Re: [PATCH V4 2/2] cpufreq: scmi: Register for limit change notifications

[Sibi Sankar]

On 5/28/24 14:38, Vincent Guittot wrote:
> Hi Sibi,

Hey Vincent,
Thanks for taking time to review the series :)

> On Thu, 28 Mar 2024 at 08:42, Sibi Sankar <quic_sibis@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> > ---
> >
> > v4:
> > * Use a interim variable to show the khz calc. [Lukasz]
> > * Use driver_data to pass on the handle and scmi_dev instead of using
> >    global variables. Dropped Lukasz's Rb due to adding these minor
> >    changes.
> >
> >   drivers/cpufreq/scmi-cpufreq.c | 44 ++++++++++++++++++++++++++++++++++
> >   1 file changed, 44 insertions(+)
> >
> > diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
> > index 3b4f6bfb2f4c..d946b7a08258 100644
> > --- a/drivers/cpufreq/scmi-cpufreq.c
> > +++ b/drivers/cpufreq/scmi-cpufreq.c
> > @@ -21,11 +21,18 @@
> >   #include <linux/types.h>
> >   #include <linux/units.h>
> >
> > +struct scmi_cpufreq_driver_data {
> > +       struct scmi_device *sdev;
> > +       const struct scmi_handle *handle;
> > +};
> > +
> >   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;
> >   };
> >
> >   static struct scmi_protocol_handle *ph;
> > @@ -174,6 +181,22 @@ 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;
> > +
> > +       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);
> > +
> > +       cpufreq_update_pressure(policy);
>
> I noticed your patch while looking for other things in the archive but
> I don't think this is the right way to do it.
>
> cpufreq_update_pressure() aims to set to the scheduler the aggregation
> of all cappings set to cpufreq through the pm_qos and
> freq_qos_add_request(). Calling this function directly in scmi
> notification callback will overwrite the pm_qos aggregation. And at
> the opposite, any update of a pm_qos constraint will overwrite scmi
> notification. Instead you should better set a pm_qos constraint like
> others

Sure, I'll drop update_pressue and use the freq_qos_update_request to
update the policy->max_freq_req with the new policy->max.

-Sibi

> > +
> > +       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_cpufreq_driver_data *data = cpufreq_get_driver_data();
> >
> >          cpu_dev = get_cpu_device(policy->cpu);
> >          if (!cpu_dev) {
> > @@ -294,6 +318,17 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
> >                  }
> >          }
> >
> > +       priv->limit_notify_nb.notifier_call = scmi_limit_notify_cb;
> > +       ret = data->handle->notify_ops->devm_event_notifier_register(data->sdev, SCMI_PROTOCOL_PERF,
> > +                                                       SCMI_EVENT_PERFORMANCE_LIMITS_CHANGED,
> > +                                                       &domain,
> > +                                                       &priv->limit_notify_nb);
> > +       if (ret)
> > +               dev_warn(cpu_dev,
> > +                        "failed to register for limits change notifier for domain %d\n", domain);
> > +
> > +       priv->policy = policy;
> > +
> >          return 0;
> >
> >   out_free_opp:
> > @@ -366,12 +401,21 @@ static int scmi_cpufreq_probe(struct scmi_device *sdev)
> >          int ret;
> >          struct device *dev = &sdev->dev;
> >          const struct scmi_handle *handle;
> > +       struct scmi_cpufreq_driver_data *data;
> >
> >          handle = sdev->handle;
> >
> >          if (!handle)
> >                  return -ENODEV;
> >
> > +       data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> > +       if (!data)
> > +               return -ENOMEM;
> > +
> > +       data->sdev = sdev;
> > +       data->handle = handle;
> > +       scmi_cpufreq_driver.driver_data = data;
> > +
> >          perf_ops = handle->devm_protocol_get(sdev, SCMI_PROTOCOL_PERF, &ph);
> >          if (IS_ERR(perf_ops))
> >                  return PTR_ERR(perf_ops);
> > --
> > 2.34.1