linux-kernel - Re: [PATCH v2 00/10] drm: bridge: dw_hdmi: Misc enable/disable, CEC and EDID cleanup

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Message-Id: <D45C28ZF5US9.1BCL9HBVRERJB@cknow.org>
Date: Fri, 13 Sep 2024 19:30:13 +0200
From: "Diederik de Haas" <didi.debian@...ow.org>
To: "Jonas Karlman" <jonas@...boo.se>, "Andrzej Hajda"
 <andrzej.hajda@...el.com>, "Neil Armstrong" <neil.armstrong@...aro.org>,
 "Robert Foss" <rfoss@...nel.org>, "Maarten Lankhorst"
 <maarten.lankhorst@...ux.intel.com>, "Maxime Ripard" <mripard@...nel.org>,
 "Thomas Zimmermann" <tzimmermann@...e.de>, "David Airlie"
 <airlied@...il.com>, "Simona Vetter" <simona@...ll.ch>
Cc: "Laurent Pinchart" <Laurent.pinchart@...asonboard.com>, "Jernej Skrabec"
 <jernej.skrabec@...il.com>, "Christian Hewitt"
 <christianshewitt@...il.com>, "Christopher Obbard" <obbardc@...il.com>,
 <dri-devel@...ts.freedesktop.org>, <linux-rockchip@...ts.infradead.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 00/10] drm: bridge: dw_hdmi: Misc enable/disable, CEC
 and EDID cleanup

Hi Jonas,

On Sun Sep 8, 2024 at 3:28 PM CEST, Jonas Karlman wrote:
> This series ensure poweron/poweroff and CEC phys addr invalidation is
> happening under drm mode_config mutex lock, and also ensure EDID is
> updated (when the dw-hdmi connector is used) after a hotplug pulse.
>
> These changes has mainly been tested on Rockchip devices together with a
> series [1] that add HDMI 2.0 4K@...z support to RK3228, RK3328, RK3399
> and RK3568.

I did some tests with this series (together with the 4K60Hz one).

Test setup:
- TV capable of display 4K@...z
- monitor capable of displaying 1080p@...z
- Quartz64 Model-A
- Rock64

When I booted up connected to the 4K TV, the boot messages were
displayed in 1080p resolution. IIUC it was to be considered an
improvement when it would be illegible at 4K, but that did not happen.
Neither on the Q64-A or the Rock64.

When executing ``cat /sys/class/graphics/*/modes`` it returned
``U:3840x2160p-0``, so that was good.

I then went on the HDMI-hot-plug-swap-test and connected it to my 1080p
monitor while the system was still online. That did not change the
output of the previous command. As my monitor doesn't support 4K it
seems to have chosen a 640p or 720p resolution.
IOW the letters were rather big. With enough output on the screen, it
went off the visible area, so all I could do then was 'blind' typing.

If I booted up connected to the 1080p monitor then it reported a 1080p
resolution and when swapping to the 4K TV, it kept reporting that value
and displaying things in 1080p resolution, but ofc there were no
abnormal big letters or output falling off the screen this time.

If I did those test when Sway was running, all the data (``swaymsg -t
get_outputs --pretty``) showed that a proper resolution switch was made
and the display was correctly adjusted accordingly.

I then tried to do the keep-swapping-until-output-breaks what Chris
reported about in the previous series.
At some point I thought I was able to reproduce the issue ... to then
conclude I had likely hit the poweroff button when swapping the cables.
And another time I thought I had managed to reproduce it ... to then
find out display wasn't working at all anymore. Turned out that likely
due to all that swapping, it was no longer properly inserted into my
monitor.
I've tried it a LOT of times, but I have to conclude that I was not able
to reproduce the problem and therefor also not the solution.

HTH,
  Diederik

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