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commit4396393fb9upstream. In commit0b8e7bbde5("drm/sun4i: tcon: Set min division of TCON0_DCLK to 1.") it was assumed that all TCON variants support a minimum divider of 1 if only DCLK was used. However, the oldest generation of hardware only supports minimum divider of 4 if only DCLK is used. If a divider of 1 was used on this old hardware, some scrolling artifact would appear. A divider of 2 seemed OK, but a divider of 3 had artifacts as well. Set the minimum divider when outputing to parallel RGB based on the hardware model, with a minimum of 4 for the oldest (A10/A10s/A13/A20) hardware, and a minimum of 1 for the rest. A value is not set for the TCON variants lacking channel 0. This fixes the scrolling artifacts seen on my A13 tablet. Fixes:0b8e7bbde5("drm/sun4i: tcon: Set min division of TCON0_DCLK to 1.") Cc: <stable@vger.kernel.org> # 5.4.x Signed-off-by: Chen-Yu Tsai <wens@csie.org> Signed-off-by: Maxime Ripard <maxime@cerno.tech> Link: https://patchwork.freedesktop.org/patch/msgid/20200107070113.28951-1-wens@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>