diff options
| author | Arnd Bergmann | 2014-11-11 19:55:45 +0100 |
|---|---|---|
| committer | Arnd Bergmann | 2014-11-11 19:55:45 +0100 |
| commit | 1c8d29696f0d79902962526d6c54ebfeb842c61d (patch) | |
| tree | 047caddef4ee91e42002bc1234d273c6fbc54967 /Documentation | |
| parent | 3ba5acf368ae415cd14d026b7cfe29de942b65fc (diff) | |
| parent | a8e0aead70b4af957e6b27b82fba849c6179b707 (diff) | |
Merge branch 'io' of git://git.kernel.org/pub/scm/linux/kernel/git/will/linux into asm-generic
* 'io' of git://git.kernel.org/pub/scm/linux/kernel/git/will/linux:
documentation: memory-barriers: clarify relaxed io accessor semantics
x86: io: implement dummy relaxed accessor macros for writes
tile: io: implement dummy relaxed accessor macros for writes
sparc: io: implement dummy relaxed accessor macros for writes
powerpc: io: implement dummy relaxed accessor macros for writes
parisc: io: implement dummy relaxed accessor macros for writes
mn10300: io: implement dummy relaxed accessor macros for writes
m68k: io: implement dummy relaxed accessor macros for writes
m32r: io: implement dummy relaxed accessor macros for writes
ia64: io: implement dummy relaxed accessor macros for writes
cris: io: implement dummy relaxed accessor macros for writes
frv: io: implement dummy relaxed accessor macros for writes
xtensa: io: remove dummy relaxed accessor macros for reads
s390: io: remove dummy relaxed accessor macros for reads
microblaze: io: remove dummy relaxed accessor macros
asm-generic: io: implement relaxed accessor macros as conditional wrappers
Conflicts:
include/asm-generic/io.h
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/memory-barriers.txt | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index 22a969cdd476..4af4cea8cff0 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -2465,10 +2465,15 @@ functions: Please refer to the PCI specification for more information on interactions between PCI transactions. - (*) readX_relaxed() - - These are similar to readX(), but are not guaranteed to be ordered in any - way. Be aware that there is no I/O read barrier available. + (*) readX_relaxed(), writeX_relaxed() + + These are similar to readX() and writeX(), but provide weaker memory + ordering guarantees. Specifically, they do not guarantee ordering with + respect to normal memory accesses (e.g. DMA buffers) nor do they guarantee + ordering with respect to LOCK or UNLOCK operations. If the latter is + required, an mmiowb() barrier can be used. Note that relaxed accesses to + the same peripheral are guaranteed to be ordered with respect to each + other. (*) ioreadX(), iowriteX() |