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From: Chen-Yu Tsai <wenst@chromium.org>
Date: Thu, 13 Jun 2024 17:10:41 +0800
Message-ID: <CAGXv+5HC_spBAc-t4cS+aCOQKdfWRzMkXK94HmD1Qg02ML4Uug@mail.gmail.com>
Subject: Re: [PATCH 3/6] dt-bindings: gpu: powervr-rogue: Add MediaTek MT8173 GPU
To: Frank Binns <Frank.Binns@imgtec.com>, Adam Ford <aford173@gmail.com>
Cc: "matthias.bgg@gmail.com" <matthias.bgg@gmail.com>, "tzimmermann@suse.de" <tzimmermann@suse.de>, 
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On Tue, Jun 4, 2024 at 12:18=E2=80=AFPM Chen-Yu Tsai <wenst@chromium.org> w=
rote:
>
> On Fri, May 31, 2024 at 9:37=E2=80=AFPM Frank Binns <Frank.Binns@imgtec.c=
om> wrote:
> >
> > Hi ChenYu,
> >
> > On Thu, 2024-05-30 at 16:35 +0800, Chen-Yu Tsai wrote:
> > > The MediaTek MT8173 comes with a PowerVR Rogue GX6250, which is one
> > > of the Series6XT GPUs, another sub-family of the Rogue family.
> >
> > I've added Adam Ford who sent out some DT related patches [1] for the R=
enesas
> > variant of GX6250 and the GX6650 (another Series6XT GPU).
> >
> > >
> > > This was part of the very first few versions of the PowerVR submissio=
n,
> > > but was later dropped. The compatible string has been updated to foll=
ow
> > > the new naming scheme adopted for the AXE series.
> > >
> > > In a previous iteration of the PowerVR binding submission [1], the
> > > number of clocks required for the 6XT family was mentioned to be
> > > always 3. This is also reflected here.
> > >
> > > [1] https://lore.kernel.org/dri-devel/6eeccb26e09aad67fb30ffcd523c793=
a43c79c2a.camel@imgtec.com/
> > >
> > > Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
> > > ---
> > >  .../bindings/gpu/img,powervr-rogue.yaml       | 24 +++++++++++++++--=
--
> > >  1 file changed, 20 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/Documentation/devicetree/bindings/gpu/img,powervr-rogue.=
yaml b/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml
> > > index 256e252f8087..48aa205b66b4 100644
> > > --- a/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml
> > > +++ b/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml
> > > @@ -12,10 +12,17 @@ maintainers:
> > >
> > >  properties:
> > >    compatible:
> > > -    items:
> > > -      - enum:
> > > -          - ti,am62-gpu
> > > -      - const: img,img-axe # IMG AXE GPU model/revision is fully dis=
coverable
> > > +    oneOf:
> > > +      - items:
> > > +          - enum:
> > > +              - mediatek,mt8173-gpu
> > > +          # PowerVR 6XT GPU model/revision is fully discoverable
> > > +          - const: img,powervr-6xt
> > > +      - items:
> > > +          - enum:
> > > +              - ti,am62-gpu
> > > +          # IMG AXE GPU model/revision is fully discoverable
> > > +          - const: img,img-axe
> >
> > The Series6XT GPU models have differing numbers of power domains (eithe=
r 2, 4 or
> > 5). Whereas, the AXE GPUs have a single power domain, so I assume there=
 should
> > be a related change here.
> >
> > The GX6250 has two power domains (lets call them A and B). There's a co=
nstraint
> > that if domain B is powered then domain A must also be powered.
> >
> > In patch 6 [2] it's setting the power domain to MT8173_POWER_DOMAIN_MFG=
, which I
> > believe corresponds to power domain B. I assume this works because the =
MTK power
> > controller driver is encoding the constraint above, meaning that when w=
e disable
> > or enable MT8173_POWER_DOMAIN_MFG it's also disabling/enabling MT8173_P=
OWER_DOMA
> > IN_MFG_2D (domain A).
>
> It could also be that the power domains are split in the glue layer and t=
here
> is some sequencing handled there. I'll reach out to MediaTek to see if th=
ey
> can dig up some design specifics.

Unfortunately they said they no longer have that information.

> I assume you would like to see the separate power domains properly modele=
d
> in the device tree?

So how should we go about this? Adam, do you have this information for
your platform?

Thanks
ChenYu

>
> Thanks
> ChenYu
>
> > Thanks
> > Frank
> >
> > [1] https://lists.freedesktop.org/archives/dri-devel/2024-February/4435=
48.html
> > [2] https://lists.freedesktop.org/archives/dri-devel/2024-May/455833.ht=
ml
> >
> > >
> > >    reg:
> > >      maxItems: 1
> > > @@ -56,6 +63,15 @@ allOf:
> > >        properties:
> > >          clocks:
> > >            maxItems: 1
> > > +  - if:
> > > +      properties:
> > > +        compatible:
> > > +          contains:
> > > +            const: img,powervr-6xt
> > > +    then:
> > > +      properties:
> > > +        clocks:
> > > +          minItems: 3
> > >
> > >  examples:
> > >    - |