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

[Eric Nelson]

On 09/21/2012 10:22 AM, Anatolij Gustschin wrote:
> Hi Eric,
>
> On Fri, 21 Sep 2012 09:38:23 -0700
> Eric Nelson<eric.nelson at 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.

This is just what we need. I'll send a patch shortly.