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superm1rafaeljw
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ACPI: CPPC: Fix enabling CPPC on AMD systems with shared memory
When commit 72f2ecb ("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 8b356e5 ("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: 72f2ecb ("ACPI: bus: Set CPPC _OSC bits for all and when CPPC_LIB is supported") Fixes: 8b356e5 ("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: Oleksandr Natalenko <oleksandr@natalenko.name> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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arch/x86/kernel/acpi/cppc.c

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@@ -16,6 +16,12 @@ bool cpc_supported_by_cpu(void)
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switch (boot_cpu_data.x86_vendor) {
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case X86_VENDOR_AMD:
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case X86_VENDOR_HYGON:
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if (boot_cpu_data.x86 == 0x19 && ((boot_cpu_data.x86_model <= 0x0f) ||
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(boot_cpu_data.x86_model >= 0x20 && boot_cpu_data.x86_model <= 0x2f)))
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return true;
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else if (boot_cpu_data.x86 == 0x17 &&
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boot_cpu_data.x86_model >= 0x70 && boot_cpu_data.x86_model <= 0x7f)
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return true;
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return boot_cpu_has(X86_FEATURE_CPPC);
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}
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return false;

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