On 20/01/2020 16:09, Quentin Perret wrote: > Hey Lukasz, > > On Monday 20 Jan 2020 at 14:52:07 (+0000), Lukasz Luba wrote: >> On 1/17/20 10:54 AM, Quentin Perret wrote: >>> 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.
