Hi Linus, Adrian, On Tue, 13 Dec 2022 10:16:57 +0100, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > 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 Just in case, here is an old series with reserved-memory solution: https://lore.kernel.org/lkml/20220806085818.9873-4-vadym.kochan@xxxxxxxxxxx/T/ But, what about to start with PIO solution (which is conceptually easier solution) with checking on ram size and then develop better one ? Thanks,
