Commit fbd74d16 authored by Mario Limonciello's avatar Mario Limonciello Committed by Rafael J. Wysocki
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ACPI: CPPC: Fix enabling CPPC on AMD systems with shared memory 

When commit 72f2ecb7 ("ACPI: bus: Set CPPC _OSC bits for all
and when CPPC_LIB is supported") was introduced, we found collateral
damage that a number of AMD systems that supported CPPC but
didn't advertise support in _OSC stopped having a functional
amd-pstate driver. The _OSC was only enforced on Intel systems at that
time.

This was fixed for the MSR based designs by commit 8b356e53
("ACPI: CPPC: Don't require _OSC if X86_FEATURE_CPPC is supported")
but some shared memory based designs also support CPPC but haven't
advertised support in the _OSC.  Add support for those designs as well by
hardcoding the list of systems.

Fixes: 72f2ecb7 ("ACPI: bus: Set CPPC _OSC bits for all and when CPPC_LIB is supported")
Fixes: 8b356e53 ("ACPI: CPPC: Don't require _OSC if X86_FEATURE_CPPC is supported")
Link: https://lore.kernel.org/all/3559249.JlDtxWtqDm@natalenko.name/


Cc: 5.18+ <stable@vger.kernel.org> # 5.18+
Reported-and-tested-by: default avatarOleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: default avatarMario Limonciello <mario.limonciello@amd.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 32346491

arch/x86/kernel/acpi/cppc.c

+6 −0
Original line number Diff line number Diff line
@@ -16,6 +16,12 @@ bool cpc_supported_by_cpu(void) 
	switch (boot_cpu_data.x86_vendor) {

	case X86_VENDOR_AMD:

	case X86_VENDOR_HYGON:

		if (boot_cpu_data.x86 == 0x19 && ((boot_cpu_data.x86_model <= 0x0f) ||

		    (boot_cpu_data.x86_model >= 0x20 && boot_cpu_data.x86_model <= 0x2f)))

			return true;

		else if (boot_cpu_data.x86 == 0x17 &&

			 boot_cpu_data.x86_model >= 0x70 && boot_cpu_data.x86_model <= 0x7f)

			return true;

		return boot_cpu_has(X86_FEATURE_CPPC);

	}

	return false;