linux-kernel - Re: [PATCH v4 4/4] drm/rockchip: vop2: Support setting custom background color

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Message-ID: <6de0071f-a442-44b3-9ba2-13271cb1f246@collabora.com>
Date: Mon, 26 Jan 2026 20:52:44 +0200
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Nícolas F. R. A. Prado <nfraprado@...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 v4 4/4] drm/rockchip: vop2: Support setting custom
 background color

Hi Nícolas,

On 1/26/26 8:30 PM, Nícolas F. R. A. Prado wrote:
> On Fri, 2025-12-19 at 23:47 +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.
>>
>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
>> ---
>>  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 13 ++++++++++++-
>>  drivers/gpu/drm/rockchip/rockchip_drm_vop2.h |  4 ++++
>>  2 files changed, 16 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
>> b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
>> index 498df0ce4680..3a232d0d4acb 100644
>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
>> @@ -1554,6 +1554,7 @@ static void vop2_post_config(struct drm_crtc
>> *crtc)
>>  	struct vop2_video_port *vp = to_vop2_video_port(crtc);
>>  	struct vop2 *vop2 = vp->vop2;
>>  	struct drm_display_mode *mode = &crtc->state->adjusted_mode;
>> +	u64 bgcolor = crtc->state->background_color;
>>  	u16 vtotal = mode->crtc_vtotal;
>>  	u16 hdisplay = mode->crtc_hdisplay;
>>  	u16 hact_st = mode->crtc_htotal - mode->crtc_hsync_start;
>> @@ -1599,7 +1600,11 @@ static void vop2_post_config(struct drm_crtc
>> *crtc)
>>  		vop2_vp_write(vp, RK3568_VP_POST_DSP_VACT_INFO_F1,
>> val);
>>  	}
>>  
>> -	vop2_vp_write(vp, RK3568_VP_DSP_BG, 0);
>> +	/* Background color is programmed with 10 bits of precision
>> */
>> +	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);
> 
> Why aren't the DRM_ARGB64_GET*_BPC() helpers used here to get the
> values with a custom precision?

That's for performance reasons, please see "Changes in v4" section in the cover
letter.  I should have probably added a comment here (noted for v5).

Thanks for the review!

Regards,
Cristian