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

[Shilimkar, Santosh]

> -----Original Message-----
> From: kernel-team-bounces at lists.ubuntu.com [mailto:kernel-team-
> bounces at lists.ubuntu.com] On Behalf Of Bryan Wu
> Sent: Thursday, September 30, 2010 7:50 PM
> To: tim.gardner at canonical.com; ricardo.salveti at canonical.com;
> nicolas.pitre at linaro.org; kernel-team at lists.ubuntu.com
> Cc: ogra at canonical.com
> Subject: [Maverick] [ti-omap4] SRU: A workaround for highmem issue on
> OMAP4 platform
> 
> 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:
> Generally when using highmem we can reproduce this issue quickly, with 10,
> 15
> minutes after started the kernel build. Using CONFIG_VMSPLIT_2G=y and
> Nicolas's
> VMALLOC_END patch, we can put 0 memory in highmem. But without highmem, we
> met
> another "Bad Mode" issue because of missing enabling errata fixing for L2
> controller PL310. As a result, 2G:2G split and errata fixing of PL310 is a
> workaround of this issue. We can fully use the whole 1G memory.
> 
CONFIG_PL310_ERRATA_588369 errata is pretty much must for OMAP4 ES1.0. This
should always be enabled on OMAP4 ES1.0 not to see any undefined behaviour.

Regards,
Santosh