[BUGFIX] video/mxsfb: fix crash when unblanking the display

[BUGFIX] video/mxsfb: fix crash when unblanking the display

[Lothar Waßmann]

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>
---
 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

Re: [BUGFIX] video/mxsfb: fix crash when unblanking the display

[Lothar Waßmann]

Hi,

Lothar Waßmann writes:
> 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>
> ---
>  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
-- 
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___________________________________________________________

Re: [BUGFIX] video/mxsfb: fix crash when unblanking the display

[Robin van der Gracht]

Hi Lothar,
> Hi,
>
> Lothar Waßmann writes:
>> 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>
>> ---
>>   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