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: <ff21cbd1-dc77-43ae-85a8-dc6a56a1cefa@linux.dev>
Date: Mon, 6 Oct 2025 16:30:19 +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,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
 Douglas Anderson <dianders@...omium.org>,
 Damon Ding <damon.ding@...k-chips.com>, Sandy Huang <hjc@...k-chips.com>,
 Heiko Stübner <heiko@...ech.de>,
 Andy Yan <andy.yan@...k-chips.com>,
 Linux Rockchip Support List <linux-rockchip@...ts.infradead.org>,
 Devarsh Thakkar <devarsht@...com>
Subject: Re: [PATCH v13 3/4] drm/atomic-helper: Re-order bridge chain
 pre-enable and post-disable

+rockchip maintainers

Hi Vicente, all,


I went through the drivers and the affected areas in the gru-kevin
chromebook pipeline last week, but nothing has stood out.


Pipeline:

rockchip,display-subsystem / rk3399-vop (Big/Lite) (CRTC) ->
rk3399-edp (Encoder) -> analogix_dp_core (Bridge) ->
sharp,lq123p (edp-panel)

I am unable to debug this further since I do not have the hardware.

I could use some help, especially from folks who understand the hardware
requirements better.


On 11/09/25 09:01, Aradhya Bhatia wrote:
> 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