Forums » Software Development »
USB device speed issue when using USB Ethernet gadget driver
Added by François Tremblay about 12 years ago
Hi,
I recompiled the kernel and I activated the Ethernet gadget driver. Everything runs fine except one thing: with one of my linux computer, the device is recognized as a USB full-speed device (12 Mbits/s) instead of high-speed device (480 Mbits/s). If I un-plug and re-plug, the device is coming back to a high-speed configuration. I tried various usb cable and nothing changed. Also, both our own IO board and Industrial IO board exhibit the same behavior. I also tried different versions of linux on the host side to see if it changes something (I tried Ubuntu 11.04 and 12.04) but again, nothing changed. I would say that 40% of the time, device is detected as a high-speed device and 60% as a full-speed device. I also tried various usb connector (in back and front).
I have another computer and with this one, the device is always recognized as a high-speed device even with my 6' long usb cable. It works fine both in Windows 7 and Ubuntu 12.04.
In our application, we need to transfer around ~1630 Kbytes/s of data at the application level. When you add TCP/IP and all USB protocol layers overheads, full-speed configuration is not enough.
Did you see this problem in the past?
Any idea?
Thanks.
Regards,
--François
Replies (1)
RE: USB device speed issue when using USB Ethernet gadget driver - Added by Bob Duke about 12 years ago
Hello François,
Based on your description, it looks like a problem with that particular USB host.
I have not seen that problem here, but problems with the kernel's usb speed negotiation are possible if there's a problem with the host chipset or cabling.
Are you connecting to a usb port directly on the motherboard or through a front panel port (connected by wires to the motherboard)? Have you tried using different USB ports?
What is the usb chipset used on the host machine?
Have you tried (1) removing the ohci-hcd kernel module, (2) confirming the ehci-hcd module is loaded and then connecting the usb device?
In addition, dmesg should provide some information on the usb negotiation which may help you understand what is going on.
-Bob
