commit d4e58e5928f8c6c49228451dd03e0714cbab299a
author Michael Neuling <mikey@neuling.org> Wed Jun 11 15:59:28 2014 +1000
committer Benjamin Herrenschmidt <benh@kernel.crashing.org> Wed Jun 11 17:05:12 2014 +1000
tree 34add9a16b4dbe03da04191f51588f3f6a6bdbf9
parent 9b6a68d94333cf19d4ec0f2aaf9f9eb68866630e

powerpc/powernv: Enable POWER8 doorbell IPIs

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@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>