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Message-ID: <CAMuHMdW1Ofjouj4P+bdg2VWmYohD73=si8R6ivZ4QiZps6=HAQ@mail.gmail.com>
Date: Fri, 7 Aug 2020 13:36:46 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Niklas Söderlund <niklas.soderlund@...natech.se>
Cc: "Lad, Prabhakar" <prabhakar.csengg@...il.com>,
Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
Jens Axboe <axboe@...nel.dk>, Rob Herring <robh+dt@...nel.org>,
Vinod Koul <vkoul@...nel.org>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Marek Vasut <marek.vasut+renesas@...il.com>,
Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
Mark Brown <broonie@...nel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Kishon Vijay Abraham I <kishon@...com>,
Liam Girdwood <lgirdwood@...il.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Magnus Damm <magnus.damm@...il.com>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@...r.kernel.org>, linux-ide@...r.kernel.org,
dmaengine <dmaengine@...r.kernel.org>,
Linux I2C <linux-i2c@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux Media Mailing List <linux-media@...r.kernel.org>,
linux-pci <linux-pci@...r.kernel.org>,
ALSA Development Mailing List <alsa-devel@...a-project.org>,
Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
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Subject: Re: [PATCH 20/20] arm64: dts: renesas: r8a774e1: Add VIN and CSI-2 nodes
Hi Niklas,
On Fri, Aug 7, 2020 at 1:27 PM Niklas Söderlund
<niklas.soderlund@...natech.se> wrote:
> On 2020-08-06 13:47:58 +0200, Geert Uytterhoeven wrote:
> > On Thu, Aug 6, 2020 at 1:17 PM Lad, Prabhakar
> > <prabhakar.csengg@...il.com> wrote:
> > > On Wed, Aug 5, 2020 at 12:19 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > > On Thu, Jul 16, 2020 at 7:20 PM Lad Prabhakar
> > > > <prabhakar.mahadev-lad.rj@...renesas.com> wrote:
> > > > > Add VIN and CSI-2 nodes to RZ/G2H (R8A774E1) SoC dtsi.
> > > > >
> > > > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > > > > Reviewed-by: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@...renesas.com>
> > > >
> > > > Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
> > > >
> > > > However, before I queue this in renesas-devel for v5.10, I'd like to
> > > > have some clarification about the issue below.
> > > >
> > > > > --- a/arch/arm64/boot/dts/renesas/r8a774e1.dtsi
> > > > > +++ b/arch/arm64/boot/dts/renesas/r8a774e1.dtsi
> > > >
> > > > > + vin4: video@...f4000 {
> > > > > + compatible = "renesas,vin-r8a774e1";
> > > > > + reg = <0 0xe6ef4000 0 0x1000>;
> > > > > + interrupts = <GIC_SPI 174 IRQ_TYPE_LEVEL_HIGH>;
> > > > > + clocks = <&cpg CPG_MOD 807>;
> > > > > + power-domains = <&sysc R8A774E1_PD_ALWAYS_ON>;
> > > > > + resets = <&cpg 807>;
> > > > > + renesas,id = <4>;
> > > > > + status = "disabled";
> > > > > +
> > > > > + ports {
> > > > > + #address-cells = <1>;
> > > > > + #size-cells = <0>;
> > > > > +
> > > > > + port@1 {
> > > > > + #address-cells = <1>;
> > > > > + #size-cells = <0>;
> > > >
> > > > "make dtbs W=1" says:
> > > >
> > > > arch/arm64/boot/dts/renesas/r8a774e1.dtsi:1562.12-1572.7: Warning
> > > > (graph_child_address): /soc/video@...f4000/ports/port@1: graph node
> > > > has single child node 'endpoint@0', #address-cells/#size-cells are not
> > > > necessary
> > > >
> > > > (same for vin5-7 below)
> > > >
> > > Referring to commit 5e53dbf4edb4d ("arm64: dts: renesas: r8a77990: Fix
> > > VIN endpoint numbering") we definitely need endpoint numbering.
> > > Probably the driver needs to be fixed to handle such cases.
> >
> > > > > +
> > > > > + reg = <1>;
> > > > > +
> > > > > + vin4csi20: endpoint@0 {
> > > > > + reg = <0>;
> > > > > + remote-endpoint = <&csi20vin4>;
> >
> > On R-Car E3, the single endpoint is at address 2, so "make dtbs W=1"doesn't
> > complain. Here it is at address 0.
> >
> > Niklas?
>
> First the R-Car VIN driver makes decisions based on which endpoint is
> described, each endpoint 0-3 represents a different CSI-2 block on the
> other end (0: CSI20, 1: CSI21, 2: CSI40 and 3: CSI41).
That's my understanding, too.
> Then how to handle the warning I'm not sure. I can only really see 2
> options.
>
> 1. Ignore the warning.
> 2. Remove #address-cells, #size-cells and reg properties from port@ if
> the only endpoint described is endpoint@0.
>
> I would prefers option 2. that is what we do in other cases (for example
> on Gen2 boards that only have a single parallel sensor in some early DTS
> files we don't have the ports node and just describe a single port with
> the same reasoning.
>
> We are not at risk at someone describing a second CSI-2 bock as an
> overlay so I see no real harm in option 2.
Yeah, no overlay possible for on-SoC wiring ;-)
> What are your thoughts Geert?
> You know more about DT then me.
You have too much faith in me ;-)
AFAIK we don't get this warning for e.g. SPI buses, which can have a
single device at address 0, and #{address,size}-cells is mandatory
there. So endpoints (or SPI?) are treated special?
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
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