I'm following up my own message here, with the 'solution' I've found to my problem. Basically, I did recompiles of various kernels under various conditions and finally came the conclusion that the issue has to do with SMP. If I turn SMP on for my kernel, the serial ports will NOT work (as described below). If turn SMP off, they will work fine. The motherboard is a single processor and the CPU has but one core. So something that is turned on by the activation of SMP is killing my serial ports. If anyone can give me any idea what's going on, I'd appreciate it - I can certainly build kernels without SMP, but I'd like to understand why I need to. Thanks! -----Original Message----- From: linux-serial-owner@xxxxxxxxxxxxxxx [mailto:linux-serial-owner@xxxxxxxxxxxxxxx]On Behalf Of Kohne, Mike Sent: Sunday, January 27, 2008 20:41 To: linux-serial@xxxxxxxxxxxxxxx Subject: Problems with serial hardware under newer kernels OK, it's been a few years, but I'm back to fooling with serial ports again. Our system runs on a semi-customized box from Advantec. Motherboard is PCM9380, extra serial ports are on an Advantec board based on the SCH3116 (an I/O chip from SMSC) (I have no docs on this board yet, I just opened up the case and had a look). This chip provides a number of functions, but the only one we seem to use it for is extra serial ports. They show up as NS16550 at various addresss: 0x3E8/IRQ7 0x2E8/IRQ7 0x3E0/IRQ7 0x2E0/IRQ7 0x4E8/IRQ7 Various setserial commands are issued by a file in rcN.d to get the ports properly configured at startup. Now this board was originally developed while we were still using Fedora Core 1 as our base system, and all ports work just fine under FC1 (that's kernel 2.4.22). I fired the whole thing up under Ubuntu 7.04 and no love - none of the ports work (as in, I can't get them to transmit bytes). If I play around with the setserial commands and set the IRQs to 0 instead of 7, I can get bytes to flow, but it's obvious from the timing that the port interrupts aren't being obeyed. Changing the selected interrupt in the BIOS (to 3,4, or 5, for instance, making sure that nothing is using the selected interrupt) has no effect. Now, I did some playing around with various distros that I had on hand and found that Fedora Core 4 works (kernel 2.6.11) and that Fedora Core 5 doesn't (kernel 2.6.15). I did check the config files on the default kernels and IRQ sharing IS turned on. I also tested with all but one port of the serial card disabled in the BIOS. I'm presently setting up a system where I can do kernel builds (the system with the serial ports has very limited disk space, and thus can't do a build). As soon as I get that setup, I will grab the 2.6.13 tarball from kernel.org and start trying to figure out exactly what changes are killing me. In the meantime, does anyone have any good ideas where I ought to be looking? Obviously there is something wierd about our serial board that the latest kernels don't like. I believe it must have something to do with the interrupt routing, but I don't have the foggiest clue where it's all going south. I'm trying to get in touch with our contacts at the manufacturer to see if they know what's up, but I'm not sure how fast they'll be able to figure it out either. Any suggestions for directions to look in would be greatfully accepted. Thanks! Michael Kohne Gilbarco Veeder-Root 336-510-4372 Mike.Kohne@xxxxxxxxxxxx This message (including any attachments) contains confidential and/or proprietary information intended only for the addressee. Any unauthorized disclosure, copying, distribution or reliance on the contents of this information is strictly prohibited and may constitute a violation of law. 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