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

zhenglifeng (A)
2025-12-26T02:55:56Z

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?

> +
> + /*
> + * 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.

> +}
> +
>
> -#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.

>
> - ret = cppc_set_auto_sel(policy->cpu, val);
> + ret = cppc_cpufreq_update_autosel_config(policy, val);
> if (ret)
> return ret;
>
> @@ -1005,7 +1077,7 @@ static ssize_t store_min_perf(struct cpufreq_policy *policy, const char *buf,
> perf = cppc_khz_to_perf(&cpu_data->perf_caps, freq_khz);
>
> guard(mutex)(&cppc_cpufreq_update_autosel_config_lock);
> - ret = cppc_cpufreq_set_min_perf(policy, perf,
> + ret = cppc_cpufreq_set_min_perf(policy, perf, true,
> cpu_data->perf_ctrls.auto_sel);
> if (ret)
> return ret;
> @@ -1063,7 +1135,7 @@ static ssize_t store_max_perf(struct cpufreq_policy *policy, const char *buf,
> perf = cppc_khz_to_perf(&cpu_data->perf_caps, freq_khz);
>
> guard(mutex)(&cppc_cpufreq_update_autosel_config_lock);
> - ret = cppc_cpufreq_set_max_perf(policy, perf,
> + ret = cppc_cpufreq_set_max_perf(policy, perf, true,
> cpu_data->perf_ctrls.auto_sel);
> if (ret)
> return ret;