Re: [PATCH v2] cpufreq/amd-pstate: Cache the max frequency in cpudata

[Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>]

On 3/23/2026 12:32 PM, Mario Limonciello (AMD) wrote:
> 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>
> ---
> v2:
>   * Remove unused variable
> ---
>   drivers/cpufreq/amd-pstate.c | 27 +++++++++------------------
>   drivers/cpufreq/amd-pstate.h |  1 +
>   2 files changed, 10 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 5aa9fcd80cf51..9f80f8b23a43f 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -757,15 +757,13 @@ 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;
>   
> @@ -952,13 +950,15 @@ 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
>   	 */
> @@ -1021,9 +1021,7 @@ 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;
>   
>   	ret = amd_pstate_cppc_enable(policy);
>   	if (ret)
> @@ -1090,14 +1088,9 @@ 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,
> @@ -1503,9 +1496,7 @@ 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 cb45fdca27a6c..485ee023d79c5 100644
> --- a/drivers/cpufreq/amd-pstate.h
> +++ b/drivers/cpufreq/amd-pstate.h
> @@ -94,6 +94,7 @@ struct amd_cpudata {
>   	u32	min_limit_freq;
>   	u32	max_limit_freq;
>   	u32	nominal_freq;
> +	u32	max_freq;

Hi Mario,

A minor finding: the new u32 max_freq field is missing a kdoc entry in
struct amd_cpudata.


>   	u32	lowest_nonlinear_freq;
>   
>   	struct amd_aperf_mperf cur;


-- 
Thx and BRs,
Zhongqiu Han