drm/sun4i: tcon: set sync polarity for tcon1 channel

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[ Upstream commit 50791f5d7b ]

Channel 1 has polarity bits for vsync and hsync signals but driver never
sets them. It turns out that with pre-HDMI2 controllers seemingly there
is no issue if polarity is not set. However, with HDMI2 controllers
(H6) there often comes to de-synchronization due to phase shift. This
causes flickering screen. It's safe to assume that similar issues might
happen also with pre-HDMI2 controllers.

Solve issue with setting vsync and hsync polarity. Note that display
stacks with tcon top have polarity bits actually in tcon0 polarity
register.

Fixes: 9026e0d122 ("drm: Add Allwinner A10 Display Engine support")
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Tested-by: Andre Heider <a.heider@gmail.com>
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20210209175900.7092-3-jernej.skrabec@siol.net
Signed-off-by: Sasha Levin <sashal@kernel.org>

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This commit is contained in:

Jernej Skrabec 2021-02-09 18:58:57 +01:00 • committed by Greg Kroah-Hartman

parent 39e855fa95

commit 7596c85a89

2 changed files with 31 additions and 0 deletions

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25

drivers/gpu/drm/sun4i/sun4i_tcon.c

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6

drivers/gpu/drm/sun4i/sun4i_tcon.h

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