Re: [U-Boot] [PATCH v4 06/27] ppc: Add initial memory barrier macros

On 03/14/2012 09:16 PM, Simon Glass wrote:

These are available on other architectures, so add them on ppc.

Signed-off-by: Simon Glass sjg@chromium.org

arch/powerpc/include/asm/io.h | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h index 56ac9fe..d246fd8 100644 --- a/arch/powerpc/include/asm/io.h +++ b/arch/powerpc/include/asm/io.h @@ -318,4 +318,12 @@ static inline phys_addr_t virt_to_phys(void * vaddr) #endif }

+/*

• • TODO: The kernel offers some more advanced versions of barriers, it might
• • have some advantages to use them instead of the simple one here.
• */

+#define dmb() __asm__ __volatile__ ("" : : : "memory") +#define __iormb() dmb() +#define __iowmb() dmb()

What are the semantics of these (they are not the standard Linux barriers), and how is a simple compiler barrier adequate?

-Scott