[PATCH v2] drm/meson: fix 1px pink line on GXM when scaling video overlay

[Christian Hewitt]

Playing media with a resolution smaller than the crtc size requires the
video overlay to be scaled for output and GXM boards display a 1px pink
line on the bottom of the scaled overlay. Comparing with the downstream
vendor driver revealed VPP_DUMMY_DATA not being set [0].

Setting VPP_DUMMY_DATA prevents the 1px pink line from being seen.

[0] https://github.com/endlessm/linux-s905x/blob/master/drivers/amlogic/amports/video.c#L7869

Fixes: bbbe775ec5b5 ("drm: Add support for Amlogic Meson Graphic Controller")
Suggested-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
Signed-off-by: Christian Hewitt <christianshewitt at gmail.com>
---
Change since v1:
This time I sent the right patch from the correct branch; the wording in
v1 is incorrect and the change to meson_registers.h is not required.

 drivers/gpu/drm/meson/meson_vpp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/meson/meson_vpp.c b/drivers/gpu/drm/meson/meson_vpp.c
index 154837688ab0..5df1957c8e41 100644
--- a/drivers/gpu/drm/meson/meson_vpp.c
+++ b/drivers/gpu/drm/meson/meson_vpp.c
@@ -100,6 +100,8 @@ void meson_vpp_init(struct meson_drm *priv)
 			       priv->io_base + _REG(VPP_DOLBY_CTRL));
 		writel_relaxed(0x1020080,
 				priv->io_base + _REG(VPP_DUMMY_DATA1));
+		writel_relaxed(0x42020,
+				priv->io_base + _REG(VPP_DUMMY_DATA));
 	} else if (meson_vpu_is_compatible(priv, VPU_COMPATIBLE_G12A))
 		writel_relaxed(0xf, priv->io_base + _REG(DOLBY_PATH_CTRL));
 
-- 
2.34.1