linux-kernel - Re: [PATCH v13 3/4] drm/atomic-helper: Re-order bridge chain pre-enable and post-disable

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Message-ID: <bea50d14-2311-46ad-bb30-9d60a4c5e3a2@linux.dev>
Date: Thu, 11 Sep 2025 09:01:50 +0100
From: Aradhya Bhatia <aradhya.bhatia@...ux.dev>
To: Vicente Bergas <vicencb@...il.com>
Cc: Laurent.pinchart@...asonboard.com, airlied@...il.com,
 alexander.sverdlin@...mens.com, andrzej.hajda@...el.com, devarsht@...com,
 dri-devel <dri-devel@...ts.freedesktop.org>, jernej.skrabec@...il.com,
 Jonas Karlman <jonas@...boo.se>,
 Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, lumag@...nel.org,
 maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
 neil.armstrong@...aro.org, nm@...com, rfoss@...nel.org, simona@...ll.ch,
 tomi.valkeinen@...asonboard.com, tzimmermann@...e.de, vigneshr@...com
Subject: Re: [PATCH v13 3/4] drm/atomic-helper: Re-order bridge chain
 pre-enable and post-disable

Hi Vicente,

Thank you for the bisection and reporting the issue.

On 10/09/25 16:17, Vicente Bergas wrote:
> Hi,
> this patch causes a regression. It has been reported in
> https://bugzilla.kernel.org/show_bug.cgi?id=220554
> 
> It affects the gru/kevin platform (arm64,RK3399) with the Panfrost DRM driver.

I believe the Panfrost DRM driver may only be for the GPU.

Based on the dts files in arm64/rockchip/, this is the pipeline of the
gru-kevin setup that I understand.

	rk3399-vop (Big/Lite) -> rk3399-edp -> sharp,lq123p (edp-panel)

The setup seems to be using the drm/rockchip drivers for the display
controller and for the bridge.

> 
> When it boots in console mode, the blinking of the cursor keeps the display on.
> If it is turned off via /sys/class/graphics/fbcon/cursor_blink, then
> the display briefly shows each key press presented on screen for less
> than one second and then powers off.
> 
> When starting the graphical mode (wayland), if there are no
> applications drawing on the screen, the only way to keep the display
> on is by continuously moving the mouse.
> 

Okay!

I will have a look through the drivers. In the meanwhile, please do
report back if you find any other observations.


-- 
Regards
Aradhya