Re: [PATCH v5 03/11] ACPI: CPPC: Add cppc_get_perf() API to read performance controls

[Sumit Gupta <sumitg@nvidia.com>]

On 25/12/25 13:51, zhenglifeng (A) wrote:
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>
> On 2025/12/23 20:12, Sumit Gupta wrote:
>> Add cppc_get_perf() function to read values of performance control
>> registers including desired_perf, min_perf, max_perf, energy_perf,
>> and auto_sel.
>>
>> This provides a read interface to complement the existing
>> cppc_set_perf() write interface for performance control registers.
>>
>> Note that auto_sel is read by cppc_get_perf() but not written by
>> cppc_set_perf() to avoid unintended mode changes during performance
>> updates. It can be updated with existing dedicated cppc_set_auto_sel()
>> API.
>>
>> Also call cppc_get_perf() in cppc_cpufreq_get_cpu_data() to initialize
>> perf_ctrls with current hardware register values during cpufreq
>> initialization for each CPU policy.
>>
>> Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
>> ---
>>   drivers/acpi/cppc_acpi.c       | 79 ++++++++++++++++++++++++++++++++++
>>   drivers/cpufreq/cppc_cpufreq.c |  6 +++
>>   include/acpi/cppc_acpi.h       |  5 +++
>>   3 files changed, 90 insertions(+)
>>
>> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
>> index e66e20d1f31b..a4e89fe6aab5 100644
>> --- a/drivers/acpi/cppc_acpi.c
>> +++ b/drivers/acpi/cppc_acpi.c
>> @@ -1732,6 +1732,85 @@ int cppc_set_enable(int cpu, bool enable)
>>        return cppc_set_reg_val(cpu, ENABLE, enable);
>>   }
>>   EXPORT_SYMBOL_GPL(cppc_set_enable);
>> +/**
>> + * cppc_get_perf - Get a CPU's performance controls.
>> + * @cpu: CPU for which to get performance controls.
>> + * @perf_ctrls: ptr to cppc_perf_ctrls. See cppc_acpi.h
>> + *
>> + * Return: 0 for success with perf_ctrls, -ERRNO otherwise.
>> + */
>> +int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>> +{
>> +     struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
>> +     struct cpc_register_resource *desired_perf_reg,
>> +                                  *min_perf_reg, *max_perf_reg,
>> +                                  *energy_perf_reg, *auto_sel_reg;
>> +     u64 desired_perf = 0, min = 0, max = 0, energy_perf = 0, auto_sel = 0;
>> +     int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
>> +     struct cppc_pcc_data *pcc_ss_data = NULL;
>> +     int ret = 0, regs_in_pcc = 0;
>> +
>> +     if (!cpc_desc) {
>> +             pr_debug("No CPC descriptor for CPU:%d\n", cpu);
>> +             return -ENODEV;
>> +     }
>> +
>> +     if (!perf_ctrls) {
>> +             pr_debug("Invalid perf_ctrls pointer\n");
>> +             return -EINVAL;
>> +     }
>> +
>> +     desired_perf_reg = &cpc_desc->cpc_regs[DESIRED_PERF];
>> +     min_perf_reg = &cpc_desc->cpc_regs[MIN_PERF];
>> +     max_perf_reg = &cpc_desc->cpc_regs[MAX_PERF];
>> +     energy_perf_reg = &cpc_desc->cpc_regs[ENERGY_PERF];
>> +     auto_sel_reg = &cpc_desc->cpc_regs[AUTO_SEL_ENABLE];
>> +
>> +     /* Are any of the regs PCC ?*/
>> +     if (CPC_IN_PCC(desired_perf_reg) || CPC_IN_PCC(min_perf_reg) ||
>> +         CPC_IN_PCC(max_perf_reg) || CPC_IN_PCC(energy_perf_reg) ||
>> +         CPC_IN_PCC(auto_sel_reg)) {
>> +             if (pcc_ss_id < 0) {
>> +                     pr_debug("Invalid pcc_ss_id for CPU:%d\n", cpu);
>> +                     return -ENODEV;
>> +             }
>> +             pcc_ss_data = pcc_data[pcc_ss_id];
>> +             regs_in_pcc = 1;
>> +             down_write(&pcc_ss_data->pcc_lock);
>> +             /* Ring doorbell once to update PCC subspace */
>> +             if (send_pcc_cmd(pcc_ss_id, CMD_READ) < 0) {
>> +                     ret = -EIO;
>> +                     goto out_err;
>> +             }
>> +     }
>> +
>> +     /* Read optional elements if present */
>> +     if (CPC_SUPPORTED(max_perf_reg))
>> +             cpc_read(cpu, max_perf_reg, &max);
>> +     perf_ctrls->max_perf = max;
>> +
>> +     if (CPC_SUPPORTED(min_perf_reg))
>> +             cpc_read(cpu, min_perf_reg, &min);
>> +     perf_ctrls->min_perf = min;
>> +
>> +     if (CPC_SUPPORTED(desired_perf_reg))
>> +             cpc_read(cpu, desired_perf_reg, &desired_perf);
>> +     perf_ctrls->desired_perf = desired_perf;
>> +
>> +     if (CPC_SUPPORTED(energy_perf_reg))
>> +             cpc_read(cpu, energy_perf_reg, &energy_perf);
>> +     perf_ctrls->energy_perf = energy_perf;
>> +
>> +     if (CPC_SUPPORTED(auto_sel_reg))
>> +             cpc_read(cpu, auto_sel_reg, &auto_sel);
>> +     perf_ctrls->auto_sel = (bool)auto_sel;
>> +
>> +out_err:
>> +     if (regs_in_pcc)
>> +             up_write(&pcc_ss_data->pcc_lock);
>> +     return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(cppc_get_perf);
>>
>>   /**
>>    * cppc_set_perf - Set a CPU's performance controls.
>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>> index 7c26ce554e29..a87e7bb2e2f1 100644
>> --- a/drivers/cpufreq/cppc_cpufreq.c
>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>> @@ -562,6 +562,12 @@ static struct cppc_cpudata *cppc_cpufreq_get_cpu_data(unsigned int cpu)
>>                goto free_mask;
>>        }
>>
>> +     ret = cppc_get_perf(cpu, &cpu_data->perf_ctrls);
>> +     if (ret) {
>> +             pr_debug("Err reading CPU%d perf ctrls: ret:%d\n", cpu, ret);
>> +             goto free_mask;
>> +     }
>> +
> If you really need energy_perf and auto_sel in cpu_data->perf_ctrls, they
> should be updated whenever they are set, i.e., in store_auto_select() and
> store_energy_performance_preference_val().

store_auto_select() is updating auto_sel in patch 09 of v5.
Didn't update energy_perf as not using the cached value currently.
Will move auto_sel update to this patch for clarity and also update
energy_perf for consistency if value is used in future.

Thank you,
Sumit Gupta

>>        return cpu_data;
>>
>>   free_mask:
>> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
>> index a090b010f5f1..12a1dc31bf2a 100644
>> --- a/include/acpi/cppc_acpi.h
>> +++ b/include/acpi/cppc_acpi.h
>> @@ -150,6 +150,7 @@ extern int cppc_get_desired_perf(int cpunum, u64 *desired_perf);
>>   extern int cppc_get_nominal_perf(int cpunum, u64 *nominal_perf);
>>   extern int cppc_get_highest_perf(int cpunum, u64 *highest_perf);
>>   extern int cppc_get_perf_ctrs(int cpu, struct cppc_perf_fb_ctrs *perf_fb_ctrs);
>> +extern int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls);
>>   extern int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls);
>>   extern int cppc_set_enable(int cpu, bool enable);
>>   extern int cppc_get_perf_caps(int cpu, struct cppc_perf_caps *caps);
>> @@ -191,6 +192,10 @@ static inline int cppc_get_perf_ctrs(int cpu, struct cppc_perf_fb_ctrs *perf_fb_
>>   {
>>        return -EOPNOTSUPP;
>>   }
>> +static inline int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>> +{
>> +     return -EOPNOTSUPP;
>> +}
>>   static inline int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>>   {
>>        return -EOPNOTSUPP;