FSL 64-bit DMA window question

[Zang Roy-R61911]

> -----Original Message-----
> From: Benjamin Herrenschmidt [mailto:benh at kernel.crashing.org]
> 
> Hi Folks !
> 
> Is there any specific reason why you chose 1T (40 bit) as the location of
> the 64-bit DMA window ?
> 
> It happens that most current radeon adapters cannot DMA there, they have
> a 40-bit DMA limit. I seem to be getting things to work fine using a 39-
> bit window, but I suppose that might collide with something else ?
T4240 has 40bit physical address ability.
"
This chip's 40-bit, physical address map consists of local space and external address
space. For the local address map, 32 local access windows (LAWs) define mapping
within the local 40-bit (1 TB) address space. Inbound and outbound translation windows
can map the chip into a larger system address space such as the RapidIO or PCIe 64-bit
address environment. This functionality is included in the address translation and
mapping units (ATMUs).

"
That should be the reason to set the DMA window to 40-bit.

> 
> Can you guys consider changing the default ?
Any collide for 40bit?
Roy