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

[Cristian Ciocaltea <cristian.ciocaltea@collabora.com>]

On 11/30/25 5:01 AM, Chaoyi Chen wrote:
> On 11/29/2025 5:50 PM, Cristian Ciocaltea wrote:
>> Hi Chaoyi,
>>
>> On 11/29/25 5:49 AM, Chaoyi Chen wrote:
>>> 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 :)
>>
>> Yes, CRTC CRC works on RK3576 for the planes, but not for the background, i.e.
>> the CRC is not updated when setting a different background color.  Unless
>> there's a way to change this default behavior, which I'm not aware of. 
>>
>> My current understanding is that the background color is applied at a later
>> stage in the display pipeline, *after* blending the planes and computing CRC.
>>
> 
> Which CRTC are you using? If you're using VP0, you might run into this
> problem. Please try VP1 instead.

Yeah, that's VP0 as there's only one HDMI output port on my Radxa ROCK 4D board.
I'll check if it's possible to switch to VP1.