Re: how to check for "optional" ppc chip features (MSR_BE)

[Kumar Gala <galak@kernel.crashing.org>]

On May 13, 2008, at 6:55 AM, Paul Mackerras wrote:

> Roland McGrath writes:
>
>> Yeah, all that stuff I could figure out as needed.  What I really  
>> meant
>> was, where is the big official table of which chips behave which  
>> ways that
>> you base all code that on?  Actually, I don't really care as long  
>> as you
>> all are happy to be responsible for figuring out what matters.   
>> With the
>> patch I posted to use MSR_BE, I took Kumar Gala's word as gospel  
>> that all
>> the chips on which we use MSR_SE also have MSR_BE.  If that's not  
>> right,
>> then I hope you'd like to pick a feature bit, populate the tables,  
>> etc.,
>> and fix the definition of arch_has_block_step() as appropriate.
>
> It turns out that the 601 doesn't support MSR_BE.  It looks like all
> the "classic" 32-bit implementations after that (603, 604, 7xx, 7xxx)
> implemented BE, as do POWER3 and RS64.  I'll check the later 64-bit
> processors -- I think they all implement BE.  4xx and Book E have it
> in a different form.  I'll let Kumar find out about 8xx and 82xx.

it appears 8xx does, and 82xx are just 603 cores so they do.

> So it looks like we need to define a new feature bit to mean "supports
> block-step".  Is this something that userspace will expect to be told
> about via the AT_HWCAP entry in the aux vector?

- k