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SubjectRE: [PATCH 1/2] ACPI / PM: Use Low Power S0 Idle on more systems
Date


> -----Original Message-----
> From: platform-driver-x86-owner@vger.kernel.org [mailto:platform-driver-x86-
> owner@vger.kernel.org] On Behalf Of Rafael J. Wysocki
> Sent: Wednesday, January 10, 2018 6:26 AM
> To: Linux ACPI <linux-acpi@vger.kernel.org>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>; Darren Hart
> <dvhart@infradead.org>; LKML <linux-kernel@vger.kernel.org>; Linux PM <linux-
> pm@vger.kernel.org>; Platform Driver <platform-driver-x86@vger.kernel.org>;
> Valentin Manea <valy@mrs.ro>
> Subject: [PATCH 1/2] ACPI / PM: Use Low Power S0 Idle on more systems
>
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.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.
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=198389
> Reported-by: Valentin Manea <valy@mrs.ro>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> drivers/acpi/sleep.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> Index: linux-pm/drivers/acpi/sleep.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/sleep.c
> +++ linux-pm/drivers/acpi/sleep.c
> @@ -707,7 +707,8 @@ static const struct acpi_device_id lps0_
> #define ACPI_LPS0_ENTRY 5
> #define ACPI_LPS0_EXIT 6
>
> -#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))
>
> static acpi_handle lps0_device_handle;
> static guid_t lps0_dsm_guid;
> @@ -910,7 +911,8 @@ static int lps0_device_attach(struct acp
> if (out_obj && out_obj->type == ACPI_TYPE_BUFFER) {
> char bitmask = *(char *)out_obj->buffer.pointer;
>
> - if ((bitmask & ACPI_S2IDLE_FUNC_MASK) ==
> ACPI_S2IDLE_FUNC_MASK) {
> + if ((bitmask & ACPI_LPS0_S2I_MASK) == ACPI_LPS0_S2I_MASK ||
> + (bitmask & ACPI_LPS0_SCREEN_MASK) ==
> ACPI_LPS0_SCREEN_MASK) {
> lps0_dsm_func_mask = bitmask;
> lps0_device_handle = adev->handle;
> /*

In making this change I believe you'll need to cache the values that you found from the
function mask to test them later too.
Here:
https://github.com/torvalds/linux/blob/master/drivers/acpi/sleep.c#L943

This is because later on both ACPI_LPS0_SCREEN_OFF and ACPI_LPS0_ENTRY are called
whether or not they both exist. Fortunately looking at the DSDT in the attached bug nothing
happens if calling the undefined Arg2 == 0x05/Arg2 == 0x06 but that might not always
be the case.

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