drm: mxsfb_crtc: Fix the framebuffer misplacement
authorFabio Estevam <fabio.estevam@nxp.com>
Thu, 2 Feb 2017 21:26:38 +0000 (19:26 -0200)
committerDave Airlie <airlied@redhat.com>
Fri, 10 Mar 2017 01:11:06 +0000 (11:11 +1000)
commitd42986b6c600da4215973878f1c889cdabbdd122
tree189e1722eb9409dda199ddaf1cace009c481ef3a
parent7ad7a5acfb96215216f46b9848bd2d341663358f
drm: mxsfb_crtc: Fix the framebuffer misplacement

Currently the framebuffer content is displayed with incorrect offsets
in both the vertical and horizontal directions.

The fbdev version of the driver does not show this problem. Breno Lima
dumped the eLCDIF controller registers on both the drm and fbdev drivers
and noticed that the VDCTRL3 register is configured incorrectly in the
drm driver.

The fbdev driver calculates the vertical and horizontal wait counts
of the VDCTRL3 register by doing: back porch + sync length.

Looking at the horizontal and vertical timing diagram from
include/drm/drm_modes.h this value corresponds to:

crtc_[hv]total - crtc_[hv]sync_start

So fix the VDCTRL3 register setting accordingly so that the eLCDIF
controller can properly show the framebuffer content in the correct
position.

Reported-by: Breno Lima <breno.lima@nxp.com>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Tested-by: Breno Lima <breno.lima@nxp.com>
Tested-by: Marek Vasut <marex@denx.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
drivers/gpu/drm/mxsfb/mxsfb_crtc.c