Re: [PATCH] xen: arm: ignore CPUs which are not marked available in the DT

[Julien Grall <julien.grall@linaro.org>]

Hi Ian,

On 23/07/14 19:36, Ian Campbell wrote:
> On Wed, 2014-07-23 at 18:15 +0100, Julien Grall wrote:
>> On 07/23/2014 05:45 PM, Ian Campbell wrote:
>>> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
>>> ---
>>>   xen/arch/arm/smpboot.c |    3 +++
>>>   1 file changed, 3 insertions(+)
>>>
>>> diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
>>> index cf149da..4b0a738 100644
>>> --- a/xen/arch/arm/smpboot.c
>>> +++ b/xen/arch/arm/smpboot.c
>>> @@ -134,6 +134,9 @@ void __init smp_init_cpus(void)
>>>           if ( !dt_device_type_is_equal(cpu, "cpu") )
>>>               continue;
>>>
>>> +        if ( !dt_device_is_available(cpu) )
>>> +            continue;
>>> +
>>
>> I can't find a such things on the Linux device tree bindings.
>
> status is a generic property which is common to all nodes, it comes from
> ePAPR.
>
>>   Do you
>> have a use case where CPU are marked disabled?
>
> I use it locally when booting with models -- it allows me to turn off
> cpus in the base .dts file using a wrapper instead of having to edit the
> original.

I read the ePAPR and the property status on CPU node. AFAIU, the 
property doesn't have this meaning for a such node.

This property means the CPU is in quiescent state and property to bring 
up the CPU is provides in the device tree node.

Section 5.5.2.2:

Before starting a client program on the boot cpu, the boot program shall 
set certain properties in the
device tree passed to the client as follows:
• Each secondary CPU’s cpu node shall have a status property with a 
value of “disabled”.

Regards,

-- 
Julien Grall