Date: Wed, 17 Jan 2001 19:52:17 -0500 From: Chuck Cranor <chuck@research.att.com> To: Richard Hodges <rh@matriplex.com> Cc: Mike Tancsa <mike@sentex.net>, freebsd-atm@FreeBSD.ORG Subject: Re: ATM under 4.x STABLE ? Message-ID: <20010117195217.A2037890@chips.research.att.com> In-Reply-To: <Pine.BSF.4.10.10101160907280.676-100000@mail.matriplex.com>; from rh@matriplex.com on Tue, Jan 16, 2001 at 09:18:43AM -0800 References: <5.0.1.4.0.20010116114713.033bd7c0@marble.sentex.ca> <Pine.BSF.4.10.10101160907280.676-100000@mail.matriplex.com>
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On Tue, Jan 16, 2001 at 09:18:43AM -0800, Richard Hodges wrote:
> On Tue, 16 Jan 2001, Mike Tancsa wrote:
> > en0: <Efficient Networks ENI-155p> mem 0xfe000000-0xfe3fffff irq 11 at
> > device 8.0 on pci1
> > en0: unexpected timeout in rx DMA test
> > en0: WARNING: DMA test detects a broken PCI chipset!
> > trying to work around the problem... but if this doesn't
> > work for you, you'd better switch to a newer motherboard.
en0: maximum DMA burst length = 64 bytes (must align)
> Ouch! Looking at /usr/src/sys/dev/en/midway.c I see some very interesting
> notes about broken DMA in the Efficient card (but not Adaptec). The
> driver is supposed to work around that, though. Your DMA message above
> seems to refer to the chipset not being able to handle "misaligned 64
> byte DMA", which might not be a major problem, but just might reduce
> the performance.
> Of course, the real authority is Chuck Cranor himself...
hi-
Adaptec totally redid the DMA interface to this card and it works
great. the Efficient version is more painful to program and gets
some things wrong. the card init code does some extensive testing
to find the best mode that will work for the card.
Mike's system supports large DMA bursts (64 byte), but the starting
address of the buffer must be aligned to a 64 byte boundary (that's
why it says "(must align)" and printed the warning). i don't think
this will be a major problem (if you've got a large DMA, you can break
it up into chunks to get the needed 64 byte alignment... the driver
will do this for you).
chuck
--
Chuck Cranor <chuck@research.att.com>
Senior Technical Staff Member, AT&T Labs-Research
Room B135, 180 Park Ave, Florham Park NJ, 07932
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