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| author |   Xiongfeng Wang <wangxiongfeng2@huawei.com> | 2021-12-21 11:55:56 +0800 |
|---|---|---|
| committer |   Catalin Marinas <catalin.marinas@arm.com> | 2021-12-22 10:44:53 +0000 |
| commit | d5624bb29f49b849ac8d1e9783dbf9c65cf33457 (patch) | |
| tree | 15c4737e7664df0afd23cbca92a32e7ed7c47a0d /include/asm-generic | |
| parent | arm64: remove __dma_*_area() aliases (diff) | |
| download | linux-dev-d5624bb29f49b849ac8d1e9783dbf9c65cf33457.tar.xz linux-dev-d5624bb29f49b849ac8d1e9783dbf9c65cf33457.zip | |
asm-generic: introduce io_stop_wc() and add implementation for ARM64
For memory accesses with write-combining attributes (e.g. those returned
by ioremap_wc()), the CPU may wait for prior accesses to be merged with
subsequent ones. But in some situation, such wait is bad for the
performance.
We introduce io_stop_wc() to prevent the merging of write-combining
memory accesses before this macro with those after it.
We add implementation for ARM64 using DGH instruction and provide NOP
implementation for other architectures.
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Suggested-by: Will Deacon <will@kernel.org>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20211221035556.60346-1-wangxiongfeng2@huawei.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'include/asm-generic')
| -rw-r--r-- | include/asm-generic/barrier.h | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h index 640f09479bdf..4c2c1b830344 100644 --- a/include/asm-generic/barrier.h +++ b/include/asm-generic/barrier.h @@ -251,5 +251,16 @@ do { \ #define pmem_wmb() wmb() #endif +/* + * ioremap_wc() maps I/O memory as memory with write-combining attributes. For + * this kind of memory accesses, the CPU may wait for prior accesses to be + * merged with subsequent ones. In some situation, such wait is bad for the + * performance. io_stop_wc() can be used to prevent the merging of + * write-combining memory accesses before this macro with those after it. + */ +#ifndef io_stop_wc +#define io_stop_wc do { } while (0) +#endif + #endif /* !__ASSEMBLY__ */ #endif /* __ASM_GENERIC_BARRIER_H */ |