FSL vs. IBM BookE

FSL vs. IBM BookE

[Benjamin Herrenschmidt]

Out of curiosity... I noticed we have both head_44x.S and
head_fsl_booke.S, the later being a fork of the former with changed from
Kumar (and possibly others) to support E200 and E500.

How bad are the differences between those cores ? Would it be possible
to reconcile those and IBM 44x into a single processor family ? Or are
there some fundamental differences making that impossible ? (even with a
bit of CPU feature patching).

Also, I suppose we should rename head_4xx.S to head_40x.S no ?

Cheers,
Ben.

Re: FSL vs. IBM BookE

[Josh Boyer]

On Sat, 2006-11-04 at 20:21 +1100, Benjamin Herrenschmidt wrote:
> Out of curiosity... I noticed we have both head_44x.S and
> head_fsl_booke.S, the later being a fork of the former with changed from
> Kumar (and possibly others) to support E200 and E500.
> 
> How bad are the differences between those cores ? Would it be possible
> to reconcile those and IBM 44x into a single processor family ? Or are
> there some fundamental differences making that impossible ? (even with a
> bit of CPU feature patching).

I'm not sure.  Maybe Kumar knows better since he made the changes to
head_fsl_booke.S.  I believe FSL can do SMP and has an SPE and some
other HID registers that 44x does not have.

> 
> Also, I suppose we should rename head_4xx.S to head_40x.S no ?

That would be fine with me.  I can send a patch if you'd like.

josh

Re: FSL vs. IBM BookE

[Kumar Gala]

On Nov 4, 2006, at 10:16 AM, Josh Boyer wrote:

> On Sat, 2006-11-04 at 20:21 +1100, Benjamin Herrenschmidt wrote:
>> Out of curiosity... I noticed we have both head_44x.S and
>> head_fsl_booke.S, the later being a fork of the former with  
>> changed from
>> Kumar (and possibly others) to support E200 and E500.
>>
>> How bad are the differences between those cores ? Would it be  
>> possible
>> to reconcile those and IBM 44x into a single processor family ? Or  
>> are
>> there some fundamental differences making that impossible ? (even  
>> with a
>> bit of CPU feature patching).
>
> I'm not sure.  Maybe Kumar knows better since he made the changes to
> head_fsl_booke.S.  I believe FSL can do SMP and has an SPE and some
> other HID registers that 44x does not have.

The big differences are in MMU architectures/programming models  
between 44x and FSL Book-E.  I tried to move as much common code into  
macros between the two head_* files.

- kumar

Re: FSL vs. IBM BookE

[Dan Malek]

On Nov 4, 2006, at 4:21 AM, Benjamin Herrenschmidt wrote:

> How bad are the differences between those cores ?

They are getting more different as the product families
evolve.    The common instruction paths are growing
smaller, and I think the amount of #ifdefs and patching
will make the code much more complex that just leaving
as it is.

> ...  Would it be possible
> to reconcile those and IBM 44x into a single processor family ?

I don't think it's worth while.  The amount of code isn't
that great and the differences outweigh the similarities.

> Also, I suppose we should rename head_4xx.S to head_40x.S no ?

Maybe, but we all know what they are :-)

Thanks.

	-- Dan