linux-kernel - Re: [PATCH v10 02/27] PM / Domains: Add support for CPU devices to genpd

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Date:   Fri, 11 Jan 2019 11:54:20 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        Mark Rutland <mark.rutland@....com>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Raju P . L . S . S . S . N" <rplsssn@...eaurora.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Tony Lindgren <tony@...mide.com>,
        Kevin Hilman <khilman@...nel.org>,
        Lina Iyer <ilina@...eaurora.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 02/27] PM / Domains: Add support for CPU devices to genpd

On Wednesday, December 19, 2018 11:02:05 AM CET Ulf Hansson wrote:
> On Wed, 19 Dec 2018 at 10:53, Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
> >
> > On 29/11/2018 18:46, Ulf Hansson wrote:
> > > To enable a device belonging to a CPU to be attached to a PM domain managed
> > > by genpd, let's do a few changes to it, as to make it convenient to manage
> > > the specifics around CPUs.
> > >
> > > To be able to quickly find out what CPUs that are attached to a genpd,
> > > which typically becomes useful from a genpd governor as following changes
> > > is about to show, let's add a cpumask to the struct generic_pm_domain. At
> > > the point when a CPU device gets attached to a genpd, let's update its
> > > cpumask. Moreover, let's also propagate changes to the cpumask upwards in
> > > the topology to the master PM domains. In this way, the cpumask for a genpd
> > > hierarchically reflects all CPUs attached to the topology below it.
> > >
> > > Finally, let's make this an opt-in feature, to avoid having to manage CPUs
> > > and the cpumask for a genpd that doesn't need it. For that reason, let's
> > > add a new genpd configuration bit, GENPD_FLAG_CPU_DOMAIN.
> > >
> > > Cc: Lina Iyer <ilina@...eaurora.org>
> > > Co-developed-by: Lina Iyer <lina.iyer@...aro.org>
> > > Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> > > ---
> > >
> > > Changes in v10:
> > >       - Don't allocate the cpumask when not used.
> > >       - Simplify the code that updates the cpumask.
> > >       - Document the GENPD_FLAG_CPU_DOMAIN.
> > >
> > > ---
> > >  drivers/base/power/domain.c | 66 ++++++++++++++++++++++++++++++++++++-
> > >  include/linux/pm_domain.h   | 13 ++++++++
> > >  2 files changed, 78 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > > index e27b91d36a2a..c3ff8e395308 100644
> > > --- a/drivers/base/power/domain.c
> > > +++ b/drivers/base/power/domain.c
> > > @@ -20,6 +20,7 @@
> > >  #include <linux/sched.h>
> > >  #include <linux/suspend.h>
> > >  #include <linux/export.h>
> > > +#include <linux/cpu.h>
> > >
> > >  #include "power.h"
> > >
> > > @@ -126,6 +127,7 @@ static const struct genpd_lock_ops genpd_spin_ops = {
> > >  #define genpd_is_irq_safe(genpd)     (genpd->flags & GENPD_FLAG_IRQ_SAFE)
> > >  #define genpd_is_always_on(genpd)    (genpd->flags & GENPD_FLAG_ALWAYS_ON)
> > >  #define genpd_is_active_wakeup(genpd)        (genpd->flags & GENPD_FLAG_ACTIVE_WAKEUP)
> > > +#define genpd_is_cpu_domain(genpd)   (genpd->flags & GENPD_FLAG_CPU_DOMAIN)
> > >
> > >  static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
> > >               const struct generic_pm_domain *genpd)
> > > @@ -1377,6 +1379,56 @@ static void genpd_free_dev_data(struct device *dev,
> > >       dev_pm_put_subsys_data(dev);
> > >  }
> > >
> > > +static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
> > > +                                int cpu, bool set, unsigned int depth)
> > > +{
> > > +     struct gpd_link *link;
> > > +
> > > +     if (!genpd_is_cpu_domain(genpd))
> > > +             return;
> >
> > With this test, we won't continue updating the cpumask for the other
> > masters. Is it done on purpose ?
> 
> Correct, and yes it's on purpose.
> 
> We are not even allocating the cpumask for the genpd in question,
> unless it has the GENPD_FLAG_CPU_DOMAIN set.

So this patch is generally fine by me.  You can add my ACK to it when
submitting it again, unless it is changed, so I know I've seen it
already.