[PATCH 1 of 3] Add idle wait support for 44x platforms

Jerone Young
2008-04-25T05:56:02Z

2 files changed, 68 insertions(+), 1 deletion(-)
arch/powerpc/platforms/44x/Makefile | 2 -
arch/powerpc/platforms/44x/idle.c | 67 +++++++++++++++++++++++++++++++++++

This patch has been accepted upstream and will be in 2.6.26. So it will eventually need to be removed when we move to 2.6.26rc.

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.

Command line options:
idle=spin <-- CPU will spin

By default will go into wait mode.

Signed-off-by: Jerone Young <jyoung5@us.ibm.com>

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 +1,67 @@
+/*
+ * 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);