Re: [PATCH 1/3] dt-bindings: gpu: img,powervr-rogue: Document GX6250 GPU in Renesas R-Car M3-W/M3-W+

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Marek,

On Wed, 15 Oct 2025 at 00:48, Marek Vasut <marek.vasut@mailbox.org> wrote:
> On 10/14/25 1:52 PM, Matt Coster wrote:
> >> diff --git a/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml b/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml
> >> index c87d7bece0ecd..c9680a2560114 100644
> >> --- a/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml
> >> +++ b/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml
> >> @@ -13,6 +13,12 @@ maintainers:
> >>   properties:
> >>     compatible:
> >>       oneOf:
> >> +      - items:
> >> +          - enum:
> >> +              - renesas,r8a77960-gpu
> >> +              - renesas,r8a77961-gpu
> >
> > I think this can just be renesas,r8a7796-gpu; most of the devices in the
> > dts for these SoCs appear to use the same pattern and the GPU is the
> > same in both.
>
> Not really, the 77960 and 77961 are different SoCs, that is why they
> each have different specific compatible. Of course, most drivers match
> on fallback compatible, since the IPs are mostly identical, see this:
>
> $ git grep compatible.*7796 arch/arm64/boot/dts/renesas/r8a77961.dtsi
> arch/arm64/boot/dts/renesas/r8a77961.dtsi:      compatible =
> "renesas,r8a77961";
> arch/arm64/boot/dts/renesas/r8a77961.dtsi:
> compatible = "renesas,r8a77961-wdt",
> arch/arm64/boot/dts/renesas/r8a77961.dtsi:
> compatible = "renesas,gpio-r8a77961",
> ...
>
> $  git grep compatible.*7796 arch/arm64/boot/dts/renesas/r8a77960.dtsi
> arch/arm64/boot/dts/renesas/r8a77960.dtsi:      compatible =
> "renesas,r8a7796";
> arch/arm64/boot/dts/renesas/r8a77960.dtsi:
> compatible = "renesas,r8a7796-wdt",
> arch/arm64/boot/dts/renesas/r8a77960.dtsi:
> compatible = "renesas,gpio-r8a7796",
> arch/arm64/boot/dts/renesas/r8a77960.dtsi:
> compatible = "renesas,gpio-r8a7796",
>
> I can turn the first entry into renesas,r8a7796-gpu to be consistent
> with the legacy 7796 name for 77960.
>
> Geert ?

Please use "renesas,r8a7796-gpu" for R-Car M3-W, and
"renesas,r8a77961-gpu" for R-Car M3-W+.

> >> +          - const: img,img-gx6250
> >> +          - const: img,img-rogue
> >>         - items:
> >>             - enum:
> >>                 - ti,am62-gpu
> >
> > You also need to add img,img-gx6250 to the appropriate conditional
> > blocks below here for the number of power domains (in this case, 2) and
> > clocks (that's more complicated).
> >
> > These older GPUs always require three clocks (core, mem and sys), but
> > it's not immediately clear from the Renesas TRM how these are hooked up.
> > I can see three "clocks" connected (fig 23.2 in my copy, clock details
> > from fig 8.1b):
>
> Which revision of the RM is that ? There should be some Rev.M.NP at the
> bottom of each page.

Rev.2.40.

> >   - Clock ZGφ: Appears to be a core clock for the GPU (3DGE). That would
> >     make it our "core" clock.
>
> This should be 600-700 MHz clock on M3-W , so that sounds like a GPU
> core clock.

Agreed.

>
> >   - Clock S2D1φ: Appears to be a core clock used on the AXI bus, making
> >     it our "sys" clock.
>
> This should be 400 MHz AXI clock, but wouldn't that make it "mem" clock
> ? I think this might be the clock which drives the AXI bus, used by the
> GPU to access data in DRAM ?

Agreed.

> >   - MSTP ST112: Appears to be a whole module on/off control of some
> >     description, and definitely doesn't align with the missing "mem"
> >     clock.
>
> Maybe this is the "sys" clock, since it toggles the register interface
> clock on/off ?

Probably.

Note that both ZGφ and S2D1φ are always-on.
MSTP ST112 is the only gateable clock, and it is controlled through
the PM Domain and Runtime PM.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds