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

[Sibi Sankar]

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@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);
> > +
> > +	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