Re: [PATCH v2 6/9] amd-pstate: Add sysfs support for floor_freq and floor_count

[Mario Limonciello (AMD) (kernel.org)]

On 3/11/2026 9:01 AM, Gautham R. Shenoy wrote:
> When Floor Performance feature is supported by the platform, expose
> two sysfs files:
>
>     * amd_pstate_floor_freq to allow userspace to request the floor
>       frequency for each CPU.
>
>     * amd_pstate_floor_count which advertises the number of distinct
>       levels of floor frequencies supported on this platform.
>
> Signed-off-by: Gautham R. Shenoy <gautham.shenoy@xxxxxxx>

One nit below.

Reviewed-by: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>
> ---
>   drivers/cpufreq/amd-pstate.c | 50 ++++++++++++++++++++++++++++++++++++
>   drivers/cpufreq/amd-pstate.h |  2 ++
>   2 files changed, 52 insertions(+)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 3122ad5af6f47..54b650f3b4e78 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -383,6 +383,8 @@ static int amd_pstate_init_floor_perf(struct cpufreq_policy *policy)
>   			return ret;
>   	}
>   
> +	cpudata->floor_freq = perf_to_freq(cpudata->perf, cpudata->nominal_freq,
> +					   floor_perf);
>   	return 0;
>   }
>   
> @@ -1284,6 +1286,44 @@ static ssize_t show_energy_performance_preference(
>   	return sysfs_emit(buf, "%s\n", energy_perf_strings[preference]);
>   }
>   
> +static ssize_t store_amd_pstate_floor_freq(struct cpufreq_policy *policy,
> +					   const char *buf, size_t count)
> +{
> +	struct amd_cpudata *cpudata = policy->driver_data;
> +	union perf_cached perf = READ_ONCE(cpudata->perf);
> +	unsigned int freq;
> +	u8 floor_perf;
> +	int ret;
> +
> +	ret = kstrtouint(buf, 0, &freq);
> +	if (ret)
> +		return ret;
> +
> +	floor_perf = freq_to_perf(perf, cpudata->nominal_freq, freq);
> +	ret = amd_pstate_set_floor_perf(policy, floor_perf);
> +
> +	if (!ret)
> +		cpudata->floor_freq = freq;
> +
> +	return ret ?: count;
> +}
> +
> +static ssize_t show_amd_pstate_floor_freq(struct cpufreq_policy *policy, char *buf)
> +{
> +	struct amd_cpudata *cpudata = policy->driver_data;
> +
> +	return sysfs_emit(buf, "%u\n", cpudata->floor_freq);
> +}
> +
> +
> +static ssize_t show_amd_pstate_floor_count(struct cpufreq_policy *policy, char *buf)
> +{
> +	struct amd_cpudata *cpudata = policy->driver_data;
> +	u8 count = cpudata->floor_perf_cnt;
> +
> +	return sysfs_emit(buf, "%u\n", count);

just return cpudata->floor_perf_cnt instead of having a local variable.

> +}
> +
>   cpufreq_freq_attr_ro(amd_pstate_max_freq);
>   cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
>   
> @@ -1292,6 +1332,8 @@ cpufreq_freq_attr_ro(amd_pstate_prefcore_ranking);
>   cpufreq_freq_attr_ro(amd_pstate_hw_prefcore);
>   cpufreq_freq_attr_rw(energy_performance_preference);
>   cpufreq_freq_attr_ro(energy_performance_available_preferences);
> +cpufreq_freq_attr_rw(amd_pstate_floor_freq);
> +cpufreq_freq_attr_ro(amd_pstate_floor_count);
>   
>   struct freq_attr_visibility {
>   	struct freq_attr *attr;
> @@ -1316,6 +1358,12 @@ static bool epp_visibility(void)
>   	return cppc_state == AMD_PSTATE_ACTIVE;
>   }
>   
> +/* Determines whether amd_pstate_floor_freq related attributes should be visible */
> +static bool floor_freq_visibility(void)
> +{
> +	return cpu_feature_enabled(X86_FEATURE_CPPC_PERF_PRIO);
> +}
> +
>   static struct freq_attr_visibility amd_pstate_attr_visibility[] = {
>   	{&amd_pstate_max_freq, always_visible},
>   	{&amd_pstate_lowest_nonlinear_freq, always_visible},
> @@ -1324,6 +1372,8 @@ static struct freq_attr_visibility amd_pstate_attr_visibility[] = {
>   	{&amd_pstate_hw_prefcore, prefcore_visibility},
>   	{&energy_performance_preference, epp_visibility},
>   	{&energy_performance_available_preferences, epp_visibility},
> +	{&amd_pstate_floor_freq, floor_freq_visibility},
> +	{&amd_pstate_floor_count, floor_freq_visibility},
>   };
>   
>   static struct freq_attr **get_freq_attrs(void)
> diff --git a/drivers/cpufreq/amd-pstate.h b/drivers/cpufreq/amd-pstate.h
> index 0c587ca200199..ab4caea39f0e8 100644
> --- a/drivers/cpufreq/amd-pstate.h
> +++ b/drivers/cpufreq/amd-pstate.h
> @@ -72,6 +72,7 @@ struct amd_aperf_mperf {
>    * @max_limit_freq: Cached value of policy->max (in khz)
>    * @nominal_freq: the frequency (in khz) that mapped to nominal_perf
>    * @lowest_nonlinear_freq: the frequency (in khz) that mapped to lowest_nonlinear_perf
> + * @floor_freq: Cached value of the user requested floor_freq
>    * @cur: Difference of Aperf/Mperf/tsc count between last and current sample
>    * @prev: Last Aperf/Mperf/tsc count value read from register
>    * @freq: current cpu frequency value (in khz)
> @@ -100,6 +101,7 @@ struct amd_cpudata {
>   	u32	max_limit_freq;
>   	u32	nominal_freq;
>   	u32	lowest_nonlinear_freq;
> +	u32	floor_freq;
>   
>   	struct amd_aperf_mperf cur;
>   	struct amd_aperf_mperf prev;