On 1/20/20 3:28 PM, Quentin Perret wrote:

On Monday 20 Jan 2020 at 15:53:35 (+0100), Dietmar Eggemann wrote:

quoted

Would be really nice if this wouldn't be required. We should really aim
for 1 framework == 1 set of interfaces.

What happens if someone calls em_get_pd() on a CPU EM?

E.g:

  static struct perf_domain *pd_init(int cpu)
  {
-       struct em_perf_domain *obj = em_cpu_get(cpu);
+       struct device *dev = get_cpu_device(cpu);
+       struct em_perf_domain *obj = em_pd_get(dev);
         struct perf_domain *pd;

Two versions of one functionality will confuse API user from the
beginning ...

Agreed, this looks a bit confusing. It should be trivial to make
em_dev_get() (or whatever we end up calling it) work for CPUs too,
though. And we could always have a em_cpu_get(int cpu) API that is a
basically a wrapper around em_dev_get() for convenience.

The problem not only here is that we have a CPU index 'int cpu'
and if we ask for device like:

struct device *dev = get_cpu_device(cpu);

It might be not the same device that was used during the
registration, when we had i.e. 4 CPUs for the same policy:

int cpu_id = cpumask_first(policy->cpus);
struct device *cpu_dev = get_cpu_device(cpu_id);
em_register_perf_domain(cpu_dev, nr_opp, &em_cb);

That's why the em_cpu_get() is different than em_get_pd(), mainly by:
if (cpumask_test_cpu(cpu, em_span_cpus(em_pd)))

It won't be simple wrapper, let me think how it could be handled
differently than it is now.

Regards,
Lukasz

Thanks,
Quentin

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