understanding an IO question

[Charles Krinke]

Dear Kumar:

Thank you very much for your advice on addressing our PCI device. It
turned out that the OutboundTranslation windows were the key.

In uboot, I setup two windows to allow accesses to 32bit cpu space
0x8400_000 & 0x8800_0000 to be translated to 64bit DAC (Dual Address
Cycles) at 0x3_0000_0000 & 0x1_0000_0000 respectively, and both the 8241
and 8541 do this quite well.

Once the potar, powbar and other outbound translation address windows
were reset to the same values in Linux that they had in uboot, outbound
transactions work fine and address the registers and memory in our ASIC.

Next, I need to study the difference between the DMA engines in the 8241
and 8541 to accomplish a similar mission. This one may be a bit trickier
and you advice would be greatly appreciated.

The 8241 DMA engine understands 64bit DMA  in that it has a high source
& destination address register for the upper 32bits of a 64bit address.
Unfortunately, the 8541 does not. It only supports 32bit DMA.

So, my assumption is that there is some way to use a different outbound
address translation window and emulate 64bit DMA transactions using the
32bit DMA engine in the 8541.

I don't know if you have studied this part at all, but if you or anyone
would be willing to offer a few hints, I would be appreciative.

Charles