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

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Message-ID: <d85cf4b299e929770a1b7f5be7ae61d76306e7d1.camel@collabora.com>
Date: Mon, 26 Jan 2026 15:30:07 -0300
From: Nícolas "F. R. A. Prado" <nfraprado@...labora.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 v4 4/4] drm/rockchip: vop2: Support setting custom
 background color

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?

-- 
Thanks,

Nícolas