ACPI: CPPC: Fix missing PCC check for guaranteed_perf

The current implementation overlooks the 'guaranteed_perf'
register in this check.

If the Guaranteed Performance register is located in the PCC
subspace, the function currently attempts to read it without
acquiring the lock and without sending the CMD_READ doorbell
to the firmware. This can result in reading stale data.

Fixes: 29523f095397 ("ACPI / CPPC: Add support for guaranteed performance")
Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
Cc: 4.20+ <stable@vger.kernel.org> # 4.20+
[ rjw: Subject and changelog edits ]
Link: https://patch.msgid.link/20251210132227.1988380-1-zhangpengjie2@huawei.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 3bdeeee3414e68c4b4752257362afa5c13ad995e..e66e20d1f31b764887f045c5e4a472c2f68bf885 100644 (file)
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1366,7 +1366,8 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
        /* Are any of the regs PCC ?*/
        if (CPC_IN_PCC(highest_reg) || CPC_IN_PCC(lowest_reg) ||
                CPC_IN_PCC(lowest_non_linear_reg) || CPC_IN_PCC(nominal_reg) ||
-               CPC_IN_PCC(low_freq_reg) || CPC_IN_PCC(nom_freq_reg)) {
+               CPC_IN_PCC(low_freq_reg) || CPC_IN_PCC(nom_freq_reg) ||
+               CPC_IN_PCC(guaranteed_reg)) {
                if (pcc_ss_id < 0) {
                        pr_debug("Invalid pcc_ss_id\n");
                        return -ENODEV;