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ACPI: PM: x86: Print messages regarding LPS0 idle support

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Because suspend-to-idle is always supported and on x86 it is the only
way to suspend the system if S3 is not supported by the platform, the
kernel attempts to enter low-power S0 idle in the suspend-to-idle flow
regardless of whether or not the ACPI_FADT_LOW_POWER_S0 flag is set in
the FADT.  However, if that flag is not set, residency counters
associated with low-power S0 idle may not count and the platform may
refuse to put the EC into a low-power mode, for example.

For this reason, print diagnostic messages when the platform should
achieve significant energy savings in low-power S0 idle (because the
ACPI_FADT_LOW_POWER_S0 flag is set in the FADT) and when
suspend-to-idle becomes the default suspend method (because low-power
S0 idle should be equally or more efficient than S3, if available).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
This commit is contained in:
Rafael J. Wysocki 2022-07-21 18:13:30 +02:00
parent 1a2dcab517
commit ec6c050319
2 changed files with 6 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/acpi/sleep.c
View File

@ -824,6 +824,9 @@ static const struct platform_s2idle_ops acpi_s2idle_ops = {
void __weak acpi_s2idle_setup(void)
{
if (acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0)
pr_info("Efficient low-power S0 idle declared\n");
s2idle_set_ops(&acpi_s2idle_ops);
}

4
drivers/acpi/x86/s2idle.c
View File

@ -423,8 +423,10 @@ static int lps0_device_attach(struct acpi_device *adev,
* line.
*/
if ((acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0) &&
mem_sleep_default > PM_SUSPEND_MEM && !acpi_sleep_default_s3)
mem_sleep_default > PM_SUSPEND_MEM && !acpi_sleep_default_s3) {
mem_sleep_current = PM_SUSPEND_TO_IDLE;
pr_info("Low-power S0 idle used by default for system suspend\n");
}
/*
* Some LPS0 systems, like ASUS Zenbook UX430UNR/i7-8550U, require the