Dave> According to the Documentation/DMA-mapping.txt file, the new
Dave> DMA mapping interfaces should allow all PCI transfers to use
Dave> 32-bit DMA addresses. Controllers on the PCI bus should never
Dave> need to use DAC PCI transfers. Based on this, writel() should
Dave> work even on ia64.
Warning: there is a big difference between *can* and *want*. On ia64
machines with an Intel chipset, the PCI DMA interface is implemented
via bounce buffers, so it will be *much* slower than DAC. For this
reason, it is preferable on ia64 to use DAC where possible (and just
in case Dave Miller starts asking about this: yes, the hp zx1 chipset
for Itanium 2 does have a hardware I/O TLB... ;-).
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