[POWERPC] 4xx: Add idle wait support for 44x platforms

This changes the cpu_idle loop for 44x platforms to utilize the Wait Enable
feature of the CPU.  This helps virtulization solutions know when the guest
Linux kernel is in an idle state.

A command line option called "idle" is also added to allow people to change
the idle loop back to the original variation.  This is done by setting
"idle=spin" on the kernel command line.

Signed-off-by: Jerone Young <jyoung5@us.ibm.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>

2 files changed, 68 insertions, 1 deletions

diff --git a/arch/powerpc/platforms/44x/Makefile b/arch/powerpc/platforms/44x/Makefile
index 2320ae5dc8a..774165f9acd 100644
--- a/arch/powerpc/platforms/44x/Makefile
+++ b/arch/powerpc/platforms/44x/Makefile
@@ -1,4 +1,4 @@
-obj-$(CONFIG_44x)	:= misc_44x.o
+obj-$(CONFIG_44x)	:= misc_44x.o idle.o
 obj-$(CONFIG_EBONY)	+= ebony.o
 obj-$(CONFIG_TAISHAN)	+= taishan.o
 obj-$(CONFIG_BAMBOO)	+= bamboo.o
diff --git a/arch/powerpc/platforms/44x/idle.c b/arch/powerpc/platforms/44x/idle.c
new file mode 100644
index 00000000000..7a81f921fef
--- /dev/null
+++ b/arch/powerpc/platforms/44x/idle.c
@@ -0,0 +1,67 @@
+/*
+ * Copyright 2008 IBM Corp. 
+ *
+ * Based on arch/powerpc/platforms/pasemi/idle.c: 
+ * Copyright (C) 2006-2007 PA Semi, Inc
+ *
+ * Added by: Jerone Young <jyoung5@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ *
+ */
+
+#include <linux/of.h>
+#include <linux/kernel.h>
+#include <asm/machdep.h>
+
+static int mode_spin;
+
+static void ppc44x_idle(void)
+{
+	unsigned long msr_save;
+
+	msr_save = mfmsr();
+	/* set wait state MSR */
+	mtmsr(msr_save|MSR_WE|MSR_EE|MSR_CE|MSR_DE);
+	isync();
+	/* return to initial state */
+	mtmsr(msr_save);
+	isync();
+}
+
+int __init ppc44x_idle_init(void)
+{
+	if (!mode_spin) {
+		/* If we are not setting spin mode 
+                   then we set to wait mode */
+		ppc_md.power_save = &ppc44x_idle;
+	}
+
+	return 0;
+}
+
+arch_initcall(ppc44x_idle_init);
+
+static int __init idle_param(char *p)
+{ 
+
+	if (!strcmp("spin", p)) {
+		mode_spin = 1;
+		ppc_md.power_save = NULL;
+	}
+
+	return 0;
+}
+
+early_param("idle", idle_param);