linux-kernel - Re: [PATCH 1/9] dt-bindings: display: renesas,du: Document r8a774e1 bindings

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Message-ID: <CA+V-a8toVwB+_=RmQ4DjhRaTyHoMOPHW2a42NTEUqW+FSv1tmg@mail.gmail.com>
Date:   Thu, 13 Aug 2020 12:20:58 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das.jz@...renesas.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Magnus Damm <magnus.damm@...il.com>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/9] dt-bindings: display: renesas,du: Document r8a774e1 bindings

Hi Laurent,

On Thu, Aug 13, 2020 at 12:11 PM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Prabhakar,
>
> On Thu, Aug 13, 2020 at 12:08:58PM +0100, Lad, Prabhakar wrote:
> > On Thu, Aug 13, 2020 at 11:59 AM Laurent Pinchart wrote:
> > > On Thu, Aug 13, 2020 at 11:38:03AM +0100, Lad, Prabhakar wrote:
> > >> On Thu, Aug 13, 2020 at 10:05 AM Geert Uytterhoeven wrote:
> > >>> On Wed, Aug 12, 2020 at 4:02 PM Lad Prabhakar wrote:
> > >>>> From: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@...renesas.com>
> > >>>>
> > >>>> Document the RZ/G2H (a.k.a. r8a774e1) SoC in the R-Car DU bindings.
> > >>>>
> > >>>> Signed-off-by: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@...renesas.com>
> > >>>> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > >>>> ---
> > >>>>  Documentation/devicetree/bindings/display/renesas,du.txt | 2 ++
> > >>>>  1 file changed, 2 insertions(+)
> > >>>>
> > >>>> diff --git a/Documentation/devicetree/bindings/display/renesas,du.txt b/Documentation/devicetree/bindings/display/renesas,du.txt
> > >>>> index 51cd4d162770..67cded5ad827 100644
> > >>>> --- a/Documentation/devicetree/bindings/display/renesas,du.txt
> > >>>> +++ b/Documentation/devicetree/bindings/display/renesas,du.txt
> > >>>> @@ -10,6 +10,7 @@ Required Properties:
> > >>>>      - "renesas,du-r8a774a1" for R8A774A1 (RZ/G2M) compatible DU
> > >>>>      - "renesas,du-r8a774b1" for R8A774B1 (RZ/G2N) compatible DU
> > >>>>      - "renesas,du-r8a774c0" for R8A774C0 (RZ/G2E) compatible DU
> > >>>> +    - "renesas,du-r8a774e1" for R8A774E1 (RZ/G2H) compatible DU
> > >>>>      - "renesas,du-r8a7779" for R8A7779 (R-Car H1) compatible DU
> > >>>>      - "renesas,du-r8a7790" for R8A7790 (R-Car H2) compatible DU
> > >>>>      - "renesas,du-r8a7791" for R8A7791 (R-Car M2-W) compatible DU
> > >>>> @@ -75,6 +76,7 @@ corresponding to each DU output.
> > >>>>   R8A774A1 (RZ/G2M)      DPAD 0         HDMI 0         LVDS 0         -
> > >>>>   R8A774B1 (RZ/G2N)      DPAD 0         HDMI 0         LVDS 0         -
> > >>>>   R8A774C0 (RZ/G2E)      DPAD 0         LVDS 0         LVDS 1         -
> > >>>> + R8A774E1 (RZ/G2H)      DPAD 0         HDMI 0         LVDS 0         -
> > >>>
> > >>> As LVDS 0 is the fourth channel (DU3), should it be listed under port 3
> > >>> instead of port 2?
> > >>>
> > >>> I know we did it the same for R-Car M3-N and RZ/G2N.
> > >>> But my main worry is adding support for R-Car H3-N later.
> > >
> > > Why should we do so ? The port number here isn't tied to the DU channel
> > > number. It only identifies the output port. Many DUs can route DU
> > > channel outputs to different output ports.
> > >
> > The binding document (renesas,du.txt) does state that "The following
> > table lists for each supported model the port number corresponding to
> > each DU output.", hence the confusion.
>
> It can be a bit confusing indeed. "DU output" here refers to the output
> of the whoel DU, made of individual DU channels. Each DU channel is
> listed as a DU device in the datasheet, and collectively they are the DU
> device that Linux handles.
>
Thanks for the clarification, that clears up the confusion.

Cheers,
Prabhakar