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

[Russell King - ARM Linux]

On Tue, Feb 08, 2011 at 01:11:51PM +0100, Arnd Bergmann wrote:
> On Tuesday 08 February 2011, Russell King - ARM Linux wrote:
> > On Tue, Feb 08, 2011 at 11:01:25AM +0000, Dave Martin wrote:
> > > 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.
> 
> I don't see any users of the sev/wfe/wfi macros in the current kernel,
> so removing them seems like a good strategy to avoid people from
> using them incorrectly.

That's because they've only just been added.  See the massive 63-patch set
from Viresh which has been posting to this mailing list.