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

From: "Luca Weiss" <luca.weiss@fairphone.com>
To: "Maxime Ripard" <mripard@kernel.org>
Cc: "Konrad Dybcio" <konrad.dybcio@linaro.org>,
	"Neil Armstrong" <neil.armstrong@linaro.org>,
	"Jessica Zhang" <quic_jesszhan@quicinc.com>,
	"Sam Ravnborg" <sam@ravnborg.org>,
	"David Airlie" <airlied@gmail.com>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Conor Dooley" <conor+dt@kernel.org>,
	"Bjorn Andersson" <andersson@kernel.org>,
	<~postmarketos/upstreaming@lists.sr.ht>,
	<phone-devel@vger.kernel.org>, <dri-devel@lists.freedesktop.org>,
	<devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<linux-arm-msm@vger.kernel.org>
Subject: Re: [PATCH 3/3] arm64: dts: qcom: sm7225-fairphone-fp4: Enable display and GPU
Date: Wed, 10 Jan 2024 12:30:37 +0100	[thread overview]
Message-ID: <CYAZQD6AWM6J.10P13VNGRYNPR@fairphone.com> (raw)
In-Reply-To: <2zkiop7xg7w4vkpjpol25qna5wwbq4ja5o6iwuqh25m34k6mgd@aemrbzqgx2oe>

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