[PATCH] powerpc/64: Fix checksum folding in csum_add

[LEROY Christophe]

Shile Zhang <shile.zhang at nokia.com> a écrit :

> fix the missed point in Paul's patch:
> "powerpc/64: Fix checksum folding in csum_tcpudp_nofold and
> ip_fast_csum_nofold"
>
> Signed-off-by: Shile Zhang <shile.zhang at nokia.com>
> ---
>  arch/powerpc/include/asm/checksum.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/include/asm/checksum.h  
> b/arch/powerpc/include/asm/checksum.h
> index 5b1a6e3..430d038 100644
> --- a/arch/powerpc/include/asm/checksum.h
> +++ b/arch/powerpc/include/asm/checksum.h
> @@ -108,7 +108,7 @@ static inline __wsum csum_add(__wsum csum, __wsum addend)
>
>  #ifdef __powerpc64__
>  	res += (__force u64)addend;
> -	return (__force __wsum)((u32)res + (res >> 32));
> +	return (__force __wsum) from64to32(res);

Did you encounter a bug due to that ?
As far as i understand, csum and addend are 32 bits so can't exceed 0xffffffff
Then their sum won't exceed 0x1fffffffe. So the sum of upper and lower  
part won't carry

Christophe

>  #else
>  	asm("addc %0,%0,%1;"
>  	    "addze %0,%0;"
> --
> 2.6.2