46f5463940
[ Upstream commit0c9856e4ed] There is some sort of corner case behavior of the controller, which could rarely be triggered at least on i.MX6SX connected to 800x480 DPI panel and i.MX8MM connected to DPI->DSI->LVDS bridged 1920x1080 panel (and likely on other setups too), where the image on the panel shifts to the right and wraps around. This happens either when the controller is enabled on boot or even later during run time. The condition does not correct itself automatically, i.e. the display image remains shifted. It seems this problem is known and is due to sporadic underflows of the LCDIF FIFO. While the LCDIF IP does have underflow/overflow IRQs, neither of the IRQs trigger and neither IRQ status bit is asserted when this condition occurs. All known revisions of the LCDIF IP have CTRL1 RECOVER_ON_UNDERFLOW bit, which is described in the reference manual since i.MX23 as " Set this bit to enable the LCDIF block to recover in the next field/frame if there was an underflow in the current field/frame. " Enable this bit to mitigate the sporadic underflows. Fixes:45d59d7040("drm: Add new driver for MXSFB controller") Signed-off-by: Marek Vasut <marex@denx.de> Cc: Daniel Abrecht <public@danielabrecht.ch> Cc: Emil Velikov <emil.l.velikov@gmail.com> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Cc: Lucas Stach <l.stach@pengutronix.de> Cc: Stefan Agner <stefan@agner.ch> Reviewed-by: Lucas Stach <l.stach@pengutronix.de> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Jagan Teki <jagan@amarulasolutions.com> Signed-off-by: Sam Ravnborg <sam@ravnborg.org> Link: https://patchwork.freedesktop.org/patch/msgid/20210620224701.189289-1-marex@denx.de Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.