On Mon, 13 Mar 2023 21:28:28 +0900, "Chan Kim" said: > which is 32-bit addressable. Even if the device indicates (via the DMA > mask) > that it may address the upper 32-bits, consistent allocation will only > return > 32-bit addresses for DMA if the consistent DMA mask has been > explicitly changed via dma_set_coherent_mask(). This is true of the > dma_pool interface as well. > ------------------------------
> By context I guess it returns the address in lower 32bit address range even > it the coherent_dma_mask is set to some bigger value. No, you have that backwards. It's not "even if". It wil give you a 32-bit address *UNLESS* the driver has called dma_set_coherent_mask() to set a wider mask *and* the device indicates it supports more than 32 bit addresses...
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