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cpufreq/amd-pstate: Cache the firmware programmed EPP value

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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@amd.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Marco Scardovi <scardracs@disroot.org>
Link: https://lore.kernel.org/r/20260609073042.81275-4-scardracs@disroot.org
Signed-off-by: Mario Limonciello <superm1@kernel.org>
This commit is contained in:
Marco Scardovi
2026-06-09 09:29:05 +02:00
committed by Mario Limonciello
parent 9dfd13f80c
commit d0f4c1c8cb
1 changed files with 2 additions and 1 deletions
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3
drivers/cpufreq/amd-pstate.c
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@@ -1922,12 +1922,13 @@ 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