of: address: Add parent_bus_addr to struct of_pci_range

Add a new field called 'parent_bus_addr' to struct of_pci_range to use
when retrieving parent bus address information.

Refer to the diagram below to better understand that the bus fabric in
some systems (like i.MX8QXP) does not always use a 1:1 address map
between input and output.

Currently, many controller drivers use the cpu_addr_fixup() callback
that would often hardcode address translation directly in the code, e.g.,
"cpu_addr & CDNS_PLAT_CPU_TO_BUS_ADDR" or "cpu_addr + BUS_IATU_OFFSET",
etc., even though those translations *should* be described via DT.

However, the cpu_addr_fixup() can be eliminated if DT correctly reflects
hardware behavior and drivers use 'parent_bus_addr' in struct of_pci_range.

            ┌─────────┐                    ┌────────────┐
 ┌─────┐    │         │ IA: 0x8ff8_0000    │            │
 │ CPU ├───►│   ┌────►├─────────────────┐  │ PCI        │
 └─────┘    │   │     │ IA: 0x8ff0_0000 │  │            │
  CPU Addr  │   │  ┌─►├─────────────┐   │  │ Controller │
0x7ff8_0000─┼───┘  │  │             │   │  │            │
            │      │  │             │   │  │            │   PCI Addr
0x7ff0_0000─┼──────┘  │             │   └──► IOSpace   ─┼────────────►
            │         │             │      │            │    0
0x7000_0000─┼────────►├─────────┐   │      │            │
            └─────────┘         │   └──────► CfgSpace  ─┼────────────►
             BUS Fabric         │          │            │    0
                                │          │            │
                                └──────────► MemSpace  ─┼────────────►
                        IA: 0x8000_0000    │            │  0x8000_0000
                                           └────────────┘

bus@5f000000 {
        compatible = "simple-bus";
        #address-cells = <1>;
        #size-cells = <1>;
        ranges = <0x80000000 0x0 0x70000000 0x10000000>;

        pcie@5f010000 {
                compatible = "fsl,imx8q-pcie";
                reg = <0x5f010000 0x10000>, <0x8ff00000 0x80000>;
                reg-names = "dbi", "config";
                #address-cells = <3>;
                #size-cells = <2>;
                device_type = "pci";
                bus-range = <0x00 0xff>;
                ranges = <0x81000000 0 0x00000000 0x8ff80000 0 0x00010000>,
                         <0x82000000 0 0x80000000 0x80000000 0 0x0ff00000>;
	...
	};
};

In the diagram above, the 'parent_bus_addr' field in struct of_pci_range
can indicate internal address (IA) address information.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Frank Li <[email protected]>
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Rob Herring (Arm) <[email protected]>
Acked-by: Manivannan Sadhasivam <[email protected]>

0 files changed, 0 insertions, 0 deletions