Re: [PATCH v3] cpufreq/amd-pstate: Cache the max frequency in cpudata

Gautham R. Shenoy
2026-03-31T09:12:38Z

Hello Mario,

On Thu, Mar 26, 2026 at 02:36:20PM -0500, Mario Limonciello wrote:
> From: "Mario Limonciello (AMD)" <superm1@kernel.org>
>
> The value of maximum frequency is fixed and never changes. Doing
> calculations every time based off of perf is unnecessary.
>
> Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>

This one looks good to me. Thanks for fixing this.

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>

--
Thanks and Regards
gautham.

> ---
> v3:
> * rebase on Gautham's CPPC perf priority series
> * add kdoc
> ---
> drivers/cpufreq/amd-pstate.c | 27 +++++++++------------------
> drivers/cpufreq/amd-pstate.h | 2 ++
> 2 files changed, 11 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index ed9fd4155a256..f207252eb5f5f 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -826,15 +826,13 @@ static void amd_pstate_adjust_perf(unsigned int cpu,
> static int amd_pstate_cpu_boost_update(struct cpufreq_policy *policy, bool on)
> {
> struct amd_cpudata *cpudata = policy->driver_data;
> - union perf_cached perf = READ_ONCE(cpudata->perf);
> - u32 nominal_freq, max_freq;
> + u32 nominal_freq;
> int ret = 0;
>
> nominal_freq = READ_ONCE(cpudata->nominal_freq);
> - max_freq = perf_to_freq(perf, cpudata->nominal_freq, perf.highest_perf);
>
> if (on)
> - policy->cpuinfo.max_freq = max_freq;
> + policy->cpuinfo.max_freq = cpudata->max_freq;
> else if (policy->cpuinfo.max_freq > nominal_freq)
> policy->cpuinfo.max_freq = nominal_freq;
>
> @@ -1021,13 +1019,15 @@ static int amd_pstate_init_freq(struct amd_cpudata *cpudata)
>
> WRITE_ONCE(cpudata->nominal_freq, nominal_freq);
>
> + /* max_freq is calculated according to (nominal_freq * highest_perf)/nominal_perf */
> max_freq = perf_to_freq(perf, nominal_freq, perf.highest_perf);
> + WRITE_ONCE(cpudata->max_freq, max_freq);
> +
> lowest_nonlinear_freq = perf_to_freq(perf, nominal_freq, perf.lowest_nonlinear_perf);
> WRITE_ONCE(cpudata->lowest_nonlinear_freq, lowest_nonlinear_freq);
>
> /**
> * Below values need to be initialized correctly, otherwise driver will fail to load
> - * max_freq is calculated according to (nominal_freq * highest_perf)/nominal_perf
> * lowest_nonlinear_freq is a value between [min_freq, nominal_freq]
> * Check _CPC in ACPI table objects if any values are incorrect
> */
> @@ -1090,9 +1090,7 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
> policy->cpuinfo.min_freq = policy->min = perf_to_freq(perf,
> cpudata->nominal_freq,
> perf.lowest_perf);
> - policy->cpuinfo.max_freq = policy->max = perf_to_freq(perf,
> - cpudata->nominal_freq,
> - perf.highest_perf);
> + policy->cpuinfo.max_freq = policy->max = cpudata->max_freq;
>
> policy->driver_data = cpudata;
> ret = amd_pstate_cppc_enable(policy);
> @@ -1167,14 +1165,9 @@ static void amd_pstate_cpu_exit(struct cpufreq_policy *policy)
> static ssize_t show_amd_pstate_max_freq(struct cpufreq_policy *policy,
> char *buf)
> {
> - struct amd_cpudata *cpudata;
> - union perf_cached perf;
> -
> - cpudata = policy->driver_data;
> - perf = READ_ONCE(cpudata->perf);
> + struct amd_cpudata *cpudata = policy->driver_data;
>
> - return sysfs_emit(buf, "%u\n",
> - perf_to_freq(perf, cpudata->nominal_freq, perf.highest_perf));
> + return sysfs_emit(buf, "%u\n", cpudata->max_freq);
> }
>
> static ssize_t show_amd_pstate_lowest_nonlinear_freq(struct cpufreq_policy *policy,
> @@ -1702,9 +1695,7 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
> policy->cpuinfo.min_freq = policy->min = perf_to_freq(perf,
> cpudata->nominal_freq,
> perf.lowest_perf);
> - policy->cpuinfo.max_freq = policy->max = perf_to_freq(perf,
> - cpudata->nominal_freq,
> - perf.highest_perf);
> + policy->cpuinfo.max_freq = policy->max = cpudata->max_freq;
> policy->driver_data = cpudata;
>
> ret = amd_pstate_cppc_enable(policy);
> diff --git a/drivers/cpufreq/amd-pstate.h b/drivers/cpufreq/amd-pstate.h
> index faead0b19a8a4..32b8b26ce388f 100644
> --- a/drivers/cpufreq/amd-pstate.h
> +++ b/drivers/cpufreq/amd-pstate.h
> @@ -73,6 +73,7 @@ struct amd_aperf_mperf {
> * @min_limit_freq: Cached value of policy->min (in khz)
> * @max_limit_freq: Cached value of policy->max (in khz)
> * @nominal_freq: the frequency (in khz) that mapped to nominal_perf
> + * @max_freq: in ideal conditions the maximum frequency (in khz) possible frequency
> * @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
> @@ -103,6 +104,7 @@ struct amd_cpudata {
> u32 min_limit_freq;
> u32 max_limit_freq;
> u32 nominal_freq;
> + u32 max_freq;
> u32 lowest_nonlinear_freq;
> u32 floor_freq;
>
> --
> 2.53.0
>