Re: [PATCH 01/39] dt-bindings: display: Add Renesas SH-Mobile LCDC bindings

From: Geert Uytterhoeven
Date: Fri Jun 23 2023 - 11:20:43 EST


Hi Laurent,

On Fri, Jun 23, 2023 at 4:43 PM Laurent Pinchart
<laurent.pinchart@xxxxxxxxxxxxxxxx> 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@xxxxxxxxx>

> > --- /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@xxxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxx

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