From: Michael Neuling <mikey@neuling.org>
Date: Wed, 11 Jun 2014 05:59:28 +0000 (+1000)
Subject: powerpc/powernv: Enable POWER8 doorbell IPIs
X-Git-Tag: omap-for-v3.16/fixes-against-rc1~30^2~6
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d4e58e5928f8c6c49228451dd03e0714cbab299a;p=pandora-kernel.git

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>
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