linux-kernel - Re: [PATCH v2] dt-bindings: display: renesas,du: Provide bindings for r8a779a0

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Date:   Tue, 7 Sep 2021 21:17:31 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Kieran Bingham <kieran.bingham@...asonboard.com>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        "open list:DRM DRIVERS FOR RENESAS" <dri-devel@...ts.freedesktop.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] dt-bindings: display: renesas,du: Provide bindings for r8a779a0

Hi Rob,

On Tue, Sep 7, 2021 at 8:45 PM Rob Herring <robh@...nel.org> wrote:
> On Mon, Sep 06, 2021 at 10:13:07AM +0200, Geert Uytterhoeven wrote:
> > On Thu, Sep 2, 2021 at 1:39 AM Kieran Bingham
> > <kieran.bingham@...asonboard.com> wrote:
> > > From: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> > >
> > > Extend the Renesas DU display bindings to support the r8a779a0 V3U.
> > >
> > > Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> > > Signed-off-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> > > ---
> > > v2:
> > >  - Collected Laurent's tag
> > >  - Remove clock-names requirement
> > >  - Specify only a single clock
> >
> > Thanks for the update!
> >
> > > --- a/Documentation/devicetree/bindings/display/renesas,du.yaml
> > > +++ b/Documentation/devicetree/bindings/display/renesas,du.yaml
> > > @@ -39,6 +39,7 @@ properties:
> > >        - renesas,du-r8a77980 # for R-Car V3H compatible DU
> > >        - renesas,du-r8a77990 # for R-Car E3 compatible DU
> > >        - renesas,du-r8a77995 # for R-Car D3 compatible DU
> > > +      - renesas,du-r8a779a0 # for R-Car V3U compatible DU
> > >
> > >    reg:
> > >      maxItems: 1
> > > @@ -773,6 +774,55 @@ allOf:
> > >          - reset-names
> > >          - renesas,vsps
> > >
> > > +  - if:
> > > +      properties:
> > > +        compatible:
> > > +          contains:
> > > +            enum:
> > > +              - renesas,du-r8a779a0
> > > +    then:
> > > +      properties:
> > > +        clocks:
> > > +          items:
> > > +            - description: Functional clock
> > > +
> > > +        clock-names:
> > > +          maxItems: 1
> > > +          items:
> > > +            - const: du
> > > +
> > > +        interrupts:
> > > +          maxItems: 2
> > > +
> > > +        resets:
> > > +          maxItems: 1
> > > +
> > > +        reset-names:
> > > +          items:
> > > +            - const: du.0
> >
> > This is now inconsistent with clock-names, which doesn't use a suffix.
>
> But it is consistent with all the other cases of 'reset-names'. The
> problem is 'clock-names' is not consistent and should be 'du.0'.

True.

> Ideally, the if/them schemas should not be defining the names. That
> should be at the top level and the if/them schema just limits the number
> of entries. That's not always possible, but I think is for clocks and
> resets in this case.

It's a bit tricky.
For clocks, there's usually one clock per channel, but not always.
Plus clocks for external inputs, if present.
For resets, there's one reset for a group of channels, with the number
of channels in a group depending on the SoC family.
And then there's the special casing for SoCs where there's a gap in
the channel numbering...

Still wondering if it would be better to have one device node per
channel, and companion links...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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