On 1/7/26 3:19 PM, Juan Martinez wrote:
When the CPU frequency policy is set to CPUFREQ_POLICY_PERFORMANCE (which occurs when EPP hint is set to "performance"), the driver incorrectly sets the MinPerf field in CPPC request MSR to nominal_perf instead of lowest_nonlinear_perf.
According to the AMD architectural programmer's manual volume 2 [1], in section "17.6.4.1 CPPC_CAPABILITY_1", lowest_nonlinear_perf represents the most energy efficient performance level (in terms of performance per watt). The MinPerf field should be set to this value even in performance mode to maintain proper power/performance characteristics.
This fixes a regression introduced by commit 0c411b39e4f4c ("amd-pstate: Set min_perf to nominal_perf for active mode performance gov"), which correctly identified that highest_perf was too high but chose nominal_perf as an intermediate value instead of lowest_nonlinear_perf.
The fix changes amd_pstate_update_min_max_limit() to use lowest_nonlinear_perf instead of nominal_perf when the policy is CPUFREQ_POLICY_PERFORMANCE.
[1] https://docs.amd.com/v/u/en-US/24593_3.43 AMD64 Architecture Programmer's Manual Volume 2: System Programming Section 17.6.4.1 CPPC_CAPABILITY_1 (Referenced in commit 5d9a354cf839a)
Fixes: 0c411b39e4f4c ("amd-pstate: Set min_perf to nominal_perf for active mode performance gov") Tested-by: Kaushik Reddy S kaushik.reddys@amd.com Cc: stable@vger.kernel.org Signed-off-by: Juan Martinez juan.martinez@amd.com
I think this change is reasonable, but I'd like to get Gautham's comments as the original author of 0c411b39e4f4c.
drivers/cpufreq/amd-pstate.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c index e4f1933dd7d47..de0bb5b325502 100644 --- a/drivers/cpufreq/amd-pstate.c +++ b/drivers/cpufreq/amd-pstate.c @@ -634,8 +634,8 @@ static void amd_pstate_update_min_max_limit(struct cpufreq_policy *policy) WRITE_ONCE(cpudata->max_limit_freq, policy->max); if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) {
perf.min_limit_perf = min(perf.nominal_perf, perf.max_limit_perf);WRITE_ONCE(cpudata->min_limit_freq, min(cpudata->nominal_freq, cpudata->max_limit_freq));
perf.min_limit_perf = min(perf.lowest_nonlinear_perf, perf.max_limit_perf);WRITE_ONCE(cpudata->min_limit_freq, min(cpudata->lowest_nonlinear_freq, cpudata->max_limit_freq));