Re: USB power usage

[Pavel Machek <pavel@ucw.cz>]

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

-- 
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