linux-kernel - Re: [PATCH 3/3] arm64: dts: qcom: sm7225-fairphone-fp4: Enable display and GPU

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Date: Wed, 10 Jan 2024 12:30:37 +0100
From: "Luca Weiss" <luca.weiss@...rphone.com>
To: "Maxime Ripard" <mripard@...nel.org>
Cc: "Konrad Dybcio" <konrad.dybcio@...aro.org>, "Neil Armstrong"
 <neil.armstrong@...aro.org>, "Jessica Zhang" <quic_jesszhan@...cinc.com>,
 "Sam Ravnborg" <sam@...nborg.org>, "David Airlie" <airlied@...il.com>,
 "Daniel Vetter" <daniel@...ll.ch>, "Maarten Lankhorst"
 <maarten.lankhorst@...ux.intel.com>, "Thomas Zimmermann"
 <tzimmermann@...e.de>, "Rob Herring" <robh+dt@...nel.org>, "Krzysztof
 Kozlowski" <krzysztof.kozlowski+dt@...aro.org>, "Conor Dooley"
 <conor+dt@...nel.org>, "Bjorn Andersson" <andersson@...nel.org>,
 <~postmarketos/upstreaming@...ts.sr.ht>, <phone-devel@...r.kernel.org>,
 <dri-devel@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH 3/3] arm64: dts: qcom: sm7225-fairphone-fp4: Enable
 display and GPU

On Wed Jan 10, 2024 at 12:23 PM CET, Maxime Ripard wrote:
> On Wed, Jan 10, 2024 at 12:00:23PM +0100, Luca Weiss wrote:
> > On Wed Jan 10, 2024 at 11:58 AM CET, Konrad Dybcio wrote:
> > >
> > >
> > > On 1/5/24 15:29, Luca Weiss wrote:
> > > > Add the description for the display panel found on this phone and remove
> > > > the simple-framebuffer that was in place until now
> > >
> > > Why? They should be able to coexist with a smooth-ish handoff
> > 
> > Does that work upstream? I'm aware that downstream can do this but
> > thought this was still missing upstream.
>
> It depends what you call smooth-ish I guess, but KMS handles the
> handover just fine. You're likely to get a flicker during the transition
> though.

Right, seems to work. Also visually looks okay.

fairphone-fp4:~$ dmesg | grep "frame buffer device"
[    0.250511] Console: switching to colour frame buffer device 135x146
[    0.284146] simple-framebuffer a0000000.framebuffer: [drm] fb0: simpledrmdrmfb frame buffer device
[    2.576712] Console: switching to colour frame buffer device 135x146
[    2.604907] msm_dpu ae01000.display-controller: [drm] fb0: msmdrmfb frame buffer device

I thought before that having two outputs like this would cause two
different framebuffers/display devices to appear, but yeah as I said
seems okay. Will change in v2.

Regards
Luca

>
> Either way, the DT isn't the right place to choose, you should enable
> both, and the distro will choose its policy through configuration.
>
> Maxime