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

From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	"Linux PM" <linux-pm@vger.kernel.org>,
	"Linux ACPI" <linux-acpi@vger.kernel.org>,
	"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
	"Darren Hart" <dvhart@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"Srinivas Pandruvada" <srinivas.pandruvada@linux.intel.com>,
	"Mika Westerberg" <mika.westerberg@linux.intel.com>,
	"Mario Limonciello" <mario.limonciello@dell.com>,
	"Tom Lanyon" <tom@oneshoeco.com>,
	"Jérôme de Bretagne" <jerome.debretagne@gmail.com>
Subject: Re: [PATCH v2 3/3] ACPI / sleep: EC-based wakeup from suspend-to-idle on recent Dell systems
Date: Tue, 20 Jun 2017 23:16:32 +0200	[thread overview]
Message-ID: <CAJZ5v0j3YnsQw1g75Y_0FYp6NmqULnKYJqrqbdPJ9vmEaHbuFQ@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFy1=pVbkKLH4p8prioOQ_Qb43ojM=8d9GsgXYWkaEN93A@mail.gmail.com>

On Tue, Jun 20, 2017 at 4:00 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Tue, Jun 20, 2017 at 9:13 AM, Rafael J. Wysocki <rafael@kernel.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