Subject: [PATCH] [v3] Add idle wait support for 44x platforms

From: Jerone Young <[email-masked]>
Date: Fri, 04 Apr 2008 10:50:11 -0500

2 files changed, 87 insertions(+), 1 deletion(-)
arch/powerpc/platforms/44x/Makefile |    2 
arch/powerpc/platforms/44x/idle.c   |   86 +++++++++++++++++++++++++++++++++++

This patch adds the ability for the CPU to go into wait state while in cpu_idle loop. This helps virtulization solutions know when the guest Linux kernel is in an idle state. There are two ways to do it.

1) Command line
	idle=spin <-- CPU will spin (this is the default)
	idle=wait <-- set CPU into wait state when idle

2) The device tree will be checked for the "/hypervisor" node
   If this node is seen it will use "wait" for idle, so that
   the hypervisor can know when guest Linux kernel it is in
   an idle state.

This patch, unlike the last, isolates the code to 44x platforms.

Signed-off-by: Jerone Young <[email-masked]>

diff --git a/arch/powerpc/platforms/44x/Makefile b/arch/powerpc/platforms/44x/Makefile
--- 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
+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
--- /dev/null
+++ b/arch/powerpc/platforms/44x/idle.c
@@ -0,0 +1,86 @@
+/*
+ * Copyright 2008 IBM Corp. 
+ *
+ * Based on arch/powerpc/platforms/pasemi/idle.c: 
+ * Copyright (C) 2006-2007 PA Semi, Inc
+ *
+ * Added by: Jerone Young <[email-masked]>
+ *
+ * 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 current_mode;
+
+struct sleep_mode {
+	char *name;
+	void (*entry)(void);
+};
+
+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);
+	isync();
+	/* return to initial state */
+	mtmsr(msr_save);
+	isync();
+}
+
+static struct sleep_mode modes[] = {
+	{ .name = "spin", .entry = NULL },
+	{ .name = "wait", .entry = &ppc44x_idle },
+};
+
+int __init ppc44x_idle_init(void)
+{
+	void *func = modes[current_mode].entry;
+	struct device_node *node;
+
+	node = of_find_node_by_path("/hypervisor");
+	if (node) {
+		/* if we find /hypervisor node is in device tree,
+		   set idle mode to wait */
+		func = &ppc44x_idle; /* wait */
+		of_node_put(node);
+	}
+
+	ppc_md.power_save = func;
+	return 0;
+}
+
+arch_initcall(ppc44x_idle_init);
+
+static int __init idle_param(char *p)
+{ 
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(modes); i++) {
+		if (!strcmp(modes[i].name, p)) {
+			current_mode = i;
+			break;
+		}
+	}
+
+	return 0;
+}
+
+early_param("idle", idle_param);