Re: [PATCH 1/7] cpufreq: remove redundant CPUFREQ_INCOMPATIBLE notifier event

[Saravana Kannan]

On 04/06/2016 02:21 PM, Rafael J. Wysocki wrote:
> On Wed, Apr 6, 2016 at 10:30 PM, Saravana Kannan <skannan@xxxxxxxxxxxxxx> wrote:
> > On 09/09/2015 05:53 PM, Rafael J. Wysocki wrote:
> > > Hi,
> > >
> > > On Thu, Sep 10, 2015 at 2:39 AM, Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> > > wrote:
> > > > On 10-09-15, 01:26, Rafael J. Wysocki wrote:
> > > > > On Monday, August 03, 2015 08:36:14 AM Viresh Kumar wrote:
> > > > > > What's being done from CPUFREQ_INCOMPATIBLE, can also be done with
> > > > > > CPUFREQ_ADJUST. There is nothing special with CPUFREQ_INCOMPATIBLE
> > > > > > notifier.
> > > > >
> > > > >
> > > > > The above part of the changelog is a disaster to me. :-(
> > > > >
> > > > > It not only doesn't explain what really goes on, but it's actively
> > > > > confusing.
> > > > >
> > > > > What really happens is that the core sends CPUFREQ_INCOMPATIBLE
> > > > > notifications
> > > > > unconditionally right after sending the CPUFREQ_ADJUST ones, so the
> > > > > former is
> > > > > just redundant and it's more efficient to merge the two into one.
> > > >
> > > >
> > > > Undoubtedly this looks far better :)
> > > >
> > > > But, isn't this series already applied some time back ?
> > >
> > >
> > > Right, never mind.  For some reason that patch was left in the "New"
> > > state.
> > >
> > > The code is OK.
> >
> >
> >
> > I guess I didn't notice this change when it was sent out.
> >
> > The comment that was deleted in this patch clearly states why the
> > INCOMPATIBLE notifier is needed. Some client might want to boost the CPU min
> > freq for performance or other reasons, but thermal might want to limit it.
> > So, by having thermal register for INCOMPATIBLE notifiers to enforce the
> > limits, we provide a way to guarantee it gets the final say.
> >
> > The real fix should have been to change drivers/thermal/cpu_cooling.c to use
> > CPUFREQ_INCOMPATIBLE instead of CPUFREQ_ADJUST.
> >
> > Is there something I'm missing? If not, can we please revert this patch?
>
> Well, nobody was using that event.

True, but that's more of a bug in drivers/thermal/cpu-cooling.c and 
drivers/acpi/processor_thermal.c. We should revert this patch and fix 
those drivers. Does that seem acceptable to you?

-Saravana


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