From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Kevin Diggs <kevdig@hypersurf.com>
Cc: linuxppc-dev@ozlabs.org
Subject: Re: pmac_zilog debugging ...
Date: Mon, 17 Nov 2008 22:40:18 +1100 [thread overview]
Message-ID: <1226922018.7178.237.camel@pasglop> (raw)
In-Reply-To: <492145BB.7080904@hypersurf.com>
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.
> >
> > _______________________________________________
> >
>
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> Linuxppc-dev mailing list
> Linuxppc-dev@ozlabs.org
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next prev parent reply other threads:[~2008-11-17 20:13 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-07 21:38 pmac_zilog debugging Kevin Diggs
2008-11-07 22:23 ` Benjamin Herrenschmidt
2008-11-13 11:38 ` Kevin Diggs
2008-11-13 21:44 ` Benjamin Herrenschmidt
2008-11-13 22:29 ` Kevin Diggs
2008-11-14 1:00 ` Benjamin Herrenschmidt
2008-11-17 8:37 ` Kevin Diggs
2008-11-17 9:00 ` Benjamin Herrenschmidt
2008-11-17 10:21 ` Kevin Diggs
2008-11-17 11:40 ` Benjamin Herrenschmidt [this message]
2008-11-08 5:52 ` Paul Mackerras
2008-11-08 10:46 ` Benjamin Herrenschmidt
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