IMX8MM 4GiB boundary issue

[Fabio Estevam]

On Thu, Oct 1, 2020 at 1:50 PM Marek Vasut <marex at denx.de> wrote:

> In Linux, R-Car3 uses IOMMU, so there is no performance hit on that
> specific hardware. On iMX8M, you would likely need to set some bit which
> indicates the hardware supports only 32bit DMA, so the DMA buffers would
> be allocated below the 32bit barrier, also no big problem. I think it is
> one of the DMA flags, DMA_BIT_MASK(32) or so.

Just saw a recent discussion on this and the recommendation was to use
the 'dma-ranges' property.

Please check:

https://www.spinics.net/lists/arm-kernel/msg843723.html