[PATCH 2/2] powerpc/powernv: Enable POWER8 doorbell IPIs

[Anton Blanchard]

Hi,

> This patch enables POWER8 doorbell IPIs on powernv.
> 
> Since doorbells can only IPI within a core, we test to see when we
> can use doorbells and if not we fall back to XICS.  This also enables
> hypervisor doorbells to wakeup us up from nap/sleep via the LPCR
> PECEDH bit.
> 
> Based on tests by Anton, the best case IPI latency between two
> threads dropped from 894ns to 512ns.
> 
> Signed-off-by: Michael Neuling <mikey at neuling.org>

Thanks Mikey!

Tested-by: Anton Blanchard <anton at samba.org>

Anton