linux-kernel - Re: [PATCH v3 4/4] drm/rockchip: vop2: Support setting custom background color

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Message-ID: <b8819463-cc61-432f-b451-db90e3b43884@rock-chips.com>
Date: Sat, 29 Nov 2025 11:49:02 +0800
From: Chaoyi Chen <chaoyi.chen@...k-chips.com>
To: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>,
 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>,
 Sandy Huang <hjc@...k-chips.com>, Heiko Stübner
 <heiko@...ech.de>, Andy Yan <andy.yan@...k-chips.com>,
 Louis Chauvet <louis.chauvet@...tlin.com>,
 Haneen Mohammed <hamohammed.sa@...il.com>,
 Melissa Wen <melissa.srw@...il.com>
Cc: Robert Mader <robert.mader@...labora.com>, kernel@...labora.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v3 4/4] drm/rockchip: vop2: Support setting custom
 background color

Hello Cristian, 

On 11/28/2025 5:44 PM, Cristian Ciocaltea wrote:
> The precision was something I initially looked into for CRC verification, in the
> context of the related IGT test.  But since I've added the VKMS support, I think
> we should not worry about that anymore. 
> 
> Moreover, as already pointed out in [1], only RK3576 supports CRC generation at
> display controller level, and that is not particularly useful because it doesn't

I believe you can get the CRTC CRC on the RK3576, even when only the 
background is visible and all plane is disabled. Feel free to let me
know if you run into any issues :)

> take the background color into account.  Therefore I had to capture the frame
> CRCs at DisplayPort AUX channel level, by using the USB-C DP AltMode capable

Oh that sounds interesting! I'm not sure how complex it would be to
implement.

> port of my RK3588-based board.  However, that solution is not yet available
> upstream, as it requires further work for cleanup and improving the overall
> USB-C reliability. 
> 
> Hence I'll move on with your suggestion and switch to the simple bit-shifting
> approach for the next revision.

-- 
Best, 
Chaoyi