On 20/01/2020 19:38, Lukasz Luba wrote:

On 1/20/20 6:27 PM, Dietmar Eggemann wrote:

quoted

On 20/01/2020 16:09, Quentin Perret wrote:

quoted

Hey Lukasz,

On Monday 20 Jan 2020 at 14:52:07 (+0000), Lukasz Luba wrote:

quoted

On 1/17/20 10:54 AM, Quentin Perret wrote:

[...]

quoted

It's true that we need the policy->cpus cpumask only for cpu devices and
we have it available when we call em_register_perf_domain()
[scmi-cpufreq.c driver] or the OPP wrapper dev_pm_opp_of_register_em()
[e.g. cpufreq-dt.c driver].

And we shouldn't make EM code dependent on OPP.

But can't we add 'struct cpumask *mask' as an additional argument to
both which can be set to NULL for (devfreq) devices?

We can check in em_register_perf_domain() that we got a valid cpumask
for a cpu device and ignore it for (devfreq) devices.

I think we could avoid this additional argument 'cpumask'. I have
checked the cpufreq_cpu_get function, which should do be good for this:

---------->8-------------------------
static int _get_sharing_cpus(struct device *cpu_dev, struct cpumask *span)
{
        struct cpufreq_policy *policy;

        policy = cpufreq_cpu_get(cpu_dev->id);
        if (policy) {
                cpumask_copy(span, policy->cpus);
                cpufreq_cpu_put(policy);
                return 0;
        } else {
                return -EINVAL;
        }
}
--------------------------8<-------------------------------

It would be a replacement for:
ret = dev_pm_opp_get_sharing_cpus(dev, span);

True. But then we hard-code that a CPU device performance domain can
only be a frequency domain (which is true today).

The task scheduler (build_perf_domains()) and thermal are already using
cpufreq_cpu_get() to access the cpufreq policy. Now the EM framework
would too for CPU devices. I assume that could work with a couple of
adaptations in Documentation/power/energy-model.rst.

BTW, there is a similar interface cpufreq_get_policy() in cpufreq.c
which is used less often?

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel