Re: [RFC PATCH 1/2] cpufreq/amd-pstate: Set min_limit_freq based on bios_min_perf

[Mario Limonciello]

On 7/15/26 02:48, K Prateek Nayak wrote:
> amd_pstate_update_min_max_limit() sets the min_limit_perf to the
> nominal_perf to avoid frequency throttling when the system is idling.
>
> This was found to be an ideal default but is suboptimal for users who
> have profiled their workload at different operating frequencies and have
> configured the optimal idling frequency via bios_min_perf.
>
> Use the bios_min_perf (if configured) as the min_limit_perf when running
> with performance governor. In absence of bios_min_perf, continue using
> nominal_perf as the default min_limit_perf to avoid throttling.
>
> Fixes: 608a76b65288 ("cpufreq/amd-pstate: Add support for the "Requested CPU Min frequency" BIOS option")
> Signed-off-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>

This patch I don't have a concern with.

Reviewed-by: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>
> ---
>   drivers/cpufreq/amd-pstate.c | 21 +++++++++++++++------
>   1 file changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index f8d8288d644f8..a6e43db6efefe 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -702,9 +702,12 @@ 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) {
> +		u8 min_limit_perf = perf.bios_min_perf ?: perf.nominal_perf;
> +		u32 min_limit_freq;
> +
>   		/*
> -		 * For performance policy, set MinPerf to nominal_perf rather than
> -		 * highest_perf or lowest_nonlinear_perf.
> +		 * For performance policy, set MinPerf to nominal_perf / bios_min_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
> @@ -712,11 +715,17 @@ static void amd_pstate_update_min_max_limit(struct cpufreq_policy *policy)
>   		 * 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.
> +		 * nominal_perf therefore provides a balanced default by avoiding
> +		 * throttling while still maintaining enough performance for HPC
> +		 * workloads when bios_min_perf is not available.
> +		 *
> +		 * When bios_min_perf is available, users have profiled their workloads
> +		 * to understand the best idling frequency. Use that instead.
>   		 */
> -		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));
> +		min_limit_freq = perf_to_freq(perf, cpudata->nominal_freq, min_limit_perf);
> +		perf.min_limit_perf = min_limit_perf;
> +
> +		WRITE_ONCE(cpudata->min_limit_freq, min(min_limit_freq, cpudata->max_limit_freq));
>   	} else {
>   		perf.min_limit_perf = freq_to_perf(perf, cpudata->nominal_freq, policy->min);
>   		WRITE_ONCE(cpudata->min_limit_freq, policy->min);