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SubjectRe: [PATCH v10 15/15] OPTIONAL: cpufreq: dt: Register an Energy Model
Hi Matthias ,

On Tuesday 08 Jan 2019 at 12:38:13 (-0800), Matthias Kaehlcke wrote:
> > static int cpufreq_init(struct cpufreq_policy *policy)
> > {
> > + struct em_data_callback em_cb = EM_DATA_CB(of_est_power);
> > struct cpufreq_frequency_table *freq_table;
> > struct opp_table *opp_table = NULL;
> > struct private_data *priv;
> > @@ -160,7 +203,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
> > unsigned int transition_latency;
> > bool fallback = false;
> > const char *name;
> > - int ret;
> > + int ret, nr_opp;
> >
> > cpu_dev = get_cpu_device(policy->cpu);
> > if (!cpu_dev) {
> > @@ -237,6 +280,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
> > ret = -EPROBE_DEFER;
> > goto out_free_opp;
> > }
> > + nr_opp = ret;
> >
> > if (fallback) {
> > cpumask_setall(policy->cpus);
> > @@ -280,6 +324,8 @@ static int cpufreq_init(struct cpufreq_policy *policy)
> > policy->cpuinfo.transition_latency = transition_latency;
> > policy->dvfs_possible_from_any_cpu = true;
> >
> > + em_register_perf_domain(policy->cpus, nr_opp, &em_cb);
>
> Shouldn't there also be a function to unregister a perf domain to be
> called from cpufreq_exit()?
>
> ->exit() is called on suspend when the CPUs are taken offline, and
> ->init() on resume, hence em_register_perf_domain() is called multiple
> times, but without doing any cleanup.

Right, but this is safe to do as em_register_perf_domain() checks for
the existence of the domain straight away. So the second time you call
this em_register_perf_domain() should just bail out. Are you seeing an
issue with this ?

As of now, the EM framework is really simple -- it justs allocates the
pd tables once during boot, and they stay in memory forever. While
arguably less than optimal, that makes things a whole lot easier to
manage on the client side (i.e. the scheduler) w/o needing RCU
protection or so.

Thanks,
Quentin

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