On Thursday, July 06, 2017 04:10:27 PM Viresh Kumar wrote: > On 06-07-17, 10:49, Dietmar Eggemann wrote: > > A frequency-invariant load-tracking solution based on cpufreq transition > > notifier will not work for future fast frequency switching policies. > > That is why a different solution is presented with this patch. > > > > Let cpufreq call the function arch_set_freq_scale() to pass the current > > frequency, the max supported frequency and the cpumask of the related > > cpus to a consumer (an arch) which defines arch_set_freq_scale(). > > > > The consumer has to associate arch_set_freq_scale with the name of its > > own implementation foo_set_freq_scale() to overwrite the empty standard > > definition in drivers/cpufreq/cpufreq.c. > > An arch could do this in one of its arch-specific header files > > (e.g. arch/$ARCH/include/asm/topology.h) which gets included in > > drivers/cpufreq/cpufreq.c. > > > > In case arch_set_freq_scale() is not defined (and because of the > > pr_debug() drivers/cpufreq/cpufreq.c is not compiled with -DDEBUG) > > The line within () needs to be improved to convey a clear message. > > > the > > function cpufreq_set_freq_scale() gets compiled out. > > > > Cc: Rafael J. Wysocki <r...@rjwysocki.net> > > Cc: Viresh Kumar <viresh.ku...@linaro.org> > > Signed-off-by: Dietmar Eggemann <dietmar.eggem...@arm.com> > > --- > > drivers/cpufreq/cpufreq.c | 26 ++++++++++++++++++++++++++ > > 1 file changed, 26 insertions(+) > > > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > > index 9bf97a366029..a04c5886a5ce 100644 > > --- a/drivers/cpufreq/cpufreq.c > > +++ b/drivers/cpufreq/cpufreq.c > > @@ -347,6 +347,28 @@ static void __cpufreq_notify_transition(struct > > cpufreq_policy *policy, > > } > > } > > > > +/********************************************************************* > > + * FREQUENCY INVARIANT CPU CAPACITY SUPPORT * > > + *********************************************************************/ > > + > > +#ifndef arch_set_freq_scale > > +static void arch_set_freq_scale(struct cpumask *cpus, unsigned long > > cur_freq, > > + unsigned long max_freq) > > +{} > > +#endif > > + > > +static void cpufreq_set_freq_scale(struct cpufreq_policy *policy, > > + struct cpufreq_freqs *freqs) > > +{ > > + unsigned long cur_freq = freqs ? freqs->new : policy->cur; > > + unsigned long max_freq = policy->cpuinfo.max_freq; > > + > > + pr_debug("cpus %*pbl cur/cur max freq %lu/%lu kHz\n", > > + cpumask_pr_args(policy->related_cpus), cur_freq, max_freq); > > + > > + arch_set_freq_scale(policy->related_cpus, cur_freq, max_freq); > > I am not sure why all these are required to be sent here and will come back to > it later on after going through other patches. > > > +} > > + > > /** > > * cpufreq_notify_transition - call notifier chain and adjust_jiffies > > * on frequency transition. > > @@ -405,6 +427,8 @@ void cpufreq_freq_transition_begin(struct > > cpufreq_policy *policy, > > > > spin_unlock(&policy->transition_lock); > > > > + cpufreq_set_freq_scale(policy, freqs); > > + > > Why do this before even changing the frequency ? We may fail while changing > it. > > IMHO, you should call this routine whenever we update policy->cur and that > happens regularly in __cpufreq_notify_transition() and few other places..
There seems to be a general problem with doing this in the core with respect to things like intel_pstate that use their own governor callbacks and don't invoke cpufreq_freq_transition_begin() then. Thanks, Rafael