Re: [PATCH v4 3/5] powerpc/mpc5121: shared DIU framebuffer support

[Anatolij Gustschin <agust@denx.de>]

On Fri, 16 Dec 2011 12:24:49 -0600
Timur Tabi <timur@freescale.com> wrote:

> Anatolij Gustschin wrote:
> 
> > We cannot guarantee that the DIU is not in these modes. Even
> > if U-Boot didn't set these modes there is still a possibility
> > that such mode is configured. E.g. I've seen U-Boot binary
> > standalone applications for other display controllers initializing
> > the display controller.
> 
> True, but modes 2 and 3 don't make any sense.  2 is just a color bar,
> and 3 writes back to memory (which means you need to have a reserved
> DMA buffer otherwise you'll crash).  Have you really seen Linux boot
> with the DIU in either of these modes?

No, but it doesn't mean that it is not possible.

> > But you are right. With this snippet, if the DIU is already
> > disabled, there will be not needed mode register access. So
> > the code should better look like:
> > 
> > diu_mode = in_be32(&dr.diu_reg->diu_mode);
> > if (diu_mode && diu_mode != MFB_MODE1)
> > 	out_be32(&dr.diu_reg->diu_mode, 0);
> 
> Ok.  I'm planning on cleaning up the driver so that it does not
> initialize the DIU until the .open call, and once that's done,
> I should be able to remove most of the code from your patch.

Will DIU splash screen functionality be preserved?

Anatolij