On Fri, 16 Oct 2020 17:08:32 +0800, Zhen Lei <thunder.leizhen@xxxxxxxxxx> wrote: > The scripts/dtc/checks.c requires that the node have empty "dma-ranges" > property must have the same "#address-cells" and "#size-cells" values as > the parent node. Otherwise, the following warnings is reported: > > arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ > (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ > its #address-cells (1) differs from / (2) > arch/arm64/boot/dts/broadcom/stingray/stingray-usb.dtsi:7.3-14: Warning \ > (dma_ranges_format): /usb:dma-ranges: empty "dma-ranges" property but \ > its #size-cells (1) differs from / (2) > > Arnd Bergmann figured out why it's necessary: > Also note that the #address-cells=<1> means that any device under > this bus is assumed to only support 32-bit addressing, and DMA will > have to go through a slow swiotlb in the absence of an IOMMU. > > Suggested-by: Arnd Bergmann <arnd@xxxxxxxx> > Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx> > --- Applied to devicetree-arm64/next, thanks! -- Florian
