[PATCH v5 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.

On shared memory systems, skipping the EPP write consequently skips
enabling auto_sel, leaving the CPU in non-autonomous mode.

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
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 7982f9d0f634..d1ed53a0f119 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