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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Fri, 23 Jun 2023 17:19:45 +0200
Message-ID: <CAMuHMdXdknNczxXod7b6znBHSgXVEb9oNZCAajKCc0Spm1SrYQ@mail.gmail.com>
Subject: Re: [PATCH 01/39] dt-bindings: display: Add Renesas SH-Mobile LCDC bindings
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Magnus Damm <magnus.damm@gmail.com>,
        dri-devel@lists.freedesktop.org, linux-renesas-soc@vger.kernel.org,
        linux-kernel@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>, devicetree@vger.kernel.org
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Hi Laurent,

On Fri, Jun 23, 2023 at 4:43 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
> On Thu, Jun 22, 2023 at 11:21:13AM +0200, Geert Uytterhoeven wrote:
> > Add device tree bindings for the LCD Controller (LCDC) found in Renesas
> > SuperH SH-Mobile and ARM SH/R-Mobile SOCs.
> >
> > Based on a plain text prototype by Laurent Pinchart.
> >
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/display/renesas,shmobile-lcdc.yaml
> > @@ -0,0 +1,108 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/display/renesas,shmobile-lcdc.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Renesas SH-Mobile LCD Controller (LCDC)
> > +
> > +maintainers:
> > +  - Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
>
> I'd be happy if you co-maintained this with me :-) Or even took
> ownership completely.

OK. Thinking about it ;-)

> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - renesas,r8a7740-lcdc # R-Mobile A1
> > +      - renesas,sh73a0-lcdc  # SH-Mobile AG5
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  interrupts:
> > +    maxItems: 1
> > +
> > +  clocks:
> > +    minItems: 1
> > +    maxItems: 5
> > +    description:
> > +      Only the functional clock is mandatory.
> > +      Some of the optional clocks are model-dependent (e.g. "video" (a.k.a.
> > +      "vou" or "dv_clk") is available on R-Mobile A1 only).
> > +
> > +  clock-names:
> > +    minItems: 1
> > +    maxItems: 5
> > +    items:
> > +      enum: [ fck, media, lclk, hdmi, video ]
>
> Switching to per-item descriptions would allow documenting which clock
> applies to which SoC.
>
> Are enum items unique by default ?

Given how about all clocks but fck are optional, it's a bit hard
to handle this in a perfect way.
Note that "pattern: '^dclkin\.[0123]$'" in renesas,du.yaml has the same issue.

> This would allow a combination of clocks that doesn't include the fck
> clock, that's not right.

Right. But when fixing the first to "fck", you have to duplicate all others.
So it should become something like:

  - const: fck
  - enum: [ media, lclk, hdmi, video ]
  - enum: [ media, lclk, hdmi, video ]
  - enum: [ media, lclk, hdmi, video ]
  - enum: [ media, lclk, hdmi, video ]

>
> > +
> > +  power-domains:
> > +    maxItems: 1
> > +
> > +  ports:
> > +    $ref: /schemas/graph.yaml#/properties/ports
> > +    description: |
> > +      The connections to the output video ports are modeled using the OF graph
> > +      bindings specified in Documentation/devicetree/bindings/graph.txt.
>
> it's available in YAML form now. I'd just drop the "specified in ...".

OK.

> > +      The number of ports and their assignment are model-dependent.
> > +      Each port shall have a single endpoint.
> > +
> > +    properties:
> > +      port@0:
> > +        $ref: /schemas/graph.yaml#/properties/port
> > +        description: LCD port (R-Mobile A1 and SH-Mobile AG5)
> > +        unevaluatedProperties: false
> > +
> > +      port@1:
> > +        $ref: /schemas/graph.yaml#/properties/port
> > +        description: HDMI port (R-Mobile A1 LCDC1 and SH-Mobile AG5)
> > +        unevaluatedProperties: false
> > +
> > +      port@2:
> > +        $ref: /schemas/graph.yaml#/properties/port
> > +        description: MIPI-DSI port (SH-Mobile AG5)
> > +        unevaluatedProperties: false
>
> Let's condition the ports on the compatible value to enable automatic
> validation.
>
> > +
> > +    required:
> > +      - port@0
>
> Based on the above, port@1 is required too as it's present on all
> supported SoCs. Let's condition this on the compatible value too.

It does not depend solely on the SoC, but also on the LCDC instance.
port@1 is not available on R-Mobile A1 LCDC0, only on LCDC1.

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