Downgrade GSM/UMTS module to USB 2.0 Fullspeed

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

Downgrade GSM/UMTS module to USB 2.0 Fullspeed

[Greg KH]

On Wed, Jan 18, 2017 at 05:05:34PM +0100, Oliver Graute wrote:
> 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?

You can't.  It's up to the device to tell the host what "speed" it is
running at.  See the USB spec for all of the crazy details.

I suggest you modify the firmware of your modem to do this, that's the
only way it is going to work (note, your device needs to be able to
support full speed, it might not be able to do that.)

good luck!

greg k-h

Downgrade GSM/UMTS module to USB 2.0 Fullspeed

[Stefan Wahren]

Hello Oliver,

Am 18.01.2017 um 17:05 schrieb 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.

i think this topic fits better into the i.MX Community [1]

Regards
Stefan

[1] - https://community.nxp.com/community/imx

Downgrade GSM/UMTS module to USB 2.0 Fullspeed

[Oliver Graute]

On 18/01/17, Greg KH wrote:
> On Wed, Jan 18, 2017 at 05:05:34PM +0100, Oliver Graute wrote:
> > 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?
> 
> You can't.  It's up to the device to tell the host what "speed" it is
> running at.  See the USB spec for all of the crazy details.
> 
ok thx for this important hint

> I suggest you modify the firmware of your modem to do this, that's the
> only way it is going to work (note, your device needs to be able to
> support full speed, it might not be able to do that.)

I know that the cinterion gsm module support full speed. I have to check their
docs how to force the module into fullspeed.

Best Regards,

Oliver