[Gta04-owner] Modem is not reset when GTA04 is powered off

thomasg thomas at gstaedtner.net
Mon Mar 5 20:41:56 CET 2012

On Mon, Mar 5, 2012 at 20:11, Neil Jerram <neil at ossau.homelinux.net> wrote:
> While testing sending DTMF tones a few days ago, I discovered that the
> modem isn't reset when GTA04 is powered off.  It appears that the
> battery has to be taken out.
> To be precise,
> - I called my other mobile phone, as part of testing DTMF tone sending
> - I didn't properly notice or check whether that call had terminated,
>  but I assumed that it would be next time I rebooted
> - then I got distracted by something else, which involved rebooting the
>  phone, several times over a 2-3 hour period
> - at the end of the evening, I powered off and pulled out the battery,
>  and _then_ the screen of my other phone came on and said "Call Ended".
> So the call had stayed up, from the network's point of view, for the
> whole evening, even through several GTA04 reboots.
> Should "poweroff" somehow reset the modem?  Other thoughts?
>       Neil
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That's a great example on how the black-box hardware in phones can do
its magic without any interaction of the application system.

Anyhow, I think the modem should be shut down completely when the
application SoC shuts down, though the proper place to do this is
probably in the init systems shutdown procedure.
There is no way to cut the power to the modem, is there? Is the only
way to switch it of pulling the appropriate GPIO pin?

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