Re: ftdi_sio urn failed to clear flow control

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On Sat, Sep 08, 2012 at 04:26:37PM -0500, Caylan Larson wrote:
> Hi,
> 
> I have three, 4-port USB-to-Serial adapters connected to a Linux
> system running kernel 3.3.7-1.  These three adapters are connected to
> the system via a USB hub.  The application is a DOS app (point of sale
> system), running in DOSEMU (DOS emulator), that connects directly to
> these serial devices.  This logs below coincide with a lock-up of the
> production application.  We are using software flow control at 38400
> baud, we are not using hardware flow control.

Any reason you can't use hardware flow control?

> Sep  8 13:44:54 prod05 kernel: [25716.429799] ftdi_sio ttyUSB11: urb failed to clear flow control
> Sep  8 13:46:15 prod05 kernel: [25797.281701] ftdi_sio ttyUSB11: ftdi_set_termios FAILED to set databits/stopbits/parity
> Sep  8 13:46:16 prod05 kernel: [25798.279805] ftdi_sio ttyUSB11: ftdi_set_termios urb failed to set baudrate
> Sep  8 13:46:21 prod05 kernel: [25803.270534] ftdi_sio ttyUSB11: urb failed to clear flow control

Something bad happened with the device, and a control message sent to it
failed.

> More of these messages are repeated for all the serial ports connected to the 3rd adapter (see below).
> 
> Here is the exact model I'm using.  And again, 3 of these connected to a USB hub.
> 
> http://www.amazon.com/dp/B004EKI4DC/ref=pe_175190_21431760_M2T1_SC_3p_dp_1
> > This PRO Grade Adapter is build around FT4232H from FTDI
> > Semiconductors which is the best and most reliable Quad Serial to
> > USB processors on the market it also uses ZT232E RS232 transciever
> > from ZyWyn USA. USB cable is 6ft Total Lenght with Port
> > Identificaiton marks on each of the DB9 Male ends.
> 
> 
> It's worth noting that this setup is not a one-off.  I have two
> production installations of the same size (12 serial ports) and this
> is the first I've seen of the issue.  The two installations may have
> different model hubs.  Lastly, the installation (prod05) that
> succumbed to this error was running perfectly for 3 days under load -
> but this Saturday afternoon was the peak of their business and it
> failed.  Bummer.
> 
> Does anyone know how to prevent this from happening?

As this is a rare occurance, possibly an electrical glitch happened to
disrupt the connection to the devices, or the hub caused the problem?  I
really don't know what happened here, sorry.

greg k-h
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