Re: [PATCH V3 2/2] cpufreq: scmi: Register for limit change notifications

From: Lukasz Luba
Date: Wed Feb 28 2024 - 08:24:53 EST




On 2/27/24 18:16, Sibi Sankar 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@xxxxxxxxxxx>
---

v3:
* Sanitize range_max received from the notifier. [Pierre]
* Update commit message.

drivers/cpufreq/scmi-cpufreq.c | 29 ++++++++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
index 76a0ddbd9d24..78b87b72962d 100644
--- a/drivers/cpufreq/scmi-cpufreq.c
+++ b/drivers/cpufreq/scmi-cpufreq.c
@@ -25,9 +25,13 @@ 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;
};
+const struct scmi_handle *handle;
+static struct scmi_device *scmi_dev;
static struct scmi_protocol_handle *ph;
static const struct scmi_perf_proto_ops *perf_ops;
static struct cpufreq_driver scmi_cpufreq_driver;
@@ -151,6 +155,20 @@ 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;
+
+ policy->max = clamp(limit_notify->range_max_freq/HZ_PER_KHZ, policy->cpuinfo.min_freq,
+ policy->cpuinfo.max_freq);

Please take the division operation out of this clamp() call, somewhere
above. Currently it 'blurs' these stuff, while it's important convertion
to khz. You can call it e.g.:

limit_freq_khz = limit_notify->range_max_freq / HZ_PER_KHZ;

then use in clamp(limit_freq_khz, ...)

+
+ cpufreq_update_pressure(policy);
+
+ return NOTIFY_OK;
+}
+
static int scmi_cpufreq_init(struct cpufreq_policy *policy)
{
int ret, nr_opp, domain;
@@ -269,6 +287,15 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
}
}
+ priv->limit_notify_nb.notifier_call = scmi_limit_notify_cb;
+ ret = handle->notify_ops->devm_event_notifier_register(scmi_dev, 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;
@@ -342,8 +369,8 @@ static int scmi_cpufreq_probe(struct scmi_device *sdev)
{
int ret;
struct device *dev = &sdev->dev;
- const struct scmi_handle *handle;

It should be a compilation error...

+ scmi_dev = sdev;
handle = sdev->handle;

due to usage here, wasn't it?

if (!handle)