drm/rockchip: vop2: Support setting custom background color

Commit bec7cbfa7d4f upstream.

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.

Tested-by: Diederik de Haas <diederik@cknow-tech.com>
Reviewed-by: Andy Yan <andyshrk@163.com>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Link: https://patch.msgid.link/20260303-rk3588-bgcolor-v8-4-fee377037ad1@collabora.com
Signed-off-by: Daniel Stone <daniels@collabora.com>

Author: cristicc

drivers/gpu/drm/rockchip/rockchip_drm_vop2.c

@@ -1058,6 +1058,13 @@ static int vop2_plane_atomic_check(struct drm_plane *plane,
 		return -EINVAL;
 	}
 
+	if ((cstate->background_color << 16) &&
+	    (fb->format->has_alpha || pstate->alpha != 0xffff)) {
+		drm_dbg_kms(vop2->drm,
+			    "Alpha-blending with background color is unsupported\n");
+		return -EINVAL;
+	}
+
 	return 0;
 }
 
@@ -1548,6 +1555,7 @@ 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;
@@ -1593,7 +1601,15 @@ 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.
+	 * Since performance is more important than accuracy here,
+	 * make use of the DRM_ARGB64_GET*_BPCS() helpers.
+	 */
+	val = FIELD_PREP(RK3568_VP_DSP_BG__DSP_BG_RED, DRM_ARGB64_GETR_BPCS(bgcolor, 10));
+	FIELD_MODIFY(RK3568_VP_DSP_BG__DSP_BG_GREEN, &val, DRM_ARGB64_GETG_BPCS(bgcolor, 10));
+	FIELD_MODIFY(RK3568_VP_DSP_BG__DSP_BG_BLUE, &val, DRM_ARGB64_GETB_BPCS(bgcolor, 10));
+	vop2_vp_write(vp, RK3568_VP_DSP_BG, val);
 }
 
 static int us_to_vertical_line(struct drm_display_mode *mode, int us)
@@ -1972,6 +1988,10 @@ static int vop2_crtc_state_dump(struct drm_crtc *crtc, struct seq_file *s)
 		   drm_get_bus_format_name(vcstate->bus_format));
 	seq_printf(s, "\toutput_mode[%x]", vcstate->output_mode);
 	seq_printf(s, " color_space[%d]\n", vcstate->color_space);
+	seq_printf(s, "\tbackground color (10bpc): r=0x%x g=0x%x b=0x%x\n",
+		   DRM_ARGB64_GETR_BPCS(cstate->background_color, 10),
+		   DRM_ARGB64_GETG_BPCS(cstate->background_color, 10),
+		   DRM_ARGB64_GETB_BPCS(cstate->background_color, 10));
 	seq_printf(s, "    Display mode: %dx%d%s%d\n",
 		   mode->hdisplay, mode->vdisplay, interlaced ? "i" : "p",
 		   drm_mode_vrefresh(mode));
@@ -2461,6 +2481,8 @@ static int vop2_create_crtcs(struct vop2 *vop2)
 			return dev_err_probe(drm->dev, ret,
 					     "crtc init for video_port%d failed\n", i);
 
+		drm_crtc_attach_background_color_property(&vp->crtc);
+
 		drm_crtc_helper_add(&vp->crtc, &vop2_crtc_helper_funcs);
 		if (vop2->lut_regs) {
 			const struct vop2_video_port_data *vp_data = &vop2_data->vp[vp->id];

drivers/gpu/drm/rockchip/rockchip_drm_vop2.h

@@ -658,6 +658,10 @@ enum dst_factor_mode {
 #define RK3588_VP_CLK_CTRL__DCLK_OUT_DIV		GENMASK(3, 2)
 #define RK3588_VP_CLK_CTRL__DCLK_CORE_DIV		GENMASK(1, 0)
 
+#define RK3568_VP_DSP_BG__DSP_BG_RED			GENMASK(29, 20)
+#define RK3568_VP_DSP_BG__DSP_BG_GREEN			GENMASK(19, 10)
+#define RK3568_VP_DSP_BG__DSP_BG_BLUE			GENMASK(9, 0)
+
 #define RK3568_VP_POST_SCL_CTRL__VSCALEDOWN		BIT(1)
 #define RK3568_VP_POST_SCL_CTRL__HSCALEDOWN		BIT(0)