Re: [PATCH v4 0/6] ACPI / EC: Fix GPE handling related races.

Rafael J. Wysocki
2015-02-05T14:56:54Z

On Thursday, February 05, 2015 04:24:29 PM Lv Zheng wrote:
> This patchset is based on ACPICA 20150204 release.
>
> This patchset introduces a GPE raw handler mode and switches EC driver into
> a GPE raw handler mode user.
>
> The EC driver is a kind of the hardware driver that wants to control the
> interrupt handling itself (for example, implementing the storming
> prevention or the burst mode). But it has no mean to do so using the EC
> firmware provided commands. The EC driver has to rely on the GPE APIs to
> achieve the interrupt controlling.
> Due to the shortcoming of the current ACPICA GPE APIs, the EC driver is
> using the GPE APIs in a racy way. We then can see many issues between the
> ACPICA internal GPE controlling and the EC driver's GPE handling. Such
> races prevents us from correctly root causing other EC issues. This
> patchset fixes the GPE related race issues by holding the EC state machine
> lock for the whole EC GPE handling process:
> Lock(EC) <- EC lock
> if (STS==1) <- GPE API
> STS=0 <- GPE API
> EC_SC read <- EC GPE handler
> EC_SC handled <- EC GPE handler
> Unlock(EC) <- EC lock
>
> We can see several GPE handling stuffs improved by applying this patchset
> because of EC/GPE races fixed:
> 1. Some platforms may suffer from GPE loss, which is because GPE is handled
> in the polling mode with its GPE indication left uncleared, the
> uncleared indication may stop further GPEs from being triggered.
> This patchset can make sure the indication has been cleared before
> handling, thus it may have fixed the potential root cause of the bugs
> that were originally fixed by the MSI quirk.
> 2. We originally can see many no-op EC GPE handler invocations, which is
> becaue GPE can be handled in the task context after the GPE IRQ handler
> is invoked, then when the driver goes back to the handler, there is no
> indication left for it to handle.
> This patchset can reduce the number of no-op EC GPE handler invocations
> to almost 0 by fixing the races, thus it may have fixed the potential
> root cause of the issues that were originally fixed by the storming
> condition threshold quirk.
>
> Lv Zheng (6):
> ACPICA: Events: Introduce ACPI_GPE_DISPATCH_RAW_HANDLER to fix 2
> issues for the current GPE APIs.
> ACPICA: Events: Introduce acpi_set_gpe()/acpi_finish_gpe() to reduce
> divergences.
> ACPICA: Events: Enable APIs to allow interrupt/polling adaptive
> request based GPE handling model.
> ACPI / EC: Fix several GPE handling issues by deploying
> ACPI_GPE_DISPATCH_RAW_HANDLER mode.
> ACPI / EC: Reduce ec_poll() by referencing the last register access
> timestamp.
> ACPI / EC: Update revision due to raw handler mode.
>
> drivers/acpi/acpica/evgpe.c | 52 +++++++++++++++---
> drivers/acpi/acpica/evgpeblk.c | 2 +
> drivers/acpi/acpica/evgpeinit.c | 6 +-
> drivers/acpi/acpica/evgpeutil.c | 6 +-
> drivers/acpi/acpica/evxface.c | 115 +++++++++++++++++++++++++++++++++++----
> drivers/acpi/acpica/evxfgpe.c | 114 ++++++++++++++++++++++++++++++++++++++
> drivers/acpi/ec.c | 104 ++++++++++++++++++++++++++++++-----
> include/acpi/acpixf.h | 8 +++
> include/acpi/actypes.h | 11 ++--
> 9 files changed, 375 insertions(+), 43 deletions(-)

Whole series queued up for 3.20, thanks!

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.