Re: [PATCH v5 10/11] cpufreq: CPPC: make scaling_min/max_freq read-only when auto_sel enabled

Sumit Gupta
2026-01-08T14:01:23Z

On 26/12/25 08:56, zhenglifeng (A) wrote:
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>
>
> On 2025/12/23 20:13, Sumit Gupta wrote:
>> When autonomous selection (auto_sel) is enabled, the hardware controls
>> performance within min_perf/max_perf register bounds making the
>> scaling_min/max_freq effectively read-only.
>>
>> Enforce this by setting policy limits to min/max_perf bounds in
>> cppc_verify_policy(). Users must use min_perf/max_perf sysfs interfaces
>> to change performance limits in autonomous mode.
>>
>> Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
>> ---
>> drivers/cpufreq/cppc_cpufreq.c | 32 +++++++++++++++++++++++++++++++-
>> 1 file changed, 31 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>> index b1f570d6de34..b3da263c18b0 100644
>> --- a/drivers/cpufreq/cppc_cpufreq.c
>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>> @@ -305,7 +305,37 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
>>
>> static int cppc_verify_policy(struct cpufreq_policy_data *policy)
>> {
>> - cpufreq_verify_within_cpu_limits(policy);
>> + unsigned int min_freq = policy->cpuinfo.min_freq;
>> + unsigned int max_freq = policy->cpuinfo.max_freq;
>> + struct cpufreq_policy *cpu_policy;
>> + struct cppc_cpudata *cpu_data;
>> + struct cppc_perf_caps *caps;
>> +
>> + cpu_policy = cpufreq_cpu_get(policy->cpu);
> Better to use:
>
> struct cpufreq_policy *cpu_policy __free(put_cpufreq_policy) = cpufreq_cpu_get(policy->cpu);

Will use this in v6.

>> + if (!cpu_policy)
>> + return -ENODEV;
>> +
>> + cpu_data = cpu_policy->driver_data;
>> + caps = &cpu_data->perf_caps;
> cpu_policy, cpu_data and cpas are only used in the if branch. Just put them
> in it.

Can move caps inside the if branch.
cpu_policy and cpu_data can't be moved inside because we need
perf_ctrls.auto_sel to evaluate the condition itself.

>> +
>> + if (cpu_data->perf_ctrls.auto_sel) {
>> + u32 min_perf, max_perf;
>> +
>> + /*
>> + * Set policy limits to HW min/max_perf bounds. In autonomous
>> + * mode, scaling_min/max_freq is effectively read-only.
>> + */
>> + min_perf = cpu_data->perf_ctrls.min_perf ?:
>> + caps->lowest_nonlinear_perf;
>> + max_perf = cpu_data->perf_ctrls.max_perf ?: caps->nominal_perf;
>> +
>> + policy->min = cppc_perf_to_khz(caps, min_perf);
>> + policy->max = cppc_perf_to_khz(caps, max_perf);
>> + } else {
>> + cpufreq_verify_within_limits(policy, min_freq, max_freq);
> Why not still using cpufreq_verify_within_cpu_limits()?

Will change to use it in v6.

Thank you,
Sumit Gupta

>> + }
>> +
>> + cpufreq_cpu_put(cpu_policy);
>> return 0;
>> }
>>