[PATCH v6 09/14] drm/mediatek: Support "Pre-multiplied" alpha blending in Mixer

[Shawn Sung <shawn.sung@mediatek.com>]

From: Hsiao Chien Sung <shawn.sung@mediatek.com>

Support "Pre-multiplied" blend mode on MediaTek's chips.
Before this patch, only the "Coverage" mode is supported.

Please refer to the description of the commit
"drm/mediatek: Support alpha blending in display driver"
for more information.

Signed-off-by: Hsiao Chien Sung <shawn.sung@mediatek.com>
---
 drivers/gpu/drm/mediatek/mtk_ethdr.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_ethdr.c b/drivers/gpu/drm/mediatek/mtk_ethdr.c
index 6bf398850e85f..4b12ca285e84b 100644
--- a/drivers/gpu/drm/mediatek/mtk_ethdr.c
+++ b/drivers/gpu/drm/mediatek/mtk_ethdr.c
@@ -5,6 +5,7 @@
 
 #include <drm/drm_fourcc.h>
 #include <drm/drm_framebuffer.h>
+#include <drm/drm_blend.h>
 #include <linux/clk.h>
 #include <linux/component.h>
 #include <linux/of.h>
@@ -35,6 +36,7 @@
 #define MIX_SRC_L0_EN				BIT(0)
 #define MIX_L_SRC_CON(n)		(0x28 + 0x18 * (n))
 #define NON_PREMULTI_SOURCE			(2 << 12)
+#define PREMULTI_SOURCE				(3 << 12)
 #define MIX_L_SRC_SIZE(n)		(0x30 + 0x18 * (n))
 #define MIX_L_SRC_OFFSET(n)		(0x34 + 0x18 * (n))
 #define MIX_FUNC_DCM0			0x120
@@ -153,7 +155,8 @@ void mtk_ethdr_layer_config(struct device *dev, unsigned int idx,
 	struct mtk_plane_pending_state *pending = &state->pending;
 	unsigned int offset = (pending->x & 1) << 31 | pending->y << 16 | pending->x;
 	unsigned int align_width = ALIGN_DOWN(pending->width, 2);
-	unsigned int alpha_con = 0;
+	unsigned int mix_con = NON_PREMULTI_SOURCE;
+	bool replace_src_a = false;
 
 	dev_dbg(dev, "%s+ idx:%d", __func__, idx);
 
@@ -170,19 +173,27 @@ void mtk_ethdr_layer_config(struct device *dev, unsigned int idx,
 		return;
 	}
 
-	if (state->base.fb && state->base.fb->format->has_alpha)
-		alpha_con = MIXER_ALPHA_AEN | MIXER_ALPHA;
+	mix_con |= MIXER_ALPHA_AEN | (state->base.alpha & MIXER_ALPHA);
 
-	mtk_mmsys_mixer_in_config(priv->mmsys_dev, idx + 1, alpha_con ? false : true,
-				  DEFAULT_9BIT_ALPHA,
+	if (state->base.pixel_blend_mode != DRM_MODE_BLEND_COVERAGE)
+		mix_con |= PREMULTI_SOURCE;
+
+	if (state->base.fb && !state->base.fb->format->has_alpha) {
+		/*
+		 * Mixer doesn't support CONST_BLD mode,
+		 * use a trick to make the output equivalent
+		 */
+		replace_src_a = true;
+	}
+
+	mtk_mmsys_mixer_in_config(priv->mmsys_dev, idx + 1, replace_src_a, MIXER_ALPHA,
 				  pending->x & 1 ? MIXER_INX_MODE_EVEN_EXTEND :
 				  MIXER_INX_MODE_BYPASS, align_width / 2 - 1, cmdq_pkt);
 
 	mtk_ddp_write(cmdq_pkt, pending->height << 16 | align_width, &mixer->cmdq_base,
 		      mixer->regs, MIX_L_SRC_SIZE(idx));
 	mtk_ddp_write(cmdq_pkt, offset, &mixer->cmdq_base, mixer->regs, MIX_L_SRC_OFFSET(idx));
-	mtk_ddp_write_mask(cmdq_pkt, alpha_con, &mixer->cmdq_base, mixer->regs, MIX_L_SRC_CON(idx),
-			   0x1ff);
+	mtk_ddp_write(cmdq_pkt, mix_con, &mixer->cmdq_base, mixer->regs, MIX_L_SRC_CON(idx));
 	mtk_ddp_write_mask(cmdq_pkt, BIT(idx), &mixer->cmdq_base, mixer->regs, MIX_SRC_CON,
 			   BIT(idx));
 }
-- 
2.18.0