On Tue, Feb 10, 2009 at 12:26:23AM +0530, Shivdas Gujare wrote: > Hi Greg, > I am currently testing my device(eZ430) using generic usb-serial > driver, and I came across some strange problem. Ick, generic usb-serial? Why? There's no flow control with that driver, and it's extreemly slow. Also, what kernel version are you using? > If I test the device with x86, it works very well. It sends character > strings to USB serial, after pressing key on device. > But when I test with ARM board(Beagle), it shows some characters > missed in between.(for ex "Hello" receives as "Helo" with "l" missed) What host controller driver are you using here? > While debugging, I enabled debug messages with debug=1 while modprobe. > And I started getting data properly with no characters missed. > I found out that it was "usb_serial_debug_data" function from > "usb_serial_generic_read_bulk_callback" printing data received.ow > > But here, If I disables debug, I starts getting data corrupted again. > in short "modprobe usbserial debug=1" works very well but "modprobe > usbserial" doesn't. So it's a buffer/timing issue :( > Is there any possibility that specific to my device, it needs the urb > flushing to be delayed some time using debug messages? Sounds like it. > What could be the probable reason? How can I debug these problems? Use a usb protocol "sniffer" to verify that the data really is not getting to/from your device to see if there is an overflow in either your device, or in the host would be a good place to start. You can use usbmon for that. good luck, greg k-h -- 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
