netdev - [PATCH] MIPS checksum fix

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Date:	Fri, 19 Sep 2008 13:47:43 +0200
From:	Ralf Baechle <ralf@...ux-mips.org>
To:	"Maciej W. Rozycki" <macro@...ux-mips.org>
Cc:	Atsushi Nemoto <anemo@....ocn.ne.jp>, u1@...ran.org,
	linux-mips@...ux-mips.org, netdev@...r.kernel.org
Subject: [PATCH] MIPS checksum fix

On Fri, Sep 19, 2008 at 01:23:04PM +0200, Ralf Baechle wrote:

> >  I can see you have done the microoptimisation I had in mind meanwhile --
> > thanks for saving me the effort. ;)  There is a delay slot to fill left
> > though -- will you take care of it too?
> 
> Will do - just couldn't be bothered (too) late last night ...

Voila.

I'm interested in test reports of this on all sorts of configurations -
32-bit, 64-bit, big / little endian, R2 processors and pre-R2.  In
particular Cavium being the only MIPS64 R2 implementation would be
interesting.  This definately is stuff which should go upstream for 2.6.27.

  Ralf

Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>

diff --git a/arch/mips/lib/csum_partial.S b/arch/mips/lib/csum_partial.S
index 8d77841..eac0d61 100644
--- a/arch/mips/lib/csum_partial.S
+++ b/arch/mips/lib/csum_partial.S
@@ -53,12 +53,14 @@
 #define UNIT(unit)  ((unit)*NBYTES)
 
 #define ADDC(sum,reg)						\
-	.set	push;						\
-	.set	noat;						\
 	ADD	sum, reg;					\
 	sltu	v1, sum, reg;					\
 	ADD	sum, v1;					\
-	.set	pop
+
+#define ADDC32(sum,reg)						\
+	addu	sum, reg;					\
+	sltu	v1, sum, reg;					\
+	addu	sum, v1;					\
 
 #define CSUM_BIGCHUNK1(src, offset, sum, _t0, _t1, _t2, _t3)	\
 	LOAD	_t0, (offset + UNIT(0))(src);			\
@@ -254,8 +256,6 @@ LEAF(csum_partial)
 1:	ADDC(sum, t1)
 
 	/* fold checksum */
-	.set	push
-	.set	noat
 #ifdef USE_DOUBLE
 	dsll32	v1, sum, 0
 	daddu	sum, v1
@@ -263,24 +263,25 @@ LEAF(csum_partial)
 	dsra32	sum, sum, 0
 	addu	sum, v1
 #endif
-	sll	v1, sum, 16
-	addu	sum, v1
-	sltu	v1, sum, v1
-	srl	sum, sum, 16
-	addu	sum, v1
 
 	/* odd buffer alignment? */
-	beqz	t7, 1f
-	 nop
-	sll	v1, sum, 8
+#ifdef CPU_MIPSR2
+	wsbh	sum, sum	
+	movn	sum, v1, t7
+#else
+	beqz	t7, 1f			/* odd buffer alignment? */
+	 lui	v1, 0x00ff
+	addu	v1, 0x00ff
+	and	t0, sum, v1
+	sll	t0, t0, 8
 	srl	sum, sum, 8
-	or	sum, v1
-	andi	sum, 0xffff
-	.set	pop
+	and	sum, sum, v1
+	or	sum, sum, t0
 1:
+#endif
 	.set	reorder
 	/* Add the passed partial csum.  */
-	ADDC(sum, a2)
+	ADDC32(sum, a2)
 	jr	ra
 	.set	noreorder
 	END(csum_partial)
@@ -656,8 +657,6 @@ EXC(	sb	t0, NBYTES-2(dst), .Ls_exc)
 	ADDC(sum, t2)
 .Ldone:
 	/* fold checksum */
-	.set	push
-	.set	noat
 #ifdef USE_DOUBLE
 	dsll32	v1, sum, 0
 	daddu	sum, v1
@@ -665,23 +664,23 @@ EXC(	sb	t0, NBYTES-2(dst), .Ls_exc)
 	dsra32	sum, sum, 0
 	addu	sum, v1
 #endif
-	sll	v1, sum, 16
-	addu	sum, v1
-	sltu	v1, sum, v1
-	srl	sum, sum, 16
-	addu	sum, v1
 
-	/* odd buffer alignment? */
-	beqz	odd, 1f
-	 nop
-	sll	v1, sum, 8
+#ifdef CPU_MIPSR2
+	wsbh	v1, sum
+	movn	sum, v1, odd
+#else
+	beqz	odd, 1f			/* odd buffer alignment? */
+	 lui	v1, 0x00ff
+	addu	v1, 0x00ff
+	and	t0, sum, v1
+	sll	t0, t0, 8
 	srl	sum, sum, 8
-	or	sum, v1
-	andi	sum, 0xffff
-	.set	pop
+	and	sum, sum, v1
+	or	sum, sum, t0
 1:
+#endif
 	.set reorder
-	ADDC(sum, psum)
+	ADDC32(sum, psum)
 	jr	ra
 	.set noreorder
 
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