Hi Niklas,

On Fri, Aug 7, 2020 at 1:27 PM Niklas Söderlund
[off-list ref] wrote:

On 2020-08-06 13:47:58 +0200, Geert Uytterhoeven wrote:

quoted

On Thu, Aug 6, 2020 at 1:17 PM Lad, Prabhakar
[off-list ref] wrote:

quoted

On Wed, Aug 5, 2020 at 12:19 PM Geert Uytterhoeven [off-list ref] wrote:

quoted

On Thu, Jul 16, 2020 at 7:20 PM Lad Prabhakar
[off-list ref] wrote:

quoted

Add VIN and CSI-2 nodes to RZ/G2H (R8A774E1) SoC dtsi.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marian-Cristian Rotariu <redacted>

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

However, before I queue this in renesas-devel for v5.10, I'd like to
have some clarification about the issue below.

quoted

--- a/arch/arm64/boot/dts/renesas/r8a774e1.dtsi
+++ b/arch/arm64/boot/dts/renesas/r8a774e1.dtsi

quoted

+               vin4: video@e6ef4000 {
+                       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@e6ef4000/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.

quoted

quoted

quoted

+
+                                       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@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