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ahci: Turn off DMA engines when there's no device attached
authorMatthew Garrett <mjg@redhat.com>
Sun, 28 Mar 2010 04:37:21 +0000 (00:37 -0400)
committerJeff Garzik <jgarzik@redhat.com>
Fri, 14 May 2010 21:08:01 +0000 (17:08 -0400)
commit96d60303fd3336893a93565d58c4f1805a327061
treee6534dabeceb4a0a0b511c17dbffe47639fff0actree
parent1c2a49f61785ebbcbfb481a2aab659020f0457f7commit | diff
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>
drivers/ata/libahci.c diff | blob | history
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