USB to RS232 converter problem (prolific chip)

[Jeremy Chadwick]

On Sun, Apr 06, 2008 at 12:33:50AM +0300, Andrei Kolu wrote:
> On Sunday 06 April 2008 00:24:38 Andrei Kolu wrote:
> > On Saturday 05 April 2008 23:48:59 you wrote:
> > > On Sat, 5 Apr 2008, Andrei Kolu wrote:
> > > > I have problems using USB to RS232  converter under FreeBSD 6.3-STABLE
> > > > when connecting to any Cisco gear over serial link. I connect my
> > > > adapter to notebook and dmesg output looks like this one:
> > > >
> > > > ucom0: Prolific Technology Inc. USB-Serial Controller D, rev 1.10/4.00,
> > > > addr 2
> > > >
> > > > I have also following modules loaded:
> > > >
> > > > 8    1 0xc0c17000 3540     umodem.ko# cu -l /dev/ttyU0
> > > > Connected
> > > >
> > > > 9    4 0xc0c1b000 3208     ucom.ko
> > > > 10    1 0xc0c1f000 2f54     uplcom.ko
> > > > 13    1 0xc0c2f000 3384     ubsa.ko
> > > >
> > > > Now I try to connect to Cisco box:
> > > >
> > > > # cu -l /dev/ttyU0
> > > > Connected
> > >
> > > Use /dev/cuaU0 instead.
> > >
> > > -Warren Block * Rapid City, South Dakota USA
> >
> > There is no difference if I connect through /dev/ttyU0 or /dev/cuaU0 and
> > even through ttyU1 or cuaU1 (when second serial converter is connected)-
> > same problem. I tried on other computer with FreeBSD 6.1 and 7.0-STABLE
> > snapshot from march- same results.
> >
> > Something is broken on FreeBSD side- strange thing is that when I turn
> > power down on cisco box and turn in on again then I see scrolling text from
> > cisco gear but there is no feedback to keyboard activity. How to debug this
> > issue?
> >
> Some progress on debugging! Just kiddin...
> 
> I removed converter from USB and FreeBSD 7.0 kernel dumped following 
> information:
> 
> ucom0: ucomreadcb: IOERROR
> ucom0: at uhub1 port 1 (addr 2) disconnected
> ucom0: uplcom_set_line_status: STALLED
> 
> 
> Fatal trap 12: page fault while in kernel mode
> cpuid = 1; apic id = 01
> fault virtual address 	= 0xb0
> fault code 			= supervisor read data, page not present
> instruction pointer 		= 0x8:0xffffffff80446f72
> stack pointer 			= 0x10:0xffffffffae796a00
> frame pointer 			= 0x10:0xffffff000172b400
> code segment 		= base 0x0, limit 0xfffff, type 0x1b
> 					= DPL 0, pres 1, long 1, def32 0, gran 1
> processor eflags		= interrupt enabled, resume, IOPL = 0
> current process		= 876 (cu)
> trap number			= 12
> panic: page fault
> cpuid: 1
> Uptime: 8m41s
> Physical memory: 2802 MB
> Dumping 126 MB: 111 95 79 63 47 31 15
> Dump complete

This is a known problem, and even more so if you still had tip or cu
connected to the tty.  Others have reported similar, with other USB
drivers.

Bottom line: the current FreeBSD USB stack is very fragile and
unreliable.  You may want to try the usb4bsd kernel patches (I think
that's what it's called), some have had better luck with those.  Search
the web.

-- 
| Jeremy Chadwick                                    jdc at parodius.com |
| Parodius Networking                           http://www.parodius.com/ |
| UNIX Systems Administrator                      Mountain View, CA, USA |
| Making life hard for others since 1977.                  PGP: 4BD6C0CB |