On Tue, Jan 07, 2020 at 03:01:13PM +0800, Chen-Yu Tsai wrote:
From: Chen-Yu Tsai wens@csie.org
In commit 0b8e7bbde5e7 ("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: 0b8e7bbde5e7 ("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
Applied, thanks
Maxime