RE: [PATCH 1/1] x86: replace cpu_up hard-coded mdelay with variable

From: Brown, Len
Date: Mon Apr 20 2015 - 08:38:02 EST


> What's the cutoff for 'modern hardware' - which CPUs stopped requiring
> the delay?

This is the topic of ongoing research, and I'm not ready to send
the patch setting a new default until I've heard back from a few more HW people.

Every system I've tested appears to work with delay 0.
Were I to guess, I'd venture that every
system that runs an X86_64 kernel might count as "modern" -- even
the 2005 AMD Turion laptop I've got in the bone pile.

> Also, is there any public document where the no-delay is specified for
> 'modern hardware'?

Unfortunately only the converse is true. There is an ancient document specifying
that the delay may be necessary.

cheers,
-Len

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