Current Bootchart / breaking SD boot

Joerg Reisenweber joerg at
Thu Jul 10 02:23:33 CEST 2008

Am Do  10. Juli 2008 schrieb Joe Pfeiffer:
> Werner Almesberger writes:
> >Michael 'Mickey' Lauer wrote:
> >> I could be wrong, but IIRC FSO is powering the modem down if you shut it 
> >> from console. gsm0710muxd is issuing AT at POFF once you SIGTERM it.
> >
> >That AT at POFF doesn't cut power to the modem. Instead, it tells the
> >modem to "power down", i.e., to enter its own standby mode, from
> >which it can be awakened by "pressing" the modem's "on" button.
> >(That "button" is in fact a transistor controlled by MODEM_ON line
> >which connect to the CPU's GPB7.)
> >
> >What does cut power to most of the GSM chipset is the GSM_ON line
> >which connects to the PMU's GPIO2.
> >
> >Alas, the modem's RF amplifier is not controlled by this (it doesn't
> >like anything to get between it and the battery), so the GSM
> >subsystem cannot be entirely cut off.
> I'm confused -- do you mean there is no way to turn off the modem's RF
> amp?  What do other phones using it do to comply with airplane
> regulations?

The amp is supposed to be inactive by default, as long as no signal is coming 
in to drive it. Think of it as an active audio box that's "always 
on"(standby) and activates whenever a signal comes in.
Oscillators (transmitter) are forced powered down.
So there should be no issues here.


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