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

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Date: Tue, 4 Jun 2024 00:18:14 +0530
From: Sibi Sankar <quic_sibis@...cinc.com>
To: Vincent Guittot <vincent.guittot@...aro.org>
CC: <sudeep.holla@....com>, <cristian.marussi@....com>, <rafael@...nel.org>,
        <viresh.kumar@...aro.org>, <morten.rasmussen@....com>,
        <dietmar.eggemann@....com>, <lukasz.luba@....com>,
        <pierre.gondois@....com>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <quic_mdtipton@...cinc.com>, <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH V4 2/2] cpufreq: scmi: Register for limit change
 notifications



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@...cinc.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@...cinc.com>
>> ---
>>
>> 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
>>
>>