Re: Slow mobile broadband detection

[Dan Williams <dcbw redhat com>]

On Tue, 2011-06-14 at 23:57 +0100, Sérgio Basto wrote:
> On Wed, 2011-06-15 at 00:30 +0200, Aleksander Morgado wrote:
> > 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).
> 
> yes my ZTE always need more than 90s to be detected , since I bought it
> (September of 2008). No matter what kernel was. 
> And speed up this detection for 20 seconds, would be great.

If you can tell me the port #s and the USB interface #s of the ports
that take a long time to probe then we can add those ports to the kernel
blacklist as such.  There are certain modems for which the firmware
simply doesn't respond to serial setup packets sent on certain
interfaces, which cause the kernel to wait for a while before timing
out.  I just fixed that issue for the Alcatel X200 device and it's
likely that we need to do the same for your device.

The second possibility is that your device does not have it's USB IDs
added to the right driver in the kernel and thus the driver that's being
used (which could be the generic 'usb-serial' driver if usb-modeswitch
force loaded it) doesn't handle flush requests when closing the port.  I
had that issue with a ZTE CDMA device and fixed that in the kernel
around 2.6.32 or so, but this only works if your device is using the
'option' driver, which all 3G modems shoudl be using.  usb-serial is not
optimized for the serial speeds that 3G devices require, and thus any
modem IDs shoudl get added to the appropriate non-generic driver (like
option, hso, sierra, etc).

Dan