Re: [PATCH v5 4/4] drm/rockchip: vop2: Support setting custom background color

Cristian Ciocaltea
2026-01-29T01:30:07Z

On 1/27/26 4:45 PM, Andy Shevchenko wrote:
> On Tue, Jan 27, 2026 at 10:45:36AM +0200, Cristian Ciocaltea wrote:
>> The Rockchip VOP2 display controller allows configuring the background
>> color of each video output port.
>>
>> Since a previous patch introduced the BACKGROUND_COLOR CRTC property,
>> which defaults to solid black, make use of it when programming the
>> hardware.
>>
>> Note the maximum precision allowed by the display controller is 10bpc,
>> while the alpha component is not supported, hence ignored.
>
> ...
>
>> + /*
>> + * Background color is programmed with 10 bits of precision.
>> + * Since performance is more important than accuracy here,
>> + * do *not* make use of the DRM_ARGB64_GET*_BPC() helpers.
>> + */
>> + val = FIELD_PREP(RK3568_VP_DSP_BG__DSP_BG_RED, DRM_ARGB64_GETR(bgcolor) >> 6);
>> + val |= FIELD_PREP(RK3568_VP_DSP_BG__DSP_BG_GREEN, DRM_ARGB64_GETG(bgcolor) >> 6);
>> + val |= FIELD_PREP(RK3568_VP_DSP_BG__DSP_BG_BLUE, DRM_ARGB64_GETB(bgcolor) >> 6);
>
> There is FIELD_MODIFY() for a few cycles already.

I've been aware, but found it more appropriate when modifying an existing value
(e.g. previously read from a register) rather than when computing one from
scratch.

> But here it probably makes no much difference.

Thinking again about this, it is actually handy when keeping the first
FIELD_PREP (for initialization), and using it just for the subsequent
operations. Hence considered this approach in v6.

> ...
>
>> + seq_printf(s, "\tbackground color (10bpc): r=0x%x g=0x%x b=0x%x\n",
>> + DRM_ARGB64_GETR(cstate->background_color) >> 6,
>> + DRM_ARGB64_GETG(cstate->background_color) >> 6,
>> + DRM_ARGB64_GETB(cstate->background_color) >> 6);
>
> Probably you want to have the alternative to the DRM_ARGB64_GETx() macros which
> incorporates a right-shift. But it all in regard to DRM style and preferences.

I tried to keep the API as simple as possible, but you're right, it's better to
have those macros rather than open-coding the bit-shift all over. Also handled
in v6.

Thanks again,
Cristian