On 09/20/2018 02:33 PM, Ard Biesheuvel wrote: > 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. What you describe definitively works with platform devices, but I am not sure this is working for PCIe devices, although, conceptually it should, yes. -- Florian
