drm/stm: ltdc: remove non-alpha color formats on layer 2 for older hw

Hw older versions support non-alpha color formats derived
from native alpha color formats only on the primary layer.
For instance, RG16 native format without alpha works fine
on 2nd layer but XR24 (derived color format from AR24)
does not work on 2nd layer.

Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
Reviewed-by: Yannick Fertré <yannick.fertre@st.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180201104243.20726-3-philippe.cornu@st.com

drivers/gpu/drm/stm/ltdc.c

@@ -703,6 +703,11 @@ static void ltdc_plane_atomic_update(struct drm_plane *plane,
 	if (!fb->format->has_alpha)
 		val = BF1_CA | BF2_1CA;
 
+	/* Manage hw-specific capabilities */
+	if (ldev->caps.non_alpha_only_l1 &&
+	    plane->type != DRM_PLANE_TYPE_PRIMARY)
+		val = BF1_PAXCA | BF2_1PAXCA;
+
 	reg_update_bits(ldev->regs, LTDC_L1BFCR + lofs,
 			LXBFCR_BF2 | LXBFCR_BF1, val);
 
@@ -785,6 +790,12 @@ static struct drm_plane *ltdc_plane_create(struct drm_device *ddev,
 		drm_fmt_no_alpha = get_pixelformat_without_alpha(drm_fmt);
 		if (!drm_fmt_no_alpha)
 			continue;
+
+		/* Manage hw-specific capabilities */
+		if (ldev->caps.non_alpha_only_l1 &&
+		    type != DRM_PLANE_TYPE_PRIMARY)
+			continue;
+
 		formats[nb_fmt++] = drm_fmt_no_alpha;
 	}
 
@@ -913,10 +924,19 @@ static int ltdc_get_caps(struct drm_device *ddev)
 	case HWVER_10300:
 		ldev->caps.reg_ofs = REG_OFS_NONE;
 		ldev->caps.pix_fmt_hw = ltdc_pix_fmt_a0;
+		/*
+		 * Hw older versions support non-alpha color formats derived
+		 * from native alpha color formats only on the primary layer.
+		 * For instance, RG16 native format without alpha works fine
+		 * on 2nd layer but XR24 (derived color format from AR24)
+		 * does not work on 2nd layer.
+		 */
+		ldev->caps.non_alpha_only_l1 = true;
 		break;
 	case HWVER_20101:
 		ldev->caps.reg_ofs = REG_OFS_4;
 		ldev->caps.pix_fmt_hw = ltdc_pix_fmt_a1;
+		ldev->caps.non_alpha_only_l1 = false;
 		break;
 	default:
 		return -ENODEV;

drivers/gpu/drm/stm/ltdc.h

@@ -17,6 +17,7 @@ struct ltdc_caps {
 	u32 reg_ofs;		/* register offset for applicable regs */
 	u32 bus_width;		/* bus width (32 or 64 bits) */
 	const u32 *pix_fmt_hw;	/* supported pixel formats */
+	bool non_alpha_only_l1; /* non-native no-alpha formats on layer 1 */
 };
 
 struct ltdc_device {