On Mon, 2008-11-17 at 02:21 -0800, Kevin Diggs wrote: > Benjamin Herrenschmidt wrote: > > > > > > That's definitely strange. I would expect the kernel to be able to get > > interrupts fast enough to service a 1200 bauds serial port. Maybe > > there's something else wrong, or an other driver causing undue interrupt > > latencies.... > > > As far as I can see the system is NOT busy. I see no evidence of excessive > interrupt loading. It does have an Adaptec 2940 u2w SCSI card, an ATI video > card, > and a USB/firewire card. The SCSI card has some disks on it. The other two > cards > are unused. I guess, in theory, something in my 2.6.27 kernel could be > causing one > of the two unused cards to throw spurious interrupts? > > I still think the hardware is mis-behaving.
That's strange. Maybe one of the drivers is occasionally hogging interrutps. Well, there may also be a bug in the code :-) One thing you can try is to disable DMA in macserial (shouldn't be hard to hack) and see if it degrades the same way. > > Out of curiosity, check that IDE properly unmasks interrupts (hdparm > > -u1 /dev/hda). > > > This is an 8600. It is SCSI only (the onboard controller is the MESH). Ah yes. > >> So, I'm on board with this approach. Since I don't really know what I am > >>doing, how do you recommend I proceed? > > > > > > Google for a document called MacTech.pdf which contains various > > documentations for bits of the ancestor of the IO chip in your machine, > > along with a description of the DBDMA engine :-) Something else you can > > do is to look at how it's properly used by other drivers such as bmac > > and look at some of the darwin source code for reference on how the HW > > works. > > > where might one find older Darwin source? Apple still has most of them back to 10.0 and even the recent ones still have an SCC serial driver afaik. Ben. > > Cheers, > > Ben. > > > > _______________________________________________ > > > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@ozlabs.org > https://ozlabs.org/mailman/listinfo/linuxppc-dev _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
