Re: [GIT PULL] arm64: dts: mediatek: changes for v5.13 (second round)

[Fabien Parent <fparent@baylibre.com>]

Hi Arnd,

On Wed, Apr 7, 2021 at 7:55 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Wed, Apr 7, 2021 at 6:34 PM Matthias Brugger <matthias.bgg@gmail.com> wrote:
> > On 07/04/2021 18:06, Arnd Bergmann wrote:
> > > On Wed, Apr 7, 2021 at 1:00 PM Matthias Brugger <matthias.bgg@gmail.com> wrote:
> > >>
> > >> Hi Olof and Arnd,
> > >>
> > >> Here comes the second round of arm64 DT patches. Hope I'm not too late.
> > >> Basically we add several node to MT8167.
> > >> ----------------------------------------------------------------
> > >> Fabien Parent (6):
> > >
> > >>       arm64: dts: mediatek: mt8167: add some DRM nodes
> > >
> > > I stumbled over this patch adding a lot of aliases:
> > >
> > > +       aliases {
> > > +               aal0 = &aal;
> > > +               ccorr0 = &ccorr;
> > > +               color0 = &color;
> > > +               dither0 = &dither;
> > > +               dsi0 = &dsi;
> > > +               ovl0 = &ovl0;
> > > +               pwm0 = &disp_pwm;
> > > +               rdma0 = &rdma0;
> > > +               rdma1 = &rdma1;
> > > +               wdma0 = &wdma;
> > > +       };
> > >
> > >
> > > Something doesn't quite feel right about this, and I checked with Rob,
> > > who also thinks this looks wrong. I suppose we need to have a set of
> > > well documented alias types rather than just having drivers make up
> > > new ones on the spot.
> >
> > These are needed in the DRM driver, see drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> >
> > I added Chun-Kuang who is the maintainer of the driver. I think it's a good idea
> > to have this alias described in the binding. Maybe a good excuse to move to yaml
> > as well :)
>
> The aliases certainly need to be described in the binding, I think someone
> would likely have complained earlier if that was part of the binding.
>
> Moving it to yaml is also a good idea, and required for any new devices.
>
> > > I also noticed that some of the referenced nodes are missing a DT
> > > binding file, so those need to be added and reviewed as well.
> >
> > I suppose you are talking about "mediatek,mt8173-vcodec-enc-vp8". The binding
> > patches are in the media tree [1]. Maybe I supposed wrongly that they will land
> > in v5.13? Or perhaps I should have mentioned that in the pull request.
> >
> > If it wasn't about this compatible and you can still remember, please let me
> > know so that we can fix that :)
> >
> > I double checked and didn't find any missing binding. Some of them only have the
> > fallback binding described, maybe that's what you are referring to.
>
> Here is what I see for all compatible strings of the added device nodes in
> this patch, as of linux-next-20210407:
>
> $ for i in mediatek,mt8167-disp-mutex mediatek,mt8167-disp-rdma
> mediatek,mt2701-disp-rdma mediatek,mt8167-disp-pwm
> mediatek,mt8173-disp-pwn mediatek,mt8167-dsi mediatek,mt2701-dsi
> mediatek,mt8167-mipi-tx mediatek,mt2701-mipi-tx
> mediatek,mt8167-disp-ovl mediatek,mt8173-disp-ovl
> mediatek,mt8167-disp-rdma mediatek,mt2701-disp-rdma
> mediatek,mt8167-disp-color mediatek,mt8173-disp-color
> mediatek,mt8167-disp-ccorr mediatek,mt8183-disp-ccorr
> mediatek,mt8167-disp-aal mediatek,mt8167-disp-gamma
> mediatek,mt8173-disp-gamma mediatek,mt8167-disp-dither
> mediatek,mt8167-disp-wdma ; do echo === $i ;  git grep -wl $i
> Documentation/devicetree/ ; done
>
> === mediatek,mt8167-disp-mutex
> === mediatek,mt8167-disp-rdma
> === mediatek,mt2701-disp-rdma
> === mediatek,mt8167-disp-pwm
> Documentation/devicetree/bindings/pwm/pwm-mtk-disp.txt
> === mediatek,mt8173-disp-pwn
> === mediatek,mt8167-dsi
> === mediatek,mt2701-dsi
> === mediatek,mt8167-mipi-tx
> === mediatek,mt2701-mipi-tx
> Documentation/devicetree/bindings/phy/mediatek,dsi-phy.yaml
> === mediatek,mt8167-disp-ovl
> === mediatek,mt8173-disp-ovl
> Documentation/devicetree/bindings/display/mediatek/mediatek,disp.txt
> === mediatek,mt8167-disp-rdma
> === mediatek,mt2701-disp-rdma
> === mediatek,mt8167-disp-color
> === mediatek,mt8173-disp-color
> Documentation/devicetree/bindings/display/mediatek/mediatek,disp.txt
> === mediatek,mt8167-disp-ccorr
> === mediatek,mt8183-disp-ccorr
> === mediatek,mt8167-disp-aal
> === mediatek,mt8167-disp-gamma
> === mediatek,mt8173-disp-gamma
> Documentation/devicetree/bindings/display/mediatek/mediatek,disp.txt
> === mediatek,mt8167-disp-dither
> === mediatek,mt8167-disp-wdma
>
> So five of the strings are documented, the others are missing. I did not check
> the other patches in your branch.

The binding documentation for these drivers are here [0]. The display
bindings are documented as:
- compatible: "mediatek,<chip>-disp-<function>", one of

The <chip> placeholder is never expanded for all the supported chips.
The 5 existings matches from your grep command comes from the example.
I guess these will be fixed whenever someone converts [0] to yaml.

[0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/display/mediatek/mediatek,disp.txt?h=v5.12-rc6#n29

>
>          Arnd

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