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

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Date: Tue, 14 May 2024 15:10:28 +0530
From: Sibi Sankar <quic_sibis@...cinc.com>
To: Cristian Marussi <cristian.marussi@....com>
CC: <sudeep.holla@....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 5/1/24 13:51, Cristian Marussi wrote:
> On Thu, Mar 28, 2024 at 01:11:31PM +0530, Sibi Sankar wrote:
>> Register for limit change notifications if supported and use the throttled
>> frequency from the notification to apply HW pressure.
>>
> 
> Hi Sibi,
> 
> a bit late on this, sorry.
> 
> Just a couple of nitpicks down below.
> 
>> 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);
>> +
>> +	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,
> 
> or &data->sdev->dev which refers to this driver ? which is more informational ? no strong opinion just a question...

Pointing to the driver is better given that we already pass on domain
info.

> 
>> +			 "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;
> 
> 	^^^ ... you dont need to pass around handle AND sdev really
>                  since you can access the handle from sdev.
> 
>> +	scmi_cpufreq_driver.driver_data = data;

Ack setting sdev as driver data would suffice. Will fix it in the next
re-spin.

-Sibi

> 
> This is slightly better, but, as said, does not solve the multi-instance issue...
> ...the scmi cpufreq driver remains a driver that works only if instantiated (probed)
> once, given how the CPUFreq core handles cpufreq_driver registration itself...
> 
> ...just a note about something to work on in the future...NOT a concern for this series.
> 
> In general,
> 
> LGTM.
> 
> Thanks,
> Cristian
>