16 May
2014
16 May
'14
5:08 p.m.
On Fri, 2014-05-16 at 13:55 +0100, Catalin Marinas wrote: [...]
It could if arm64 would restrict the DMA addresses to 32-bit, but it doesn't and I end up on my platform with USB DMA buffers allocated >4GB address.
dma_alloc_coherent() on arm64 should return 32-bit addresses if the coherent_dma_mask is set to 32-bit.
Not if you have CONFIG_DMA_CMA. Unless I have misread the code, enabling CMA means memory comes from a common pool carved out at boot with no way for drivers to specify it's restrictions [1]. It's what I've spent most of the week trying to work around in a clean way, and have finally given up.
[1] There is a partial, stalled attempt at doing device specific CMA allocation: http://lkml.org/lkml/2014/2/28/237
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Tixy