From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: USB power usage Date: Tue, 26 Dec 2006 15:40:08 +0100 Message-ID: <20061226144008.GA2062@elf.ucw.cz> References: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.osdl.org Errors-To: linux-pm-bounces@lists.osdl.org To: Alan Stern , kernel list Cc: Linux-pm mailing list List-Id: linux-pm@vger.kernel.org Hi! > > Couple of watts is not that bad, considering usb still eats 4W more > > than it should. > = > The USB autosuspend mechanism has been present for a while in -mm and is > included in 2.6.20-rc (although you have to turn on CONFIG_USB_SUSPEND, > which is off by default -- it would be nice to change that). Has anybody > tried doing some real-world measurements to see if it actually makes a > significant improvement in power usage? I did measurements while in -mm, and yes it helped. And yes, it works in 2.6.20-rc2, too: root@amd:~# cat /proc/acpi/battery/BAT0/state ; sleep 20; cat /proc/acpi/battery/BAT0/state ; sleep 20; cat /proc/acpi/battery/BAT0/state ; sleep 20 present: yes capacity state: ok charging state: discharging present rate: 14245 mW remaining capacity: 50020 mWh present voltage: 15793 mV (turned off bluetooth hanging off USB here). present: yes capacity state: ok charging state: discharging present rate: 11650 mW remaining capacity: 49940 mWh present voltage: 15830 mV present: yes capacity state: ok charging state: discharging present rate: 10935 mW remaining capacity: 49870 mWh present voltage: 15826 mV root@amd:~# As you can see, it saves ~3.5W, which is huge deal on machine that eats 11W total. (X60 owners, get 2.6.20, and _disable that bluetooth_ while not in use). Pavel -- = (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html