OpenRISC only supports hardware instructions that perform 4 byte atomic
operations. For enabling qrwlocks for upcoming SMP support 1 and 2 byte
implementations are needed. To do this we leverage the 4 byte atomic
operations and shift/mask the 1 and 2 byte areas as needed.
This heavily borrows ideas and routines from sh and mips, which do
something similar.
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Stafford Horne <shorne@gmail.com>
When building allmodconfig this warning shows.
fs/ocfs2/file.c: In function 'ocfs2_file_write_iter':
./arch/openrisc/include/asm/cmpxchg.h:81:3: warning: value computed is
not used [-Wunused-value]
((typeof(*(ptr)))__xchg((unsigned long)(with), (ptr), sizeof(*(ptr))))
^
Applying the same patch logic that was done to the cmpxchg macro.
Signed-off-by: Stafford Horne <shorne@gmail.com>
Optimized version that make use of the l.lwa and l.swa atomic instruction
pair.
Most openrisc cores provide these instructions now, if not available
emulation is provided.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
[shorne@gmail.com: remove OPENRISC_HAVE_INST_LWA_SWA config suggesed by
Alan Cox https://lkml.org/lkml/2014/7/23/666]
[shorne@gmail.com: fixed unused calculated value compiler warning in
define cmpxchg]
Signed-off-by: Stafford Horne <shorne@gmail.com>
