Message-ID: <e759ecad-9533-a294-9ee0-1b42effe5b82@quicinc.com>
Date: Thu, 31 Oct 2024 18:51:45 +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 V6 1/1] cpufreq: scmi: Register for limit change
 notifications



On 10/30/24 20:17, Vincent Guittot wrote:
> On Wed, 30 Oct 2024 at 14:32, 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>
>> Tested-by: Mike Tipton <quic_mdtipton@...cinc.com>
>> Reviewed-by: Cristian Marussi <cristian.marussi@....com>
>> Reviewed-by: Lukasz Luba <lukasz.luba@....com>
>> ---
>>
>> v6:
>> * Unregister the notifier in the exit path to make sure
>>    the cpus work across suspend/resume cycles.
>>
>>   drivers/cpufreq/scmi-cpufreq.c | 38 ++++++++++++++++++++++++++++++++++
>>   1 file changed, 38 insertions(+)
>>
>> diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
>> index 5892c73e129d..fb3534eae722 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 +26,9 @@ 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 +177,25 @@ 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);
>> +
>> +       ret = freq_qos_update_request(policy->max_freq_req, policy->max);
> 
> If I don't get it wrong, you are using policy->max_freq_req which is
> also used by the sysfs scaling_max_freq
> 
> This means that your request will be overwritten by the next write
> into scaling_max_freq and/or you will overwrite a constraint set by
> userspace.
> 
> You have to create your own freq_qos_request and add it to the list of
> cpufreq qos request

Thanks for catching this. Will get it fixed in the next re-spin.

-Sibi

> 
> 
> 
>> +       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 +203,7 @@ 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 +317,17 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>>                  }
>>          }
>>
>> +       priv->limit_notify_nb.notifier_call = scmi_limit_notify_cb;
>> +       ret = sdev->handle->notify_ops->devm_event_notifier_register(sdev, SCMI_PROTOCOL_PERF,
>> +                                                       SCMI_EVENT_PERFORMANCE_LIMITS_CHANGED,
>> +                                                       &domain,
>> +                                                       &priv->limit_notify_nb);
>> +       if (ret)
>> +               dev_warn(&sdev->dev,
>> +                        "failed to register for limits change notifier for domain %d\n", domain);
>> +
>> +       priv->policy = policy;
>> +
>>          return 0;
>>
>>   out_free_opp:
>> @@ -310,8 +344,10 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>>
>>   static void scmi_cpufreq_exit(struct cpufreq_policy *policy)
>>   {
>> +       struct scmi_device *sdev = cpufreq_get_driver_data();
>>          struct scmi_data *priv = policy->driver_data;
>>
>> +       sdev->handle->notify_ops->devm_event_notifier_unregister(sdev, &priv->limit_notify_nb);
>>          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);
>> @@ -370,6 +406,8 @@ 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
>>

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