Messages in this thread | | | From | Ulf Hansson <> | Date | Thu, 3 Jun 2021 11:16:16 +0200 | Subject | Re: [PATCH 2/3] PM: domains: Drop/restore performance state votes for devices at runtime PM |
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On Thu, 3 Jun 2021 at 04:37, Viresh Kumar <viresh.kumar@linaro.org> wrote: > > On 03-06-21, 08:04, Viresh Kumar wrote: > > On 02-06-21, 12:12, Ulf Hansson wrote: > > > A subsystem/driver that need to manage OPPs for its device, should > > > typically drop its vote for the OPP when the device becomes runtime > > > suspended. In this way, the corresponding aggregation of the performance > > > state votes that is managed in genpd for the attached PM domain, may find > > > that the aggregated vote can be decreased. Hence, it may allow genpd to set > > > the lower performance state for the PM domain, thus avoiding to waste > > > energy. > > > > > > To accomplish this, typically a subsystem/driver would need to call > > > dev_pm_opp_set_rate|opp() for its device from its ->runtime_suspend() > > > callback, to drop the vote for the OPP. Accordingly, it needs another call > > > to dev_pm_opp_set_rate|opp() to restore the vote for the OPP from its > > > ->runtime_resume() callback. > > > > > > To avoid boilerplate code in subsystems/driver to deal with these things, > > > let's instead manage this internally in genpd. > > > > > > Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> > > > --- > > > drivers/base/power/domain.c | 21 +++++++++++++++++++-- > > > include/linux/pm_domain.h | 1 + > > > 2 files changed, 20 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c > > > index a3b6e751f366..81b9d4652b90 100644 > > > --- a/drivers/base/power/domain.c > > > +++ b/drivers/base/power/domain.c > > > @@ -397,6 +397,18 @@ static int genpd_set_performance_state(struct device *dev, unsigned int state) > > > return ret; > > > } > > > > > > +static int genpd_drop_performance_state(struct device *dev) > > > +{ > > > + struct generic_pm_domain_data *gpd_data = dev_gpd_data(dev); > > > + unsigned int prev_state; > > > + > > > + prev_state = gpd_data->performance_state; > > > + if (prev_state && !genpd_set_performance_state(dev, 0)) > > > > What about adding this prev_state check in > > genpd_set_performance_state() itself ? We already have one for the > > genpd in _genpd_set_performance_state(), why not one for the device ? > > > > > + return prev_state; > > > + > > > + return 0; > > > > Hmm, we will return 0 in case genpd_set_performance_state() fails, > > which will make us set the state to 0 again on resume. Maybe add a > > comment for this somewhere ? > > No, we won't as you check for rpm_saved_pstate there, so the device > will stay disabled. > > Again adding the check into genpd_set_performance_state() may help > reducing similar checks elsewhere.
Yes, at closer look, I think it makes sense to me as well.
Although, as it means a change in behaviour, I decided to make it a separate patch. Let me respin the series to fold it in.
[...]
Thanks for reviewing!
Kind regards Uffe
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