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