[kvm-ppc-devel] [PATCH 1 of 2] Add idle power save for ppc 4xx

[kvm-ppc-devel] [PATCH 1 of 2] Add idle power save for ppc 4xx

[Jerone Young]

# HG changeset patch
# User Jerone Young <jyoung5@us.ibm.com>
# Date 1206933796 18000
# Node ID 15675e59e019c4800a834ae79090d92b07f1d0ce
# Parent  1506aa38ddabb0bf73fff3ac3f3db5f9ef6458cc
Add idle power save for ppc 4xx

This patch sets the wait state MSR when power_save is called in cpu_idle loop for ppc4xx. This is mainly to help out virtualization solutions such as KVM. This way the virtualization soultions are able to tell if the guest kernel is idle.

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

diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsy
 obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsync.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 obj-$(CONFIG_6xx)		+= idle_6xx.o l2cr_6xx.o cpu_setup_6xx.o
+obj-$(CONFIG_4xx)		+= idle_4xx.o
 obj-$(CONFIG_TAU)		+= tau_6xx.o
 obj-$(CONFIG_HIBERNATION)	+= swsusp.o suspend.o \
 				   swsusp_$(CONFIG_WORD_SIZE).o
diff --git a/arch/powerpc/kernel/idle_4xx.c b/arch/powerpc/kernel/idle_4xx.c
new file mode 100644
--- /dev/null
+++ b/arch/powerpc/kernel/idle_4xx.c
@@ -0,0 +1,24 @@
+/*
+ * This file contains the power_save function for 4xx CPUs
+ *
+ * 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
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <asm/processor.h>
+#include <asm/machdep.h>
+
+void ppc4xx_idle()
+{
+	unsigned long msr_save;
+
+	/* set wait state MSR */
+	local_irq_enable();
+	msr_save = mfmsr();
+	mtmsr(msr_save|MSR_WE);
+	local_irq_disable();
+}
diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -132,6 +132,10 @@ void __init machine_init(unsigned long d
 	if (cpu_has_feature(CPU_FTR_CAN_DOZE) ||
 	    cpu_has_feature(CPU_FTR_CAN_NAP))
 		ppc_md.power_save = ppc6xx_idle;
+#endif
+
+#ifdef CONFIG_4xx
+	ppc_md.power_save = ppc4xx_idle;
 #endif
 
 	if (ppc_md.progress)
diff --git a/include/asm-powerpc/machdep.h b/include/asm-powerpc/machdep.h
--- a/include/asm-powerpc/machdep.h
+++ b/include/asm-powerpc/machdep.h
@@ -266,6 +266,7 @@ extern void power4_idle(void);
 extern void power4_idle(void);
 extern void power4_cpu_offline_powersave(void);
 extern void ppc6xx_idle(void);
+extern void ppc4xx_idle(void);
 
 /*
  * ppc_md contains a copy of the machine description structure for the

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[kvm-ppc-devel] [PATCH 1 of 2] Add idle power save for ppc 4xx for

[Jerone Young]

# HG changeset patch
# User Jerone Young <jyoung5@us.ibm.com>
# Date 1207122427 18000
# Node ID 6e9ae9e1e5992339ca1f3efa93f8200cf24cbee5
# Parent  1506aa38ddabb0bf73fff3ac3f3db5f9ef6458cc
Add idle power save for ppc 4xx for 2.6.25

This patch sets the wait state MSR when power_save is called in cpu_idle loop for ppc4xx. This is mainly to help out virtualization solutions such as KVM. This way the virtualization soultions are able to tell if the guest kernel is idle.

I have tested this on hardware & KVM virtual guest.

The issue though is this is a temporary patch. As the one that will be sent upstream is based on linux-next (2.6.26) and is not the same as the 2.6.25 patch.

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

diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsy
 obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsync.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 obj-$(CONFIG_6xx)		+= idle_6xx.o l2cr_6xx.o cpu_setup_6xx.o
+obj-$(CONFIG_4xx)		+= idle_4xx.o
 obj-$(CONFIG_TAU)		+= tau_6xx.o
 obj-$(CONFIG_HIBERNATION)	+= swsusp.o suspend.o \
 				   swsusp_$(CONFIG_WORD_SIZE).o
diff --git a/arch/powerpc/kernel/idle_4xx.c b/arch/powerpc/kernel/idle_4xx.c
new file mode 100644
--- /dev/null
+++ b/arch/powerpc/kernel/idle_4xx.c
@@ -0,0 +1,22 @@
+/*
+ * This file contains the power_save function for 4xx CPUs
+ *
+ * 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
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <asm/processor.h>
+#include <asm/machdep.h>
+
+void ppc4xx_idle(void)
+{
+	unsigned long msr_save;
+
+	/* set wait state MSR */
+	msr_save = mfmsr();
+	mtmsr(msr_save|MSR_WE|MSR_EE|MSR_CE);
+}
diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -132,6 +132,10 @@ void __init machine_init(unsigned long d
 	if (cpu_has_feature(CPU_FTR_CAN_DOZE) ||
 	    cpu_has_feature(CPU_FTR_CAN_NAP))
 		ppc_md.power_save = ppc6xx_idle;
+#endif
+
+#ifdef CONFIG_4xx
+	ppc_md.power_save = ppc4xx_idle;
 #endif
 
 	if (ppc_md.progress)
diff --git a/include/asm-powerpc/machdep.h b/include/asm-powerpc/machdep.h
--- a/include/asm-powerpc/machdep.h
+++ b/include/asm-powerpc/machdep.h
@@ -266,6 +266,7 @@ extern void power4_idle(void);
 extern void power4_idle(void);
 extern void power4_cpu_offline_powersave(void);
 extern void ppc6xx_idle(void);
+extern void ppc4xx_idle(void);
 
 /*
  * ppc_md contains a copy of the machine description structure for the

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Re: [kvm-ppc-devel] [PATCH 1 of 2] Add idle power save for ppc 4xx

[Jimi Xenidis]

On Apr 2, 2008, at 3:52 AM, Jerone Young wrote:

> # HG changeset patch
> # User Jerone Young <jyoung5@us.ibm.com>
> # Date 1207122427 18000
> # Node ID 6e9ae9e1e5992339ca1f3efa93f8200cf24cbee5
> # Parent  1506aa38ddabb0bf73fff3ac3f3db5f9ef6458cc
> Add idle power save for ppc 4xx for 2.6.25
>
> This patch sets the wait state MSR when power_save is called in  
> cpu_idle loop for ppc4xx. This is mainly to help out virtualization  
> solutions such as KVM. This way the virtualization soultions are  
> able to tell if the guest kernel is idle.
>
> I have tested this on hardware & KVM virtual guest.
>
> The issue though is this is a temporary patch. As the one that will  
> be sent upstream is based on linux-next (2.6.26) and is not the  
> same as the 2.6.25 patch.
>
> Signed-off-by: Jerone Young <jyoung5@us.ibm.com>
>
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/ 
> Makefile
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -39,6 +39,7 @@ obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsy
>  obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsync.o
>  obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
>  obj-$(CONFIG_6xx)		+= idle_6xx.o l2cr_6xx.o cpu_setup_6xx.o
> +obj-$(CONFIG_4xx)		+= idle_4xx.o
>  obj-$(CONFIG_TAU)		+= tau_6xx.o
>  obj-$(CONFIG_HIBERNATION)	+= swsusp.o suspend.o \
>  				   swsusp_$(CONFIG_WORD_SIZE).o
> diff --git a/arch/powerpc/kernel/idle_4xx.c b/arch/powerpc/kernel/ 
> idle_4xx.c
> new file mode 100644
> --- /dev/null
> +++ b/arch/powerpc/kernel/idle_4xx.c
> @@ -0,0 +1,22 @@
> +/*
> + * This file contains the power_save function for 4xx CPUs
> + *
> + * 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
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#include <asm/processor.h>
> +#include <asm/machdep.h>
> +
> +void ppc4xx_idle(void)
> +{
> +	unsigned long msr_save;
> +
> +	/* set wait state MSR */
> +	msr_save = mfmsr();
> +	mtmsr(msr_save|MSR_WE|MSR_EE|MSR_CE);

1) I think you also want MSR_DE here, no?
2) Just to be safe, I'd also append an isync();
3) In case MSR_WE does nothing, or continues from here I'd append  
"mstmsr(msr_save); isync();" as well

-JX



> +}
> diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/ 
> setup_32.c
> --- a/arch/powerpc/kernel/setup_32.c
> +++ b/arch/powerpc/kernel/setup_32.c
> @@ -132,6 +132,10 @@ void __init machine_init(unsigned long d
>  	if (cpu_has_feature(CPU_FTR_CAN_DOZE) ||
>  	    cpu_has_feature(CPU_FTR_CAN_NAP))
>  		ppc_md.power_save = ppc6xx_idle;
> +#endif
> +
> +#ifdef CONFIG_4xx
> +	ppc_md.power_save = ppc4xx_idle;
>  #endif
>
>  	if (ppc_md.progress)
> diff --git a/include/asm-powerpc/machdep.h b/include/asm-powerpc/ 
> machdep.h
> --- a/include/asm-powerpc/machdep.h
> +++ b/include/asm-powerpc/machdep.h
> @@ -266,6 +266,7 @@ extern void power4_idle(void);
>  extern void power4_idle(void);
>  extern void power4_cpu_offline_powersave(void);
>  extern void ppc6xx_idle(void);
> +extern void ppc4xx_idle(void);
>
>  /*
>   * ppc_md contains a copy of the machine description structure for  
> the
>
> ---------------------------------------------------------------------- 
> ---
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> just about anything Open Source.
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Re: [kvm-ppc-devel] [PATCH 1 of 2] Add idle power save for ppc

[Jerone Young]

On Wed, 2008-04-02 at 08:14 -0400, Jimi Xenidis wrote:
> On Apr 2, 2008, at 3:52 AM, Jerone Young wrote:
> 
> > # HG changeset patch
> > # User Jerone Young <jyoung5@us.ibm.com>
> > # Date 1207122427 18000
> > # Node ID 6e9ae9e1e5992339ca1f3efa93f8200cf24cbee5
> > # Parent  1506aa38ddabb0bf73fff3ac3f3db5f9ef6458cc
> > Add idle power save for ppc 4xx for 2.6.25
> >
> > This patch sets the wait state MSR when power_save is called in  
> > cpu_idle loop for ppc4xx. This is mainly to help out virtualization  
> > solutions such as KVM. This way the virtualization soultions are  
> > able to tell if the guest kernel is idle.
> >
> > I have tested this on hardware & KVM virtual guest.
> >
> > The issue though is this is a temporary patch. As the one that will  
> > be sent upstream is based on linux-next (2.6.26) and is not the  
> > same as the 2.6.25 patch.
> >
> > Signed-off-by: Jerone Young <jyoung5@us.ibm.com>
> >
> > diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/ 
> > Makefile
> > --- a/arch/powerpc/kernel/Makefile
> > +++ b/arch/powerpc/kernel/Makefile
> > @@ -39,6 +39,7 @@ obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsy
> >  obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsync.o
> >  obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
> >  obj-$(CONFIG_6xx)		+= idle_6xx.o l2cr_6xx.o cpu_setup_6xx.o
> > +obj-$(CONFIG_4xx)		+= idle_4xx.o
> >  obj-$(CONFIG_TAU)		+= tau_6xx.o
> >  obj-$(CONFIG_HIBERNATION)	+= swsusp.o suspend.o \
> >  				   swsusp_$(CONFIG_WORD_SIZE).o
> > diff --git a/arch/powerpc/kernel/idle_4xx.c b/arch/powerpc/kernel/ 
> > idle_4xx.c
> > new file mode 100644
> > --- /dev/null
> > +++ b/arch/powerpc/kernel/idle_4xx.c
> > @@ -0,0 +1,22 @@
> > +/*
> > + * This file contains the power_save function for 4xx CPUs
> > + *
> > + * 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
> > + * as published by the Free Software Foundation; either version
> > + * 2 of the License, or (at your option) any later version.
> > + */
> > +
> > +#include <asm/processor.h>
> > +#include <asm/machdep.h>
> > +
> > +void ppc4xx_idle(void)
> > +{
> > +	unsigned long msr_save;
> > +
> > +	/* set wait state MSR */
> > +	msr_save = mfmsr();
> > +	mtmsr(msr_save|MSR_WE|MSR_EE|MSR_CE);
> 
> 1) I think you also want MSR_DE here, no?
> 2) Just to be safe, I'd also append an isync();
> 3) In case MSR_WE does nothing, or continues from here I'd append  
> "mstmsr(msr_save); isync();" as well

Looks like using local_irq_enable() just might have been a better idea
after all. 

So the MSR_DE is yet another case that could go here. If it was on
coming into power_save...I'm assuming it would get disabled by
local_irq_disable().

Looks like using isync after the mtmsr looks to be a good safety net.

> 
> -JX
> 
> 
> 
> > +}
> > diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/ 
> > setup_32.c
> > --- a/arch/powerpc/kernel/setup_32.c
> > +++ b/arch/powerpc/kernel/setup_32.c
> > @@ -132,6 +132,10 @@ void __init machine_init(unsigned long d
> >  	if (cpu_has_feature(CPU_FTR_CAN_DOZE) ||
> >  	    cpu_has_feature(CPU_FTR_CAN_NAP))
> >  		ppc_md.power_save = ppc6xx_idle;
> > +#endif
> > +
> > +#ifdef CONFIG_4xx
> > +	ppc_md.power_save = ppc4xx_idle;
> >  #endif
> >
> >  	if (ppc_md.progress)
> > diff --git a/include/asm-powerpc/machdep.h b/include/asm-powerpc/ 
> > machdep.h
> > --- a/include/asm-powerpc/machdep.h
> > +++ b/include/asm-powerpc/machdep.h
> > @@ -266,6 +266,7 @@ extern void power4_idle(void);
> >  extern void power4_idle(void);
> >  extern void power4_cpu_offline_powersave(void);
> >  extern void ppc6xx_idle(void);
> > +extern void ppc4xx_idle(void);
> >
> >  /*
> >   * ppc_md contains a copy of the machine description structure for  
> > the
> >
> > ---------------------------------------------------------------------- 
> > ---
> > Check out the new SourceForge.net Marketplace.
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> > just about anything Open Source.
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> > marketplace
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> > kvm-ppc-devel@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/kvm-ppc-devel
> 


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[kvm-ppc-devel] [PATCH 1 of 2] Add idle power save for ppc 4xx for

[Jerone Young]

# HG changeset patch
# User Jerone Young <jyoung5@us.ibm.com>
# Date 1207159627 18000
# Node ID 007c135cb5f14f5eb025c103623c2ebfcc76ab11
# Parent  1506aa38ddabb0bf73fff3ac3f3db5f9ef6458cc
Add idle power save for ppc 4xx for 2.6.25

This patch sets the wait state MSR when power_save is called in cpu_idle loop for ppc4xx. This is mainly to help out virtualization solutions such as KVM. This way the virtualization soultions are able to tell if the guest kernel is idle.

I have tested this on hardware & KVM virtual guest.

The issue though is this is a temporary patch. As the one that will be sent upstream is based on linux-next (2.6.26) and is not the same as the 2.6.25 patch.

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

diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsy
 obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsync.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 obj-$(CONFIG_6xx)		+= idle_6xx.o l2cr_6xx.o cpu_setup_6xx.o
+obj-$(CONFIG_4xx)		+= idle_4xx.o
 obj-$(CONFIG_TAU)		+= tau_6xx.o
 obj-$(CONFIG_HIBERNATION)	+= swsusp.o suspend.o \
 				   swsusp_$(CONFIG_WORD_SIZE).o
diff --git a/arch/powerpc/kernel/idle_4xx.c b/arch/powerpc/kernel/idle_4xx.c
new file mode 100644
--- /dev/null
+++ b/arch/powerpc/kernel/idle_4xx.c
@@ -0,0 +1,24 @@
+/*
+ * This file contains the power_save function for 4xx CPUs
+ *
+ * Copyright 2008 IBM Corporation.
+ * 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
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <asm/processor.h>
+#include <asm/machdep.h>
+
+void ppc4xx_idle(void)
+{
+	unsigned long msr_save;
+
+	/* set wait state MSR */
+	msr_save = mfmsr();
+	mtmsr(msr_save|MSR_WE|MSR_EE|MSR_CE|MSR_DE);
+	isync();
+}
diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -132,6 +132,10 @@ void __init machine_init(unsigned long d
 	if (cpu_has_feature(CPU_FTR_CAN_DOZE) ||
 	    cpu_has_feature(CPU_FTR_CAN_NAP))
 		ppc_md.power_save = ppc6xx_idle;
+#endif
+
+#ifdef CONFIG_4xx
+	ppc_md.power_save = ppc4xx_idle;
 #endif
 
 	if (ppc_md.progress)
diff --git a/include/asm-powerpc/machdep.h b/include/asm-powerpc/machdep.h
--- a/include/asm-powerpc/machdep.h
+++ b/include/asm-powerpc/machdep.h
@@ -266,6 +266,7 @@ extern void power4_idle(void);
 extern void power4_idle(void);
 extern void power4_cpu_offline_powersave(void);
 extern void ppc6xx_idle(void);
+extern void ppc4xx_idle(void);
 
 /*
  * ppc_md contains a copy of the machine description structure for the

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Re: [kvm-ppc-devel] [PATCH 1 of 2] Add idle power save for ppc 4xx

[Christian Ehrhardt]

Jerone Young wrote:
> # HG changeset patch
> # User Jerone Young <jyoung5@us.ibm.com>
> # Date 1207159627 18000
> # Node ID 007c135cb5f14f5eb025c103623c2ebfcc76ab11
> # Parent  1506aa38ddabb0bf73fff3ac3f3db5f9ef6458cc
> Add idle power save for ppc 4xx for 2.6.25
> 
> This patch sets the wait state MSR when power_save is called in cpu_idle loop for ppc4xx. This is mainly to help out virtualization solutions such as KVM. This way the virtualization soultions are able to tell if the guest kernel is idle.
> 
> I have tested this on hardware & KVM virtual guest.
> 
> The issue though is this is a temporary patch. As the one that will be sent upstream is based on linux-next (2.6.26) and is not the same as the 2.6.25 patch.
> 
> Signed-off-by: Jerone Young <jyoung5@us.ibm.com>
> 
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -39,6 +39,7 @@ obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsy
>  obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsync.o
>  obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
>  obj-$(CONFIG_6xx)		+= idle_6xx.o l2cr_6xx.o cpu_setup_6xx.o
> +obj-$(CONFIG_4xx)		+= idle_4xx.o
>  obj-$(CONFIG_TAU)		+= tau_6xx.o
>  obj-$(CONFIG_HIBERNATION)	+= swsusp.o suspend.o \
>  				   swsusp_$(CONFIG_WORD_SIZE).o
> diff --git a/arch/powerpc/kernel/idle_4xx.c b/arch/powerpc/kernel/idle_4xx.c
> new file mode 100644
> --- /dev/null
> +++ b/arch/powerpc/kernel/idle_4xx.c
> @@ -0,0 +1,24 @@
> +/*
> + * This file contains the power_save function for 4xx CPUs
> + *
> + * Copyright 2008 IBM Corporation.
> + * 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
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#include <asm/processor.h>
> +#include <asm/machdep.h>
> +
> +void ppc4xx_idle(void)
> +{
> +	unsigned long msr_save;
> +
> +	/* set wait state MSR */
> +	msr_save = mfmsr();
> +	mtmsr(msr_save|MSR_WE|MSR_EE|MSR_CE|MSR_DE);
> +	isync();
> +}

I think Jimi's comment #3 is still worth to be considered:
3) In case MSR_WE does nothing, or continues from here I'd append  
"mstmsr(msr_save); isync();" as well

And another comment that was from Arnd Bergmann into the same direction:
[...] if only to make the function return with the same state that it was entered.

wich would then be something like

> +void ppc4xx_idle(void)
> +{
> +	unsigned long msr_save;
> +
> +	/* set wait state MSR */
> +	msr_save = mfmsr();
> +	mtmsr(msr_save|MSR_WE|MSR_EE|MSR_CE|MSR_DE);
> +	isync();
->	mtspr(msr_save);
->	isync();
> +}

I think it's more correct to leave as we enter.

btw - Hollis was faster, but I wanted to add for the kvm kernel part I also think placing it in emulate_instruction would save checks on every exit.

> diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
> --- a/arch/powerpc/kernel/setup_32.c
> +++ b/arch/powerpc/kernel/setup_32.c
> @@ -132,6 +132,10 @@ void __init machine_init(unsigned long d
>  	if (cpu_has_feature(CPU_FTR_CAN_DOZE) ||
>  	    cpu_has_feature(CPU_FTR_CAN_NAP))
>  		ppc_md.power_save = ppc6xx_idle;
> +#endif
> +
> +#ifdef CONFIG_4xx
> +	ppc_md.power_save = ppc4xx_idle;
>  #endif
> 
>  	if (ppc_md.progress)
> diff --git a/include/asm-powerpc/machdep.h b/include/asm-powerpc/machdep.h
> --- a/include/asm-powerpc/machdep.h
> +++ b/include/asm-powerpc/machdep.h
> @@ -266,6 +266,7 @@ extern void power4_idle(void);
>  extern void power4_idle(void);
>  extern void power4_cpu_offline_powersave(void);
>  extern void ppc6xx_idle(void);
> +extern void ppc4xx_idle(void);
> 
>  /*
>   * ppc_md contains a copy of the machine description structure for the
> 
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-- 

Grüsse / regards, 
Christian Ehrhardt
IBM Linux Technology Center, Open Virtualization

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[kvm-ppc-devel] [PATCH 1 of 2] Add idle power save for ppc 4xx for

[Jerone Young]

# HG changeset patch
# User Jerone Young <jyoung5@us.ibm.com>
# Date 1207250239 18000
# Node ID b7794c1fa50b531c9b84382c3f3d9a5466d86c0d
# Parent  1506aa38ddabb0bf73fff3ac3f3db5f9ef6458cc
Add idle power save for ppc 4xx for 2.6.25

This patch sets the wait state MSR when power_save is called in cpu_idle loop for ppc4xx. This is mainly to help out virtualization solutions such as KVM. This way the virtualization soultions are able to tell if the guest kernel is idle.

I have tested this on hardware & KVM virtual guest.

The issue though is this is a temporary patch. As the one that will be sent upstream is based on linux-next (2.6.26) and is not the same as the 2.6.25 patch.

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

diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsy
 obj-$(CONFIG_GENERIC_TBSYNC)	+= smp-tbsync.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 obj-$(CONFIG_6xx)		+= idle_6xx.o l2cr_6xx.o cpu_setup_6xx.o
+obj-$(CONFIG_4xx)		+= idle_4xx.o
 obj-$(CONFIG_TAU)		+= tau_6xx.o
 obj-$(CONFIG_HIBERNATION)	+= swsusp.o suspend.o \
 				   swsusp_$(CONFIG_WORD_SIZE).o
diff --git a/arch/powerpc/kernel/idle_4xx.c b/arch/powerpc/kernel/idle_4xx.c
new file mode 100644
--- /dev/null
+++ b/arch/powerpc/kernel/idle_4xx.c
@@ -0,0 +1,23 @@
+/*
+ * This file contains the power_save function for 4xx CPUs
+ *
+ * Copyright 2008 IBM Corporation.
+ * 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
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <asm/processor.h>
+#include <asm/machdep.h>
+
+void ppc4xx_idle(void)
+{
+	unsigned long msr_save;
+
+	/* set wait state MSR */
+	msr_save = mfmsr();
+	mtmsr(msr_save|MSR_WE|MSR_EE|MSR_CE);
+}
diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -132,6 +132,10 @@ void __init machine_init(unsigned long d
 	if (cpu_has_feature(CPU_FTR_CAN_DOZE) ||
 	    cpu_has_feature(CPU_FTR_CAN_NAP))
 		ppc_md.power_save = ppc6xx_idle;
+#endif
+
+#ifdef CONFIG_4xx
+	ppc_md.power_save = ppc4xx_idle;
 #endif
 
 	if (ppc_md.progress)
diff --git a/include/asm-powerpc/machdep.h b/include/asm-powerpc/machdep.h
--- a/include/asm-powerpc/machdep.h
+++ b/include/asm-powerpc/machdep.h
@@ -266,6 +266,7 @@ extern void power4_idle(void);
 extern void power4_idle(void);
 extern void power4_cpu_offline_powersave(void);
 extern void ppc6xx_idle(void);
+extern void ppc4xx_idle(void);
 
 /*
  * ppc_md contains a copy of the machine description structure for the

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