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

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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





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