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 -- Tixy -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
