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

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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>
This commit is contained in:
Jerone Young 2008-04-12 05:03:33 +10:00 committed by Josh Boyer
parent 478d5dcb62
commit e92716f2aa
2 changed files with 68 additions and 1 deletions
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2
arch/powerpc/platforms/44x/Makefile
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@ -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

67
arch/powerpc/platforms/44x/idle.c Normal file
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@ -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);