[Maverick] [ti-omap4] SRU: A workaround for highmem issue on OMAP4 platform

[Ricardo Salveti de Araujo]

On Fri, Sep 24, 2010 at 11:21:01AM +0800, Bryan Wu wrote:
> SRU Justification:
> 
> Impact:
> There is a critical highmem issue on our latest OMAP4 ES2.0 platform. When we
> build kernel package natively on ES2.0 platform with mem=1G and highmem
> enabled, we will meet 'Bus Error' corruption from gcc shortly. And 'Unhandled
> imprecised external abort' kernel oops messages. Then the whole system will be
> very instable.
> 
> Fix: After some debugging, this issue is related to highmem. If we don't use
> mem=1G (no memory in highmem), the corruption is gone. So there is a workaround
> which is CONFIG_VMSPLIT_2G=y. So user and kernel memory split is 2G:2G instead
> of default 3G:1G. We can use all the 1G memory on ES2.0, but don't put any
> memory in highmem. As a result, the issue is gone.

Generally when using highmem we can reproduce this issue quickly, with 10, 15
minutes after started the kernel build. Currently without highmem I was able to
build the whole kernel 3 times already, and didn't face this issue.

I just started another batch that will run at least more 5 times during this
night, and will reply tomorrow with the test result.

Meanwhile we're debugging the highmem issue with Nicolas's help.

Cheers,
-- 
Ricardo Salveti de Araujo