Re: [PATCH v5 09/11] cpufreq: CPPC: sync policy limits when toggling auto_select

[Sumit Gupta <sumitg@nvidia.com>]

On 26/12/25 08:25, zhenglifeng (A) wrote:
> External email: Use caution opening links or attachments
>
>
> On 2025/12/23 20:13, Sumit Gupta wrote:
>> When CPPC autonomous selection (auto_select) is enabled or disabled,
>> the policy min/max frequency limits should be updated appropriately to
>> reflect the new operating mode.
>>
>> Currently, toggling auto_select only changes the hardware register but
>> doesn't update the cpufreq policy constraints, which can lead to
>> inconsistent behavior between the hardware state and the policy limits
>> visible to userspace.
>>
>> Add cppc_cpufreq_update_autosel_config() function to handle the
>> auto_select toggle by syncing min/max_perf values with policy
>> constraints. When enabling auto_sel, restore preserved min/max_perf
>> values to policy limits. When disabling, reset policy to defaults
>> while preserving hardware register values for later use.
>>
>> Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
>> ---
>>   drivers/cpufreq/cppc_cpufreq.c | 112 +++++++++++++++++++++++++++------
>>   1 file changed, 92 insertions(+), 20 deletions(-)
>>
>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>> index 0202c7b823e6..b1f570d6de34 100644
>> --- a/drivers/cpufreq/cppc_cpufreq.c
>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>> @@ -544,14 +544,20 @@ static void populate_efficiency_class(void)
>>    * cppc_cpufreq_set_mperf_limit - Set min/max performance limit
>>    * @policy: cpufreq policy
>>    * @val: performance value to set
>> + * @update_reg: whether to update hardware register
>>    * @update_policy: whether to update policy constraints
>>    * @is_min: true for min_perf, false for max_perf
>>    *
>> + * When @update_reg is true, writes to HW registers and preserves values.
>>    * When @update_policy is true, updates cpufreq policy frequency limits.
>> + *
>> + * @update_reg is false when disabling auto_sel to preserve HW values.
>> + * The preserved value is used on next enabling of the autonomous mode.
>>    * @update_policy is false during cpu_init when policy isn't fully set up.
>>    */
>>   static int cppc_cpufreq_set_mperf_limit(struct cpufreq_policy *policy, u64 val,
>> -                                     bool update_policy, bool is_min)
>> +                                     bool update_reg, bool update_policy,
>> +                                     bool is_min)
>>   {
>>        struct cppc_cpudata *cpu_data = policy->driver_data;
>>        struct cppc_perf_caps *caps = &cpu_data->perf_caps;
>> @@ -563,19 +569,22 @@ static int cppc_cpufreq_set_mperf_limit(struct cpufreq_policy *policy, u64 val,
>>
>>        perf = clamp(val, caps->lowest_perf, caps->highest_perf);
>>
>> -     ret = is_min ? cppc_set_min_perf(cpu, perf) :
>> -                    cppc_set_max_perf(cpu, perf);
>> -     if (ret) {
>> -             if (ret != -EOPNOTSUPP)
>> -                     pr_warn("Failed to set %s_perf (%llu) on CPU%d (%d)\n",
>> -                             is_min ? "min" : "max", (u64)perf, cpu, ret);
>> -             return ret;
>> -     }
>> +     if (update_reg) {
>> +             ret = is_min ? cppc_set_min_perf(cpu, perf) :
>> +                            cppc_set_max_perf(cpu, perf);
>> +             if (ret) {
>> +                     if (ret != -EOPNOTSUPP)
>> +                             pr_warn("CPU%d: set %s_perf=%llu failed (%d)\n",
>> +                                     cpu, is_min ? "min" : "max",
>> +                                     (u64)perf, ret);
>> +                     return ret;
>> +             }
>>
>> -     if (is_min)
>> -             cpu_data->perf_ctrls.min_perf = perf;
>> -     else
>> -             cpu_data->perf_ctrls.max_perf = perf;
>> +             if (is_min)
>> +                     cpu_data->perf_ctrls.min_perf = perf;
>> +             else
>> +                     cpu_data->perf_ctrls.max_perf = perf;
>> +     }
>>
>>        if (update_policy) {
>>                freq = cppc_perf_to_khz(caps, perf);
>> @@ -592,11 +601,74 @@ static int cppc_cpufreq_set_mperf_limit(struct cpufreq_policy *policy, u64 val,
>>        return 0;
>>   }
>>
>> -#define cppc_cpufreq_set_min_perf(policy, val, update_policy) \
>> -     cppc_cpufreq_set_mperf_limit(policy, val, update_policy, true)
>> +#define cppc_cpufreq_set_min_perf(policy, val, update_reg, update_policy)     \
>> +     cppc_cpufreq_set_mperf_limit(policy, val, update_reg, update_policy,  \
>> +                                  true)
>> +
>> +#define cppc_cpufreq_set_max_perf(policy, val, update_reg, update_policy)     \
>> +     cppc_cpufreq_set_mperf_limit(policy, val, update_reg, update_policy,  \
>> +                                  false)
>> +
>> +/**
>> + * cppc_cpufreq_update_autosel_config - Update autonomous selection config
>> + * @policy: cpufreq policy
>> + * @is_auto_sel: enable/disable autonomous selection
>> + *
>> + * Return: 0 on success, negative error code on failure
>> + */
>> +static int cppc_cpufreq_update_autosel_config(struct cpufreq_policy *policy,
>> +                                           bool is_auto_sel)
>> +{
>> +     struct cppc_cpudata *cpu_data = policy->driver_data;
>> +     struct cppc_perf_caps *caps = &cpu_data->perf_caps;
>> +     u64 min_perf = caps->lowest_nonlinear_perf;
>> +     u64 max_perf = caps->nominal_perf;
>> +     unsigned int cpu = policy->cpu;
>> +     bool update_reg = is_auto_sel;
>> +     bool update_policy = true;
>> +     int ret;
>> +
>> +     guard(mutex)(&cppc_cpufreq_update_autosel_config_lock);
>> +
>> +     if (is_auto_sel) {
>> +             /* Use preserved values if available, else use defaults */
>> +             if (cpu_data->perf_ctrls.min_perf)
>> +                     min_perf = cpu_data->perf_ctrls.min_perf;
>> +             if (cpu_data->perf_ctrls.max_perf)
>> +                     max_perf = cpu_data->perf_ctrls.max_perf;
>> +     }
> So if !is_auto_sel, min_perf and max_perf reg will be set to
> lowest_nonlinear_perf and nominal_perf, but perf_ctrls.min_perf and
> perf_ctrls.max_perf remain the old value. A little bit strange I think. And
> when this happen, min_freq_req and max_freq_req will retain the value last
> set by the users through min_perf and max_perf. It's that alright?

When disabling: Reset policy to defaults for normal governor control,
but preserve HW min/max_perf values and cached values for when
auto_sel is re-enabled.
When enabling: Restore policy to preserved min/max_perf values.

>> +
>> +     /*
>> +      * Set min/max performance and update policy constraints.
>> +      *   When enabling: update both HW registers and policy.
>> +      *   When disabling: update policy only, preserve HW registers.
>> +      * Continue even if min/max are not supported, as EPP and autosel
>> +      * might still be supported.
>> +      */
>> +     ret = cppc_cpufreq_set_min_perf(policy, min_perf, update_reg,
>> +                                     update_policy);
>> +     if (ret && ret != -EOPNOTSUPP)
>> +             return ret;
>> +
>> +     ret = cppc_cpufreq_set_max_perf(policy, max_perf, update_reg,
>> +                                     update_policy);
>> +     if (ret && ret != -EOPNOTSUPP)
>> +             return ret;
>> +
>> +     /* Update auto_sel register */
>> +     ret = cppc_set_auto_sel(cpu, is_auto_sel);
>> +     if (ret && ret != -EOPNOTSUPP) {
>> +             pr_warn("Failed to set auto_sel=%d for CPU%d (%d)\n",
>> +                     is_auto_sel, cpu, ret);
>> +             return ret;
>> +     }
>> +     if (!ret)
>> +             cpu_data->perf_ctrls.auto_sel = is_auto_sel;
>> +
>> +     return 0;
> Better to return ret.

Here, return 0 is intentional.
If cppc_set_auto_sel() returns -EOPNOTSUPP, we still consider the
function successful since auto_sel is an optional register.

>> +}
>> +
>>
>> -#define cppc_cpufreq_set_max_perf(policy, val, update_policy) \
>> -     cppc_cpufreq_set_mperf_limit(policy, val, update_policy, false)
>>   static struct cppc_cpudata *cppc_cpufreq_get_cpu_data(unsigned int cpu)
>>   {
>>        struct cppc_cpudata *cpu_data;
>> @@ -889,7 +961,7 @@ static ssize_t store_auto_select(struct cpufreq_policy *policy,
>>        if (ret)
>>                return ret;
> Since you already store auto_sel value in perf_ctrls, We can compare the
> new value with perf_ctrls.auto_sel here, and just return if they are the
> same.

Will add in v6.

Thank you,
Sumit Gupta

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