video: mxsfb: fix crash when unblanking the display

The VDCTRL4 register does not provide the MXS SET/CLR/TOGGLE feature.
The write in mxsfb_disable_controller() sets the data_cnt for the LCD
DMA to 0 which obviously means the max. count for the LCD DMA and
leads to overwriting arbitrary memory when the display is unblanked.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Acked-by: Juergen Beisert <jbe@pengutronix.de>
Tested-by: Lauri Hintsala <lauri.hintsala@bluegiga.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/video/mxsfb.c b/drivers/video/mxsfb.c
index 49619b441500..f2a49ef772f3 100644
--- a/drivers/video/mxsfb.c
+++ b/drivers/video/mxsfb.c
@@ -369,7 +369,8 @@ static void mxsfb_disable_controller(struct fb_info *fb_info)
                 loop--;
         }
 
-        writel(VDCTRL4_SYNC_SIGNALS_ON, host->base + LCDC_VDCTRL4 + REG_CLR);
+        reg = readl(host->base + LCDC_VDCTRL4);
+        writel(reg & ~VDCTRL4_SYNC_SIGNALS_ON, host->base + LCDC_VDCTRL4);
 
         clk_disable_unprepare(host->clk);