Current Bootchart / breaking SD boot

[Werner Almesberger]

Michael 'Mickey' Lauer wrote:
> I could be wrong, but IIRC FSO is powering the modem down if you shut it down 
> 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.

- Werner