linux-kernel - Re: [PATCH 1/2] ACPI / PM: Use Low Power S0 Idle on more systems

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Date:   Wed, 10 Jan 2018 23:25:00 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Darren Hart <dvhart@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Valentin Manea <valy@....ro>
Subject: Re: [PATCH 1/2] ACPI / PM: Use Low Power S0 Idle on more systems

On Wed, Jan 10, 2018 at 2:24 PM, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
> On Wed, 2018-01-10 at 13:26 +0100, Rafael J. Wysocki wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>
>> Some systems don't support the ACPI_LPS0_ENTRY and ACPI_LPS0_EXIT
>> functions in their Low Power S0 Idle _DSM, but still expect EC
>> events to be processed in the suspend-to-idle state for power button
>> wakeup (among other things) to work.  Surface Pro3 turns out to be
>> one of them.
>>
>> Fortunately, it still provides Low Power S0 Idle _DSM with the screen
>> on/off functions supported, so modify the ACPI suspend-to-idle to use
>> the Low Power S0 Idle code path for all systems supporting the
>> ACPI_LPS0_ENTRY and ACPI_LPS0_EXIT or the ACPI_LPS0_SCREEN_OFF and
>> ACPI_LPS0_SCREEN_ON functions in their Low Power S0 Idle _DSM.
>>
>> Potentially, that will cause more systems to use suspend-to-idle by
>> default, so some future corrections may be necessary if it leads
>> to issues, but let it remain more straightforward for now.
>
>> -#define ACPI_S2IDLE_FUNC_MASK        ((1 << ACPI_LPS0_ENTRY) | (1 <<
>> ACPI_LPS0_EXIT))
>> +#define ACPI_LPS0_SCREEN_MASK        ((1 << ACPI_LPS0_SCREEN_OFF) |
>> (1 << ACPI_LPS0_SCREEN_ON))
>
>> +#define ACPI_LPS0_S2I_MASK   ((1 << ACPI_LPS0_ENTRY) | (1 <<
>> ACPI_LPS0_EXIT))
>
> Just a nitpick: Can we leave S2IDLE instead of S2I?
> Would it make sense for potential code readers?

I wanted it to be shorter, but if that is a problem, I'd rather call
it PLATFORM than S2IDLE (as technically they are related to the
low-power mode of the platform).

I'll send an update shortly.