cdc_acm causes Pantech UML295 reset

[Charles Kiorpes]

Description: Ubuntu 14.04.1 LTS
Release: 14.04

When I upgraded to 14.04 (3.13 kernel), the Pantech UML295 4G Modem stopped functioning properly.

Expected behavior:
    The modem starts up with a red LED lit while it initialized. Once a connection is established, linux recognizes a USB ethernet connection (cdc_ether), and the LED on the device goes green and flashing, indicating active connection. This status remains until the device is disconnected.

Observed behavior:
    The modem starts up normally, getting to the point that a cdc_ether device is set up and a working internet connection is established. Shortly after this, the modem's light goes blue (an LED color that the documentation shows no information for), the ethernet connection fails, and the device goes back to the beginning of its initialization. The process will repeat indefinitely.

This behavior can be avoided, and a connection maintaned, by blacklisting cdc_acm. However, this breaks many other USB serial devices.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-3.13.0-35-generic 3.13.0-35.62
ProcVersionSignature: Ubuntu 3.13.0-35.62-generic 3.13.11.6
Uname: Linux 3.13.0-35-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.4
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: charlie 1799 F.... pulseaudio
 /dev/snd/controlC0: charlie 1799 F.... pulseaudio
 /dev/snd/pcmC0D0c: charlie 1799 F...m pulseaudio
CurrentDesktop: X-Cinnamon
Date: Tue Sep 23 16:16:04 2014
EcryptfsInUse: Yes
InstallationDate: Installed on 2014-09-04 (18 days ago)
InstallationMedia: Kubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
MachineType: LENOVO Lenovo IdeaPad P580
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-35-generic.efi.signed root=/dev/mapper/sysvg-lvroot ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.13.0-35-generic N/A
 linux-backports-modules-3.13.0-35-generic N/A
 linux-firmware 1.127.5
SourcePackage: linux
StagingDrivers: rts5139
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/14/2013
dmi.bios.vendor: LENOVO
dmi.bios.version: 5ECN96WW(V9.01)
dmi.board.asset.tag: No Asset Tag
dmi.board.name: INVALID
dmi.board.vendor: LENOVO
dmi.board.version: 00000000INVALID
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Lenovo IdeaPad P580
dmi.modalias: dmi:bvnLENOVO:bvr5ECN96WW(V9.01):bd03/14/2013:svnLENOVO:pnLenovoIdeaPadP580:pvrLenovoIdeaPadP580:rvnLENOVO:rnINVALID:rvr00000000INVALID:cvnLENOVO:ct10:cvrLenovoIdeaPadP580:
dmi.product.name: Lenovo IdeaPad P580
dmi.product.version: Lenovo IdeaPad P580
dmi.sys.vendor: LENOVO

[Brad Figg (brad-figg)]

This change was made by a bot.

[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v3.17 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

If you are unable to test the mainline kernel, for example it will not boot, please add the tag: 'kernel-unable-to-test-upstream'.
Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.17-rc6-utopic/

[Charles Kiorpes (ckiorpes)]

The issue still exists in the v3.17-rc6 kernel.

[Nate (nathanlesko)]

bump

Anyone get this modem working? Works in 13.10 but getting same behavior as above in 14.04.

[Nate (nathanlesko)]

Got it working by downgrading modemmanager as described here http://ubuntuforums.org/showthread.php?t=2239564

[Mark Monson (mhmonson)]

I found that if you downgrade the modemmanager the UML295 indeed works as it should. However, it breaks my Sierra Wireless 340U. If you use a recent modem manager the 340U works but it breaks the UML295. Know that I am dual booting with Win10 and Ubuntu.

I have a workaround. It seems that the initiation sequence takes a certain amount of time for the UML295 to complete properly. If you interrupt the boot process and let it sit you can allow the UML295 enough time to initiate and then it works. It doesn't take very long actually.

When you enter GRUB the default choice gives you 15 second hold before booting. This is not long enough. If you drop down to the next choice "Advanced Options for Ubuntu" the timer is killed and it will sit in GRUB indefinitely. Now plug in the UML295. All you have to do is wait long enough for the UML295 to initiate and stick on. You know this has happened after it flashes green 3-4 times and then becomes green without flashing. Now you can proceed to boot Ubuntu and the UML295 will work fine.

The caveat is that you cannot unplug it and plug it back in again but you don't really do that anyway so it is not a big problem. You can toggle it on and off in network manager without a problem. This works for my Lenovo and Toshiba notebooks.

This did not work for my Asus notebooks but using the paradigm and being persistent I discovered that if you boot into the BIOS you also stop the boot process. Now you can plug in the UML295 and wait in the same way for it to initialize as above. Then you can exit BIOS without saving and continue into GRUB and boot in the usual way and it sticks.

Humm... So I tried the BIOS trick and it did not work with the Lenovo. Go figure. The Toshiba has a different kind of BIOS forcing me to boot into the Win10 login screen and then exit from there into GRUB so can't say about that computer.

In my mind's eye it is all about the initiate timing of the UML295 and how it interacts with the Ubuntu boot. It's hard for me to think that more than few lines of code would fix it if this problem has enough priority for someone to look at it. So now with the latest modem manager (good) my 340U just works and my UML295 works fine with a little dance when I boot.