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

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?

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.

-- 
Timur Tabi
Linux kernel developer at Freescale