handy and
   non-quirk bug fix, he tried to use correct EC settings from namespace
   and broke the spec purpose. We can even see that the developer was
   suffered from many regrssions. One interesting one is 14086, where the
   actual root cause obviously should be: _REG is evaluated too early. But
   unfortunately, the bug is fixed in a totally wrong way.

So everything goes wrong from these commits:
   Commit: c6cb0e87
   Subject: ACPI: EC: Don't trust ECDT tables from ASUS
   Commit: a5032bfd
   Subject: ACPI: EC: Always parse EC device

This patch reverts Linux behavior to simple ECDT quirk support in order to
stop early _CRS/_GPE/_REG evaluations.
For Bug 9399, 12461, since it is reported that the platforms require early
EC accesses, this patch restores the simple ECDT quirks for them.
For Bug 11880, since it is not reported that the platform requires early EC
accesses and its ACPI tables contain correct ECAV, we choose an ECDT
enumeration failure for this platform.

Link 1: https://bugzilla.kernel.org/show_bug.cgi?id=9916
        http://bugzilla.kernel.org/show_bug.cgi?id=10100
        https://lkml.org/lkml/2008/2/25/282
Link 2: https://bugzilla.kernel.org/show_bug.cgi?id=9399
        https://bugzilla.kernel.org/show_bug.cgi?id=12461
        https://bugzilla.kernel.org/show_bug.cgi?id=11880
Link 3: https://bugzilla.kernel.org/show_bug.cgi?id=11884
        https://bugzilla.kernel.org/show_bug.cgi?id=14081
        https://bugzilla.kernel.org/show_bug.cgi?id=14086
        https://bugzilla.kernel.org/show_bug.cgi?id=14446
Link 4: https://bugzilla.kernel.org/show_bug.cgi?id=112911Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Tested-by: NChris Bainbridge <chris.bainbridge@gmail.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch splits EC_FLAGS_HANDLERS_INSTALLED so that address space handler
can be installed when it is not possible to install GPE handler during
early stage.
This patch also tunes address space handler installation, making it
happening earlier than GPE handler installation for the same purpose.

Since acpi_ec_start()/acpi_ec_stop() will be entered multiple times after
applying this change, it is also required to protect acpi_enable_gpe()/
acpi_disable_gpe() invocations.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=112911Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Tested-by: NChris Bainbridge <chris.bainbridge@gmail.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The acpi_ec_delete_query() function tests whether its argument is NULL
and then returns immediately. Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.
Signed-off-by: NMarkus Elfring <elfring@users.sourceforge.net>
[ rjw: Subject ]
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

In acpi_ec_guard_event(), EC transaction state machine variables should be
checked with the EC spinlock locked.
The bug doesn't trigger any real issue now because this bug can only occur
when the ec_event_clearing=event mode is applied while there is no user
currently using this mode.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

1. acpi_ec_remove_query_handlers()
This patch refines the query handler removal logic implemented in
acpi_ec_remove_query_handler(), making it to invoke new
acpi_ec_remove_query_handlers() API, and ensuring all other removal code
paths to invoke the new API to honor the reference count of the query
handlers.

2. acpi_ec_get_query_handler_by_value()
This patch also refines the query handler search logic originally
implemented in acpi_ec_query(), collecting it into
acpi_ec_get_query_handler_by_value(). And since schedule_work() can ensure
the serilization of acpi_ec_event_handler(), we needn't put the
mutex_lock() around schedule_work().
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

When query handler is not found, "result" is actually stil 0, and
"struct acpi_ec_query" is not NULL, so the deletion code of
"struct acpi_ec_query" at the end of the function cannot be invoked.
As a consequence, memory leak can be observed.

The issue is introduced by this commit:
  Commit: 02b771b6
  Subject: ACPI / EC: Fix an issue caused by the serialized _Qxx

This patch fixes such memory leakage.

Fixes: 02b771b6 (ACPI / EC: Fix an issue caused by the serialized _Qxx evaluations)
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

It is proven that Windows evaluates _Qxx handlers in a parallel way. This
patch follows this fact, splits _Qxx evaluations from the NOTIFY queue to
form a separate queue, so that _Qxx evaluations can be queued up on
different CPUs rather than being queued up on a CPU0 bound queue.
Event handling related callbacks are also renamed and sorted in this patch.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=94411Reported-and-tested-by: NGabriele Mazzotta <gabriele.mzt@gmail.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

There is no need to carry potentially outdated Free Software Foundation
mailing address in file headers since the COPYING file includes it.
Signed-off-by: NJarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NGabriele Mazzotta <gabriele.mzt@gmail.com>
Reported-and-tested-by: NTigran Gabrielyan <tigrangab@gmail.com>
Reported-and-tested-by: NAdrien D <ghbdtn@openmailbox.org>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NGabriele Mazzotta <gabriele.mzt@gmail.com>
Reported-and-tested-by: NTigran Gabrielyan <tigrangab@gmail.com>
Reported-and-tested-by: NAdrien D <ghbdtn@openmailbox.org>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NLv Zheng <lv.zheng@intel.com>
Tested-by: NGabriele Mazzotta <gabriele.mzt@gmail.com>
Tested-by: NTigran Gabrielyan <tigrangab@gmail.com>
Tested-by: NAdrien D <ghbdtn@openmailbox.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NLv Zheng <lv.zheng@intel.com>
Tested-by: NGabriele Mazzotta <gabriele.mzt@gmail.com>
Tested-by: NTigran Gabrielyan <tigrangab@gmail.com>
Tested-by: NAdrien D <ghbdtn@openmailbox.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

{ Update to correct 1 patch subject in the description }

We have fixed a lot of race issues in the EC driver recently.

The following commit introduces MSI udelay()/msleep() quirk to MSI laptops
to make EC firmware working for bug 12011 without root causing any EC
driver race issues:
  Commit: 5423a0cb
  Subject: ACPI: EC: Add delay for slow MSI controller
  Commit: 34ff4dbc
  Subject: ACPI: EC: Separate delays for MSI hardware

The following commit extends ECDT validation quirk to MSI laptops to make
EC driver locating EC registers properly for bug 12461:
  Commit: a5032bfd
  Subject: ACPI: EC: Always parse EC device
This is a different quirk than the MSI udelay()/msleep() quirk. This patch
keeps validating ECDT for only "Micro-Star MS-171F" as reported.

The following commit extends MSI udelay()/msleep() quirk to Quanta laptops
to make EC firmware working for bug 20242, there is no requirement to
validate ECDT for Quanta laptops:
  Commit: 534bc4e3 Mon Sep 17 00:00:00 2001
  Subject: ACPI EC: enable MSI workaround for Quanta laptops

The following commit extends MSI udelay()/msleep() quirk to Clevo laptops
to make EC firmware working for bug 77431, there is no requirement to
validate ECDT for Clevo laptops:
  Commit: 777cb382
  Subject: ACPI / EC: Add msi quirk for Clevo W350etq

All udelay()/msleep() quirks for MSI/Quanta/Clevo seem to be the wrong
fixes generated without fixing the EC driver race issues.
And even if it is not wrong, the guarding can be covered by the following
commits in wait polling mode:
  Commit: 9e295ac1
  Subject: ACPI / EC: Reduce ec_poll() by referencing the last register access timestamp.
  Commit: commit in the same series
  Subject: ACPI / EC: Fix and clean up register access guarding logics.
The only case that is not covered is the inter-transaction guarding. And
there is no evidence that we need the inter-transaction guarding upon
reading the noted bug entries.

So it is time to remove the quirks and let the users to try again. If there
is a regression, the only thing we need to do is to restore the
inter-transaction guarding for the reported platforms.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=12011
Link: https://bugzilla.kernel.org/show_bug.cgi?id=12461
Link: https://bugzilla.kernel.org/show_bug.cgi?id=20242
Link: https://bugzilla.kernel.org/show_bug.cgi?id=77431Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

We have 2 polling modes in the EC driver:
1. busy polling: originally used for the MSI quirks. udelay() is used to
   perform register access guarding.
2. wait polling: normal code path uses wait_event_timeout() and it can be
   woken up as soon as the transaction is completed in the interrupt mode.
   It also contains the register acces guarding logic in case the interrupt
   doesn't arrive and the EC driver is about to advance the transaction in
   task context (the polling mode).
The wait polling is useful for interrupt mode to allow other tasks to use
the CPU during the wait.
But for the polling mode, the busy polling takes less time than the wait
polling, because if no interrupt arrives, the wait polling has to wait the
minimal HZ interval.

We have a new use case for using the busy polling mode. Some GPIO drivers
initialize PIN configuration which cause a GPIO multiplexed EC GPE to be
disabled out of the GPE register's control. Busy polling mode is useful
here as it takes less time than the wait polling. But the guarding logic
prevents it from responding even faster. We should spinning around the EC
status rather than spinning around the nop execution lasted a determined
period.

This patch introduces 2 module params for the polling mode switch and the
guard time, so that users can use the busy polling mode without the
guarding in case the guarding is not necessary. This is an example to use
the 2 module params for this purpose:
  acpi.ec_busy_polling acpi.ec_polling_guard=0

We've tested the patch on a test platform. The platform suffers from such
kind of the GPIO PIN issue. The GPIO driver resets all PIN configuration
and after that, EC interrupt cannot arrive because of the multiplexing.
Then the platform suffers from a long delay carried out by the
wait_event_timeout() as all further EC transactions will run in the polling
mode. We switched the EC driver to use the busy polling mechanism instead
of the wait timeout polling mechanism and the delay is still high:
[   44.283005] calling  PNP0C0B:00+ @ 1305, parent: platform
[   44.417548] call PNP0C0B:00+ returned 0 after 131323 usecs
And this patch can significantly reduce the delay:
[   44.502625] calling  PNP0C0B:00+ @ 1308, parent: platform
[   44.503760] call PNP0C0B:00+ returned 0 after 1103 usecs
Tested-by: NChen Yu <yu.c.chen@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

In the polling mode, EC driver shouldn't access the EC registers too
frequently. Though this statement is concluded from the non-root caused
bugs (see links below), we've maintained the register access guarding
logics in the current EC driver. The guarding logics can be found here and
there, makes it hard to root cause real timing issues. This patch collects
the guarding logics into one single function so that all hidden logics
related to this can be seen clearly.

The current guarding related code also has several issues:
1. Per-transaction timestamp prevents inter-transaction guarding from being
   implemented in the same place. We have an inter-transaction udelay() in
   acpi_ec_transaction_unblocked(), this logic can be merged into ec_poll()
   if we can use per-device timestamp. This patch completes such merge to
   form a new ec_guard() function and collects all guarding related hidden
   logics in it.
   One hidden logic is: there is no inter-transaction guarding performed
   for non MSI quirk (wait polling mode), this patch skips
   inter-transaction guarding before wait_event_timeout() for the wait
   polling mode to reveal the hidden logic.
   The other hidden logic is: there is msleep() inter-transaction guarding
   performed when the GPE storming is observed. As after merging this
   commit:
     Commit: e1d4d90f
     Subject: ACPI / EC: Refine command storm prevention support
   EC_FLAGS_COMMAND_STORM is ensured to be cleared after invoking
   acpi_ec_transaction_unlocked(), the msleep() guard logic will never
   happen now. Since no one complains such change, this logic is likely
   added during the old times where the EC race issues are not fixed and
   the bugs are false root-caused to the timing issue. This patch simply
   removes the out-dated logic. We can restore it by stop skipping
   inter-transaction guarding for wait polling mode.
   Two different delay values are defined for msleep() and udelay() while
   they are merged in this patch to 550us.
2. time_after() causes additional delay in the polling mode (can only be
   observed in noirq suspend/resume processes where polling mode is always
   used) before advance_transaction() is invoked ("wait polling" log is
   added before wait_event_timeout()). We can see 2 wait_event_timeout()
   invocations. This is because time_after() ensures a ">" validation while
   we only need a ">=" validation here:
   [   86.739909] ACPI: Waking up from system sleep state S3
   [   86.742857] ACPI : EC: 2: Increase command
   [   86.742859] ACPI : EC: ***** Command(RD_EC) started *****
   [   86.742861] ACPI : EC: ===== TASK (0) =====
   [   86.742871] ACPI : EC: EC_SC(R) = 0x20 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=0
   [   86.742873] ACPI : EC: EC_SC(W) = 0x80
   [   86.742876] ACPI : EC: ***** Event started *****
   [   86.742880] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.743972] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.747966] ACPI : EC: ===== TASK (0) =====
   [   86.747977] ACPI : EC: EC_SC(R) = 0x20 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=0
   [   86.747978] ACPI : EC: EC_DATA(W) = 0x06
   [   86.747981] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.751971] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.755969] ACPI : EC: ===== TASK (0) =====
   [   86.755991] ACPI : EC: EC_SC(R) = 0x21 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=1
   [   86.755993] ACPI : EC: EC_DATA(R) = 0x03
   [   86.755994] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.755995] ACPI : EC: ***** Command(RD_EC) stopped *****
   [   86.755996] ACPI : EC: 1: Decrease command
   This patch corrects this by using time_before() instead in ec_guard():
   [   54.283146] ACPI: Waking up from system sleep state S3
   [   54.285414] ACPI : EC: 2: Increase command
   [   54.285415] ACPI : EC: ***** Command(RD_EC) started *****
   [   54.285416] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   54.285417] ACPI : EC: ===== TASK (0) =====
   [   54.285424] ACPI : EC: EC_SC(R) = 0x20 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=0
   [   54.285425] ACPI : EC: EC_SC(W) = 0x80
   [   54.285427] ACPI : EC: ***** Event started *****
   [   54.285429] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   54.287209] ACPI : EC: ===== TASK (0) =====
   [   54.287218] ACPI : EC: EC_SC(R) = 0x20 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=0
   [   54.287219] ACPI : EC: EC_DATA(W) = 0x06
   [   54.287222] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   54.291190] ACPI : EC: ===== TASK (0) =====
   [   54.291210] ACPI : EC: EC_SC(R) = 0x21 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=1
   [   54.291213] ACPI : EC: EC_DATA(R) = 0x03
   [   54.291214] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   54.291215] ACPI : EC: ***** Command(RD_EC) stopped *****
   [   54.291216] ACPI : EC: 1: Decrease command

After cleaning up all guarding logics, we have one single function
ec_guard() collecting all old, non-root-caused, hidden logics. Then we can
easily tune the logics in one place to respond to the bug reports.

Except the time_before() change, all other changes do not change the
behavior of the EC driver.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=12011
Link: https://bugzilla.kernel.org/show_bug.cgi?id=20242
Link: https://bugzilla.kernel.org/show_bug.cgi?id=77431Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The following commit merges polling and interrupt modes for EC driver:
  Commit: 2a84cb98 Mon Sep 17 00:00:00 2001
  Subject: ACPI: EC: Merge IRQ and POLL modes
The irqs_disabled() check introduced in it tries to fall into busy polling
mode when the context of ec_poll() cannot sleep.

Actually ec_poll() is ensured to be invoked in the contexts that can sleep
(from a sysfs /sys/kernel/debug/ec/ec0/io access, or from
acpi_evaluate_object(), or from acpi_ec_gpe_poller()). Without the MSI
quirk, we never saw the udelay() logic invoked. Thus this check is useless
and can be removed.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch removes the storming threashold enlarging quirk.

After applying the following commit, we can notice that there is no no-op
GPE handling invocation can be observed, thus it is unlikely that the
no-op counts can exceed the storming threashold:
  Commit: ca37bfdf
  Subject: ACPI / EC: Fix several GPE handling issues by deploying ACPI_GPE_DISPATCH_RAW_HANDLER mode.
Even when the storming happens, we have already limited its affection to
the only transaction and no further transactions will be affected. This is
done by this commit:
  Commit: e1d4d90f
  Subject: ACPI / EC: Refine command storm prevention support

So it's time to remove this quirk.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=45151Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch updates acpi_ec_is_gpe_raised() according to the following
commit:
  Commit: 09af8e82
  Subject: ACPICA: Events: Add support to return both enable/status register values for GPE and fixed event.
This is actually a no-op change as both the flags are defined to a same
value.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Use list_for_each_entry_safe for iterating because handler may be freed
in the loop.

BUG: unable to handle kernel NULL pointer dereference at 000000000000002c
IP: [<ffffffff814d69c8>] acpi_ec_put_query_handler+0x7/0x1a
Call Trace:
 acpi_ec_remove_query_handler+0x87/0x97
 acpi_smbus_hc_remove+0x2a/0x44 [sbshc]
 acpi_device_remove+0x7b/0x9a
 __device_release_driver+0x7e/0x110
 driver_detach+0xb0/0xc0
 bus_remove_driver+0x54/0xe0
 driver_unregister+0x2b/0x60
 acpi_bus_unregister_driver+0x10/0x12
 acpi_smb_hc_driver_exit+0x10/0x12 [sbshc]
 SyS_delete_module+0x1b8/0x210
 system_call_fastpath+0x12/0x6a
Signed-off-by: NChris Bainbridge <chris.bainbridge@gmail.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

On some machines(E,G Mircosoft surface 3), ACPI battery depends on
the EC operation region and it has _DEP method which contains EC.
Current code doesn't support such devices whose dep_unmet will be
not be decreased after EC opregion handler being installed. This
blocks battery device to be attached with its driver. This patch
is to fix the issue.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=90161Reported-and-tested-by: NLompik <lompik@voila.fr>
Tested-by: NValentin Lab <valentin.lab_bugzilla.kernel.org@kalysto.org>
Signed-off-by: NLan Tianyu <tianyu.lan@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch enhances debugging with the GPE reference count messages added.

This kind of log entries can be used by the platform validators to validate
if there is an EC transaction broken because of firmware/driver bugs.

No functional changes.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch refines logging/debugging splitter support so that when DEBUG is
disabled, splitters won't be visible in the kernel logs while they are
still available for developers when DEBUG is enabled.

This patch also refines the splitters to mark the following handling
process boundaries:
  +++++: boundary of driver starting/stopping
         boundary of IRQ storming
  =====: boundary of transaction advancement
  *****: boundary of EC command
         boundary of EC query
  #####: boundary of EC _Qxx evaluation

The following 2 log entries are originally logged using pr_info() in order
to be used as the boot/suspend/resume log entries for the EC device, this
patch also restores them to pr_info() logging level:
 ACPI : EC: EC started
 ACPI : EC: EC stopped

In this patch, one log entry around "Polling quirk" is converted into
ec_dbg_raw() which doesn't contain the boundary marker.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Remove unusual pr_info() visual emphasis introduced in ad479e7f
"ACPI / EC: Introduce STARTED/STOPPED flags to replace BLOCKED flag".
Signed-off-by: NScot Doyle <lkml14@scotdoyle.com>
[ rjw: Change pr_info() to pr_debug() too in those places. ]
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Revert commit f252cb09 (ACPI / EC: Add query flushing support),
because it breaks system suspend on Acer Aspire S5.  The machine
just hangs solid at the last stage of suspend (after taking non-boot
CPUs offline).
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Revert commit b5bca896 (ACPI / EC: Add GPE reference counting
debugging messages), because it depends on commit f252cb09
(ACPI / EC: Add query flushing support) which breaks system suspend
on Acer Aspire S5 and needs to be reverted.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch enhances debugging with the GPE reference count messages added.
No functional changes.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch implementes the QR_EC flushing support.

Grace periods are implemented from the detection of an SCI_EVT to the
submission/completion of the QR_EC transaction. During this period, all
EC command transactions are allowed to be submitted.

Note that query periods and event periods are intentionally distiguished to
allow further improvements.
1. Query period: from the detection of an SCI_EVT to the sumission of the
   QR_EC command. This period is used for storming prevention, as currently
   QR_EC is deferred to a work queue rather than directly issued from the
   IRQ context even there is no other transactions pending, so malicous
   SCI_EVT GPE can act like "level triggered" to trigger a GPE storm. We
   need to be prepared for this. And in the future, we may change it to be
   a part of the advance_transaction() where we will try QR_EC submission
   in appropriate positions to avoid such GPE storming.
2. Event period: from the detection of an SCI_EVT to the completion of the
   QR_EC command. We may extend it to the completion of _Qxx evaluation.
   This is actually a grace period for event flushing, but we only flush
   queries due to the reason stated in known issue 1. That's also why we
   use EC_FLAGS_EVENT_xxx. During this period, QR_EC transactions need to
   pass the flushable submission check.

In this patch, the following flags are implemented:
1. EC_FLAGS_EVENT_ENABLED: this is derived from the old
   EC_FLAGS_QUERY_PENDING flag which can block SCI_EVT handlings.
   With this flag, the logics implemented by the original flag are
   extended:
   1. Old logic: unless both of the flags are set, the event poller will
                 not be scheduled, and
   2. New logic: as soon as both of the flags are set, the evet poller will
                 be scheduled.
2. EC_FLAGS_EVENT_DETECTED: this is also derived from the old
   EC_FLAGS_QUERY_PENDING flag which can block SCI_EVT detection. It thus
   can be used to indicate the storming prevention period for query
   submission.
   acpi_ec_submit_request()/acpi_ec_complete_request() are invoked to
   implement this period so that acpi_set_gpe() can be invoked under the
   "reference count > 0" condition.
3. EC_FLAGS_EVENT_PENDING: this is newly added to indicate the grace period
   for event flushing (query flushing for now).
   acpi_ec_submit_request()/acpi_ec_complete_request() are invoked to
   implement this period so that the flushing process can wait until the
   event handling (query transaction for now) to be completed.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=82611
Link: https://bugzilla.kernel.org/show_bug.cgi?id=77431Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Tested-by: NOrtwin Glück <odi@odi.ch>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch refines EC command storm prevention support.

Current command storming code is wrong, when the storming condition is
detected, it only flags the condition without doing anything for the
current command but performing storming prevention for the follow-up
commands. So:
1. The first command which suffers from the storming still suffers from
   storming.
2. The follow-up commands which may not suffer from the storming are
   unconditionally forced into the storming prevention mode.
Ideally, we should only enable storm prevention immediately after detection
for the current command so that the next command can try the
power/performance efficient interrupt mode again.

This patch improves the command storm prevention by disabling GPE right
after the detection and re-enabling it right before completing the command
transaction using the GPE storming prevention APIs. This thus deploys the
following GPE handling model:
1. acpi_enable_gpe()/acpi_disable_gpe() for reference count changes:
   This set of APIs are used for EC usage reference counting.
2. acpi_set_gpe(ACPI_GPE_ENABLE)/acpi_set_gpe(ACPI_GPE_DISABLE):
   This set of APIs are used for preventing GPE storm. They must be invoked
   when the reference count > 0.
   Note that as the storming prevention should always happen when there is
   an outstanding request, or GPE enabling value will be messed up by the
   races. This patch also adds BUG_ON() to enforces this rule to prevent
   future bugs.

The msleep(1) used after completing a transaction is useless now as this
sounds like a guard time only useful for platforms that need the
EC_FLAGS_MSI quirks while we have fixed GPE race issues using the previous
raw handler mode enabling. It is kept to avoid regressions. A seperate
patch which deletes EC_FLAGS_MSI quirks should take care of deleting it.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch implements the EC command flushing support.

During the grace period indicated by EC_FLAGS_STARTED and EC_FLAGS_STOPPED,
all submitted EC command transactions can be completed and new submissions
are prevented before suspending so that the EC hardware can be ensured to
be in the idle state when the system is resumed.

There is a good indicator for flush support:
All acpi_ec_submit_request() is invoked after checking driver state with
acpi_ec_started() except the first one. This means all code paths can be
flushed as fast as possible by discarding the requests occurred after the
flush operation. The reference increased for such kind of code path is
wrapped by acpi_ec_submit_flushable_request().
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Tested-by: NOrtwin Glück <odi@odi.ch>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

By using the 2 flags, we can indicate an inter-mediate state where the
current transactions should be completed while the new transactions should
be dropped.

The comparison of the old flag and the new flags:
  Old			New
  about to set BLOCKED	STOPPED set / STARTED set
  BLOCKED set		STOPPED clear / STARTED clear
  BLOCKED clear		STOPPED clear / STARTED set
A new period can be indicated by the 2 flags. The new period is between the
point where we are about to set BLOCKED and the point when the BLOCKED is
set. The new flags facilitate us with acpi_ec_started() check to allow the
EC transaction to be submitted during the new period. This period thus can
be used as a grace period for the EC transaction flushing.

The only functional change after applying this patch is:
1. The GPE enabling/disabling is protected by the EC specific lock. We can
   do this because of recent ACPICA GPE API enhancement. This is reasonable
   as the GPE disabling/enabling state should only be determined by the EC
   driver's state machine which is protected by the EC spinlock.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Tested-by: NOrtwin Glück <odi@odi.ch>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The bug fixes around GPE races have been done to the EC driver by the
previous commits. This patch increases the revision to 3 to indicate the
behavior differences between the old and the new drivers. The
copyright/authorship notices are also updated.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Timeout in the ec_poll() doesn't refer to the last register access time. It
thus can win the competition against the acpi_ec_gpe_handler() if a
transaction takes longer than 1ms but individual register accesses are less
than 1ms.  In some cases, it can make the following silicon bug easier to
be triggered:
 GPE EN is not wired to the GPE trigger line, so when GPE STS is already
 set when 1 is written to GPE EN, no GPE can be triggered.

This patch adds register access timestamp reference support for ec_poll()
to reduce the number of ec_poll() invocations.
Reported-by: NVenkat Raghavulu <venkat.raghavulu@intel.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch switches EC driver into ACPI_GPE_DISPATCH_RAW_HANDLER mode where
the GPE lock is not held for acpi_ec_gpe_handler() and the ACPICA internal
GPE enabling/disabling/clearing operations are bypassed so that further
improvements are possible with the GPE APIs.

There are 2 strong reasons for deploying raw GPE handler mode in the EC
driver:
1. Some hardware logics can control their interrupts via their own
   registers, so their interrupts can be disabled/enabled/acknowledged
   without using the super IRQ controller provided functions. While there
   is no mean (EC commands) for the EC driver to achieve this.
2. During suspending, the EC driver is still working for a while to
   complete the platform firmware provided functionailities using ec_poll()
   after all GPEs are disabled (see acpi_ec_block_transactions()), which
   means the EC driver will drive the EC GPE out of the GPE core's control.

Without deploying the raw GPE handler mode, we can see many races between
the EC driver and the GPE core due to the above restrictions:
1. There is a race condition due to ACPICA internal GPE
   disabling/clearing/enabling logics in acpi_ev_gpe_dispatch():
     Orignally EC GPE is disabled (EN=0), cleared (STS=0) before invoking a
     GPE handler and re-enabled (EN=1) after invoking a GPE handler in
     acpi_ev_gpe_dispatch(). When re-enabling appears, GPE may be flagged
     (STS=1).
       =================================================================
       (event pending A)
       =================================================================
       acpi_ev_gpe_dispatch()    ec_poll()
         EN=0
         STS=0
         acpi_ec_gpe_handler()
       *****************************************************************
       (event handling A)
           Lock(EC)
           advance_transaction()
             EC_SC read
       =================================================================
       (event pending B)
       =================================================================
             EC_SC handled
           Unlock(EC)
       *****************************************************************
       *****************************************************************
       (event handling B)
                                   Lock(EC)
                                   advance_transaction()
                                     EC_SC read
       =================================================================
       (event pending C)
       =================================================================
                                     EC_SC handled
                                   Unlock(EC)
       *****************************************************************
           EN=1
   This race condition is the root cause of different issues on different
   silicon variations.
   A. Silicon variation A:
      On some platforms, GPE will be triggered due to "writing 1 to EN when
      STS=1". This is because both EN and STS lines are wired to the GPE
      trigger line.
      1. Issue 1:
         We can see no-op acpi_ec_gpe_handler() invoked on such platforms.
         This is because:
         a. event pending B: An event can arrive after ACPICA's GPE
            clearing performed in acpi_ev_gpe_dispatch(), this event may
            fail to be detected by EC_SC read that is performed before its
            arrival;
         b. event handling B: The event can be handled in ec_poll() because
            EC lock is released after acpi_ec_gpe_handler() invocation;
         c. There is no code in ec_poll() to clear STS but the GPE can
            still be triggered by the EN=1 write performed in
            acpi_ev_finish_gpe(), this leads to a no-op EC GPE handler
            invocation;
         d. As no-op GPE handler invocations are counted by the EC driver
            to trigger the command storming conditions, the wrong no-op
            GPE handler invocations thus can easily trigger wrong command
            storming conditions.
         Note 1:
         If we removed GPE disabling/enabling code from
         acpi_ev_gpe_dispatch(), we could still see no-op GPE handlers
         triggered by the event arriving after the GPE clearing and before
         the GPE handling on both silicon variation A and B. This can only
         occur if the CPU is very slow (timing slice between STS=0 write
         and EC_SC read should be short enough before hardware sets another
         GPE indication). Thus this is very rare and is not what we need to
         fix.
   B. Silicon variation B:
      On other platforms, GPE may not be triggered due to "writing 1 to EN
      when STS=1". This is because only STS line is wired to the GPE
      trigger line.
      2. Issue 2:
         We can see GPE loss on such platforms. This is because:
         a. event pending B vs. event handling A: An event can arrive after
            ACPICA's GPE handling performed in acpi_ev_gpe_dispatch(), or
            event pending C vs. event handling B: An event can arrive after
            Linux's GPE handling performed in ec_poll(),
            these events may fail to be detected by EC_SC read that is
            performed before their arrival;
         b. The GPE cannot be triggered by EN=1 write performed in
            acpi_ev_finish_gpe();
         c. If no polling mechanism is implemented in the driver for the
            pending event (for example, SCI_EVT), this event is lost due to
            no GPE being triggered.
         Note 2:
         On most platforms, there might be another rule that GPE may not be
         triggered due to "writing 1 to STS when STS=1 and EN=1".
         Then on silicon variation B, an even worse case is if the issue 2
         event loss happens, further events may never trigger GPE again on
         such platforms due to being blocked by the current STS=1. Unless
         someone clears STS, all events have to be polled.
2. There is a race condition due to lacking in GPE status checking in EC
   driver:
     Originally, GPE status is checked in ACPICA core but not checked in
     the GPE handler. Thus since the status checking and handling is not
     locked, it can be interrupted by another handling path.
       =================================================================
       (event pending A)
       =================================================================
       acpi_ev_gpe_detect()        ec_poll()
         if (EN==1 && STS==1)
       *****************************************************************
       (event handling A)
                                     Lock(EC)
                                     advance_transaction()
                                       EC_SC read
                                       EC_SC handled
                                     Unlock(EC)
       *****************************************************************
         acpi_ev_gpe_dispatch()
           EN=0
           STS=0
           acpi_ec_gpe_handler()
       *****************************************************************
       (event handling B)
             Lock(EC)
             advance_transaction()
               EC_SC read
             Unlock(EC)
       *****************************************************************
      3. Issue 3:
         We can see no-op acpi_ec_gpe_handler() invoked on both silicon
         variation A and B. This is because:
         a. event pending A: An event can arrive to trigger an EC GPE and
            ACPICA checks it and is about to invoke the EC GPE handler;
         b. event handling A: The event can be handled in ec_poll() because
            EC lock is not held after the GPE status checking;
         c. event handling B: Then when the EC GPE handler is invoked, it
            becomes a no-op GPE handler invocation.
         d. As no-op GPE handler invocations are counted by the EC driver
            to trigger the command storming conditions, the wrong no-op
            GPE handler invocations thus can easily trigger wrong command
            storming conditions.
      Note 3:
      This no-op GPE handler invocation is rare because the time between
      the IRQ arrival and the acpi_ec_gpe_handler() invocation is less than
      the timeout value waited in ec_poll(). So most of the no-op GPE
      handler invocations are caused by the reason described in issue 1.
3. There is a race condition due to ACPICA internal GPE clearing logic in
   acpi_enable_gpe():
     During runtime, acpi_enable_gpe() can be invoked by the EC storming
     prevention code. When it is invoked, GPE may be flagged (STS=1).
       =================================================================
       (event pending A)
       =================================================================
       acpi_ev_gpe_dispatch()    acpi_ec_transaction()
         EN=0
         STS=0
         acpi_ec_gpe_handler()
       *****************************************************************
       (event handling A)
           Lock(EC)
           advance_transaction()
             EC_SC read
             EC_SC handled
           Unlock(EC)
       *****************************************************************
         EN=1 ?
                                   Lock(EC)
                                   Unlock(EC)
       =================================================================
       (event pending B)
       =================================================================
                                   acpi_enable_gpe()
                                     STS=0
                                     EN=1
    4. Issue 4:
       We can see GPE loss on both silicon variation A and B platforms.
       This is because:
       a. event pending B: An event can arrive right before ACPICA's GPE
          clearing performed in acpi_enable_gpe();
       b. If the GPE is cleared when GPE is disabled, then EN=1 write in
          acpi_enable_gpe() cannot trigger this GPE;
       c. If no polling mechanism is implemented in the driver for this
          event (for example, SCI_EVT), this event is lost due to no GPE
          being triggered.
       Note 4:
       Currently we don't have this issue, but after we switch the EC
       driver into ACPI_GPE_DISPATCH_RAW_HANDLER mode, we need to take care
       of handling this because the EN=1 write in acpi_ev_gpe_dispatch()
       will be abandoned.

There might be more race issues for the current GPE handler usages. This is
because the EC IRQ's enabling/disabling/checking/clearing/handling
operations should be locked by a single lock that is under the EC driver's
control to achieve the serialization. Which means we need to invoke GPE
APIs with EC driver's lock held and all ACPICA internal GPE operations
related to the GPE handler should be abandoned. Invoking GPE APIs inside of
the EC driver lock and bypassing ACPICA internal GPE operations requires
the ACPI_GPE_DISPATCH_RAW_HANDLER mode where the same lock used by the APIs
are released prior than invoking the handlers. Otherwise, we can see dead
locks due to circular locking dependencies (see Reference below).

This patch then switches the EC driver into the
ACPI_GPE_DISPATCH_RAW_HANDLER mode so that it can perform correct GPE
operations using the GPE APIs:
1. Bypasses EN modifications performed in acpi_ev_gpe_dispatch() by
   using acpi_install_gpe_raw_handler() and invoking all GPE APIs with EC
   spin lock held. This can fix issue 1 as it makes a non frequent GPE
   enabling/disabling environment.
2. Bypasses STS clearing performed in acpi_enable_gpe() by replacing
   acpi_enable_gpe()/acpi_disable_gpe() with acpi_set_gpe(). This can fix
   issue 4. And this can also help to fix issue 1 as it makes a no sudden
   GPE clearing environment when GPE is frequently enabled/disabled.
3. Ensures STS acknowledged before handling by invoking acpi_clear_gpe()
   in advance_transaction(). This can finally fix issue 1 even in a
   frequent GPE enabling/disabling environment. And this can also finally
   fix issue 3 when issue 2 is fixed.
   Note 3:
   GPE clearing is edge triggered W1C, which means we can clear it right
   before handling it. Since all EC GPE indications are handled in
   advance_transaction() by previous commits, we can now move GPE clearing
   into it to implement the correct GPE clearing.
   Note 4:
   We can use acpi_set_gpe() which is not shared GPE safer instead of
   acpi_enable_gpe()/acpi_disable_gpe() because EC GPE is not shared by
   other hardware, which is mentioned in the ACPI specification 5.0, 12.6
   Interrupt Model: "OSPM driver treats this as an edge event (the EC SCI
   cannot be shared)". So we can stop using shared GPE safer APIs
   acpi_enable_gpe()/acpi_disable_gpe() in the EC driver. Otherwise
   cleanups need to be made in acpi_ev_enable_gpe() to bypass the GPE
   clearing logic before keeping acpi_enable_gpe().
This patch also invokes advance_transaction() when GPE is re-enabled in the
task context which:
1. Ensures EN=1 can trigger GPE by checking and handling EC status register
   right after EN=1 writes. This can fix issue 2.

After applying this patch, without frequent GPE enablings considered:
       =================================================================
       (event pending A)
       =================================================================
       acpi_ec_gpe_handler()     ec_poll()
       *****************************************************************
       (event handling A)
         Lock(EC)
           advance_transaction()
             if STS==1
               STS=0
             EC_SC read
       =================================================================
       (event pending B)
       =================================================================
             EC_SC handled
         Unlock(EC)
       *****************************************************************
       *****************************************************************
       (event handling B)
                                   Lock(EC)
                                     advance_transaction()
                                       if STS==1
                                         STS=0
                                       EC_SC read
       =================================================================
       (event pending C)
       =================================================================
                                       EC_SC handled
                                   Unlock(EC)
       *****************************************************************
The event pending for issue 1 (event pending B) can arrive as a next GPE
due to the previous IRQ context STS=0 write. And if it is handled by
ec_poll() (event handling B), as it is also acknowledged by ec_poll(), the
event pending for issue 2 (event pending C) can properly arrive as a next
GPE after the task context STS=0 write. So no GPE will be lost and never
triggered due to GPE clearing performed in the wrong position. And since
all GPE handling is performed after a locked GPE status checking, we can
hardly see no-op GPE handler invocations due to issue 1 and 3. We may still
see no-op GPE handler invocations due to "Note 1", but as it is inevitable,
it needn't be fixed.

After applying this patch, with frequent GPE enablings considered:
       =================================================================
       (event pending A)
       =================================================================
       acpi_ec_gpe_handler()     acpi_ec_transaction()
       *****************************************************************
       (event handling A)
         Lock(EC)
           advance_transaction()
             if STS==1
               STS=0
             EC_SC read
       =================================================================
       (event pending B)
       =================================================================
             EC_SC handled
         Unlock(EC)
       *****************************************************************
       *****************************************************************
       (event handling B)
                                   Lock(EC)
                                     EN=1
                                     if STS==1
                                       advance_transaction()
                                         if STS==1
                                           STS=0
                                         EC_SC read
       =================================================================
       (event pending C)
       =================================================================
                                         EC_SC handled
                                   Unlock(EC)
       *****************************************************************
The event pending for issue 2 can be manually handled by
advance_transaction(). And after the STS=0 write performed in the manual
triggered advance_transaction(), GPE can always arrive. So no GPE will be
lost due to frequent GPE disabling/enabling performed in the driver like
issue 4.
Note 5:
It's ideally when EN=1 write occurred, an IRQ thread should be woken up to
handle the GPE when the GPE was raised. But this requires the IRQ thread to
contain the poller code for all EC GPE indications, while currently some of
the indications are handled in the user tasks. It then is very hard for the
code to determine whether a user task should be invoked or the poller work
item should be scheduled. So we have to invoke advance_transaction()
directly now and it leaves us such a restriction for the GPE re-enabling:
it must be performed in the task context to avoid starving the GPEs.

As a conclusion: we can see the EC GPE is always handled in serial after
deploying the raw GPE handler mode:
  Lock(EC)
  if (STS==1)
    STS=0
  EC_SC read
  EC_SC handled
  Unlock(EC)
The EC driver specific lock is responsible to make the EC GPE handling
processes serialized so that EC can handle its GPE from both IRQ and task
contexts and the next IRQ can be ensured to arrive after this process.

Note 6:
We have many EC_FLAGS_MSI qurik users in the current driver. They all seem
to be suffering from unexpected GPE triggering source lost. And they are
false root caused to a timing issue. Since EC communication protocol has
already flow control defined, timing shouldn't be the root cause, while
this fix might be fixing the root cause of the old bugs.

Link: https://lkml.org/lkml/2014/11/4/974
Link: https://lkml.org/lkml/2014/11/18/316
Link: https://www.spinics.net/lists/linux-acpi/msg54340.htmlSigned-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The QR_EC related code pieces have redundants, this patch merges them into
acpi_ec_query() which invokes acpi_ec_transaction() where EC mutex and the
global lock are already held. After doing so, query handler traversal still
need to be locked by EC mutex after invoking acpi_ec_transaction().

Note that EC event handling is sequential. We fetch one event from firmware
event queue and process it until 0x00 or error returned. So we don't need
to hold mutex for whole acpi_ec_clear() process to determine whether we
should continue to drain. And for the same reason, we don't need to hold
mutex for the whole procedure from the QR_EC transaction to the query
handler traversal.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch fixes 2 issues related to the draining behavior. But it doesn't
implement the draining support, it only cleans up code so that further
draining support is possible.

The draining behavior is expected by some platforms (for example, Samsung)
where SCI_EVT is set only once for a set of events and might be cleared for
the very first QR_EC command issued after SCI_EVT is set. EC firmware on
such platforms will return 0x00 to indicate "no outstanding event". Thus
after seeing an SCI_EVT indication, EC driver need to fetch events until
0x00 returned (see acpi_ec_clear()).

Issue 1 - acpi_ec_submit_query():
It's reported on Samsung laptops that SCI_EVT isn't checked when the
transactions are advanced in ec_poll(), which leads to SCI_EVT triggering
source lost:
 If no EC GPE IRQs are arrived after that, EC driver cannot detect this
 event and handle it.
See comment 244/247 for kernel bugzilla 44161.
This patch fixes this issue by moving SCI_EVT checks into
advance_transaction(). So that SCI_EVT is checked each time we are going to
handle the EC firmware indications. And this check will happen for both IRQ
context and task context.
Since after doing that, SCI_EVT is also checked after completing a
transaction, ec_check_sci() and ec_check_sci_sync() can be removed.

Issue 2 - acpi_ec_complete_query():
We expect to clear EC_FLAGS_QUERY_PENDING to allow queuing another draining
QR_EC after writing a QR_EC command and before reading the event. After
reading the event, SCI_EVT might be cleared by the firmware, thus it may
not be possible to queue such a draining QR_EC at that time.
But putting the EC_FLAGS_QUERY_PENDING clearing code after
start_transaction() is wrong as there are chances that after
start_transaction(), QR_EC can fail to be sent. If this happens,
EC_FLAG_QUERY_PENDING will be cleared earlier. As a consequence, the
draining QR_EC will also be queued earlier than expected.
This patch also moves this code into advance_transaction() where QR_EC is
just sent (ACPI_EC_COMMAND_POLL flagged) to fix this issue.

Notes:
1. After introducing the 2 SCI_EVT related handlings into
   advance_transaction(), a next QR_EC can be queued right after writing
   the current QR_EC command and before reading the event. But this still
   hasn't implemented the draining behavior as the draining support
   requires:
     If a previous returned event value isn't 0x00, a draining QR_EC need
     to be issued even when SCI_EVT isn't set.
2. In this patch, acpi_os_execute() is also converted into a seperate work
   item to avoid invoking kmalloc() in the atomic context. We can do this
   because of the previous global lock fix.
3. Originally, EC_FLAGS_EVENT_PENDING is also used to avoid queuing up
   multiple work items (created by acpi_os_execute()), this can be covered
   by only using a single work item. But this patch still keeps this flag
   as there are different usages in the driver initialization steps relying
   on this flag.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=44161Reported-by: NKieran Clancy <clancy.kieran@gmail.com>
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Currently QR_EC is queued up on CPU 0 to be safe with SMM because there is
no global lock held for acpi_ec_gpe_query(). As we are about to move QR_EC
to a non CPU 0 bound work queue to avoid invoking kmalloc() in
advance_transaction(), we have to acquire global lock for the new QR_EC
work item to avoid regressions.

Known issue:
1. Global lock for acpi_ec_clear().
   This is an existing issue that acpi_ec_clear() which invokes
   acpi_ec_sync_query() also suffers from the same issue. But this patch's
   target is only the code to invoke acpi_ec_sync_query() in a CPU 0 bound
   work queue item, and the acpi_ec_clear() can be automatically fixed by
   further patch that merges the redundant code, so it is left unchanged.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The returning value of acpi_os_execute() is erroneously handled as errno.
This patch corrects it by returning EBUSY to indicate the work queue item
creation failure.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>