Problem: When connecting to a Huawei E3276 LTE modem using 'AT+CGACT=1,1' in minicom over /dev/cdc-wdm1, the cdc-wdm device freezes for 3-5 minutes until accepting AT commands again. Keywords: huawei_cdc_ncm, LTE, AT commands, cdc-wdm Detailed problem description: I am using a 4G mobile USB dongle with the huawei_cdc_ncm driver in Linux kernel 3.16. In general, the driver works well, but one major issue is that bringing the modem up using 'AT+CGACT=1.1' freezes the /dev/cdc-wdm1 control device for 3-5 minutes. After that, the device accepts more commands over minicom. Note that I do get connectivity, directly after the CGACT I can get a DHCP address for wwan0 and the bandwidth is approx 20 Mbit/s downstream and 6 Mbit/s upstream. I have tried building a custom 3.16 kernel with a few printk:s in cdc_ncm.c and huawei_cdc_ncm.c, but found nothing suspicious. Kernel version (from /proc/version): 3.16 Environment: Thinkpad L440 64-bit x86 (Intel Core i5-4200M cpu) laptop with Kubuntu 14.04.1 LTS Kernel modules: huawei_cdc_ncm,cdc_ncm Workaround: Bring up the device with AT^NDISDUP=1,1,"internet.telenor.se" instead. Also worth noting is that AT+CGACT=1,1 does not freeze the control connection if using /dev/ttyUSB0. If more info is needed, let me know and I will provide it. /Erik Alapää -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
