Re: Slow mobile broadband detection

[Aleksander Morgado <aleksander lanedo com>]

On Tue, 2011-06-14 at 23:33 +0200, dave guandalino wrote:
> 2011/6/14 Aleksander Morgado <aleksander lanedo com>:
> > :-( Sorry, I forgot one step... You need to:
> 
> Np :-) Btw, thanks for watching.

So, this modem is reported as being a ZTE modem, and therefore uses the
ZTE plugin in ModemManager.

3 ports are found, (ttyUSB0,ttyUSB1 and ttyUSB2):
 * Opening ttyUSB2 port doesn't take any time.
 * Opening ttyUSB1 and ttyUSB0 need 15s each, and as they are done one
after the other, before even starting to probe the first port, it
consumed already 40s. This 15s delays opening the ports are likely to be
kernel issues.

I actually have similar issues, even worse, with a Huawei modem in
Natty: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/772577 

Then, probing ttyUSB1 and ttyUSB2, which are both AT ports, takes ~22s.
Closing the ports also seem to take long here, up to 5s each.

But the modem is not fully exported until all ports are probed, and
ttyUSB0 is not an AT port, so it takes much much longer: needs to
timeout all AT commands sent to it (including extra ATE0+CPMS? in the
case of the ZTE plugin), until the QCDM ones are sent.

So the overall modem detection needs up to 113s in your case, which
really is a lot, and mainly caused by the open/close port delays from
the kernel. Without these huge delays, the modem detection should take
around 20-25 max (guessing from the max time the QCDM port needs to get
detected).

Cheers,

-- 
Aleksander