On Wed, Jan 17, 2024 at 04:11:16PM +0530, Sibi Sankar wrote:
> Register for limit change notifications if supported with the help of
> perf_notify_support interface and determine the throttled frequency
> using the perf_freq_xlate to apply HW pressure.
>
> Signed-off-by: Sibi Sankar <quic_sibis@xxxxxxxxxxx>
> ---
>
> v2:
> * Export cpufreq_update_pressure and use it directly [Lukasz]
>
> drivers/cpufreq/scmi-cpufreq.c | 42 +++++++++++++++++++++++++++++++++-
> 1 file changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
> index 4ee23f4ebf4a..e0aa85764451 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;
>
> @@ -144,6 +148,22 @@ scmi_get_cpu_power(struct device *cpu_dev, unsigned long *power,
> return 0;
> }
>
> +static int scmi_limit_notify_cb(struct notifier_block *nb, unsigned long event, void *data)
> +{
> + unsigned long freq_hz;
> + struct scmi_perf_limits_report *limit_notify = data;
> + struct scmi_data *priv = container_of(nb, struct scmi_data, limit_notify_nb);
> + struct cpufreq_policy *policy = priv->policy;
> +
> + if (perf_ops->perf_freq_xlate(ph, priv->domain_id, limit_notify->range_max, &freq_hz))
> + return NOTIFY_OK;
> +
> + policy->max = freq_hz / HZ_PER_KHZ;
> + cpufreq_update_pressure(policy);
> +
> + return NOTIFY_OK;
> +}
> +
> static int scmi_cpufreq_init(struct cpufreq_policy *policy)
> {
> int ret, nr_opp, domain;
> @@ -151,6 +171,7 @@ 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_perf_notify_info info = {};
>
> cpu_dev = get_cpu_device(policy->cpu);
> if (!cpu_dev) {
> @@ -250,6 +271,25 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
> policy->fast_switch_possible =
> perf_ops->fast_switch_possible(ph, domain);
>
> + ret = perf_ops->perf_notify_support(ph, domain, &info);
> + if (ret)
> + dev_warn(cpu_dev, "failed to get supported notifications: %d\n", ret);
> +
> + if (info.perf_limit_notify) {
> + 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_err(cpu_dev, "Error in registering limit change notifier for domain %d\n",
> + domain);
> + return ret;
> + }
Is there a reason to fail completely here if it was not possible to register
the notifier ? (even though expected to succeed given perf_limit_notify
was true...)
Maybe a big fat warn that the system perf could be degraded, but
carrying on ?
Or maybe you have in mind a good reason to fail like you did, so please
explain in that case in a comment.
Thanks,
Cristian
