linux-kernel - [PATCH v2 2/2] powerpc32: add support for csum

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Date:	Tue,  3 Feb 2015 12:39:27 +0100 (CET)
From:	Christophe Leroy <christophe.leroy@....fr>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>, scottwood@...escale.com
CC:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	Joakim Tjernlund <joakim.tjernlund@...nsmode.se>
Subject: [PATCH v2 2/2] powerpc32: add support for csum_add()

The C version of csum_add() as defined in include/net/checksum.h gives the
following assembly:
       0:       7c 04 1a 14     add     r0,r4,r3
       4:       7c 64 00 10     subfc   r3,r4,r0
       8:       7c 63 19 10     subfe   r3,r3,r3
       c:       7c 63 00 50     subf    r3,r3,r0

include/net/checksum.h also offers the possibility to define an arch specific
function.
This patch provides a ppc32 specific csum_add() inline function.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>

---
v2: changed constraints on the __asm__

 arch/powerpc/include/asm/checksum.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/powerpc/include/asm/checksum.h b/arch/powerpc/include/asm/checksum.h
index cfe806a..1e48cc7 100644
--- a/arch/powerpc/include/asm/checksum.h
+++ b/arch/powerpc/include/asm/checksum.h
@@ -141,6 +141,18 @@ static inline __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
 {
 	return csum_fold(csum_tcpudp_nofold(saddr, daddr, len, proto, sum));
 }
+
+#define HAVE_ARCH_CSUM_ADD
+static inline __wsum csum_add(__wsum csum, __wsum addend)
+{
+    __asm__("\n\
+	addc %0,%0,%1 \n\
+	addze %0,%0 \n\
+	"
+	: "+r" (csum) : "r" (addend));
+	return csum;
+}
+
 #endif
 #endif
 #endif /* __KERNEL__ */
-- 
2.1.0

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