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.
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).
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?
Cheers,
Ben.
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