On Mon, 7 Jun 2021 at 06:47, Viresh Kumar [off-list ref] wrote:

On 04-06-21, 09:45, Ulf Hansson wrote:

quoted

Starting calls from the subsystem/driver:

------
dev_pm_genpd_set_performance_state(dev, 100);
"run a use case with device runtime resumed"
...
"use case ends"
dev_pm_genpd_set_performance_state(dev, 0);
pm_runtime_put()
    ->genpd_runtime_suspend()
    gpd_data->performance_state == 0, -> gpd_data->rpm_pstate = 0;
...
"new use case start"
dev_pm_genpd_set_performance_state(dev, 100);
pm_runtime_get_sync()
    ->genpd_runtime_resume()
    gpd_data->performance_state == 100, -> gpd_data->rpm_pstate = 0;
(This is where we need to check for "zero" to not override the value)
.....
------

I wouldn't say that the above is the way how I see the calls to
dev_pm_genpd_set_performance_state (or actually
dev_pm_opp_set_rate|opp()) being deployed. The calls should rather be
done from the subsystem/driver's ->runtime_suspend|resume() callback,
then the path above would work in the way you suggest.

Although, as we currently treat performance states and power states in
genpd orthogonally, I wanted to make sure we could cope with both
situations.

I think letting the drivers to call
dev_pm_genpd_set_performance_state(dev, 0) from suspend/resume makes
it really ugly/racy as both depend on the gpd_data->performance_state
for this. It doesn't look nice. And we shouldn't try to protect such
drivers.

Anyway, your call :)

Well, I am not sure we have an option at this point. As long as we
allow performance states to be managed orthogonally to on/off states
in genpd, the check in genpd_restore_performance_state() is needed.

I have started to prepare a new version of the series - and will add a
comment about this in the code to try to clarify this.

[...]

Kind regards
Uffe