[PATCH v2 0/4] PCI: ep: dwc/imx6: Add bus address support for PCI endpoint devices

[Frank Li]

Endpoint          Root complex
                             ┌───────┐        ┌─────────┐
               ┌─────┐       │ EP    │        │         │      ┌─────┐
               │     │       │ Ctrl  │        │         │      │ CPU │
               │ DDR │       │       │        │ ┌────┐  │      └──┬──┘
               │     │◄──────┼─ATU ◄─┼────────┼─┤BarN│◄─┼─────────┘
               │     │       │       │        │ └────┘  │ Outbound Transfer
               └─────┘       │       │        │         │
                             │       │        │         │
                             │       │        │         │
                             │       │        │         │ Inbound Transfer
                             │       │        │         │      ┌──▼──┐
              ┌───────┐      │       │        │ ┌───────┼─────►│DDR  │
              │       │ outbound Transfer*    │ │       │      └─────┘
   ┌─────┐    │ Bus   ┼─────►│ ATU  ─┬────────┼─┘       │
   │     │    │ Fabric│Bus   │       │ PCI Addr         │
   │ CPU ├───►│       │Addr  │       │ 0xA000_0000      │
   │     │CPU │       │0x8000_0000   │        │         │
   └─────┘Addr└───────┘      │       │        │         │
          0x7000_0000        └───────┘        └─────────┘

Add `bus_addr_base` to configure the outbound window address for CPU write.
The BUS fabric generally passes the same address to the PCIe EP controller,
but some BUS fabrics convert the address before sending it to the PCIe EP
controller.

Above diagram, CPU write data to outbound windows address 0x7000_0000,
Bus fabric convert it to 0x8000_0000. ATU should use BUS address
0x8000_0000 as input address and convert to PCI address 0xA000_0000.

Previously, `cpu_addr_fixup()` was used to handle address conversion. Now,
the device tree provides this information, preferring a common method.

bus at 5f000000 {
	compatible = "simple-bus";
	ranges = <0x5f000000 0x0 0x5f000000 0x21000000>,
		 <0x80000000 0x0 0x70000000 0x10000000>;

	pcie-ep at 5f010000 {
		reg = <0x5f010000 0x00010000>,
		      <0x80000000 0x10000000>;
		reg-names = "dbi", "addr_space";
		...
	};
	...
};

'ranges' in bus at 5f000000 descript how address convert from CPU address
to BUS address.

Use `of_property_read_reg()` to obtain the BUS address and set it to the
ATU correctly, eliminating the need for vendor-specific cpu_addr_fixup().

The 1st patch implement above method in dwc common driver.
The 2nd patch update imx6's binding doc to add fsl,imx8q-pcie-ep.
The 3rd patch fix a pci-mx6's a bug
The 4th patch enable pci ep function.

The imx8q's dts is usptreaming, the pcie-ep part is below.

hsio_subsys: bus at 5f000000 {
        compatible = "simple-bus";
        #address-cells = <1>;
        #size-cells = <1>;
        /* Only supports up to 32bits DMA, map all possible DDR as inbound ranges */
        dma-ranges = <0x80000000 0 0x80000000 0x80000000>;
        ranges = <0x5f000000 0x0 0x5f000000 0x21000000>,
                 <0x80000000 0x0 0x70000000 0x10000000>;

	pcieb_ep: pcie-ep at 5f010000 {
                compatible = "fsl,imx8q-pcie-ep";
                reg = <0x5f010000 0x00010000>,
                      <0x80000000 0x10000000>;
                reg-names = "dbi", "addr_space";
                num-lanes = <1>;
                interrupts = <GIC_SPI 104 IRQ_TYPE_LEVEL_HIGH>;
                interrupt-names = "dma";
                clocks = <&pcieb_lpcg IMX_LPCG_CLK_6>,
                         <&pcieb_lpcg IMX_LPCG_CLK_4>,
                         <&pcieb_lpcg IMX_LPCG_CLK_5>;
                clock-names = "dbi", "mstr", "slv";
                power-domains = <&pd IMX_SC_R_PCIE_B>;
                fsl,max-link-speed = <3>;
                num-ib-windows = <6>;
                num-ob-windows = <6>;
        };
};

Signed-off-by: Frank Li <Frank.Li at nxp.com>
---
Changes in v2:
- Totally rewrite with difference method. 'range' should in bus node
instead pcie-ep node because address convert happen at bus fabric. Needn't
add 'range' property at pci-ep node.
- Link to v1: https://lore.kernel.org/r/20240919-pcie_ep_range-v1-0-b3e9d62780b7@nxp.com

---
Frank Li (4):
      PCI: dwc: ep: Add bus_addr_base for outbound window
      dt-bindings: PCI: fsl,imx6q-pcie-ep: Add compatible string fsl,imx8q-pcie-ep
      PCI: imx6: Pass correct sub mode when calling phy_set_mode_ext()
      PCI: imx6: Add i.MX8Q PCIe Endpoint (EP) support

 .../devicetree/bindings/pci/fsl,imx6q-pcie-ep.yaml | 38 +++++++++++++++++++++-
 drivers/pci/controller/dwc/pci-imx6.c              | 24 +++++++++++++-
 drivers/pci/controller/dwc/pcie-designware-ep.c    | 12 ++++++-
 drivers/pci/controller/dwc/pcie-designware.h       |  1 +
 4 files changed, 72 insertions(+), 3 deletions(-)
---
base-commit: 4ed76e3b7438dd6e3d9b11d6a4cb853a350ec407
change-id: 20240918-pcie_ep_range-4c5c5e300e19

Best regards,
---
Frank Li <Frank.Li at nxp.com>