Re: [Q] Why does dma_alloc_coherent() of ia64 GFP_DMA?

[Christoph Lameter]

On Mon, 10 Nov 2008, Yasunori Goto wrote:

> Even if a device allows over 4G access and the driver doesn't specify
> GFP_DMA, dma_alloc_coherent() returns under 4G area.

GFP_DMA can become 0 for configurations that have
!CONFIG_ZONE_DMA. Then all of memory is available.

The call is subarch specific. So f.e. Altix sn_dma_alloc_coherent does
not set __GFP_DMA.

If you have an IA64 arch that only support 32bit I/O then __GFP_DMA in
dma_alloc_coherent makes sense.





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