Re: PCI DMA address

[Jiri Slaby]

On 02/18/2008 04:05 PM, Ke wrote:
> Hello all,
>       How can kernel get the PCI DMA address above 16MB or 64MB?

Documentation/DMA*

>       I hope that the all PCI devices can use a dma address above
> 0x1000000 at a higher memory.

Depends on how much is the device broken or what it can do.

IIRC you'll always get memory from DMA-zone for < ~0U dma_masks on kernels older 
than 2.6.(around 10). If you set dma_masks to < ~0U, you will probably (in the 
meaning, kernel will try to allocate from higher space and fall back to the 
dma-zone) get higher pages nowadays. However I don't know how far this applies 
also to systems with iommu in retrospective.
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