linux-kernel - Re: [PATCH 4/4] PM / Domains: Propagate performance state updates

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Date:   Wed, 21 Nov 2018 10:46:26 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Rajendra Nayak <rnayak@...eaurora.org>
Cc:     ulf.hansson@...aro.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>, Nishanth Menon <nm@...com>,
        niklas.cassel@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] PM / Domains: Propagate performance state updates

On 21-11-18, 10:33, Rajendra Nayak wrote:
> Hi Viresh,
> 
> On 11/5/2018 12:06 PM, Viresh Kumar wrote:
> > This commit updates genpd core to start propagating performance state
> > updates to master domains that have their set_performance_state()
> > callback set.
> > 
> > A genpd handles two type of performance states now. The first one is the
> > performance state requirement put on the genpd by the devices and
> > sub-domains under it, which is already represented by
> > genpd->performance_state. The second type, introduced in this commit, is
> > the performance state requirement(s) put by the genpd on its master
> > domain(s). There is a separate value required for each master that the
> > genpd has and so a new field is added to the struct gpd_link
> > (link->performance_state), which represents the link between a genpd and
> > its master. The struct gpd_link also got another field
> > prev_performance_state, which is used by genpd core as a temporary
> > variable during transitions.
> > 
> > We need to propagate setting performance state while powering-on a genpd
> > as well, as we ignore performance state requirements from sub-domains
> > which are powered-off. For this reason _genpd_power_on() also received
> > the additional parameter, depth, which is used for hierarchical locking
> > within genpd.
> > 
> > Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> > ---
> >   drivers/base/power/domain.c | 107 +++++++++++++++++++++++++++++-------
> >   include/linux/pm_domain.h   |   4 ++
> >   2 files changed, 92 insertions(+), 19 deletions(-)
> > 
> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > index 6d2e9b3406f1..81e02c5f753f 100644
> > --- a/drivers/base/power/domain.c
> > +++ b/drivers/base/power/domain.c
> > @@ -239,28 +239,86 @@ static void genpd_update_accounting(struct generic_pm_domain *genpd)
> >   static inline void genpd_update_accounting(struct generic_pm_domain *genpd) {}
> >   #endif
> > +static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
> > +					   unsigned int state, int depth);
> > +
> >   static int _genpd_set_performance_state(struct generic_pm_domain *genpd,
> > -					unsigned int state)
> > +					unsigned int state, int depth)
> >   {
> > +	struct generic_pm_domain *master;
> > +	struct gpd_link *link;
> > +	unsigned int mstate;
> >   	int ret;
> >   	if (!genpd_status_on(genpd))
> >   		goto out;
> 
> This check here would mean we only propogate performance state
> to masters if the genpd is ON?

Yeah, isn't that what should we do anyway? It is similar to clk-enable
etc. Why increase the reference count if the device isn't enabled and
isn't using the clock ?

Also you can see that I have updated the genpd power-on code to start
propagation to make sure we don't miss anything.

-- 
viresh