On 20 September 2018 at 14:31, Florian Fainelli <f.fainelli@xxxxxxxxx> wrote: > On 09/20/2018 02:04 PM, Ard Biesheuvel wrote: >> On 20 September 2018 at 13:55, Florian Fainelli <f.fainelli@xxxxxxxxx> wrote: >>> On 09/19/2018 07:19 PM, Ard Biesheuvel wrote: >>>> On 19 September 2018 at 07:31, Jim Quinlan <jim2101024@xxxxxxxxx> wrote: >>>>> The Broadcom STB PCIe host controller is intimately related to the >>>>> memory subsystem. This close relationship adds complexity to how cpu >>>>> system memory is mapped to PCIe memory. Ideally, this mapping is an >>>>> identity mapping, or an identity mapping off by a constant. Not so in >>>>> this case. >>>>> >>>>> Consider the Broadcom reference board BCM97445LCC_4X8 which has 6 GB >>>>> of system memory. Here is how the PCIe controller maps the >>>>> system memory to PCIe memory: >>>>> >>>>> memc0-a@[ 0....3fffffff] <=> pci@[ 0....3fffffff] >>>>> memc0-b@[100000000...13fffffff] <=> pci@[ 40000000....7fffffff] >>>>> memc1-a@[ 40000000....7fffffff] <=> pci@[ 80000000....bfffffff] >>>>> memc1-b@[300000000...33fffffff] <=> pci@[ c0000000....ffffffff] >>>>> memc2-a@[ 80000000....bfffffff] <=> pci@[100000000...13fffffff] >>>>> memc2-b@[c00000000...c3fffffff] <=> pci@[140000000...17fffffff] >>>>> >>>> >>>> So is describing this as >>>> >>>> dma-ranges = <0x0 0x0 0x0 0x0 0x0 0x40000000>, >>>> <0x0 0x40000000 0x1 0x0 0x0 0x40000000>, >>>> <0x0 0x80000000 0x0 0x40000000 0x0 0x40000000>, >>>> <0x0 0xc0000000 0x3 0x0 0x0 0x40000000>, >>>> <0x1 0x0 0x0 0x80000000 0x0 0x40000000>, >>>> <0x1 0x40000000 0x0 0xc0000000 0x0 0x40000000>; >>>> >>>> not working for you? I haven't tried this myself, but since DT permits >>>> describing the inbound mappings this way, we should fix the code if it >>>> doesn't work at the moment. >>> >>> You mean encoding the memory controller index in the first cell? If that >>> works, that's indeed a much cleaner solution, though is it standard >>> compliant in any form? >> >> No those are just memory addresses (although I may have screwed up the >> order). From Documentation/devicetree/booting-without-of.txt: >> >> """ >> Optional property: >> - dma-ranges: <prop-encoded-array> encoded as arbitrary number of triplets of >> (child-bus-address, parent-bus-address, length). Each triplet specified >> describes a contiguous DMA address range. >> """ >> > > Then I am confused by your comment, that's what this patch does, it adds > support for reading "dma-ranges" from Device Tree and setting up inbound > windows using that. The only caveat is that because the PCIe root > complex has some ties with the memory bus architecture it is connected > to (SCB in our case) there is still a requirement to know the > translation between a given physical address and its backing memory > controller/aperture. > Ah ok, apologies for the noise then. I was hoping that having working support for dma-ranges would remove the need for the special phys<->dma conversion routines.
