Hi Vishal, hi all, On Fri, Oct 9, 2009 at 7:31 AM, Vishal Thanki <vishalthanki@xxxxxxxxx> wrote: > Hi all, > > I am debugging an issue for a USB device (usb wifi dongle from TP-LINK which > is using Ralink chipset). I am using it on an embedded board running Linux > 2.6.30 on ARM architecture. The board has USB controller from synopsys, and > they've provided the driver for the same. The controller has the feature to > switch between USB speeds (i.e. 1.0 and 2.0). When I configure the USB > controller in USB 1.0 speed, my USB device (i.e. usb wifi dongle) works > perfectly fine. But when the USB controller is configured for USB 2.0, the > device stops working after some time when doing large data transfer at high > speed. I think I am experiencing the same problem, on x86 architecture, with cdc-acm driver, on a device I am developing, using an FPGA connected to a UTMI from SMSC. In addition to what you describe, the data is somewhat corrupted at high speeds starting around 5 MB/s. It seems the device is re-sending a data packet when the host is expecting a new one. I always assumed it was my fault. Do you observe the same? > Its not crashing the Linux, but the system becomes non-responsive. You mean, the device becomes unresponsive? The cdc-acm driver creates /dev/ttyACM0, from which I can read the data. Re-opening the file starts the process again, sending data until it arbitrarily stops, re-open again... Does something like this work for you, too? > I could capture the USB packets (using analyzer) between controller and device > and found that there was continuous PING - NAK token exchanges were > happening. I could re-confirm this scenario by putting some debug prints in > controller driver. From this observation, I assumed that it may happen that > device is not able to release the buffers and because of that its sending > NAK to each incoming PING request. When I reduced the number of PINGs sent > out by USB controller driver, the device was working fine. Currently I am > skipping every alternate PING token from controller driver. How do you limit the number of PINGs sent out? I would like to try that, too. > > I want to understand that what should be the ideal frequency to send PING > tokens. Should it be very aggressive? I searched through the code of ehci > driver in linux kernel, but could not figure out where the exactly PING > protocol is implemented in that. Can you please point out the part of source > code, so that I can look into it and see how it is implemented ? I would be very much interested in that, too. All I could find in the kernel source were these measely lines: $ git grep USB_PID_PING arch/x86/kernel/early_printk.c:#define USB_PID_PING 0xb4 drivers/usb/core/hcd.h:#define USB_PID_PING 0xb4 /* USB 2.0 */ Please let me know if you find a solution. > > Thanks, > Vishal Thanks, Henry -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
