linux-kernel - Re: [PATCH v5 2/9] cpufreq: Auto-register the driver as a thermal cooling device if asked

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Message-ID: <CAJZ5v0iXv3yLtGqti1OLbh-7LF1hZyvW+HTTG5mVFmEJ8a1SAA@mail.gmail.com>
Date:   Tue, 29 Jan 2019 10:16:15 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Amit Kucheria <amit.kucheria@...aro.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Sudeep Holla <sudeep.holla@....com>,
        Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v5 2/9] cpufreq: Auto-register the driver as a thermal
 cooling device if asked

On Tue, Jan 29, 2019 at 8:09 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 29-01-19, 11:50, Amit Kucheria wrote:
> > On Tue, Jan 29, 2019 at 11:16 AM Amit Kucheria <amit.kucheria@...aro.org> wrote:
> > >
> > > On Tue, Jan 29, 2019 at 11:06 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
> > > >
> > > > On 29-01-19, 10:25, Amit Kucheria wrote:
> > > > > All cpufreq drivers do similar things to register as a cooling device.
> > > > > Provide a cpufreq driver flag so drivers can just ask the cpufreq core
> > > > > to register the cooling device on their behalf. This allows us to get
> > > > > rid of duplicated code in the drivers.
> > > > >
> > > > > In order to allow this, we add a struct thermal_cooling_device pointer
> > > > > to struct cpufreq_policy so that drivers don't need to store it in a
> > > > > private data structure.
> > > > >
> > > > > Suggested-by: Stephen Boyd <swboyd@...omium.org>
> > > > > Suggested-by: Viresh Kumar <viresh.kumar@...aro.org>
> > > > > Signed-off-by: Amit Kucheria <amit.kucheria@...aro.org>
> > > > > Reviewed-by: Matthias Kaehlcke <mka@...omium.org>
> > > > > Tested-by: Matthias Kaehlcke <mka@...omium.org>
> > > > > Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> > > > > ---
> > > > >  drivers/cpufreq/cpufreq.c | 13 +++++++++++++
> > > > >  include/linux/cpufreq.h   |  9 +++++++++
> > > > >  2 files changed, 22 insertions(+)
> > > > >
> > > > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > > > > index e35a886e00bc..0f9b50d3ee91 100644
> > > > > --- a/drivers/cpufreq/cpufreq.c
> > > > > +++ b/drivers/cpufreq/cpufreq.c
> > > > > @@ -19,6 +19,7 @@
> > > > >
> > > > >  #include <linux/cpu.h>
> > > > >  #include <linux/cpufreq.h>
> > > > > +#include <linux/cpu_cooling.h>
> > > > >  #include <linux/delay.h>
> > > > >  #include <linux/device.h>
> > > > >  #include <linux/init.h>
> > > > > @@ -1318,6 +1319,11 @@ static int cpufreq_online(unsigned int cpu)
> > > > >       if (cpufreq_driver->ready)
> > > > >               cpufreq_driver->ready(policy);
> > > > >
> > > > > +#if IS_ENABLED(CONFIG_CPU_THERMAL)
> > > > > +     if (cpufreq_driver->flags & CPUFREQ_IS_COOLING_DEV)
> > > > > +             policy->cdev = of_cpufreq_cooling_register(policy);
> > > > > +#endif
> > > >
> > > > I am not sure if Rafael wanted it this way but maybe something like this:
> > > >
> > > >         if (IS_ENABLED(CONFIG_CPU_THERMAL) &&
> > > >             cpufreq_driver->flags & CPUFREQ_IS_COOLING_DEV))
> > > >                 policy->cdev = of_cpufreq_cooling_register(policy);
> > > >
> > > > We never wanted ifdef hackery to be in there :)
> > >
> > > OK, that makes more sense. Should I just send out a fixup patch or the
> > > entire series?
>
> Single patch should be fine I believe.
>
> > FWIW, I checked drivers/cpufreq and drivers/thermal before converting
> > over and there is a mixed use of #if IS_ENABLED and if(IS_ENABLED).
> >
> > Perhaps we should clean it up?
>
> No objections from me on that.

Generally speaking, though, "if (IS_ENABLED(SYMBOL))" can only be used
if all of the symbols in the conditional branch are defined regardless
of whether or not SYMBOL itself is defined, so careful there.