Subject: Re: [PATCH 1/2] powerpc: document the MPIC device tree binding

From: Meador Inge <[email-masked]>
Date: Wed, 19 Jan 2011 18:08:03 -0600

On 01/19/2011 04:14 PM, Yoder Stuart-B08248 wrote:
>
>> +** Optional properties:
>> +
>> +   - no-reset : The presence of this property indicates that the MPIC
>> +                should not be reset during runtime initialization.
>> +   - protected-sources : Specifies a list of interrupt sources that are
>> + not
>> +                         available for use and whose corresponding
>> + vectors
>> +                         should not be initialized.  A typical use case
>> + for
>> +                         this property is in AMP systems where multiple
>> +                         independent operating systems need to share
>> + the MPIC
>> +                         without clobbering each other.
>
> Is "protected-sources" really needed for AMP systems to
> tell the OSes not to clobber each other?  Won't each
> OS be given a device tree with only its interrupt
> sources?  ...so you know what you are allowed to touch.

This was discussed a little bit already [1, 2].  The MPIC driver 
currently initializes the VECPRI register for all interrupt sources, 
which can lead to the aforementioned clobbering.

-- 
Meador Inge     | meador_inge AT mentor.com
Mentor Embedded | http://www.mentor.com/embedded-software

[1] 
http://lists.ozlabs.org/pipermail/devicetree-discuss/2010-December/003850.html
[2] 
http://lists.ozlabs.org/pipermail/devicetree-discuss/2011-January/003936.html