6.6-stable review patch. If anyone has any objections, please let me know.
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From: René Rebe rene@exactco.de
[ Upstream commit 17e7972979e147cc51d4a165e6b6b0f93273ca68 ]
On all AMD AM4 systems I have seen, e.g ASUS X470-i, Pro WS X570 Ace and equivalent Gigabyte, amd-pstate does not initialize when the x2apic is enabled in the BIOS. Kernel debug messages include:
[ 0.315438] acpi LNXCPU:00: Failed to get CPU physical ID. [ 0.354756] ACPI CPPC: No CPC descriptor for CPU:0 [ 0.714951] amd_pstate: the _CPC object is not present in SBIOS or ACPI disabled
I tracked this down to map_x2apic_id() checking device_declaration passed in via the type argument of acpi_get_phys_id() via map_madt_entry() while map_lapic_id() does not.
It appears these BIOSes use Processor statements for declaring the CPUs in the ACPI namespace instead of processor device objects (which should have been used). CPU declarations via Processor statements were deprecated in ACPI 6.0 that was released 10 years ago. They should not be used any more in any contemporary platform firmware.
I tried to contact Asus support multiple times, but never received a reply nor did any BIOS update ever change this.
Fix amd-pstate w/ x2apic on am4 by allowing map_x2apic_id() to work with CPUs declared via Processor statements for IDs less than 255, which is consistent with ACPI 5.0 that still allowed Processor statements to be used for declaring CPUs.
Fixes: 7237d3de78ff ("x86, ACPI: add support for x2apic ACPI extensions") Signed-off-by: René Rebe rene@exactco.de [ rjw: Changelog edits ] Link: https://patch.msgid.link/20251126.165513.1373131139292726554.rene@exactco.de Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/acpi/processor_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c index 7dd6dbaa98c34..dea60d694343f 100644 --- a/drivers/acpi/processor_core.c +++ b/drivers/acpi/processor_core.c @@ -54,7 +54,7 @@ static int map_x2apic_id(struct acpi_subtable_header *entry, if (!(apic->lapic_flags & ACPI_MADT_ENABLED)) return -ENODEV;
- if (device_declaration && (apic->uid == acpi_id)) { + if (apic->uid == acpi_id && (device_declaration || acpi_id < 255)) { *apic_id = apic->local_apic_id; return 0; }