[PATCH v6 3/3] cpufreq/amd-pstate: Cache the firmware programmed EPP value

[Marco Scardovi]

At CPU EPP initialization, the private cpudata structure is allocated via
kzalloc, which means cpudata->cppc_req_cached is initialized to 0. This
makes the default cached EPP value 0 (AMD_CPPC_EPP_PERFORMANCE).

When initializing a system that defaults to performance EPP, the driver
attempts to configure the EPP via amd_pstate_set_epp(). Because the
requested EPP (0) matches the uninitialized cached value (0), the cache
guard check triggers, and the driver skips writing to the hardware.

Cache the firmware-programmed default EPP value in cppc_req_cached during
CPU EPP initialization. This saves on an unnecessary reprogramming later
when the EPP is first set.

Assisted-by: Antigravity:gemini-3.5-flash
Reviewed-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Signed-off-by: Marco Scardovi <scardracs@xxxxxxxxxxx>
---
 drivers/cpufreq/amd-pstate.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index c67e02f77059..a30f6fff72a0 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1924,12 +1924,13 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
 
 	policy->boost_supported = READ_ONCE(cpudata->boost_supported);
 
-	/* Fetch the firmware programmed default EPP value */
+	/* Cache the firmware programmed EPP */
 	default_epp = amd_pstate_get_epp(cpudata);
 	if (default_epp < 0) {
 		ret = default_epp;
 		goto free_cpudata1;
 	}
+	FIELD_MODIFY(AMD_CPPC_EPP_PERF_MASK, &cpudata->cppc_req_cached, default_epp);
 
 	/*
 	 * Set the policy to provide a valid fallback value in case
-- 
2.54.0