Re: [PATCH 3/4] ARM: dts: rockchip: add display nodes for rk322x

Stephen Boyd
2019-06-14T20:36:09Z

Quoting Heiko Stuebner (2019-06-14 12:33:12)
> Am Freitag, 14. Juni 2019, 20:32:35 CEST schrieb Justin Swartz:
> > On 2019-06-14 19:45, Stephen Boyd wrote:
> > >> diff --git a/arch/arm/boot/dts/rk322x.dtsi
> > >> b/arch/arm/boot/dts/rk322x.dtsi
> > >> index da102fff96a2..148f9b5157ea 100644
> > >> --- a/arch/arm/boot/dts/rk322x.dtsi
> > >> +++ b/arch/arm/boot/dts/rk322x.dtsi
> > >> @@ -143,6 +143,11 @@
> > >> #clock-cells = <0>;
> > >> };
> > >>
> > >> + display_subsystem: display-subsystem {
> > >> + compatible = "rockchip,display-subsystem";
> > >> + ports = <&vop_out>;
> > >> + };
> > >> +
> > >
> > > What is this? It doesn't have a reg property so it looks like a virtual
> > > device. Why is it in DT?
> >
> > This is a virtual device.
> >
> > I assumed it would be acceptable to it find in a device tree due to
> > binding documentation,
> > "Documentation/devicetree/bindings/display/rockchip/rockchip-drm.txt,
> > which states:
> >
> > <quote>
> > The Rockchip DRM master device is a virtual device needed to list all
> > vop devices or other display interface nodes that comprise the
> > graphics subsystem.
> > </quote>
> >
> > Without the "display_subsystem" device node, the HDMI PHY and
> > rockchipdrmfb frame buffer device are not initialized.
> >
> > Perhaps I should have included this in my commit message? :)
>
> As Justin said, that is very much common as the root of the components
> that make up the drm device and pretty much common in a lot of devicetrees
> for the last 5 years and longer ;-) .
>
> Also gpio-keys also don't have a reg property ;-) .
>

Do you have a SoC node? If so, this virtual device should live in the
root, away from the nodes that have reg properties and are thus in the
SoC node.