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

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Date:   Wed, 12 Feb 2020 10:08:26 +0800
From:   Nicolas Boichat <drinkcat@...omium.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Rob Herring <robh+dt@...nel.org>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Steven Price <steven.price@....com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v4 5/7] drm/panfrost: Add support for multiple power domains

On Wed, Feb 12, 2020 at 4:09 AM Saravana Kannan <saravanak@...gle.com> wrote:
>
> On Tue, Feb 11, 2020 at 11:44 AM Rob Herring <robh+dt@...nel.org> wrote:
> >
> > +Saravana
> >
> > On Thu, Feb 6, 2020 at 11:27 PM Nicolas Boichat <drinkcat@...omium.org> 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@...omium.org>
> > >
> > > ---
> > > [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.