linux-kernel - [PATCH v2] drm/arm/malidp: Disable pixel alpha blending for colors that do not have alpha

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Message-Id: <1516726169-12000-1-git-send-email-ayan.halder@arm.com>
Date:   Tue, 23 Jan 2018 16:49:29 +0000
From:   Ayan Kumar Halder <ayan.halder@....com>
To:     liviu.dudau@....com, brian.starkey@....com, malidp@...s.arm.com,
        airlied@...ux.ie, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Cc:     nd@....com, Ayan Halder <ayan.halder@....com>
Subject: [PATCH v2] drm/arm/malidp: Disable pixel alpha blending for colors that do not have alpha

From: Ayan Halder <ayan.halder@....com>

Mali dp needs to disable pixel alpha blending (use layer alpha blending) to
display color formats that do not contain alpha bits per pixel

This patch depends on:

"[PATCH v2 01/19] drm/fourcc: Add a alpha field to drm_format_info"

Signed-off-by: Ayan Kumar Halder <ayan.halder@....com>
---
Change in v2:
- Use struct drm_format_info->has_alpha (boolean) to determine if a color
format has alpha channel

 drivers/gpu/drm/arm/malidp_planes.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/arm/malidp_planes.c b/drivers/gpu/drm/arm/malidp_planes.c
index e741979..3b445d9 100644
--- a/drivers/gpu/drm/arm/malidp_planes.c
+++ b/drivers/gpu/drm/arm/malidp_planes.c
@@ -35,6 +35,9 @@
 #define   LAYER_COMP_MASK		(0x3 << 12)
 #define   LAYER_COMP_PIXEL		(0x3 << 12)
 #define   LAYER_COMP_PLANE		(0x2 << 12)
+#define   LAYER_ALPHA_OFFSET		(16)
+#define   LAYER_ALPHA_MASK		(0xff)
+#define   LAYER_ALPHA(x)		(((x) & LAYER_ALPHA_MASK) << LAYER_ALPHA_OFFSET)
 #define MALIDP_LAYER_COMPOSE		0x008
 #define MALIDP_LAYER_SIZE		0x00c
 #define   LAYER_H_VAL(x)		(((x) & 0x1fff) << 0)
@@ -268,6 +271,7 @@ static void malidp_de_plane_update(struct drm_plane *plane,
 	struct malidp_plane_state *ms = to_malidp_plane_state(plane->state);
 	u32 src_w, src_h, dest_w, dest_h, val;
 	int i;
+	bool format_has_alpha = plane->state->fb->format->has_alpha;
 
 	mp = to_malidp_plane(plane);
 
@@ -319,12 +323,25 @@ static void malidp_de_plane_update(struct drm_plane *plane,
 	if (plane->state->rotation & DRM_MODE_REFLECT_Y)
 		val |= LAYER_V_FLIP;
 
-	/*
-	 * always enable pixel alpha blending until we have a way to change
-	 * blend modes
-	 */
 	val &= ~LAYER_COMP_MASK;
-	val |= LAYER_COMP_PIXEL;
+	if (format_has_alpha) {
+
+		/*
+		 * always enable pixel alpha blending until we have a way
+		 * to change blend modes
+		 */
+		val |= LAYER_COMP_PIXEL;
+	} else {
+
+		/*
+		 * do not enable pixel alpha blending as the color channel
+		 * does not have any alpha information
+		 */
+		val |= LAYER_COMP_PLANE;
+
+		/* Set layer alpha coefficient to 0xff ie fully opaque */
+		val |= LAYER_ALPHA(0xff);
+	}
 
 	val &= ~LAYER_FLOWCFG(LAYER_FLOWCFG_MASK);
 	if (plane->state->crtc) {
-- 
2.7.4