Re: WLAN power saving

On Wed, Oct 20, 2004 at 09:50:06AM +0300, Jaakko H Kyro wrote:
> On Tuesday 19 October 2004 21:51, Erik Hovland wrote:
> > On Tue, Oct 19, 2004 at 09:13:31AM +0300, jkyro@cs.helsinki.fi wrote:
> > > Hi!
> > >
> > > Anybody have experience using the WLAN power saving mode on the iPAQ
> > > 5550? It seems it's not supported by the vnetusb driver. It works with
> > > the at76c503, except that the power management parameters seem to have
> > > no effect.
> >
> > I do know that if you just remove the wlan driver and reboot the iPAQ
> > the battery savings are definitely noticable.
>
> Is a reboot really necessary too?

It isn't clear to me whether it is. Meaning, it should be possible to
just unload the modules. But module unloading is no gaurantee that the
radio will be turned off. If you want to be sure, reboot. But it is easy
to tell just by watching battery life with the modules in and out.

> > Do you mean that the at76c503a driver provides an interface to the low
> > power mode? I am pretty sure that the driver tries to put itself in low
> > power mode at initialization. The module provides module arguments to
> > switch modes. I have no idea if they actually have any effect on the
> > device in the h5550.
>
> Judging by the source, it doesn't activate the power saving mode. In normal
> operation the wifi card consumes quite a lot of power regardless of whether
> there is traffic or not, because it needs to be able to receive data at any
> point of time. In the power saving mode, the card polls the access point for
> incoming data and is able to turn off the radio in the meantime. The polling
> period is adjustable according to the Wifi spec.
>
> The potential for power saving is quite significant when the Power saving
> mode can be used.

You have me interested. To take it farther someone would probably have
to go through the machinations in getting a working ipk of the driver
for a current kernel series. I may try that, but I doubt it will be
soon.

E

-- 
Erik Hovland
mail: erik AT hovland DOT org
web: http://hovland.org/
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