Patch "rtc: rtc-cmos: Do not check ACPI_FADT_LOW_POWER_S0" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    rtc: rtc-cmos: Do not check ACPI_FADT_LOW_POWER_S0

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     rtc-rtc-cmos-do-not-check-acpi_fadt_low_power_s0.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 3870d76e5891bf7a187273dfb80fb21c6ccb955d
Author: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Date:   Mon Aug 8 20:23:59 2022 +0200

    rtc: rtc-cmos: Do not check ACPI_FADT_LOW_POWER_S0
    
    [ Upstream commit 6492fed7d8c95f53b0b804ef541324d924d95d41 ]
    
    The ACPI_FADT_LOW_POWER_S0 flag merely means that it is better to
    use low-power S0 idle on the given platform than S3 (provided that
    the latter is supported) and it doesn't preclude using either of
    them (which of them will be used depends on the choices made by user
    space).
    
    For this reason, there is no benefit from checking that flag in
    use_acpi_alarm_quirks().
    
    First off, it cannot be a bug to do S3 with use_acpi_alarm set,
    because S3 can be used on systems with ACPI_FADT_LOW_POWER_S0 and it
    must work if really supported, so the ACPI_FADT_LOW_POWER_S0 check is
    not needed to protect the S3-capable systems from failing.
    
    Second, suspend-to-idle can be carried out on a system with
    ACPI_FADT_LOW_POWER_S0 unset and it is expected to work, so if setting
    use_acpi_alarm is needed to handle that case correctly, it should be
    set regardless of the ACPI_FADT_LOW_POWER_S0 value.
    
    Accordingly, drop the ACPI_FADT_LOW_POWER_S0 check from
    use_acpi_alarm_quirks().
    
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
    Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxx>
    Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
    Link: https://lore.kernel.org/r/12054246.O9o76ZdvQC@kreacher
    Stable-dep-of: 83ebb7b3036d ("rtc: cmos: Disable ACPI RTC event on removal")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index 60271ea2a28d..398b4fb8d934 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -1203,9 +1203,6 @@ static void use_acpi_alarm_quirks(void)
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
 		return;
 
-	if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0))
-		return;
-
 	if (!is_hpet_enabled())
 		return;