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cpufreq/amd-pstate: Add comment explaining nominal_perf usage for performance policy

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Add comment explaining why nominal_perf is used for MinPerf when the
CPU frequency policy is set to CPUFREQ_POLICY_PERFORMANCE, rather than
using highest_perf or lowest_nonlinear_perf.

Signed-off-by: Juan Martinez <juan.martinez@amd.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
This commit is contained in:
Juan Martinez 2026-01-16 15:45:39 -06:00 committed by Viresh Kumar
parent 8c376f337a
commit 94dbce6c13
1 changed files with 13 additions and 0 deletions
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13
drivers/cpufreq/amd-pstate.c
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@ -636,6 +636,19 @@ 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) {
/*
* For performance policy, set MinPerf to nominal_perf rather than
* highest_perf or lowest_nonlinear_perf.
*
* Per commit 0c411b39e4f4c, using highest_perf was observed
* to cause frequency throttling on power-limited platforms, leading to
* performance regressions. Using lowest_nonlinear_perf would limit
* performance too much for HPC workloads requiring high frequency
* operation and minimal wakeup latency from idle states.
*
* nominal_perf therefore provides a balance by avoiding throttling
* while still maintaining enough performance for HPC workloads.
*/
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));
} else {