[ARM PATCH] 2507/1: work around ixp2400 erratum #66

Patch from Lennert Buytenhek

Intel's ixp2400 can occasionally corrupt writes to its on-chip
registers, leading to system crashes.  The suggested workaround for
this is to map in those registers using XCB=101 instead of XCB=000.
Patch 2491/1 makes all mappings of ixp2000 on-chip I/O regions use
section mappings.  This patch makes all iotable section mappings use
XCB=101.  This patch depends on 2491/1.
Kernel iotable mappings that are not 1MB-aligned, ioremap(), and
userspace mappings using mmap() on /dev/mem will still generate
XCB=000 mappings, which can trigger erratum #66 quite easily.
For this, an extra patch (to arch/arm/mm/proc-xscale.S) is needed,
which is maintained out-of-tree because it has been rejected in
the past.  See http://ixp2xxx.sourceforge.net/kernel/ and look
for 'ixp2000-erratum66-ptes.diff'.
2.6.11-rc4 with 2491/1 plus this patch survives a week of heavy
testing on my ENP-2611, while 2.6.11-rc4 vanilla doesn't stand a
chance and crashes within 30 minutes under the same workload.

Signed-off-by: Lennert BuytenhekSigned-off-by: Deepak Saxena
Signed-off-by: Russell King

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