Re: [PATCH v3 3/3] mmc: xenon: Fix 2G limitation on AC5 SoC

[Linus Walleij]

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