linux-kernel - Re: [PATCH v2 3/3] ACPI / sleep: EC-based wakeup from suspend-to-idle on recent Dell systems

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Date:   Tue, 20 Jun 2017 23:16:32 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Darren Hart <dvhart@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Mario Limonciello <mario.limonciello@...l.com>,
        Tom Lanyon <tom@...shoeco.com>,
        Jérôme de Bretagne 
        <jerome.debretagne@...il.com>
Subject: Re: [PATCH v2 3/3] ACPI / sleep: EC-based wakeup from suspend-to-idle
 on recent Dell systems

On Tue, Jun 20, 2017 at 4:00 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Tue, Jun 20, 2017 at 9:13 AM, Rafael J. Wysocki <rafael@...nel.org> wrote:
>>
>> My understanding is that Windows uses the ACPI_FADT_LOW_POWER_S0 flag.
>> It generally enables non-S3 suspend/resume when this flag is set and
>> it doesn't touch S3 then.  Keeping the EC GPE (and other GPEs for that
>> matter) enabled over suspend/resume is part of that if my
>> understanding is correct.
>>
>> During suspend we generally disable all GPEs that are not expected to
>> generate wakeup events in order to avoid spurious wakeups, but we can
>> try to keep them enabled if ACPI_FADT_LOW_POWER_S0 is set.  That will
>> reduce the ugliness, but the cost may be more energy used while
>> suspended on some systems.
>
> I think trying to do something similar to what windows does is likely
> the right thing, since that is (sadly) the only thing that tends to
> get extensive testing still.
>
> Of course, different versions of Windows then probably do different
> things, but I guess ACPI_FADT_LOW_POWER_S0 ends up being a good sign
> of "new machine designed for windows 10", so it's probably a good
> thing to trigger that behavior on.
>
> So I suspect it's worth testing, particularly if we're going to be in
> the situation that a lot of machines are going to do this going
> forward (ie the "all Dell" may end up being more than just Dell too?
> Dell usually doesn't do particularly odd and out-of-the-norm design
> choices like some vendors do).

Well, involving the EC in power button events processing has not been
a common practice so far.

Anyway, I will replace this patch with something that ought to be more
in line with what Windows does.

Thanks,
Rafael