linux-kernel - [PATCH] drm/sun4i: Enable output signal premultiplication for DE2/DE3

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Date:   Thu,  2 Jun 2022 10:10:57 +0000
From:   Roman Stratiienko <r.stratiienko@...il.com>
To:     mripard@...nel.org, wens@...e.org, jernej.skrabec@...il.com,
        airlied@...ux.ie, daniel@...ll.ch, samuel@...lland.org,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org, megi@....cz
Cc:     Roman Stratiienko <r.stratiienko@...il.com>
Subject: [PATCH] drm/sun4i: Enable output signal premultiplication for DE2/DE3

Otherwise alpha value is discarded, resulting incorrect pixel
apperance on the display.

This also fixes missing transparency for the most bottom layer.

Test applications and videos w/ w/o this patch are available at [1].

[1]: https://github.com/GloDroid/glodroid_tests/issues/1
Signed-off-by: Roman Stratiienko <r.stratiienko@...il.com>
---
 drivers/gpu/drm/sun4i/sun8i_mixer.c | 2 ++
 drivers/gpu/drm/sun4i/sun8i_mixer.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.c b/drivers/gpu/drm/sun4i/sun8i_mixer.c
index 6b1711a9a71f..71ab0a00b4de 100644
--- a/drivers/gpu/drm/sun4i/sun8i_mixer.c
+++ b/drivers/gpu/drm/sun4i/sun8i_mixer.c
@@ -320,6 +320,8 @@ static void sun8i_mixer_mode_set(struct sunxi_engine *engine,
 	else
 		val = 0;
 
+	val |= SUN8I_MIXER_BLEND_OUTCTL_PREMULTIPLY;
+
 	regmap_update_bits(engine->regs, SUN8I_MIXER_BLEND_OUTCTL(bld_base),
 			   SUN8I_MIXER_BLEND_OUTCTL_INTERLACED, val);
 
diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.h b/drivers/gpu/drm/sun4i/sun8i_mixer.h
index ebfc276b2464..bc12c95af6f3 100644
--- a/drivers/gpu/drm/sun4i/sun8i_mixer.h
+++ b/drivers/gpu/drm/sun4i/sun8i_mixer.h
@@ -65,6 +65,7 @@
 #define SUN8I_MIXER_BLEND_ROUTE_PIPE_MSK(n)	(0xf << ((n) << 2))
 #define SUN8I_MIXER_BLEND_ROUTE_PIPE_SHIFT(n)	((n) << 2)
 
+#define SUN8I_MIXER_BLEND_OUTCTL_PREMULTIPLY	BIT(0)
 #define SUN8I_MIXER_BLEND_OUTCTL_INTERLACED	BIT(1)
 
 #define SUN50I_MIXER_BLEND_CSC_CTL_EN(ch)	BIT(ch)
-- 
2.30.2