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From:   David Daney <ddaney.cavm@gmail.com>
To:     linux-mips@linux-mips.org, ralf@linux-mips.org
Cc:     David Daney <david.daney@cavium.com>
Subject: [PATCH] MIPS: Don't save/restore OCTEON wide multiplier state on syscalls.
Date:   Fri, 21 Jun 2013 15:14:53 -0700
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From: David Daney <david.daney@cavium.com>

The ABI allows these to be clobbered on syscalls, so only save and
restore the multiplier state when the temporary registers need to be
preserved.

Signed-off-by: David Daney <david.daney@cavium.com>
---
 arch/mips/include/asm/stackframe.h | 29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/arch/mips/include/asm/stackframe.h b/arch/mips/include/asm/stackframe.h
index a89d1b1..23fc95e 100644
--- a/arch/mips/include/asm/stackframe.h
+++ b/arch/mips/include/asm/stackframe.h
@@ -70,6 +70,14 @@
 #ifndef CONFIG_CPU_HAS_SMARTMIPS
 		LONG_S	v1, PT_LO(sp)
 #endif
+#ifdef CONFIG_CPU_CAVIUM_OCTEON
+		/*
+		 * The Octeon multiplier state is affected by general
+		 * multiply instructions. It must be saved before and
+		 * kernel code might corrupt it
+		 */
+		jal     octeon_mult_save
+#endif
 		.endm
 
 		.macro	SAVE_STATIC
@@ -218,17 +226,8 @@
 		ori	$28, sp, _THREAD_MASK
 		xori	$28, _THREAD_MASK
 #ifdef CONFIG_CPU_CAVIUM_OCTEON
-		.set	mips64
-		pref	0, 0($28)	/* Prefetch the current pointer */
-		pref	0, PT_R31(sp)	/* Prefetch the $31(ra) */
-		/* The Octeon multiplier state is affected by general multiply
-		    instructions. It must be saved before and kernel code might
-		    corrupt it */
-		jal	octeon_mult_save
-		LONG_L	v1, 0($28)  /* Load the current pointer */
-			 /* Restore $31(ra) that was changed by the jal */
-		LONG_L	ra, PT_R31(sp)
-		pref	0, 0(v1)    /* Prefetch the current thread */
+		.set    mips64
+		pref    0, 0($28)       /* Prefetch the current pointer */
 #endif
 		.set	pop
 		.endm
@@ -248,6 +247,10 @@
 		.endm
 
 		.macro	RESTORE_TEMP
+#ifdef CONFIG_CPU_CAVIUM_OCTEON
+		/* Restore the Octeon multiplier state */
+		jal	octeon_mult_restore
+#endif
 #ifdef CONFIG_CPU_HAS_SMARTMIPS
 		LONG_L	$24, PT_ACX(sp)
 		mtlhx	$24
@@ -360,10 +363,6 @@
 		DVPE	5				# dvpe a1
 		jal	mips_ihb
 #endif /* CONFIG_MIPS_MT_SMTC */
-#ifdef CONFIG_CPU_CAVIUM_OCTEON
-		/* Restore the Octeon multiplier state */
-		jal	octeon_mult_restore
-#endif
 		mfc0	a0, CP0_STATUS
 		ori	a0, STATMASK
 		xori	a0, STATMASK
-- 
1.7.11.7