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

zhenglifeng (A)
2025-12-25T08:22:06Z

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().

> 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;