Re: IDE DMA on AXP & barriers

[Ivan Kokshaysky <ink@jurassic.park.msu.ru>]

On Fri, Dec 07, 2001 at 03:48:15PM +0100, Kurt Garloff wrote:
> > Hmm, it seems to be a pyxis bug; the hardware workaround exists, but
> > I guess that it might be not implemented properly on early miatas.
> > This also explains why I don't have that problem on lx164 and sx164.
> > >From pyxis manual:
> > "A.1 Read Page Problem
> >  PCI DMA reads that attempt to cross 8K page boundaries cause data corruption
> >  problems. A fix has been implemented with an Altera 7032 and two Pericom
> >  PI5C3400 bus switches and a diode."
> 
> Hey, where did you find that manual? I could not find one at Compaq's web
> site.

IIRC, few years ago someone posted a link on axp-list, and I picked it up.
Anyway, I've placed it on
ftp://ftp.park.msu.ru/ink/docs/21174_SI.pdf

> How do I recognize the broken PYXIS in software? (Except for waiting for
> your hard disk to be corrupted?)

Put the chip into PCI loopback mode, read some memory (crossing the
page boundary) via direct PCI window and check for corruption -
perhaps this will work.

> Unfortunately, I see no 21174 on my PCI bus where I could just check the
> revision.

Checking the revision won't help - that bug should be fixed with some
off-chip logic.

> Or should I just put an #ifdef CONFIG_ALPHA_PYXIS in my patch?
> What about the users of generic alpha kernels?

#ifdef CONFIG_ALPHA_PYXIS won't work for them.

> Or a config option?

Maybe...
Jay, your opinion? Perhaps you have the info which systems are affected?

Ivan.