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

[Bryan Wu]

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.

Testcase: Add kernel boot command line mem=1G, build kernel package on ES2.0
hardware after booting the kernel. The issue is supposed to be gone with 2G:2G
split config.

A testing kernel is also here:
http://people.canonical.com/~roc/kernel/lp633227/

Notes: the VMALLOC_END value is wrong in mach-omap2, Nicolas Pitre posted a fixing
patch to upstream, which is required in this workaround.

BugLink: http://bugs.launchpad.net/bugs/#633227

Plese consider pull from
 git://kernel.ubuntu.com/roc/ubuntu-maverick lp633227

Bryan Wu (1):
  UBUNTU: [Config] Enable CONFIG_VMSPLIT_2G=y for OMAP4

Nicolas Pitre (1):
  ARM: do not define VMALLOC_END relative to PAGE_OFFSET

 arch/arm/mach-aaec2000/include/mach/vmalloc.h   |    2 +-
 arch/arm/mach-bcmring/include/mach/vmalloc.h    |    2 +-
 arch/arm/mach-clps711x/include/mach/vmalloc.h   |    2 +-
 arch/arm/mach-ebsa110/include/mach/vmalloc.h    |    2 +-
 arch/arm/mach-footbridge/include/mach/vmalloc.h |    2 +-
 arch/arm/mach-h720x/include/mach/vmalloc.h      |    2 +-
 arch/arm/mach-integrator/include/mach/vmalloc.h |    2 +-
 arch/arm/mach-msm/include/mach/vmalloc.h        |    2 +-
 arch/arm/mach-netx/include/mach/vmalloc.h       |    2 +-
 arch/arm/mach-omap1/include/mach/vmalloc.h      |    2 +-
 arch/arm/mach-omap2/include/mach/vmalloc.h      |    2 +-
 arch/arm/mach-pnx4008/include/mach/vmalloc.h    |    2 +-
 arch/arm/mach-rpc/include/mach/vmalloc.h        |    2 +-
 arch/arm/mach-shark/include/mach/vmalloc.h      |    2 +-
 arch/arm/mach-versatile/include/mach/vmalloc.h  |    2 +-
 debian.ti-omap4/config/config.common.ubuntu     |    6 +++---
 16 files changed, 18 insertions(+), 18 deletions(-)