Re: [Qemu-devel] ARM QOM conversion / class hierarchy

[Peter Maydell]

On 20 March 2012 17:14, Paul Brook <address@hidden> wrote:
>> >> Yes, I think I'd agree there. So should we just have an init function
>> >> that provides the implementation-specific cp15 registers based on the
>> >> value provided in the QOM property for the main ID register?
>> >
>> > Something like that, yes.  I'm not convinced the main ID register is the
>> > right property to use, but for actual implementation specific bits
>> > (rather than bits where an implementation picks one of a few common
>> > options) I guess we don't have any alternative but enumerating the
>> > implementations we support.
>>
>> Mmm, the disgusting thing the TI925T has where it can programmatically
>> change the value of its main ID register does somewhat argue against using
>> it for this.
>
> I was thinking more for when we have multiple revisions of a chip that are
> (for these purposes) the same. Currently we only have this for pxa, but in
> principle we probably want it for others.

I had in mind that we'd do it based on the main ID with the revision/variant
fields masked out, which makes all the PXA chips the same. On the other hand
that also makes 1136 and 1136_R2 the same, which is a pain because they're
really pretty different.

> As I mentioned on IRC, this isn't particularly interesting for Linux, which
> will happily run on pretty much anything.  However there are other systems
> that care[1] whether the core reports itself as e.g. arm1136-r0p1 v.s.
> arm1136-r0p2.

Yeah, I've encountered this before too.

-- PMM