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

[Scott Wood]

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 at 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