ACPI: CPPC: Move reference performance to capabilities

Currently, the `Reference Performance` register is read every time
the CPU frequency is sampled in `cppc_get_perf_ctrs()`. This function
is on the hot path of the cppc_cpufreq driver.

Reference Performance indicates the performance level that corresponds
to the Reference Counter incrementing and is not expected to change
dynamically during runtime (unlike the Delivered and Reference counters).

Reading this register in the hot path incurs unnecessary overhead,
particularly on platforms where CPC registers are located in the PCC
(Platform Communication Channel) subspace. This patch moves
`reference_perf` from the dynamic feedback counters structure
(`cppc_perf_fb_ctrs`) to the static capabilities structure
(`cppc_perf_caps`).

Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
[ rjw: Changelog adjustment ]
Link: https://patch.msgid.link/20260213100935.19111-1-zhangpengjie2@huawei.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
index f7afa20b8ad9..d8e405becdc3 100644
--- a/include/acpi/cppc_acpi.h
+++ b/include/acpi/cppc_acpi.h
@@ -121,6 +121,7 @@ struct cppc_perf_caps {
 	u32 guaranteed_perf;
 	u32 highest_perf;
 	u32 nominal_perf;
+	u32 reference_perf;
 	u32 lowest_perf;
 	u32 lowest_nonlinear_perf;
 	u32 lowest_freq;
@@ -138,7 +139,6 @@ struct cppc_perf_ctrls {
 struct cppc_perf_fb_ctrs {
 	u64 reference;
 	u64 delivered;
-	u64 reference_perf;
 	u64 wraparound_time;
 };