From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kristen Carlson Accardi Subject: [patch 0/2] libata: power usage patches Date: Tue, 25 Mar 2008 15:27:58 -0700 Message-ID: <20080325152758.6ee5bb81@appleyard> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from mga11.intel.com ([192.55.52.93]:54890 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753770AbYCYWjG (ORCPT ); Tue, 25 Mar 2008 18:39:06 -0400 Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: jeff@garzik.org Cc: linux-ide@vger.kernel.org, arjan@linux.intel.com Hi, The libata core leaves the phy powered on for unoccupied ports, costing us about .75 Watts of extra power usage. If the port is not hotpluggable, there's no reason to leave the port powered on if there are no devices attached after initial probe. As I was investigating this issue I also ran across a bug in the ahci driver - it sets PxCMD.ST without checking to see if any devices are attached. thanks, Kristen --