[Gta04-owner] Modem crashing?

Dr. H. Nikolaus Schaller hns at goldelico.com
Wed Feb 15 17:31:23 CET 2012


Am 15.02.2012 um 17:21 schrieb Marcel Holtmann:

> Hi Radek,
> 
>>> Another idea for a workaround:
>>> Does QtMoko have a timeout if a AT command does not respond with OK or
>>> ERROR within let's say 2 seconds? You could then rescan the interfaces and
>>> reopen the /dev/ttyHS? file.
>> 
>> I think it can still be problem if modem disappears while we dont send 
>> anything. E.g. we can be waiting for another call.
>> 
>> I think the most clean solution is to use netlink or libudev. Udev can notice 
>> device removal/new devices - we can use the same trick. While the device is 
>> removed we can suspend sending AT commands and when it's added we can resume.
> 
> that is not a clean solution by any means. If the TTY can't stay up you
> really have some serious problems.
> 
> Try to run oFono and see if it encounters the same problem. If we trust
> the other report than that just worked fine with oFono. At least with
> all my Option cards I have never seen this.

It also happens if you don't use any middleware. Just type the AT commands.

> You also need to figure out what really happens. Does the modem just
> does a HUP on the TTY or does it actually reset. If it only does HUP

Neither. It appears to interrupt the USB connection and makes the USB
re-enumerate. Which ends up in a re-initialization of the usb tty interfaces.

> then you have some funky AT configuration commands in your Qtopia. Keep
> in mind that the underlying modem is actually a Qualcomm one, so it will
> have actually that behavior for V.250 commands.

Radek has tested that and it looks as if it is not the modem that resets. Because
it does not ask again for a PIN. Or is our assumption wrong that it should after
a reset?

Well, it may also be a very different problem. I remember that i did read somewhere
that there may be a problem with USB suspend on the USB3322/OMAP3 combination.

The modem may be correctly indicating some suspend state (for whatever reasons)
but the Linux driver may handle that wrongly.

So we need two things
a) a workaround (short-term)
b) a solution (long-term)

BR,
Nikolaus



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