linux-kernel - Re: [PATCH v2 2/2] arm64: dts: rockchip: add RK3588 DP carrier from Theobroma Systems

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Message-ID: <0582b7bc-e5b2-4b5e-821e-8d2c4301579f@cherry.de>
Date: Fri, 25 Jul 2025 14:29:12 +0200
From: Quentin Schulz <quentin.schulz@...rry.de>
To: Heiko Stuebner <heiko@...ech.de>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
 damon.ding@...k-chips.com, Heiko Stuebner <heiko.stuebner@...rry.de>
Subject: Re: [PATCH v2 2/2] arm64: dts: rockchip: add RK3588 DP carrier from
 Theobroma Systems

Hi Heiko,

On 7/23/25 9:09 PM, Heiko Stuebner wrote:
> From: Heiko Stuebner <heiko.stuebner@...rry.de>
> 
> The DisplayPort carrier is a very simple baseboard only providing serial,
> ethernet and a displayport output.
> 
> But its main functionality is that it routes the Analogix eDP controller
> to this DisplayPort output, which allows to test that controller simply
> by hooking it up to a suitable monitor.
> 
> The Analogix-DP controller supports eDP 1.3 and DP 1.2, so can drive
> both eDP displays as well as full DP monitors. It does not support DP+
> so passive DP-to-HDMI adapters won't work.
> 

I tested this on master (2942242dde896) + v2 of the eDP driver as listed 
in the cover letter, or with v3 of the eDP driver + 
48f05c3b4b701ae7687fd44d462c88b7ac67e952 and in both cases I have weird 
behaviors.

First, `reboot` is stuck for a very long time before actually rebooting. 
I think you have a stacktrace when you tried yourself, I don't so cannot 
send one.

Also, I tested on two different DP displays, one has a green tint, the 
other one purple. When trying out other resolutions with modetest, the 
kernel would often crash (no trace, just nothing on console, SSH dead). 
Note that the same HW setup with downstream kernel from 
https://git.theobroma-systems.com/tiger-linux.git/log/?h=linux-6.1-stan-rkr3.2-tiger 
works just fine. I would assume this has nothing to do with this Device 
Tree patch here but rather the eDP patches missing some bits maybe?

@Damon do you have some idea?

The display with green tint is a Iiyama ProLite XU2294HSU and the one 
with the purple tint is a Dell P2319H if that helps.

modetest output: https://paste.debian.net/1387797/.
modetest output with downstream kernel: https://paste.debian.net/1387798/

The Device Tree looks good to me otherwise.

Cheers,
Quentin