usb-serial modem connection speed issue

[julesh]

Hi, I'm currently having trouble with my connection speeds on my USB modem. My setup is as follows:

AthlonXP @ 2.4GHz
ZTE MF622 (supplied by 3 mobile broadband) modem connected over a USB 2.0 port.
Debian Etch (with stock 2.6.18 kernel)
Dialing using wvdial, after configuring using usb_modeswitch.

The problem, essentially, is that I cannot get data transfer speeds in excess of about 500kbit/s. If I plug the same modem into my Windows XP box, however, I can easily get twice this.

Any suggestions what might be going on here?

[julesh]

Just as a followup, I found this article which appears to have some bearing on the problem. The 60KB/s (= 480Kb/s) mentioned by the article as the limit on the usbserial driver is very close to the max I'm experiencing.

I'm not hopeful that the solution suggested by the article will help me specifically (the device I'm using isn't on the list of supported devices) but at least it gives me a direction to work from.

[julesh]

I failed to get the airprime solution to work (the patch was for 2.6.17, and didn't seem to want to apply to 2.6.18 ), but the simpler solution of patching the generic serial device to support larger buffer sizes worked perfectly. I used the patch available here for the purpose.