[PATCH V7 2/2] cpufreq: scmi: Register for limit change notifications

[Vincent Guittot]

On Thu, 31 Oct 2024 at 14:28, Sibi Sankar <quic_sibis at quicinc.com> wrote:
>
> Register for limit change notifications if supported and use the throttled
> frequency from the notification to apply HW pressure.
>
> Signed-off-by: Sibi Sankar <quic_sibis at quicinc.com>
> Tested-by: Mike Tipton <quic_mdtipton at quicinc.com>
> Reviewed-by: Cristian Marussi <cristian.marussi at arm.com>
> Reviewed-by: Lukasz Luba <lukasz.luba at arm.com>
> ---
>
> v7:
> * Add a new request instead of reusing the max_freq_req [Vincent]
> * Use the non-devm versions of register/unregister of event notifier
>   since we have to remove them when the cpus get removed anyway.
> * Add new patch to fix cleanup path on boost enablement failure.
>
>  drivers/cpufreq/scmi-cpufreq.c | 51 ++++++++++++++++++++++++++++++++++
>  1 file changed, 51 insertions(+)
>
> diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
> index 07d6f9a9b7c8..ff13f7d4b2c9 100644
> --- a/drivers/cpufreq/scmi-cpufreq.c
> +++ b/drivers/cpufreq/scmi-cpufreq.c
> @@ -16,6 +16,7 @@
>  #include <linux/export.h>
>  #include <linux/module.h>
>  #include <linux/pm_opp.h>
> +#include <linux/pm_qos.h>
>  #include <linux/slab.h>
>  #include <linux/scmi_protocol.h>
>  #include <linux/types.h>
> @@ -25,7 +26,10 @@ struct scmi_data {
>         int domain_id;
>         int nr_opp;
>         struct device *cpu_dev;
> +       struct cpufreq_policy *policy;
>         cpumask_var_t opp_shared_cpus;
> +       struct notifier_block limit_notify_nb;
> +       struct freq_qos_request limits_freq_req;
>  };
>
>  static struct scmi_protocol_handle *ph;
> @@ -174,6 +178,25 @@ static struct freq_attr *scmi_cpufreq_hw_attr[] = {
>         NULL,
>  };
>
> +static int scmi_limit_notify_cb(struct notifier_block *nb, unsigned long event, void *data)
> +{
> +       struct scmi_data *priv = container_of(nb, struct scmi_data, limit_notify_nb);
> +       struct scmi_perf_limits_report *limit_notify = data;
> +       struct cpufreq_policy *policy = priv->policy;
> +       unsigned int limit_freq_khz;
> +       int ret;
> +
> +       limit_freq_khz = limit_notify->range_max_freq / HZ_PER_KHZ;
> +
> +       policy->max = clamp(limit_freq_khz, policy->cpuinfo.min_freq, policy->cpuinfo.max_freq);

I don't think that the above is needed or correct, the cpufreq qos
notifier will take care of updating policy->max with handle_update()

> +
> +       ret = freq_qos_update_request(&priv->limits_freq_req, policy->max);
> +       if (ret < 0)
> +               pr_warn("failed to update freq constraint: %d\n", ret);
> +
> +       return NOTIFY_OK;
> +}
> +
>  static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>  {
>         int ret, nr_opp, domain;
> @@ -181,6 +204,7 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>         struct device *cpu_dev;
>         struct scmi_data *priv;
>         struct cpufreq_frequency_table *freq_table;
> +       struct scmi_device *sdev = cpufreq_get_driver_data();
>
>         cpu_dev = get_cpu_device(policy->cpu);
>         if (!cpu_dev) {
> @@ -294,6 +318,25 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>                 }
>         }
>
> +       ret = freq_qos_add_request(&policy->constraints, &priv->limits_freq_req, FREQ_QOS_MAX,
> +                                  FREQ_QOS_MAX_DEFAULT_VALUE);
> +       if (ret < 0) {
> +               dev_err(cpu_dev, "failed to add qos limits request: %d\n", ret);
> +               goto out_free_table;
> +       }
> +
> +       priv->limit_notify_nb.notifier_call = scmi_limit_notify_cb;
> +       ret = sdev->handle->notify_ops->event_notifier_register(sdev->handle, SCMI_PROTOCOL_PERF,
> +                                                       SCMI_EVENT_PERFORMANCE_LIMITS_CHANGED,
> +                                                       &priv->domain_id,
> +                                                       &priv->limit_notify_nb);
> +       if (ret)
> +               dev_warn(&sdev->dev,
> +                        "failed to register for limits change notifier for domain %d\n",
> +                        priv->domain_id);
> +
> +       priv->policy = policy;
> +
>         return 0;
>
>  out_free_table:
> @@ -313,7 +356,13 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>  static void scmi_cpufreq_exit(struct cpufreq_policy *policy)
>  {
>         struct scmi_data *priv = policy->driver_data;
> +       struct scmi_device *sdev = cpufreq_get_driver_data();
>
> +       sdev->handle->notify_ops->event_notifier_unregister(sdev->handle, SCMI_PROTOCOL_PERF,
> +                                                           SCMI_EVENT_PERFORMANCE_LIMITS_CHANGED,
> +                                                           &priv->domain_id,
> +                                                           &priv->limit_notify_nb);
> +       freq_qos_remove_request(&priv->limits_freq_req);
>         dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
>         dev_pm_opp_remove_all_dynamic(priv->cpu_dev);
>         free_cpumask_var(priv->opp_shared_cpus);
> @@ -372,6 +421,8 @@ static int scmi_cpufreq_probe(struct scmi_device *sdev)
>         if (!handle)
>                 return -ENODEV;
>
> +       scmi_cpufreq_driver.driver_data = sdev;
> +
>         perf_ops = handle->devm_protocol_get(sdev, SCMI_PROTOCOL_PERF, &ph);
>         if (IS_ERR(perf_ops))
>                 return PTR_ERR(perf_ops);
> --
> 2.34.1
>