Downgrade GSM/UMTS module to USB 2.0 Fullspeed

[Oliver Graute]

Hello list,

i'am using a GSM/UMTS Module on a PCB which is connected with USB 2.0
Hi-Speed to my imx6ul CPU. To reduce our Electromagnetic compatibility
and to make my hardware colleges happy again I want to downgrade to USB
Full Speed.

How can I tell the Linux Kernel to Do so?

I already tried this and looked around in /sys/bus/usb/devices
but can't find appropirate place to force it to lower speed.

dmesg | grep USB
[  175.775175] usb 1-1: new high-speed USB device number 2 using ci_hdrc
[  175.938753] usb 1-1: New USB device found, idVendor=1e2d, idProduct=005a
[  175.938797] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[  176.021420] cdc_acm 1-1:1.0: ttyACM0: USB ACM device
[  176.068150] cdc_acm 1-1:1.2: ttyACM1: USB ACM device
[  176.102410] cdc_acm 1-1:1.4: ttyACM2: USB ACM device
[  176.131074] cdc_acm 1-1:1.6: ttyACM3: USB ACM device
[  176.172841] cdc_acm 1-1:1.11: ttyACM4: USB ACM device
[  176.208768] cdc_acm 1-1:1.13: ttyACM5: USB ACM device

/sys/bus/usb/devices# lsusb -t
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ci_hdrc/1p, 480M
    |__ Port 1: Dev 2, If 0, Class=, Driver=cdc_acm, 480M
    |__ Port 1: Dev 2, If 1, Class=, Driver=cdc_acm, 480M
    |__ Port 1: Dev 2, If 2, Class=, Driver=cdc_acm, 480M
    |__ Port 1: Dev 2, If 3, Class=, Driver=cdc_acm, 480M
    |__ Port 1: Dev 2, If 4, Class=, Driver=cdc_acm, 480M
    |__ Port 1: Dev 2, If 5, Class=, Driver=cdc_acm, 480M
    |__ Port 1: Dev 2, If 6, Class=, Driver=cdc_acm, 480M
    |__ Port 1: Dev 2, If 7, Class=, Driver=cdc_acm, 480M
    |__ Port 1: Dev 2, If 8, Class=, Driver=, 480M
    |__ Port 1: Dev 2, If 9, Class=, Driver=, 480M
    |__ Port 1: Dev 2, If 10, Class=, Driver=, 480M
    |__ Port 1: Dev 2, If 11, Class=, Driver=cdc_acm, 480M
    |__ Port 1: Dev 2, If 12, Class=, Driver=cdc_acm, 480M
    |__ Port 1: Dev 2, If 13, Class=, Driver=cdc_acm, 480M
    |__ Port 1: Dev 2, If 14, Class=, Driver=cdc_acm, 480M
    |__ Port 1: Dev 2, If 15, Class=, Driver=, 480M

Best Regards,

Oliver