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

[Juergen Beisert]

Hi Lothar,

Lothar Waßmann wrote:
> > 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.

Overwriting? It should be a reading DMA unit, shouldn't it?

> > Note: I already sent this patch in December 2011 but noone picked it up
> > obviously.
> >
> > Signed-off-by: Lothar Waßmann <LW at 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 49619b4..f2a49ef 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);
> >
> > --
> > 1.7.2.5
>
> ping? 

I'm not sure if the missing SET/CLR feature for this register is a typo in the 
i.MX23/i.MX28 data sheets or if it is intended. Lets assume its the truth 
what they have written:

Acked-by: Juergen Beisert <jbe at pengutronix.de>

Regards,
Juergen

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