On 02/25/19 14:39, Viresh Kumar wrote:
> On 25-02-19, 08:58, Qais Yousef wrote:
> > On 02/25/19 10:01, Viresh Kumar wrote:
> > > > > + min = dev_pm_qos_read_value(cpu_dev, DEV_PM_QOS_MIN_FREQUENCY);
> > > > > + max = dev_pm_qos_read_value(cpu_dev, DEV_PM_QOS_MAX_FREQUENCY);
> > > > > +
> > > > > + if (min > new_policy->min)
> > > > > + new_policy->min = min;
> > > > > + if (max < new_policy->max)
> > > > > + new_policy->max = max;
>
> > And this is why we need to check here if the PM QoS value doesn't conflict
> > with
> > the current min/max, right? Until the current notifier code is removed they
> > could trip over each others.
>
> No. The above if/else block is already removed as part of patch 5/5. It was
> required because of conflict between userspace specific min/max and qos
> min/max,
> which are migrated to use qos by patc 5/5.
>
> The cpufreq notifier mechanism already lets users play with min/max and that
> is
> already safe from conflicts.
>
>
> > It would be nice to add a comment here about PM QoS managing and remembering
> > values
>
> I am not sure if that would add any value. Some documentation update may be
> useful for people looking for details though, that I shall do after all the
> changes get in and things become a bit stable.
>
Up to you. But not everyone is familiar with the code and a one line comment
that points to where aggregation is happening would be helpful for someone
scanning this code IMHO.
> > and that we need to be careful that both mechanisms don't trip over
> > each others until this transient period is over.
>
> The second mechanism will die very very soon once this is merged, migrating
> them
> shouldn't be a big challenge AFAICT. I didn't attempt that because I didn't
> wanted to waste time updating things in case this version also doesn't make
> sense to others.
>
> > I have a nit too. It would be nice to explicitly state this is
> > CPU_{MIN,MAX}_FREQUENCY. I can see someone else adding {MIN,MAX}_FREQUENCY
> > for
> > something elsee (memory maybe?)
>
> This is not CPU specific, but any device. The same interface shall be used by
> devfreq as well, who wanted to use freq-constraints initially.
>
I don't get that to be honest. I probably have to read more.
Is what you're saying that when applying a MIN_FREQUENCY constraint the same
value will be applied to both cpufreq and devfreq? Isn't this too coarse?
> > Although I looked at the previous series briefly, but this one looks more
> > compact and easier to follow, so +1 for that.
>
> Thanks for looking into this Qais.
>
> --
> viresh
Thanks
--
Qais Yousef
