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

[Rajendra Nayak]

On 11/21/2018 10:46 AM, Viresh Kumar wrote:
> 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@xxxxxxxxxx>
> > > ---
> > >    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 ?

I would think this is analogous to a driver calling clk_set_rate() first and
then a clk_enable(), which is certainly valid.
So my question is, if calling a dev_pm_genpd_set_performance_state()
and then runtime enabling the device would work (and take care of propagating the performance
state). In my testing I found it does not.

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