From dc061c8d1e82d505a8e7489869fc5d159b01eb64 Mon Sep 17 00:00:00 2001
From: Mark Kettenis <kettenis@cvs.openbsd.org>
Date: Sat, 8 Sep 2012 20:58:51 +0000
Subject: On SPARC64 VI/VII CPUs, use the lseep instruction in the idle loop to
 force a thread switch in the hope the other thread can do some useful work.

---
 sys/arch/sparc64/sparc64/cpu.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

(limited to 'sys/arch/sparc64')

diff --git a/sys/arch/sparc64/sparc64/cpu.c b/sys/arch/sparc64/sparc64/cpu.c
index bcdf288a3df..29ee24bb25d 100644
--- a/sys/arch/sparc64/sparc64/cpu.c
+++ b/sys/arch/sparc64/sparc64/cpu.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpu.c,v 1.56 2011/01/13 22:55:33 matthieu Exp $	*/
+/*	$OpenBSD: cpu.c,v 1.57 2012/09/08 20:58:50 kettenis Exp $	*/
 /*	$NetBSD: cpu.c,v 1.13 2001/05/26 21:27:15 chs Exp $ */
 
 /*
@@ -788,10 +788,24 @@ cpu_idle_cycle(void)
 		sparc_wrpr(pstate, sparc_rdpr(pstate) & ~PSTATE_IE, 0);
 	}
 #endif
+
+	/*
+	 * On processors with multiple threads we simply force a
+	 * thread switch.  Using the sleep instruction seems to work
+	 * just as well as using the suspend instruction and makes the
+	 * code a little bit less complicated.
+	 */
+	__asm __volatile(
+		"999:	nop					\n"
+		"	.section .sun4u_mtp_patch, \"ax\"	\n"
+		"	.word	999b				\n"
+		"	.word	0x81b01060	! sleep		\n"
+		"	.previous				\n"
+		: : : "memory");
 }
 
 void
-cpu_idle_leave()
+cpu_idle_leave(void)
 {
 	if (CPU_ISSUN4V) {
 		sparc_wrpr(pstate, sparc_rdpr(pstate) | PSTATE_IE, 0);
-- 
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