Kernel Bug Tracker – Bug 5967
Novatel Wireless CDMA Card (V620) disconnects or hangs on large transferrs
Last modified: 2006-01-27 14:11:49 UTC
Most recent kernel where this bug did not occur: none
Distribution: Debian Sarge x86 (custom built vanilla 2.6.15 kernel)
Hardware Environment: Sony Vaio PCG-FXA36 (Athlon Mobile, VIA Chipset)
Software Environment: Debian Sarge x86
Problem Description: The V620 is Verizon Wireless's branded version of the
Novatel Wireless 620 CDMA 1xRTT EVDO Modem Card. The device is a CardBus device
with a Qualcomm (MDM6500?) EVDO Modem chip, which happens to be a USB client
device with two serial endpoints. That is connected to a (in my case, reports
of the exact part vary) NEC USB 1.1 PCI Host Controller. The 2.6.15 kernel
introduced the airprime driver, which has vendor and device IDs for this product.
The problem occurs when transferring large amounts of data, or a large number of
packets (broadband speed test, kernel download, and VPN traffic are examples)
the airprime driver will "hang" in interesting ways. Sometimes pppd will
disconnect. Sometimes it can only move data in one direction (upload only, or
download only). The problem can be reset by performing a "cardctl eject" and
then re-inserting it. The device will work correctly, for a time. The folks at
Junxion had the same problem, and have released a patch (against usb-serial, as
the patch was written before the airprime driver was released). Their patch can
be found at [http://www.junxion.com/opensource/linux_highspeed_usbserial.html].
I do not know if this is an optimal or even correct solution to the problem.
Steps to reproduce: Download a large file, or use a VPN on the EVDO network
(Verizon refers to this as the Broadband Access or vCast network, the max speed
is up to 4Mbps). The problem does not seem to occur on the 1xRTT networks
(Verizon refers to these as the National Access networks, the max speed is
160kbps). There is a Sprint version of this device (the S620), and as I
understand it the device is identical component wise (with the exception of the
radio front end, which is Sprint specific).
As per my linux-usb-devel response to this problem, we can't fix it as we do
not know how to control this device properly.
Try asking the manufacturer for this information, and then we can work
with it from there.
I've sent a support request to Novatel Wireless. If I hear anything back, I'll
post it here. Is there anything in specific I should be asking for?
Information about the usb protocol used to control the device.
Specifically information about how the flow control is set and handled.