On Mon, Dec 12, 2022 at 9:43 AM Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: > >> Right but I guess I meant what about 0x3_00000000..0x3_ffffffff ? > >> Isn't that also in DMA_BIT_MASK(34) > > > > Yes, you are right. > > So it would fail in that case? Is it possible to use devicetree > reserved memory or some such, to set aside 64k for the bounce > buffer DMA mapping? Yups spot on, reserved-memory can be used along with the kernel CONFIG_DMA_CMA to achieve exactly this: Documentation/devicetree/bindings/reserved-memory/reserved-memory.yaml kernel/dma/Kconfig Yours, Linus Walleij
