Re: [PATCH v4 5/7] drm/panfrost: Add support for multiple power domains

[Nicolas Boichat]

On Wed, Feb 12, 2020 at 4:09 AM Saravana Kannan <saravanak@xxxxxxxxxx> wrote:
>
> On Tue, Feb 11, 2020 at 11:44 AM Rob Herring <robh+dt@xxxxxxxxxx> wrote:
> >
> > +Saravana
> >
> > On Thu, Feb 6, 2020 at 11:27 PM Nicolas Boichat <drinkcat@xxxxxxxxxxxx> wrote:
> > >
> > > When there is a single power domain per device, the core will
> > > ensure the power domain is switched on (so it is technically
> > > equivalent to having not power domain specified at all).
> > >
> > > However, when there are multiple domains, as in MT8183 Bifrost
> > > GPU, we need to handle them in driver code.
> > >
> > > Signed-off-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
> > >
> > > ---
> > > [snip]
> > > +               pfdev->pm_domain_links[i] = device_link_add(pfdev->dev,
> > > +                               pfdev->pm_domain_devs[i], DL_FLAG_PM_RUNTIME |
> > > +                               DL_FLAG_STATELESS | DL_FLAG_RPM_ACTIVE);
> >
> > We're in the process of adding device links based on DT properties.
> > Shouldn't we add power domains to that? See drivers/of/property.c for
> > what's handled.
>
> Rob,
>
> drivers/of/property.c doesn't enable the RPM_ACTIVE AND PM_RUNTIME
> flags. Wanted to start off conservative. But adding command line ops
> to change the default flags shouldn't be difficult. But before I do
> that, I want to change of_devlink to
> fw_devlink=<disabled|permissive|enabled>. May be I can extend that to
> "disabled, permissive, suspend, runtime".
>
> Nicholas,
>
> And the adding and removing of device links for power domains will be
> a 2 line change. I've been meaning to add a few more bindings like
> hwspinlocks and pinctrl. I can roll power domains support into that if
> you want.

Adding power domains makes sense to me, as there are a bunch of other
users (git grep dev_pm_domain_attach_by_name).

This seems to be a bit orthogonal to this patch though. If your
solution lands before this (and not something that is behind a command
line option), then I'm happy to make use of it. Either way, happy to
test things.