Re: IDE DMA on AXP & barriers

[Ivan Kokshaysky]

On Fri, Dec 07, 2001 at 01:25:05PM +0100, Kurt Garloff wrote:
> So I  wonder where the bug actually is. Somewhere in hardware; but I wonder
> whether the CMD646 or the 2117x (PYXIS/CIA) is to blame. The QLogicISP seems
> to happily do BM-DMA, so I'd point to the CMD646.

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.
"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."

> OTOH, the QLogic sits on
> the 2nd PCI bus (32bit), which could make a difference as well.

Certainly - the 2nd bus is behind PCI-PCI bridge.

Ivan.