On Thu, 3 Jun 2021 at 04:37, Viresh Kumar [off-list ref] wrote:

On 03-06-21, 08:04, Viresh Kumar wrote:

quoted

On 02-06-21, 12:12, Ulf Hansson wrote:

quoted

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 <redacted>
---
 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 ?

quoted

+           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