In case perf IRQ is the highest of the medium-level IRQs, and is alone
on its level, it may be treated as NMI:
- LOCKLEVEL is defined to be one level less than EXCM level,
- IRQ masking never lowers current IRQ level,
- new fake exception cause code, EXCCAUSE_MAPPED_NMI is assigned to that
  IRQ; new second level exception handler, do_nmi, assigned to it
  handles it as NMI,
- atomic operations in configurations without s32c1i still need to mask
  all interrupts.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

When compiling with 'allmodconfig', some of drivers need cmpxchg64(),
xtensa does not supply 64-bit implementation for 'xchg', so use the
'generic' implementation.

e.g. (for next-20130527 tree):
  drivers/block/blockconsole.c:164:2: error: implicit declaration of function ‘cmpxchg64’ [-Werror=implicit-function-declaration]

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

Remove heading and trailing spaces, trim trailing lines, and wrap lines
that are longer than 80 characters.

Signed-off-by: Chris Zankel <chris@zankel.net>

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

- reference SRs by names where possible, not by numbers;
- get rid of __stringify around SR names where possible;
- remove unneeded SR names from asm/regs.h;
- add SREG_ prefix to remaining SR names;

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

Disintegrate asm/system.h for Xtensa.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Chris Zankel <chris@zankel.net>