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

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

Suggested alternative: have two registration functions like so:

	int em_register_dev_pd(struct device *dev, unsigned int nr_states,
			       struct em_data_callback *cb);
	int em_register_cpu_pd(cpumask_t *span, unsigned int nr_states,
			       struct em_data_callback *cb);

Interesting, in the internal review Dietmar asked me to remove these two
functions. I had the same idea, which would simplify a bit the
registration and it does not need to check the dev->bus if it is CPU.

Unfortunately, we would need also two function in drivers/opp/of.c:
dev_pm_opp_of_register_cpu_em(policy->cpus);
and
dev_pm_opp_of_register_dev_em(dev);

Thus, I have created only one registration function, which you can see
in this patch set.

Right, I can see how having a unified API would be appealing, but the
OPP dependency is a nono, so we'll need to work around one way or
another.

FWIW, I don't think having separate APIs for CPUs and other devices is
that bad given that we already have entirely different frameworks to
drive their respective frequencies. And the _cpu variants are basically
just wrappers around the _dev ones, so not too bad either IMO :).

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);

Regards,
Lukasz

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