(switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface). On Thu, 6 Aug 2009 23:15:31 GMT bugzilla-daemon@xxxxxxxxxxxxxxxxxxx wrote: > http://bugzilla.kernel.org/show_bug.cgi?id=13928 > > Summary: latency_timer of ftdi_sio device 8U232AM needs to be > >= 6 > Product: Drivers > Version: 2.5 > Kernel Version: 2.6.31-rc5 > Platform: All > OS/Version: Linux > Tree: Mainline > Status: NEW > Severity: normal > Priority: P1 > Component: USB > AssignedTo: greg@xxxxxxxxx > ReportedBy: pierre@xxxxxxxxxxxxxxxxxxxx > Regression: No > > > I am using an ftdi 8U232AM (usb id 0403:6001). This worked fine up to commit > 557aaa7ffab639d0190b935a041b16ae44606342(ft232: support the ASYNC_LOW_LATENCY > flag) which started to actually set the latency_timer during device open. > > After this commit, i need to switch off low_latency and make sure the > latency_timer is >= 6. > > This problem was probably existing for as long as the latency_timer could be > set, but did not show up due to nobody bothering to change the sysfs attribute. > > FYI: Setting latency_timer while the device is open seems to take effect only > after closing and reopening, although the relevant usb packet is sent. > Additionally, this device does report a latency_timer of 0 when requested. The > latency_timer with low_latency enabled(default) is hardcoded to 1. > > Using ftdi_sio.debug=1, I get only this when opening the device with > latency_timer < 6(for debugging, this kernel does not automatically set the > latency_timer during open. I have no idea, where the ioctl call is from -- this > is just a hexdump -C /dev/ttyUSB0): > > drivers/usb/serial/ftdi_sio.c: ftdi_open > drivers/usb/serial/ftdi_sio.c: ftdi_set_termios > drivers/usb/serial/ftdi_sio.c: Setting CS8 > drivers/usb/serial/ftdi_sio.c: get_ftdi_divisor - tty_get_baud_rate reports > speed 115200 > drivers/usb/serial/ftdi_sio.c: get_ftdi_divisor - Baud rate set to 115200 > (divisor 0x1A) on chip FT232RL > drivers/usb/serial/ftdi_sio.c: ftdi_set_termios Turning off hardware flow > control > drivers/usb/serial/ftdi_sio.c: ftdi_read_bulk_callback - port 0 > drivers/usb/serial/ftdi_sio.c: update_mctrl - DTR HIGH, RTS HIGH > drivers/usb/serial/ftdi_sio.c: ftdi_ioctl cmd 0x5401 > drivers/usb/serial/ftdi_sio.c: ftdi_ioctl arg not supported - it was 0x5401 - > check /usr/include/asm/ioctls.h > Thanks. So I guess I'll set the `regression' tag on this one. I have a feeling that it got discussed before but I forget the outcome. -- 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
