Messages in this thread | | | From | David Mosberger <> | Date | Tue, 24 Sep 2002 10:11:26 -0700 | Subject | Re: DAC960 in 2.5.38, with new changes |
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>>>>> On Tue, 24 Sep 2002 09:54:56 -0700, Dave Olien <dmo@osdl.org> said:
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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