Re: [PATCH] video imx-ipu-fb: add clear screen

[Sascha Hauer <s.hauer@pengutronix.de>]

On Mon, Sep 10, 2012 at 01:16:26PM +0300, Alex Gershgorin wrote:
> Hi Sascha,
> 
>  On Fri, Sep 07, 2012 at 01:46:39PM +0300, Alex Gershgorin wrote:
> > This patch clear screen before usage
> >
> > Signed-off-by: Alex Gershgorin <alexg@meprolight.com>
> > ---
> >  drivers/video/imx-ipu-fb.c |    4 ++++
> >  1 files changed, 4 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/video/imx-ipu-fb.c b/drivers/video/imx-ipu-fb.c
> > index 8039de0..d46cced 100644
> > --- a/drivers/video/imx-ipu-fb.c
> > +++ b/drivers/video/imx-ipu-fb.c
> > @@ -1012,6 +1012,10 @@ static int imxfb_probe(struct device_d *dev)
> >                                              (info->bits_per_pixel >> 3));
> >               if (!fbi->info.screen_base)
> >                       return -ENOMEM;
> > +
> > +             /* Clear the screen */
> > +             memset((char *)fbi->info.screen_base, 0,
> > +             info->xres * info->yres * (info->bits_per_pixel >> 3));
> 
> > > Not clearing the screen is intentional. Normally the fb drivers do not
> > > enable the framebuffer until explicitely requested via fb0.enable=1. The
> > > environment normally is supposed to set a picture on the screen and
> > > enable it afterwards.
> > > That said, we can clear the screen as with MMU enabled this probably
> > > does not take long time. But then it should be done in the fb core.
> 
> Thanks for your explanation.
> In my case, I displayed picture on the screen, of course as you said I added to "init" script   
> fb0.enable = 1
> bmp / env / logo.bmp

I would exchange the above commands. I don't know how this looks on your
hardware, but often enough it looks a lot nicer if you draw the logo
first and enable the framebuffer (the backlight most importantly)
afterwards.

> it was easy.
> 
> The problem is that I have a screen with resolution 800x600, but
> picture that I displayed on the my screen is much smaller, resulting
> in a picture is displayed fine, but on the sides I get garbage.  This
> patch fixes this issue, of course it is not the only way to solve this
> issue.

Yes, I thought that. 'cp /dev/zero /dev/fb0' would be another solution.
I think the memset in the fb code is fine, but it should be done in the
generic code.

Sascha


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