how to check for "optional" ppc chip features (MSR_BE)
galak at kernel.crashing.org
Tue May 13 23:47:04 EST 2008
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
>> 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
>> then I hope you'd like to pick a feature bit, populate the tables,
>> 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?
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