tree 936f6a4695607261e81a740ebef3e23d8ecf2d0e
parent 60b6aae072494917807be8366a013a7bc3a18d7b
author Mario Limonciello <mario.limonciello@amd.com> 1645816006 -0600
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1650025121 +0200

ACPI: processor idle: Check for architectural support for LPI

commit eb087f305919ee8169ad65665610313e74260463 upstream.

When `osc_pc_lpi_support_confirmed` is set through `_OSC` and `_LPI` is
populated then the cpuidle driver assumes that LPI is fully functional.

However currently the kernel only provides architectural support for LPI
on ARM.  This leads to high power consumption on X86 platforms that
otherwise try to enable LPI.

So probe whether or not LPI support is implemented before enabling LPI in
the kernel.  This is done by overloading `acpi_processor_ffh_lpi_probe` to
check whether it returns `-EOPNOTSUPP`. It also means that all future
implementations of `acpi_processor_ffh_lpi_probe` will need to follow
these semantics as well.

Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>