[BUGFIX] 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 <redacted>
---
 drivers/video/mxsfb.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/video/mxsfb.c b/drivers/video/mxsfb.c
index d837d63..03cb95a 100644
--- a/drivers/video/mxsfb.c
+++ b/drivers/video/mxsfb.c

@@ -366,7 +366,8 @@ 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(host->clk);
 

-- 
1.5.6.5

Hi,

Lothar Waßmann writes:

Ping. Any comments on this?


Lothar Waßmann
-- 
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Hi Lothar,

Hi,

Lothar Waßmann writes:

quoted

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<redacted>
---
  drivers/video/mxsfb.c |    3 ++-
  1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/video/mxsfb.c b/drivers/video/mxsfb.c
index d837d63..03cb95a 100644
--- a/drivers/video/mxsfb.c
+++ b/drivers/video/mxsfb.c

@@ -366,7 +366,8 @@ 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(host->clk);

-- 
1.5.6.5

Ping. Any comments on this?


Lothar Waßmann

I've encountered this problem to, and i can confirm your patch fixed it.
The VDCTRL4 register has no CLR feature.

Regards,

-- 
Robin van der Gracht
Protonic Holland.
tel.: +31 (0) 229 212928
fax.: +31 (0) 229 210930
Factorij 36 / 1689 AL Zwaag