On Tue, Nov 19, 2024 at 02:44:20PM -0500, Frank Li wrote:
> parent_bus_addr in struct of_range can indicate address information just
> ahead of PCIe controller. Most system's bus fabric use 1:1 map between
> input and output address. but some hardware like i.MX8QXP doesn't use 1:1
> map. See below diagram:
>
> ┌─────────┐ ┌────────────┐
> ┌─────┐ │ │ 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>;
> ...
> };
> };
>
> Term internal address (IA) here means the address just before PCIe
> controller. After ATU use this IA instead CPU address, cpu_addr_fixup() can
> be removed.
> @@ -730,9 +779,15 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
>
> atu.index = i;
> atu.type = PCIE_ATU_TYPE_MEM;
> - atu.cpu_addr = entry->res->start;
> + parent_bus_addr = entry->res->start;
> atu.pci_addr = entry->res->start - entry->offset;
>
> + ret = dw_pcie_get_parent_addr(pci, entry->res->start, &parent_bus_addr);
> + if (ret)
> + return ret;
> +
> + atu.cpu_addr = parent_bus_addr;
Here you set atu.cpu_addr to the intermediate bus address instead
of the CPU physical address before calling
dw_pcie_prog_outbound_atu().
But what about other callers of dw_pcie_prog_outbound_atu()? Don't
all of them need to use the intermediate bus address?
Maybe struct dw_pcie_ob_atu_cfg.cpu_addr should be renamed since it is
not necessarily a CPU physical address?
> + if (pci->ops && pci->ops->cpu_addr_fixup) {
> + /*
> + * If the parent 'ranges' property in DT correctly describes
> + * the address translation, cpu_addr_fixup() callback is not
> + * needed.
> + */
> + dev_warn_once(pci->dev, "cpu_addr_fixup() usage detected. Please fix DT!\n");
> + }
I kinda wish this warning were in a separate patch because it will be
a little cleaner if we ever want to revert or remove the warning.
