[PATCH v5 04/12] PCI: brcmstb: add dma-range mapping for inbound traffic

On 09/19/2018 07:19 PM, Ard Biesheuvel wrote:

On 19 September 2018 at 07:31, Jim Quinlan [off-list ref] wrote:

quoted

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?
-- 
Florian