[Gta04-owner] Modem off

NeilBrown neilb at suse.de
Sat Sep 21 00:19:38 CEST 2013


On Fri, 20 Sep 2013 15:00:28 +0200 Radek Polak <psonek2 at seznam.cz> wrote:

> On Thursday, September 19, 2013 03:47:47 AM NeilBrown wrote:
> 
> > I have some more evidence.
> > 
> > I currently have ehci_hcd compiled as a module, so it needs to be loaded
> > before the modem can be seen.
> > 
> > On a fresh reboot of 3.7 without loading the module or toggling the GPIO to
> > turn on the 3G modem, I see a current draw during suspend of 21.6mA and
> > 23.7mA If I then "insmod ehci_hcd" the suspend-time current usage goes up
> > to  30.1mA and 32.2mA.
> > I then "rmmod ehci_hcd" and the current drops to 12.9 and 15.1 mA.
> > 
> > So in each case I see two different measurements with a 2.1mA difference.
> > 
> > Loading the module turns something on which was only partly one before.
> > Removing the module turns it off properly.
> > 
> > If I can get "suspend" to turn off whatever "rmmod" turns off, we might be
> > able to get power usage down by several milliAmps.
> > 
> > If anyone else would like to try this and report the results I would love
> > to hear them.
> > You need to set:
> > 
> > CONFIG_USB_EHCI_HCD=m
> > 
> > in .config and make sure nothing turns the modem on at boot time.
> > Then measure the suspend current.  Then insmod and measure it again.  Then
> > rmmod and measure it a third time.
> 
> Hi,
> i have tested it today. I used qtmoko v55 kernel - the one which has enabled 
> omap off mode.
> 
> Attached is screenshot with graph.
> 
> First current is 22mA - after boot.
> Then there are values 31mA and 32mA - with ehci_hcd module loaded
> The last values are 16mA 15mA and 15mA - after rmmod ehci_hcd
> 
> So i think we have quite similar results.

Thanks.  It is good to know it isn't just some thing strange that I'm
doing :-)

I've experimented with "rmmod ehci_hcd" just before suspend, and "modprobe"
on resume, but so far that has just caused a mess.
I've looked at the code, and it is rather complex.
It has also changed a lot in 3.10.  So I'm going to defer exploring this more
until I start on 3.10+ again, probably in a couple of weeks.

Thanks,
NeilBrown
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