linux-kernel - Re: [PATCH] dt-bindings: display: msm: dsi: remove address/size cells

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Date:   Tue, 29 Mar 2022 10:52:30 -0500
From:   Rob Herring <robh@...nel.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dt-bindings: display: msm: dsi: remove address/size cells

On Tue, Mar 29, 2022 at 12:01:52PM +0530, Vinod Koul wrote:
> On 28-03-22, 13:21, Rob Herring wrote:
> > On Mon, Mar 28, 2022 at 12:18 PM Krzysztof Kozlowski
> > <krzysztof.kozlowski@...aro.org> wrote:
> > >
> > > On 28/03/2022 19:16, Vinod Koul wrote:
> > > > On 28-03-22, 19:43, Dmitry Baryshkov wrote:
> > > >> On Mon, 28 Mar 2022 at 18:30, Krzysztof Kozlowski
> > > >> <krzysztof.kozlowski@...aro.org> wrote:
> > > >>>
> > > >>> The DSI node is not a bus and the children do not have unit addresses.
> > > >>>
> > > >>> Reported-by: Vinod Koul <vkoul@...nel.org>
> > > >>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> > > >>
> > > >> NAK.
> > > >> DSI panels are children of the DSI device tree node with the reg = <0>; address.
> > > >> This is the convention used by other platforms too (see e.g.
> > > >> arch/arm64/boot/dts/freescale/imx8mq-evk.dts).
> > > >
> > > > So we should add reg = 0, i will update my dtsi fix
> > > >
> > >
> > > To "ports" node? No. The reg=0 is for children of the bus, so the
> > > panels. How to combine both without warnings - ports and panel@0 - I
> > > don't know yet...
> > 
> > I don't think that should case a warning. Or at least it's one we turn off.
> 
> Well in this case I think we might need a fix:
> Here is the example quoted in the binding. We have ports{} and then the
> two port@0 and port@1 underneath.

It's the #address-cells/#size-cells under 'ports' that applies to 'port' 
nodes. As 'ports' has no address (reg) itself, it doesn't need 
#address-cells/#size-cells in its parent node.

> 
> So it should be okay to drop #address-cells/#size-cells from dsi node
> but keep in ports node...

Yes.

> Thoughts...?

But I thought a panel@0 node was being added? If so then you need to add 
them back.

Rob