Bug 5730

Summary:	FTDI USB serial adaptor problems
Product:	Drivers	Reporter:	Chris Bainbridge (chris.bainbridge)
Component:	USB	Assignee:	Greg Kroah-Hartman (greg)
Status:	REJECTED WILL_NOT_FIX
Severity:	normal
Priority:	P2
Hardware:	i386
OS:	Linux
Kernel Version:	2.6.14	Subsystem:
Regression:	---	Bisected commit-id:
Bug Depends on:
Bug Blocks:	5089

Description Chris Bainbridge 2005-12-12 04:04:59 UTC

PC: Dell SC420
Hardware: 4-port VScom USB serial port adaptor 
Web page: http://www.vscom.de/produkte/vscom_usb-4com.html
Modules: ftdi_sio, usbserial

I have observed two problems with this driver:

1) Driver disconnects ports and reassigns /dev/tts/USBx to a new device number
2) Flushing the IO buffers doesn't work.

Problem 1

I have a 4-port Vscom adaptor. When using it I get errors where some
of the /dev/tts/USBx devices seem to get disconnected, then be
connected again on a different device. eg. /dev/tts/USB2 and USB3 will
be involved in some transfer, then will move to /dev/tts/USB4 and
USB5. The other ports stay on the same devices, and I'm not touching
the hardware cables or psu. The logs are full of errors like:

drivers/usb/serial/ftdi_sio.c: ftdi_tiocmget Could not get modem
status of device - err: -19 (or -71).

Sample of log follows:

Nov 10 13:28:30 funky drivers/usb/serial/ftdi_sio.c: ftdi_tiocmget
Could not get modem status of device - err: -71
Nov 10 13:28:30 funky drivers/usb/serial/ftdi_sio.c: ftdi_tiocmget
Could not get modem status of device - err: -71
Nov 10 13:28:30 funky drivers/usb/serial/ftdi_sio.c: ftdi_tiocmget
Could not get modem status of device - err: -71
Nov 10 13:28:30 funky drivers/usb/serial/ftdi_sio.c: ftdi_tiocmget
Could not get modem status of device - err: -71
Nov 10 13:28:30 funky hub 2-0:1.0: port 1 disabled by hub (EMI?), re-enabling...
Nov 10 13:28:30 funky usb 2-1: USB disconnect, address 2
Nov 10 13:28:30 funky usb 2-1.1: USB disconnect, address 3
Nov 10 13:28:30 funky ftdi_sio ttyUSB0: FTDI USB Serial Device
converter now disconnected from ttyUSB0
Nov 10 13:28:30 funky ftdi_sio 2-1.1:1.0: device disconnected
Nov 10 13:28:30 funky usb 2-1.2: USB disconnect, address 4
Nov 10 13:28:30 funky ftdi_sio ttyUSB1: FTDI USB Serial Device
converter now disconnected from ttyUSB1
Nov 10 13:28:30 funky ftdi_sio 2-1.2:1.0: device disconnected
Nov 10 13:28:30 funky usb 2-1.3: USB disconnect, address 5
Nov 10 13:28:30 funky ftdi_sio 2-1.3:1.0: device disconnected
Nov 10 13:28:30 funky usb 2-1.4: USB disconnect, address 7
Nov 10 13:28:30 funky ftdi_sio ttyUSB4: FTDI USB Serial Device
converter now disconnected from ttyUSB4
Nov 10 13:28:30 funky ftdi_sio 2-1.4:1.0: device disconnected
Nov 10 13:28:30 funky drivers/usb/serial/ftdi_sio.c: ftdi_tiocmget
Could not get modem status of device - err: -71
Nov 10 13:28:30 funky usb 2-1: new full speed USB device using
uhci_hcd and address 8
Nov 10 13:28:30 funky hub 2-1:1.0: USB hub found
Nov 10 13:28:30 funky hub 2-1:1.0: 4 ports detected
Nov 10 13:28:30 funky usb 2-1.1: new full speed USB device using
uhci_hcd and address 9
Nov 10 13:28:30 funky ftdi_sio 2-1.1:1.0: FTDI USB Serial Device
converter detected
Nov 10 13:28:30 funky drivers/usb/serial/ftdi_sio.c: Detected FT232BM
Nov 10 13:28:30 funky usb 2-1.1: FTDI USB Serial Device converter now
attached to ttyUSB0
Nov 10 13:28:30 funky usb 2-1.2: new full speed USB device using
uhci_hcd and address 10
Nov 10 13:28:31 funky ftdi_sio 2-1.2:1.0: FTDI USB Serial Device
converter detected
Nov 10 13:28:31 funky drivers/usb/serial/ftdi_sio.c: Detected FT232BM
Nov 10 13:28:31 funky usb 2-1.2: FTDI USB Serial Device converter now
attached to ttyUSB1
Nov 10 13:28:31 funky usb 2-1.3: new full speed USB device using
uhci_hcd and address 11
Nov 10 13:28:31 funky ftdi_sio 2-1.3:1.0: FTDI USB Serial Device
converter detected
Nov 10 13:28:31 funky drivers/usb/serial/ftdi_sio.c: Detected FT232BM
Nov 10 13:28:31 funky usb 2-1.3: FTDI USB Serial Device converter now
attached to ttyUSB4
Nov 10 13:28:31 funky usb 2-1.4: new full speed USB device using
uhci_hcd and address 12
Nov 10 13:28:31 funky ftdi_sio 2-1.4:1.0: FTDI USB Serial Device
converter detected
Nov 10 13:28:31 funky drivers/usb/serial/ftdi_sio.c: Detected FT232BM
Nov 10 13:28:31 funky usb 2-1.4: FTDI USB Serial Device converter now
attached to ttyUSB5
Nov 10 13:29:11 funky ftdi_sio ttyUSB2: FTDI USB Serial Device
converter now disconnected from ttyUSB2
Nov 10 13:29:11 funky ftdi_sio ttyUSB3: FTDI USB Serial Device
converter now disconnected from ttyUSB3

Problem 2

tcflush(ser.fd, TCIOFLUSH) doesn't work. I suspect it doesn't flush all the way
down the stack (usb buffers, usb hub, usb->rs232 interface chip). I've seen both
input and output buffers fail to flush, so when apps start they get flooded with
 new data that they aren't expecting. Moving to a real serial port fixed the
problem.

Comment 1 Greg Kroah-Hartman 2006-02-14 16:37:40 UTC

The disconnections are not done by the kernel, but by a loose cable, or 
connection, or low power on the bus.

If you have a externally powered hub, try using that instead.

As for the flush command, this driver does not directly
support that, probably because it can not determine when
the data is really sent out the serial port at the end
of the usb device (a common problems for a lot of usb to serial
devices.)  So there's nothing we can do for that here, sorry.