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SubjectRe: [Bug fix]mips 64bits checksum error -- csum_tcpudp_nofold
On Wed, Jan 25, 2017 at 6:33 PM, Mark Zhang <bomb.zhang@gmail.com> wrote:
> Hi Alex,
>
> Thanks for your reply.
> I tested your correction. The result is correct.
> The C language will cause this function(csum_tcpudp_nofold) become
> 176 MIPS instructions. The assemble code is 150 MIPS instruction.
> If the MIPS CPU is running as 1GHz, C language cause more 60 nano
> seconds during send/receive each tcp/udp packet. I'm not sure whether
> it will cause any negative result if the frequency of CPU was lower.
> MIPS arch is usually used in networking equipments.
> I think Ralf's correction is better.
>
> - Mark
>
> Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
>
> arch/mips/include/asm/checksum.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/mips/include/asm/checksum.h b/arch/mips/include/asm/checksum.h
> index 5c585c5..08b6ba3 100644
> --- a/arch/mips/include/asm/checksum.h
> +++ b/arch/mips/include/asm/checksum.h
> @@ -186,7 +186,9 @@ static inline __wsum csum_tcpudp_nofold(__be32 saddr,
> " daddu %0, %4 \n"
> " dsll32 $1, %0, 0 \n"
> " daddu %0, $1 \n"
> + " sltu $1, %0, $1 \n"
> " dsra32 %0, %0, 0 \n"
> + " daddu %0, $1 \n"
> #endif
> " .set pop"
> : "=r" (sum)
>

This looks good to me.

Acked-by: Alexander Duyck <alexander.h.duyck@intel.com>

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