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

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Message-Id: <D4LKOUTND4C9.A02Z06OBACZE@cknow.org>
Date: Wed, 02 Oct 2024 21:38:32 +0200
From: "Diederik de Haas" <didi.debian@...ow.org>
To: "Laurent Pinchart" <Laurent.pinchart@...asonboard.com>, "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: "Diederik de Haas" <didi.debian@...ow.org>, "Heiko Stuebner"
 <heiko@...ech.de>, "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 and Laurent,

I may be showing my n00bness ... or I actually found something ...

On Fri Sep 13, 2024 at 7:30 PM CEST, Diederik de Haas wrote:
> 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).
>
> ...
>
> 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.

A DT validation on rk3328-rock64.dtb reported this:

rockchip/rk3328-rock64.dtb: hdmi@...c0000: interrupts: [[0, 35, 4], [0, 71, 4]] is too long

That's because `display/bridge/synopsys,dw-hdmi.yaml` dt-binding has
interrupts : maxItems : 1

and the rk3328.dtsi file has 2 interrupts in its hdmi node.

Easiest solution is to just remove the 2nd one and that makes DT
validation happy.

Looking at the rk3328 TRM, I found these hdmi related interrupts:
67  hdmi_intr
103 hdmi_intr_wakeup

Looking at the rk3399 TRM, I found these hdmi related interrupts:
23  hdmi_irq
24  hdmi_wakeup_irq

Looking at the rk3568 TRM, I found these hdmi related interrupts:
76  hdmi_wakeup
77  hdmi

So my thinking is:
- what if the dt-binding is incorrect? (-> maxItems : 2?)
- wakeup 'sounds like' Hot Plug Detection?

which makes it relevant for this series and it could mean that the
rk3399-base.dtsi and rk356x.dtsi are actually missing an interrupt
definition in their DT files?

Or I am completely talking nonsense, which is the most likely scenario.

Cheers,
  Diederik

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