Date: Wed, 3 Dec 2008 07:47:25 -0800
From: Greg KH <greg@kroah.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Marc Haber <mh+linux-kernel@zugschlus.de>, linux-kernel@vger.kernel.org,
       linux-usb@vger.kernel.org
Subject: Re: pl2303 - pl2303_open - failed submitting interrupt urb, error
	-28
Message-ID: <20081203154725.GB15968@kroah.com>
References: <20081202131821.GA25217@torres.zugschlus.de> <20081203014208.55dfeb8d.akpm@linux-foundation.org>
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On Wed, Dec 03, 2008 at 01:42:08AM -0800, Andrew Morton wrote:
> (cc linux-usb)
> 
> On Tue, 2 Dec 2008 14:18:21 +0100 Marc Haber <mh+linux-kernel@zugschlus.de> wrote:
> 
> > Hi,
> > 
> > the following applies to a "vanilla" 2.6.27.7 kernel built and running
> > on a Debian unstable system.
> > 
> > To obtain out-of-band access to a number of switches and routers, I
> > have a seven-port USB hub to which seven identical USB-to-serial
> > adaptors using the PL2303 chip and driver are connected. All seven
> > work when only one of them is used at a time.
> > 
> > Cereal is an application which keeps a process (GNU screen) attached
> > to the tty at all times to be able to log what happens on the serial
> > port. When I start cereal on all seven ports, I start getting
> > "pl2303_open - failed submitting interrupt urb, error -28" errors in
> > my syslog:
> > 
> > Dec  2 14:07:36 alemana kernel: pl2303 ttyUSB2: pl2303_open - failed submitting interrupt urb, error -28
> > Dec  2 14:07:37 alemana kernel: pl2303 ttyUSB5: pl2303_open - failed submitting interrupt urb, error -28
> > Dec  2 14:07:38 alemana kernel: pl2303 ttyUSB6: pl2303_open - failed submitting interrupt urb, error -28
> > Dec  2 14:07:41 alemana kernel: pl2303 ttyUSB2: pl2303_open - failed submitting interrupt urb, error -28
> > Dec  2 14:07:43 alemana kernel: pl2303 ttyUSB5: pl2303_open - failed submitting interrupt urb, error -28
> > Dec  2 14:07:43 alemana kernel: pl2303 ttyUSB6: pl2303_open - failed submitting interrupt urb, error -28
> > Dec  2 14:07:47 alemana kernel: pl2303 ttyUSB2: pl2303_open - failed submitting interrupt urb, error -28
> > Dec  2 14:07:48 alemana kernel: pl2303 ttyUSB5: pl2303_open - failed submitting interrupt urb, error -28
> > Dec  2 14:07:49 alemana kernel: pl2303 ttyUSB6: pl2303_open - failed submitting interrupt urb, error -28
> > 
> > The corresponding ports are not useable in that case.
> > 
> > When one googles for this error message, one finds a thread from 2006
> > with Greg KH commenting. In my case, the error doesn't hose the USB
> > subsystem, I can unplug the adapters and plug them in again one and a
> > time without a problem, and I can even use the ports that don't throw
> > this error message.
> > 
> > As in the 2006 thread, unloading the EHCI driver (ehci_hcd) solves the
> > issue, but is of course not an attractive option as soon as one wants
> > to use even a USB stick on the same machine.

I would suggest using a USB 1.1 hub instead if you have to use this kind
of hardware set up.  I think the core is just not able to schedule so
many interrupt urbs with such a setup, running USB 1.1 devices behind a
USB 2.0 hub like this is a very difficult thing to do.

Sorry I don't have a better solution.

thanks,

greg k-h
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