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Message-ID: <011bebf3-ebd4-4245-88ce-5e826faae66f@arm.com>
Date: Thu, 27 Nov 2025 15:53:43 +0100
From: Pierre Gondois <pierre.gondois@....com>
To: Sumit Gupta <sumitg@...dia.com>
Cc: linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
acpica-devel@...ts.linux.dev, linux-doc@...r.kernel.org,
linux-acpi@...r.kernel.org, linux-pm@...r.kernel.org,
zhanjie9@...ilicon.com, ionela.voinescu@....com, perry.yuan@....com,
mario.limonciello@....com, gautham.shenoy@....com, ray.huang@....com,
rdunlap@...radead.org, zhenglifeng1@...wei.com, lenb@...nel.org,
robert.moore@...el.com, rafael@...nel.org, viresh.kumar@...aro.org,
treding@...dia.com, jonathanh@...dia.com, vsethi@...dia.com,
ksitaraman@...dia.com, sanjayc@...dia.com, nhartman@...dia.com,
bbasu@...dia.com, corbet@....net
Subject: Re: [PATCH v4 2/8] ACPI: CPPC: Add cppc_get_perf() API to read
performance controls
Hello Sumit,
Sorry for the late review.
I think it would be nice to split the patchset in 2 as handling the
auto_sel and
min/max_perf values in the cppc_cpufreq driver might lead to more
discussion.
I.e. the ACPI: CPPC: XXX patches should be straightforward to upstream.
This is just a personal opinion, feel free to ignore it.
On 11/5/25 12:38, Sumit Gupta wrote:
> Add cppc_get_perf() function to read values of performance control
> registers including desired_perf, min_perf, max_perf, and energy_perf.
>
> This provides a read interface to complement the existing cppc_set_perf()
> write interface for performance control registers.
>
> Signed-off-by: Sumit Gupta<sumitg@...dia.com>
> ---
> drivers/acpi/cppc_acpi.c | 73 ++++++++++++++++++++++++++++++++++++++++
> include/acpi/cppc_acpi.h | 5 +++
> 2 files changed, 78 insertions(+)
>
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index ab4651205e8a..05672c30187c 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -1731,6 +1731,79 @@ 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;
> + u64 desired_perf = 0, min = 0, max = 0, energy_perf = 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];
> +
> + /* 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)) {
> + if (pcc_ss_id < 0) {
> + pr_debug("Invalid pcc_ss_id forCPU:%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) {
> + pr_debug("Failed to send PCC command for CPU:%d, ret:%d\n", cpu, ret);
> + 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;
> +
NIT: I think the 'desired_perf_reg' register is mandatory, so the check
could be removed.
> + 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;
> +
> +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/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
> index 13fa81504844..7190afeead8b 100644
> --- a/include/acpi/cppc_acpi.h
> +++ b/include/acpi/cppc_acpi.h
> @@ -151,6 +151,7 @@ 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);
> @@ -192,6 +193,10 @@ 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;
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