PCI DMA Problems With 82xx?

Rune Torgersen runet at innovsys.com
Wed Jun 18 07:51:50 EST 2008

linuxppc-embedded-bounces+runet=innovsys.com at ozlabs.org wrote:
> linuxppc-embedded-bounces+runet=innovsys.com at ozlabs.org wrote:
>> Mike Winter wrote:
>>> We are developing with an 8248-based platform, and we have a vendor
>>> telling us that the PCI hardware is unreliable on this CPU family,
>>> in particular the DMA functionality.  A quick search of this list
>>> doesn't turn up any horror stories, although the processor does have
>>> some PCI errata listed.  Does anybody have any practical experience
>>> using PCI on the 8248 or similar that they can share with me?
>>> Thanks.
> We're using all four PCI DMA's on 8265 and 8280 CPU's.
> The only issue we have run into was that we get an occational
> bus error
> (timeout) reading the PCI-DMA status registers...
> We've worked around that by using an exception handler to
> just retry the
> access when (not if) it fails.

And we have to read the status register multiple times and compare to
make sure we have a valid read, as we've seen wacky reads occationally.

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