On 2020/10/14 21:36, Leizhen (ThunderTown) wrote: > > > On 2020/10/14 15:38, Arnd Bergmann wrote: >> On Wed, Oct 14, 2020 at 5:15 AM Florian Fainelli <f.fainelli@xxxxxxxxx> wrote: >>> On 10/12/2020 11:06 PM, Zhen Lei wrote: >>>> stingray-usb.dtsi is finally included by three dts files: >>>> bcm958802a802x.dts, bcm958742k.dts and bcm958742t.dts. I searched all >>>> these three entire expanded dts files, and each of them contains only one >>>> dma-ranges. No conversion range is specified, so it cannot work properly. >>>> I think this property "dma-ranges" is added by mistake, just remove it. >>>> Otherwise, the following error will be reported when any YAML detection >>>> is performed on arm64. >>>> >>>> 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) >>>> >>>> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx> >>> >>> This looks fine to me, Scott, Ray do you want to Ack this patch before I >>> take it? >> >> Does it mean that there are no devices on this bus that can do DMA? >> >> Usually there should be a dma-ranges property to identify that DMA >> is possible and what the limits are, though we have failed to enforce >> that. > > Documentation/devicetree/bindings/iommu/iommu.txt +79 > When an "iommus" property is specified in a device tree node, the IOMMU will > be used for address translation. If a "dma-ranges" property exists in the > device's parent node it will be ignored. An exception to this rule is if the > referenced IOMMU is disabled, in which case the "dma-ranges" property of the > parent shall take effect. > > The dma-ranges is only required by IOMMU disabled case. And should exist in > the parent node of IOMMU device. But this deleted dma-ranges is under the usb > bus node. > >> >> 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. > > The dma_alloc_coherent() will allocate memory with GFP_DMA32 flag and > try the 0-4G first. The reserved swiotlb buffer memory is used only > when the allocation failed. ----- Sorry, my mistake, please ignore the following. > > memory@80000000: > device_type: ["memory"] > reg: [[0x0, 0x80000000, 0x0, 0x80000000], [0x8, 0x80000000, 0x1, 0x80000000]] > > If this is the actual physical memory size, the #address-cells should be set to <1>. > >> >> Arnd >> >> . >>
