[PATCH 205/222] video: mxsfb: fix crash when unblanking the display

[Herton Ronaldo Krzesinski]

3.5.7.3 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: =?UTF-8?q?Lothar=20Wa=C3=9Fmann?= <LW at KARO-electronics.de>

commit 6c1ecba8d84841277d68140ef485335d5be28485 upstream.

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 at KARO-electronics.de>
Acked-by: Juergen Beisert <jbe at pengutronix.de>
Tested-by: Lauri Hintsala <lauri.hintsala at bluegiga.net>
Signed-off-by: Shawn Guo <shawn.guo at linaro.org>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 drivers/video/mxsfb.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/video/mxsfb.c b/drivers/video/mxsfb.c
index abbe691..fc2c4381 100644
--- a/drivers/video/mxsfb.c
+++ b/drivers/video/mxsfb.c
@@ -367,7 +367,8 @@ 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);
 
-- 
1.7.9.5