Re: Sierra C885 nightmares

[Aleksander Morgado <aleksander lanedo com>]

> 
>     1) SIM lock after power up
>     So, we power-down the modem with CFUN=4 and we recover full
>     functionality mode with CFUN=1,0 (0 to avoid the reset). But, if the SIM
>     has PIN enabled, the modem will require SIM unlock before going on. If
>     you don't provide the SIM, it will end up replying ERROR to every next
>     command sent.
> 
> 
> I don't understand the problem. Why not just run +cfun? and check if an
> unlock is required (instead of waiting for errors), and if so, unlock
> it. Is the problem that modemmanager does not have the PIN at that time?
>  

This issue itself is not a big problem. If we need to re-send the PIN
after power-up, we can just do it. See the sierra-pin-after-power-up
branch in upstream git.


> 
>     2) The modem is not reliable at all. Lots of times, CFUN=1,0 really ends
>     up resetting the modem while we're waiting for the OK reply. Fixing the
>     lock after power-up is only meaningful if the modem really always
>     powers-up without reset in CFUN=1,0.
> 
> 
> Hmm, do we power down for saving power, or also save init time? Why not
> just assume that the modem is reset after running cfun=1,0, unlock and
> init it if required?
> 

We currently power down because that is what we want in 'disabled'
state. So we power down during init, and we power down when
transitioning from enabled to disabled. Note that when the modem is
reset it will reboot and start probing from scratch. Currently it may
end up rebooting forever as we power down during init and we power up
again during enabling. That's why we should probably have power-down a
separate state triggered only by user request.

-- 
Aleksander