From: Ayan Halder <ayan.halder@arm.com>
To: liviu.dudau@arm.com, brian.starkey@arm.com, malidp@foss.arm.com,
        airlied@linux.ie, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
Cc: nd@arm.com, Ayan Halder <ayan.halder@arm.com>
Subject: [PATCH] drm/arm/malidp: Disable pixel alpha blending for colors that do not have alpha
Date: Fri, 12 Jan 2018 16:33:07 +0000
Message-Id: <1515774787-19324-1-git-send-email-ayan.halder@arm.com>
MIME-Version: 1.0
Content-Type: text/plain
NoDisclaimer: True
SpamDiagnosticOutput: 1:99
SpamDiagnosticMetadata: NSPM
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Jan 2018 16:33:16.3617 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 74e04459-dfd5-4fcd-f013-08d559da2f3b
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d
X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR0802MB2411
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Return-Path: <linux-kernel-owner@vger.kernel.org>

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

Signed-off-by: Ayan Kumar Halder <ayan.halder@arm.com>
---
 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..4d7d564 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;
+	u8 alpha_bits = plane->state->fb->format->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 (alpha_bits > 0) {
+
+		/*
+		 * 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