Re: [PATCH v2] ARM: Define wfi() macro for v6 processors

On Tue, Feb 08, 2011 at 11:08:08AM +0000, Russell King - ARM Linux wrote:

On Tue, Feb 08, 2011 at 11:01:25AM +0000, Dave Martin wrote:

quoted

For v6, wfi is architected as a defined MCR instruction, so
use that definition.

Doing a no-op instead of wfi() is probably bad, so for older
processors than v6, wfi() is not defined.  If needed, some CPU-
specific wfi() will have to be defined elsewhere.

This is something we kind-of already handle in a different way - see
the individual processor idle function in arch/arm/mm/proc*.S.

There's various errata work-arounds older CPUs need for wfi (or rather
its mcr equivalent) so maybe wfi() should just be an alias for a call
to that function.  Or maybe we shouldn't have a wfi() macro at all.

OK-- I'll hold off on this for now.

The patch was prompted by a build failure, but I can't remember the
exact circumstances now...  if I hit the same problem again,
then it might be worth discussing further...

Cheers
---Dave