Re: [Linux-ia64] patch to no longer use ia64's software mmu

[Alan Cox]

> I think the issue at hand is whether, longer term, it is desirable to
> move all bounce buffer handling into the PCI DMA layer or whether
> Linux should continue to make bounce buffer management visible to
> drivers.  I'd be interested in hearing opinions.

I think the performance figures we see currently answer that already. Bounce
management in a sense is PCI layer, but its PCI layer in the sense of
helpers called by subsystems or devices not as a global layer in the middle.

On a box with 32bit limited cards you need to do zone stuff and play with
the high zone even though your kmap is a nop. It's not ideal but its the
real world. IA64 also needs to correct its GFP_DMA to mean "low 16Mb" for
ISA DMA. While there is no ISA DMA on ia64 (thankfully) many PCI cards have
26-31 bit limits.

Alan