Re: Apparent problems with interrupt latency with PCI2PCI bridges (register_serial(): autoconfig failed)

["Michael R. Head" <burner@suppressingfire.org>]

In case anyone else ends up with this problem, here's how it's
resolving... 

I've been told that this is a result of PCI interface controller on the
card (a PLX PCI9050) having trouble with PCI bridges. All of the cards
that I have been having trouble with use this interface controller, so
that seems to explain my problems.

On Wed, 2006-01-04 at 13:18 -0500, Michael R. Head wrote:
> Hello, I'm having some trouble with a number of PCI cards and several
> PCI bridges. In order to reduce the problem, I'm going to ask about 1
> specific card and one specific bridge.
> 
> The hardware I'm working with is a P4 2.4Ghz machine in a 4U rackmount
> chassis. On board are 3 PCI slots connected to the main PCI bus and 9
> PCI slots connected to a bridge to the main PCI bus.
> 
> The software I'm running is an up to date RHEL3 (kernel 2.4.21-37.EL),
> but I experience the same problems when I boot off an Ubuntu Breezy
> LiveCD (which uses 2.6.12).
> 
> I have an 8 port RS232 card using 16550A UARTs (Sealevel Systems Inc
> Eight Port RS-232 Interface). When I plug it into the main PCI bus (#2),
> it works perfectly and I get ttyS4-11 working automatically and
> properly.
> 
> However, when I put the card in a PCI slot on bus #3 (which is on the
> other side of a Pericom Semiconductor PCI to PCI Bridge), I see this
> during boot:
> 
> $ dmesg | grep -2 serial
> ttyS3 at 0x02e8 (irq = 3) is 16550A
> register_serial(): autoconfig failed
> Real Time Clock Driver v1.10e
> 
> 
> When I plug it into a slot on bus #2, I get this from setserial:
> $ setserial -g /dev/ttyS4
> /dev/ttyS4, UART: 16550A, Port 0xd200, IRQ: 2
> 
> When I plut the card into a slot on bus #3, setserial tells me this (by
> default);
> $ setserial -g /dev/ttyS4
> /dev/ttyS4, UART: unknown, Port: 0xc100, IRQ: 2
> 
> If I attempt to reconfigure ttyS4 to have the settings from above, I get
> the dreaded "ttyS4: LSR safety check engaged!" and from then on, any
> access to /dev/ttyS4 results in "/dev/ttyS4: No such device".
> 
> 
> 
> Now, I also have some other PCI cards that are having trouble with
> living on the other side of a PCI bridge, but their drivers are
> available separately from the kernel. I figure that if I can get the
> serial card working, then hopefully the rest will work, too.
> 
> I also have an external 4U rackmount chassis containing 12 additional
> PCI slots that are connected via 4 Intel 21142 PCI-to-PCI bridges, and
> when I connect the serial card into any of those busses, I get the same
> problem.
> 
> 
> I've tried fiddling with all sorts of kernel PCI options at boot and
> fiddling with various setpci commands. Nothing seems to help. Any
> suggestions or information would be greatly appreciated.
> 
> thanks,
> mike
> 
-- 
Michael R. Head <burner@suppressingfire.org>
GPG: http://www.suppressingfire.org/~burner/gpg.key.txt [0x4C9DA1D0]

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