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

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Date:   Thu, 31 Mar 2022 10:51:33 -0500
From:   Rob Herring <robh@...nel.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Vinod Koul <vkoul@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...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 Thu, Mar 31, 2022 at 4:35 AM Dmitry Baryshkov
<dmitry.baryshkov@...aro.org> wrote:
>
> On Thu, 31 Mar 2022 at 09:05, Vinod Koul <vkoul@...nel.org> wrote:
> >
> > On 29-03-22, 10:52, Rob Herring wrote:
> > > 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.
> >
> > I guess we should make this optional, keep it when adding panel@0 node
> > and skip for rest where not applicable..? Dmitry is that fine with you?
>
> This sounds like a workaround. When a panel node is added together
> with the '#address-cells' / '#size-cells' properties, we will get
> warnings for the 'ports' node.

What warning exactly? Is that with W=1?

Some warnings are more "don't do this on new designs" rather than
never allowed and need to fix current bindings/dts. As such, these
warnings will probably never be enabled by default.

Rob