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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 ahci_update_initial_lpm_policy(). First off, it cannot be a bug to do S3 with policy set to either ATA_LPM_MIN_POWER_WITH_PARTIAL or ATA_LPM_MIN_POWER, because S3 can be used on systems with ACPI_FADT_LOW_POWER_S0 set 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 policy to either ATA_LPM_MIN_POWER_WITH_PARTIAL or ATA_LPM_MIN_POWER is needed to handle that case correctly, it should be done regardless of the ACPI_FADT_LOW_POWER_S0 value. Accordingly, replace the ACPI_FADT_LOW_POWER_S0 check in ahci_update_initial_lpm_policy() with pm_suspend_default_s2idle() which is more general and also takes the user's preference into account and drop the CONFIG_ACPI #ifdef around it that is not necessary any more. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com> Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.