[U-Boot] Disabling video in bootm (cleanup_before_linux)

[Anatolij Gustschin <agust@denx.de>]

Hi Eric,

On Fri, 21 Sep 2012 09:38:23 -0700
Eric Nelson <eric.nelson@boundarydevices.com> wrote:

> Hi all,
> 
> While looking into some trouble booting the latest Linux kernel patches
> for i.MX6 display support, I found that the kernel driver was thrown off by
> the interrupt status bits in the i.MX6 IPU.
> 
> Until and unless we have the ability to hand off a 'live' display, it seems
> that we should disable the video driver as a part of the 'bootm' process.
> 
> At the very least, doing this will avoid the possibility of trash on the
> display during the transition.
> 
> I've been looking, and I don't see a place to tap into this process.
> It seems that having a shutdown routine for the display drivers
> (cfb_console?) is the way to go.

cfb_console driver is a renderer of the characters and bitmaps
to the framebuffer memory and is not a good place for a shutdown
routine, I think. But we can add a shutdown function to the IPU
driver drivers/video/mxc_ipuv3_fb.c and call it before booting.
bootm code in common/cmd_bootm.c has a weak arch_preboot_os()
function that can be overridden by platform specific preboot
routine. We could define a preboot function in

    arch/arm/cpu/armv7/mx6/soc.c
or in
    arch/arm/cpu/armv7/imx-common/cpu.c

and call IPU shutdown routine in it.

Thanks,
Anatolij