[PATCH] powerpc: move epapr paravirt init of power_save to an initcall

[PATCH] powerpc: move epapr paravirt init of power_save to an initcall

[Stuart Yoder]

From: Stuart Yoder <stuart.yoder@freescale.com>

some restructuring of epapr paravirt init resulted in
ppc_md.power_save being set, and then overwritten to
NULL during machine_init.  This patch splits the
initialization of ppc_md.power_save out into a postcore
init call.

Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
---
 arch/powerpc/kernel/epapr_paravirt.c |   25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kernel/epapr_paravirt.c b/arch/powerpc/kernel/epapr_paravirt.c
index 6300c13..c49b69c 100644
--- a/arch/powerpc/kernel/epapr_paravirt.c
+++ b/arch/powerpc/kernel/epapr_paravirt.c
@@ -52,11 +52,6 @@ static int __init early_init_dt_scan_epapr(unsigned long node,
 #endif
 	}
 
-#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
-	if (of_get_flat_dt_prop(node, "has-idle", NULL))
-		ppc_md.power_save = epapr_ev_idle;
-#endif
-
 	epapr_paravirt_enabled = true;
 
 	return 1;
@@ -69,3 +64,23 @@ int __init epapr_paravirt_early_init(void)
 	return 0;
 }
 
+static int __init epapr_idle_init_dt_scan(unsigned long node,
+					   const char *uname,
+					   int depth, void *data)
+{
+#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
+	if (of_get_flat_dt_prop(node, "has-idle", NULL))
+		ppc_md.power_save = epapr_ev_idle;
+#endif
+	return 0;
+}
+
+static int __init epapr_idle_init(void)
+{
+	if (epapr_paravirt_enabled)
+		of_scan_flat_dt(epapr_idle_init_dt_scan, NULL);
+
+	return 0;
+}
+
+postcore_initcall(epapr_idle_init);
-- 
1.7.9.7

Re: [PATCH] powerpc: move epapr paravirt init of power_save to an initcall

[Alexander Graf]

On 30.04.14 21:54, Stuart Yoder wrote:
> From: Stuart Yoder <stuart.yoder@freescale.com>
>
> some restructuring of epapr paravirt init resulted in
> ppc_md.power_save being set, and then overwritten to
> NULL during machine_init.  This patch splits the
> initialization of ppc_md.power_save out into a postcore
> init call.
>
> Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
> ---
>   arch/powerpc/kernel/epapr_paravirt.c |   25 ++++++++++++++++++++-----
>   1 file changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/kernel/epapr_paravirt.c b/arch/powerpc/kernel/epapr_paravirt.c
> index 6300c13..c49b69c 100644
> --- a/arch/powerpc/kernel/epapr_paravirt.c
> +++ b/arch/powerpc/kernel/epapr_paravirt.c
> @@ -52,11 +52,6 @@ static int __init early_init_dt_scan_epapr(unsigned long node,
>   #endif
>   	}
>   
> -#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
> -	if (of_get_flat_dt_prop(node, "has-idle", NULL))
> -		ppc_md.power_save = epapr_ev_idle;
> -#endif
> -
>   	epapr_paravirt_enabled = true;
>   
>   	return 1;
> @@ -69,3 +64,23 @@ int __init epapr_paravirt_early_init(void)
>   	return 0;
>   }
>   
> +static int __init epapr_idle_init_dt_scan(unsigned long node,
> +					   const char *uname,
> +					   int depth, void *data)
> +{
> +#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
> +	if (of_get_flat_dt_prop(node, "has-idle", NULL))
> +		ppc_md.power_save = epapr_ev_idle;
> +#endif
> +	return 0;
> +}
> +
> +static int __init epapr_idle_init(void)
> +{
> +	if (epapr_paravirt_enabled)
> +		of_scan_flat_dt(epapr_idle_init_dt_scan, NULL);

Doesn't this scan all nodes? We only want to match on 
/hypervisor/has-idle, no?


Alex

RE: [PATCH] powerpc: move epapr paravirt init of power_save to an initcall

[Stuart Yoder]

> -----Original Message-----
> From: Alexander Graf [mailto:agraf@suse.de]
> Sent: Wednesday, April 30, 2014 2:56 PM
> To: Yoder Stuart-B08248; benh@kernel.crashing.org; Wood Scott-B07421
> Cc: linuxppc-dev@lists.ozlabs.org
> Subject: Re: [PATCH] powerpc: move epapr paravirt init of power_save to
> an initcall
>=20
>=20
> On 30.04.14 21:54, Stuart Yoder wrote:
> > From: Stuart Yoder <stuart.yoder@freescale.com>
> >
> > some restructuring of epapr paravirt init resulted in
> > ppc_md.power_save being set, and then overwritten to
> > NULL during machine_init.  This patch splits the
> > initialization of ppc_md.power_save out into a postcore
> > init call.
> >
> > Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
> > ---
> >   arch/powerpc/kernel/epapr_paravirt.c |   25 ++++++++++++++++++++-----
> >   1 file changed, 20 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/epapr_paravirt.c
> b/arch/powerpc/kernel/epapr_paravirt.c
> > index 6300c13..c49b69c 100644
> > --- a/arch/powerpc/kernel/epapr_paravirt.c
> > +++ b/arch/powerpc/kernel/epapr_paravirt.c
> > @@ -52,11 +52,6 @@ static int __init early_init_dt_scan_epapr(unsigned
> long node,
> >   #endif
> >   	}
> >
> > -#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
> > -	if (of_get_flat_dt_prop(node, "has-idle", NULL))
> > -		ppc_md.power_save =3D epapr_ev_idle;
> > -#endif
> > -
> >   	epapr_paravirt_enabled =3D true;
> >
> >   	return 1;
> > @@ -69,3 +64,23 @@ int __init epapr_paravirt_early_init(void)
> >   	return 0;
> >   }
> >
> > +static int __init epapr_idle_init_dt_scan(unsigned long node,
> > +					   const char *uname,
> > +					   int depth, void *data)
> > +{
> > +#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
> > +	if (of_get_flat_dt_prop(node, "has-idle", NULL))
> > +		ppc_md.power_save =3D epapr_ev_idle;
> > +#endif
> > +	return 0;
> > +}
> > +
> > +static int __init epapr_idle_init(void)
> > +{
> > +	if (epapr_paravirt_enabled)
> > +		of_scan_flat_dt(epapr_idle_init_dt_scan, NULL);
>=20
> Doesn't this scan all nodes? We only want to match on
> /hypervisor/has-idle, no?

I cut/pasted from  the approach the existing code in that file
took, but yes you're right we just need the one property.
Let me respin that to look at the hypervisor node only.

Stuart

Re: [PATCH] powerpc: move epapr paravirt init of power_save to an initcall

[Alexander Graf]

On 30.04.14 22:03, Stuart Yoder wrote:
>
>> -----Original Message-----
>> From: Alexander Graf [mailto:agraf@suse.de]
>> Sent: Wednesday, April 30, 2014 2:56 PM
>> To: Yoder Stuart-B08248; benh@kernel.crashing.org; Wood Scott-B07421
>> Cc: linuxppc-dev@lists.ozlabs.org
>> Subject: Re: [PATCH] powerpc: move epapr paravirt init of power_save to
>> an initcall
>>
>>
>> On 30.04.14 21:54, Stuart Yoder wrote:
>>> From: Stuart Yoder <stuart.yoder@freescale.com>
>>>
>>> some restructuring of epapr paravirt init resulted in
>>> ppc_md.power_save being set, and then overwritten to
>>> NULL during machine_init.  This patch splits the
>>> initialization of ppc_md.power_save out into a postcore
>>> init call.
>>>
>>> Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
>>> ---
>>>    arch/powerpc/kernel/epapr_paravirt.c |   25 ++++++++++++++++++++-----
>>>    1 file changed, 20 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/arch/powerpc/kernel/epapr_paravirt.c
>> b/arch/powerpc/kernel/epapr_paravirt.c
>>> index 6300c13..c49b69c 100644
>>> --- a/arch/powerpc/kernel/epapr_paravirt.c
>>> +++ b/arch/powerpc/kernel/epapr_paravirt.c
>>> @@ -52,11 +52,6 @@ static int __init early_init_dt_scan_epapr(unsigned
>> long node,
>>>    #endif
>>>    	}
>>>
>>> -#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
>>> -	if (of_get_flat_dt_prop(node, "has-idle", NULL))
>>> -		ppc_md.power_save = epapr_ev_idle;
>>> -#endif
>>> -
>>>    	epapr_paravirt_enabled = true;
>>>
>>>    	return 1;
>>> @@ -69,3 +64,23 @@ int __init epapr_paravirt_early_init(void)
>>>    	return 0;
>>>    }
>>>
>>> +static int __init epapr_idle_init_dt_scan(unsigned long node,
>>> +					   const char *uname,
>>> +					   int depth, void *data)
>>> +{
>>> +#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
>>> +	if (of_get_flat_dt_prop(node, "has-idle", NULL))
>>> +		ppc_md.power_save = epapr_ev_idle;
>>> +#endif
>>> +	return 0;
>>> +}
>>> +
>>> +static int __init epapr_idle_init(void)
>>> +{
>>> +	if (epapr_paravirt_enabled)
>>> +		of_scan_flat_dt(epapr_idle_init_dt_scan, NULL);
>> Doesn't this scan all nodes? We only want to match on
>> /hypervisor/has-idle, no?
> I cut/pasted from  the approach the existing code in that file
> took, but yes you're right we just need the one property.
> Let me respin that to look at the hypervisor node only.

The other function aborts early if it doesn't find a 
"hcall-instructions" property. I'm still surprised we don't limit the 
scope to /hypervisor at all though. Is this on purpose maybe?


Alex

Re: [PATCH] powerpc: move epapr paravirt init of power_save to an initcall

[Alexander Graf]

On 30.04.14 22:03, Stuart Yoder wrote:
>
>> -----Original Message-----
>> From: Alexander Graf [mailto:agraf@suse.de]
>> Sent: Wednesday, April 30, 2014 2:56 PM
>> To: Yoder Stuart-B08248; benh@kernel.crashing.org; Wood Scott-B07421
>> Cc: linuxppc-dev@lists.ozlabs.org
>> Subject: Re: [PATCH] powerpc: move epapr paravirt init of power_save to
>> an initcall
>>
>>
>> On 30.04.14 21:54, Stuart Yoder wrote:
>>> From: Stuart Yoder <stuart.yoder@freescale.com>
>>>
>>> some restructuring of epapr paravirt init resulted in
>>> ppc_md.power_save being set, and then overwritten to
>>> NULL during machine_init.  This patch splits the
>>> initialization of ppc_md.power_save out into a postcore
>>> init call.
>>>
>>> Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
>>> ---
>>>    arch/powerpc/kernel/epapr_paravirt.c |   25 ++++++++++++++++++++-----
>>>    1 file changed, 20 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/arch/powerpc/kernel/epapr_paravirt.c
>> b/arch/powerpc/kernel/epapr_paravirt.c
>>> index 6300c13..c49b69c 100644
>>> --- a/arch/powerpc/kernel/epapr_paravirt.c
>>> +++ b/arch/powerpc/kernel/epapr_paravirt.c
>>> @@ -52,11 +52,6 @@ static int __init early_init_dt_scan_epapr(unsigned
>> long node,
>>>    #endif
>>>    	}
>>>
>>> -#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
>>> -	if (of_get_flat_dt_prop(node, "has-idle", NULL))
>>> -		ppc_md.power_save = epapr_ev_idle;
>>> -#endif
>>> -
>>>    	epapr_paravirt_enabled = true;
>>>
>>>    	return 1;
>>> @@ -69,3 +64,23 @@ int __init epapr_paravirt_early_init(void)
>>>    	return 0;
>>>    }
>>>
>>> +static int __init epapr_idle_init_dt_scan(unsigned long node,
>>> +					   const char *uname,
>>> +					   int depth, void *data)
>>> +{
>>> +#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
>>> +	if (of_get_flat_dt_prop(node, "has-idle", NULL))
>>> +		ppc_md.power_save = epapr_ev_idle;
>>> +#endif
>>> +	return 0;
>>> +}
>>> +
>>> +static int __init epapr_idle_init(void)
>>> +{
>>> +	if (epapr_paravirt_enabled)
>>> +		of_scan_flat_dt(epapr_idle_init_dt_scan, NULL);
>> Doesn't this scan all nodes? We only want to match on
>> /hypervisor/has-idle, no?
> I cut/pasted from  the approach the existing code in that file
> took, but yes you're right we just need the one property.
> Let me respin that to look at the hypervisor node only.

Yeah, the same commit that introduced the breakage on has-idle also 
removed the explicit check for /hypervisor.

Laurentiu, was this change on purpose?



commit 4e21b94c9c644c43223878f4c848e852743e789c
Author: Laurentiu TUDOR <Laurentiu.Tudor@freescale.com>
Date:   Wed Jul 3 17:13:15 2013 +0300

     powerpc/85xx: Move ePAPR paravirt initialization earlier

     At console init, when the kernel tries to flush the log buffer
     the ePAPR byte-channel based console write fails silently,
     losing the buffered messages.
     This happens because The ePAPR para-virtualization init isn't
     done early enough so that the hcall instruction to be set,
     causing the byte-channel write hcall to be a nop.
     To fix, change the ePAPR para-virt init to use early device
     tree functions and move it in early init.

     Signed-off-by: Laurentiu Tudor <Laurentiu.Tudor@freescale.com>
     Signed-off-by: Scott Wood <scottwood@freescale.com>
[...]
diff --git a/arch/powerpc/kernel/epapr_paravirt.c 
b/arch/powerpc/kernel/epapr_paravirt.c
index d44a571..6300c13 100644
--- a/arch/powerpc/kernel/epapr_paravirt.c
+++ b/arch/powerpc/kernel/epapr_paravirt.c
@@ -30,22 +30,20 @@ extern u32 epapr_ev_idle_start[];

  bool epapr_paravirt_enabled;

-static int __init epapr_paravirt_init(void)
+static int __init early_init_dt_scan_epapr(unsigned long node,
+                                          const char *uname,
+                                          int depth, void *data)
  {
-       struct device_node *hyper_node;
         const u32 *insts;
-       int len, i;
+       unsigned long len;
+       int i;

-       hyper_node = of_find_node_by_path("/hypervisor");
-       if (!hyper_node)
-               return -ENODEV;
-
-       insts = of_get_property(hyper_node, "hcall-instructions", &len);
+       insts = of_get_flat_dt_prop(node, "hcall-instructions", &len);
         if (!insts)
-               return -ENODEV;
+               return 0;

         if (len % 4 || len > (4 * 4))
-               return -ENODEV;
+               return -1;
[...]


Alex

Re: [PATCH] powerpc: move epapr paravirt init of power_save to an initcall

[Tudor Laurentiu]

On 04/30/2014 11:09 PM, Alexander Graf wrote:
>
> On 30.04.14 22:03, Stuart Yoder wrote:
>>
>>> -----Original Message-----
>>> From: Alexander Graf [mailto:agraf@suse.de]
>>> Sent: Wednesday, April 30, 2014 2:56 PM
>>> To: Yoder Stuart-B08248; benh@kernel.crashing.org; Wood Scott-B07421
>>> Cc: linuxppc-dev@lists.ozlabs.org
>>> Subject: Re: [PATCH] powerpc: move epapr paravirt init of power_save to
>>> an initcall
>>>
>>>
>>> On 30.04.14 21:54, Stuart Yoder wrote:
>>>> From: Stuart Yoder <stuart.yoder@freescale.com>
>>>>
>>>> some restructuring of epapr paravirt init resulted in
>>>> ppc_md.power_save being set, and then overwritten to
>>>> NULL during machine_init.  This patch splits the
>>>> initialization of ppc_md.power_save out into a postcore
>>>> init call.
>>>>
>>>> Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
>>>> ---
>>>>    arch/powerpc/kernel/epapr_paravirt.c |   25
>>>> ++++++++++++++++++++-----
>>>>    1 file changed, 20 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/arch/powerpc/kernel/epapr_paravirt.c
>>> b/arch/powerpc/kernel/epapr_paravirt.c
>>>> index 6300c13..c49b69c 100644
>>>> --- a/arch/powerpc/kernel/epapr_paravirt.c
>>>> +++ b/arch/powerpc/kernel/epapr_paravirt.c
>>>> @@ -52,11 +52,6 @@ static int __init early_init_dt_scan_epapr(unsigned
>>> long node,
>>>>    #endif
>>>>        }
>>>>
>>>> -#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
>>>> -    if (of_get_flat_dt_prop(node, "has-idle", NULL))
>>>> -        ppc_md.power_save = epapr_ev_idle;
>>>> -#endif
>>>> -
>>>>        epapr_paravirt_enabled = true;
>>>>
>>>>        return 1;
>>>> @@ -69,3 +64,23 @@ int __init epapr_paravirt_early_init(void)
>>>>        return 0;
>>>>    }
>>>>
>>>> +static int __init epapr_idle_init_dt_scan(unsigned long node,
>>>> +                       const char *uname,
>>>> +                       int depth, void *data)
>>>> +{
>>>> +#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
>>>> +    if (of_get_flat_dt_prop(node, "has-idle", NULL))
>>>> +        ppc_md.power_save = epapr_ev_idle;
>>>> +#endif
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +static int __init epapr_idle_init(void)
>>>> +{
>>>> +    if (epapr_paravirt_enabled)
>>>> +        of_scan_flat_dt(epapr_idle_init_dt_scan, NULL);
>>> Doesn't this scan all nodes? We only want to match on
>>> /hypervisor/has-idle, no?
>> I cut/pasted from  the approach the existing code in that file
>> took, but yes you're right we just need the one property.
>> Let me respin that to look at the hypervisor node only.
>
> Yeah, the same commit that introduced the breakage on has-idle also
> removed the explicit check for /hypervisor.
>
> Laurentiu, was this change on purpose?
>

Alex,

IIRC, at that time i had to switch from the normal "of" functions to a 
completely different api that's available in early init stage. This 
early "of" api is pretty limited (e.g. doesn't have a way to address a 
specific node) and i had to use that function that scans the whole tree.

---
Best Regards, Laurentiu

Re: [PATCH] powerpc: move epapr paravirt init of power_save to an initcall

[Alexander Graf]

On 05/05/2014 02:17 PM, Tudor Laurentiu wrote:
> On 04/30/2014 11:09 PM, Alexander Graf wrote:
>>
>> On 30.04.14 22:03, Stuart Yoder wrote:
>>>
>>>> -----Original Message-----
>>>> From: Alexander Graf [mailto:agraf@suse.de]
>>>> Sent: Wednesday, April 30, 2014 2:56 PM
>>>> To: Yoder Stuart-B08248; benh@kernel.crashing.org; Wood Scott-B07421
>>>> Cc: linuxppc-dev@lists.ozlabs.org
>>>> Subject: Re: [PATCH] powerpc: move epapr paravirt init of 
>>>> power_save to
>>>> an initcall
>>>>
>>>>
>>>> On 30.04.14 21:54, Stuart Yoder wrote:
>>>>> From: Stuart Yoder <stuart.yoder@freescale.com>
>>>>>
>>>>> some restructuring of epapr paravirt init resulted in
>>>>> ppc_md.power_save being set, and then overwritten to
>>>>> NULL during machine_init.  This patch splits the
>>>>> initialization of ppc_md.power_save out into a postcore
>>>>> init call.
>>>>>
>>>>> Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
>>>>> ---
>>>>>    arch/powerpc/kernel/epapr_paravirt.c |   25
>>>>> ++++++++++++++++++++-----
>>>>>    1 file changed, 20 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/arch/powerpc/kernel/epapr_paravirt.c
>>>> b/arch/powerpc/kernel/epapr_paravirt.c
>>>>> index 6300c13..c49b69c 100644
>>>>> --- a/arch/powerpc/kernel/epapr_paravirt.c
>>>>> +++ b/arch/powerpc/kernel/epapr_paravirt.c
>>>>> @@ -52,11 +52,6 @@ static int __init 
>>>>> early_init_dt_scan_epapr(unsigned
>>>> long node,
>>>>>    #endif
>>>>>        }
>>>>>
>>>>> -#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
>>>>> -    if (of_get_flat_dt_prop(node, "has-idle", NULL))
>>>>> -        ppc_md.power_save = epapr_ev_idle;
>>>>> -#endif
>>>>> -
>>>>>        epapr_paravirt_enabled = true;
>>>>>
>>>>>        return 1;
>>>>> @@ -69,3 +64,23 @@ int __init epapr_paravirt_early_init(void)
>>>>>        return 0;
>>>>>    }
>>>>>
>>>>> +static int __init epapr_idle_init_dt_scan(unsigned long node,
>>>>> +                       const char *uname,
>>>>> +                       int depth, void *data)
>>>>> +{
>>>>> +#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
>>>>> +    if (of_get_flat_dt_prop(node, "has-idle", NULL))
>>>>> +        ppc_md.power_save = epapr_ev_idle;
>>>>> +#endif
>>>>> +    return 0;
>>>>> +}
>>>>> +
>>>>> +static int __init epapr_idle_init(void)
>>>>> +{
>>>>> +    if (epapr_paravirt_enabled)
>>>>> +        of_scan_flat_dt(epapr_idle_init_dt_scan, NULL);
>>>> Doesn't this scan all nodes? We only want to match on
>>>> /hypervisor/has-idle, no?
>>> I cut/pasted from  the approach the existing code in that file
>>> took, but yes you're right we just need the one property.
>>> Let me respin that to look at the hypervisor node only.
>>
>> Yeah, the same commit that introduced the breakage on has-idle also
>> removed the explicit check for /hypervisor.
>>
>> Laurentiu, was this change on purpose?
>>
>
> Alex,
>
> IIRC, at that time i had to switch from the normal "of" functions to a 
> completely different api that's available in early init stage. This 
> early "of" api is pretty limited (e.g. doesn't have a way to address a 
> specific node) and i had to use that function that scans the whole tree.

Ok, so it is an accident. Could you please post a patch that checks that 
the node we're looking at is called "hypervisor"? The simple API should 
give you enough information for that at least. Maybe you could even 
check that the parent node is the root node.


Alex

Re: [PATCH] powerpc: move epapr paravirt init of power_save to an initcall

[Tudor Laurentiu]

On 05/05/2014 03:21 PM, Alexander Graf wrote:
> On 05/05/2014 02:17 PM, Tudor Laurentiu wrote:
>> On 04/30/2014 11:09 PM, Alexander Graf wrote:
>>>
>>> On 30.04.14 22:03, Stuart Yoder wrote:
>>>>
>>>>> -----Original Message-----
>>>>> From: Alexander Graf [mailto:agraf@suse.de]
>>>>> Sent: Wednesday, April 30, 2014 2:56 PM
>>>>> To: Yoder Stuart-B08248; benh@kernel.crashing.org; Wood Scott-B07421
>>>>> Cc: linuxppc-dev@lists.ozlabs.org
>>>>> Subject: Re: [PATCH] powerpc: move epapr paravirt init of
>>>>> power_save to
>>>>> an initcall
>>>>>
>>>>>
>>>>> On 30.04.14 21:54, Stuart Yoder wrote:
>>>>>> From: Stuart Yoder <stuart.yoder@freescale.com>
>>>>>>
>>>>>> some restructuring of epapr paravirt init resulted in
>>>>>> ppc_md.power_save being set, and then overwritten to
>>>>>> NULL during machine_init.  This patch splits the
>>>>>> initialization of ppc_md.power_save out into a postcore
>>>>>> init call.
>>>>>>
>>>>>> Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
>>>>>> ---
>>>>>>    arch/powerpc/kernel/epapr_paravirt.c |   25
>>>>>> ++++++++++++++++++++-----
>>>>>>    1 file changed, 20 insertions(+), 5 deletions(-)
>>>>>>
>>>>>> diff --git a/arch/powerpc/kernel/epapr_paravirt.c
>>>>> b/arch/powerpc/kernel/epapr_paravirt.c
>>>>>> index 6300c13..c49b69c 100644
>>>>>> --- a/arch/powerpc/kernel/epapr_paravirt.c
>>>>>> +++ b/arch/powerpc/kernel/epapr_paravirt.c
>>>>>> @@ -52,11 +52,6 @@ static int __init
>>>>>> early_init_dt_scan_epapr(unsigned
>>>>> long node,
>>>>>>    #endif
>>>>>>        }
>>>>>>
>>>>>> -#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
>>>>>> -    if (of_get_flat_dt_prop(node, "has-idle", NULL))
>>>>>> -        ppc_md.power_save = epapr_ev_idle;
>>>>>> -#endif
>>>>>> -
>>>>>>        epapr_paravirt_enabled = true;
>>>>>>
>>>>>>        return 1;
>>>>>> @@ -69,3 +64,23 @@ int __init epapr_paravirt_early_init(void)
>>>>>>        return 0;
>>>>>>    }
>>>>>>
>>>>>> +static int __init epapr_idle_init_dt_scan(unsigned long node,
>>>>>> +                       const char *uname,
>>>>>> +                       int depth, void *data)
>>>>>> +{
>>>>>> +#if !defined(CONFIG_64BIT) || defined(CONFIG_PPC_BOOK3E_64)
>>>>>> +    if (of_get_flat_dt_prop(node, "has-idle", NULL))
>>>>>> +        ppc_md.power_save = epapr_ev_idle;
>>>>>> +#endif
>>>>>> +    return 0;
>>>>>> +}
>>>>>> +
>>>>>> +static int __init epapr_idle_init(void)
>>>>>> +{
>>>>>> +    if (epapr_paravirt_enabled)
>>>>>> +        of_scan_flat_dt(epapr_idle_init_dt_scan, NULL);
>>>>> Doesn't this scan all nodes? We only want to match on
>>>>> /hypervisor/has-idle, no?
>>>> I cut/pasted from  the approach the existing code in that file
>>>> took, but yes you're right we just need the one property.
>>>> Let me respin that to look at the hypervisor node only.
>>>
>>> Yeah, the same commit that introduced the breakage on has-idle also
>>> removed the explicit check for /hypervisor.
>>>
>>> Laurentiu, was this change on purpose?
>>>
>>
>> Alex,
>>
>> IIRC, at that time i had to switch from the normal "of" functions to a
>> completely different api that's available in early init stage. This
>> early "of" api is pretty limited (e.g. doesn't have a way to address a
>> specific node) and i had to use that function that scans the whole tree.
>
> Ok, so it is an accident. Could you please post a patch that checks that
> the node we're looking at is called "hypervisor"? The simple API should
> give you enough information for that at least. Maybe you could even
> check that the parent node is the root node.
>

Just had a quick look and it looks that that early fdt api was improved 
with a function that allows specifying a starting path for the scan 
(of_scan_flat_dt_by_path() added in commit 
57d74bcf3072b65bde5aa540cedc976a75c48e5c). So i think we can simply use 
that instead.

---
Best Regards, Laurentiu