On Thu, Oct 1, 2020 at 1:50 PM Marek Vasut <ma...@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
