From: Matthew Garrett <mjg@redhat.com>
Date: Sun, 28 Mar 2010 04:37:21 +0000 (-0400)
Subject: ahci: Turn off DMA engines when there's no device attached
X-Git-Tag: v2.6.35-rc1~481^2~38
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=96d60303fd3336893a93565d58c4f1805a327061;p=pandora-kernel.git

ahci: Turn off DMA engines when there's no device attached

According to section 10.3.1 of the AHCI spec, PxCMD.ST must not be set
unless there's a device attached. Following this saves us a measurable
quantity of power and does not impair hotplug support. Based on a patch
by Kristen Carlson Accardi.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Cc: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
---

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