linux-kernel - Re: [PATCH v2 4/5] dt-bindings: display/msm: dsi-controller-main: Document dual panel property

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Message-ID: <dqbosrbwgbeii26wwj3tfsqnjgvq7har7nvs2ifato6nmxqbie@2cexn4xyyh3p>
Date: Thu, 20 Feb 2025 18:01:15 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Jun Nie <jun.nie@...aro.org>
Cc: Rob Clark <robdclark@...il.com>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>, Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Sean Paul <sean@...rly.run>, Marijn Suijten <marijn.suijten@...ainline.org>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Krishna Manikandan <quic_mkrishn@...cinc.com>, linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 4/5] dt-bindings: display/msm: dsi-controller-main:
 Document dual panel property

On Thu, Feb 20, 2025 at 11:40:03PM +0800, Jun Nie wrote:
> Dmitry Baryshkov <dmitry.baryshkov@...aro.org> 于2025年2月20日周四 18:33写道：
> >
> > On Thu, Feb 20, 2025 at 06:07:55PM +0800, Jun Nie wrote:
> > > The DSI interface can be connected to a panel that has a dual DSI channel,
> > > or to two separate panels, each equipped with a single DSI channel. To
> > > prevent the DSC configuration for the dual panel setup from disrupting the
> > > current configuration of a single panel with a dual DSI channel, add a dual
> > > panel property to support the use of two panels.
> >
> > Please use the terms from the standard. The "channel" is mostly used for
> > the "Virtual Channel" or the "logical channel".
> 
> OK, will use DSI link for all later description.
> >
> > Also I don't follow how DSC configuration for a dual panel setup can
> > disrupt current (?) configuration of a single panel.
> 
> For the disruption, Marijn mentioned it in the last post.
> https://gitlab.freedesktop.org/drm/msm/-/issues/41#note_2411541

So, why is it happening?

> 
> >
> > >
> > > Signed-off-by: Jun Nie <jun.nie@...aro.org>
> > > ---
> > >  .../devicetree/bindings/display/msm/dsi-controller-main.yaml      | 8 +++++++-
> > >  1 file changed, 7 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/Documentation/devicetree/bindings/display/msm/dsi-controller-main.yaml b/Documentation/devicetree/bindings/display/msm/dsi-controller-main.yaml
> > > index ffbd1dc9470e2091b477b0c88392d81802119f48..e3f2eabde27609a66d6d81fafcb14e1bc014613c 100644
> > > --- a/Documentation/devicetree/bindings/display/msm/dsi-controller-main.yaml
> > > +++ b/Documentation/devicetree/bindings/display/msm/dsi-controller-main.yaml
> > > @@ -88,9 +88,15 @@ properties:
> > >    qcom,dual-dsi-mode:
> > >      type: boolean
> > >      description: |
> > > -      Indicates if the DSI controller is driving a panel which needs
> > > +      Indicates if the DSI controller is driving display device which needs
> >
> > Unrelated change
> >
> > >        2 DSI links.
> > >
> > > +  qcom,dual-panel:
> > > +    type: boolean
> > > +    description: |
> > > +      Indicates if the DSI controller is driving display device that composed
> > > +      with 2 independent panels and needs 2 DSI links.
> >
> > How is tht different from qcom,dual-dsi-mode?
> 
> Your questioning is right. The dual panel case is a subset of
> dual-dsi-mode, not parallel with
> dual-dsi-mode. It is single panel with 2 DSI link by default, and 2
> panel with 1 DSI link in
> each panel if property dual-panel is present.

And what if it is one panel having two 'logical' panels inside?
I'm trying to point out that this should be a property of the
struct mipi_dsi_device (or an option in the struct drm_dsc_config).
There is no need to describe this in DT.

> >
> > > +
> > >    qcom,master-dsi:
> > >      type: boolean
> > >      description: |
> > >
> > > --
> > > 2.34.1
> > >
> >
> > --
> > With best wishes
> > Dmitry

-- 
With best wishes
Dmitry