Re: [PATCH v8 0/7] PCI: dwc: opitimaze RC Host/EP pci_fixup_addr()

[Krzysztof Wilczyński]

Hello,

> == RC side:
> 
>             ┌─────────┐                    ┌────────────┐
>  ┌─────┐    │         │ 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
>                                            └────────────┘
> 
> Current dwc implimemnt, pci_fixup_addr() call back is needed when bus
> fabric convert cpu address before send to PCIe controller.
> 
>     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>;
>             ...
>             };
>     };
> 
> Device tree already can descript all address translate. Some hardware
> driver implement fixup function by mask some bits of cpu address. Last
> pci-imx6.c are little bit better by fetch memory resource's offset to do
> fixup.
> 
> static u64 imx_pcie_cpu_addr_fixup(struct dw_pcie *pcie, u64 cpu_addr)
> {
> 	...
> 	entry = resource_list_first_type(&pp->bridge->windows, IORESOURCE_MEM);
> 	return cpu_addr - entry->offset;
> }
> 
> But it is not good by using IORESOURCE_MEM to fix up io/cfg address map
> although address translate is the same as IORESOURCE_MEM.
> 
> This patches to fetch untranslate range information for PCIe controller
> (pcie@5f010000: ranges). So current config ATU without cpu_fixup_addr().
> 
> == EP side:
> 
>                    Endpoint
>   ┌───────────────────────────────────────────────┐
>   │                             pcie-ep@5f010000  │
>   │                             ┌────────────────┐│
>   │                             │   Endpoint     ││
>   │                             │   PCIe         ││
>   │                             │   Controller   ││
>   │           bus@5f000000      │                ││
>   │           ┌──────────┐      │                ││
>   │           │          │ Outbound Transfer     ││
>   │┌─────┐    │  Bus     ┼─────►│ ATU  ──────────┬┬─────►
>   ││     │    │  Fabric  │Bus   │                ││PCI Addr
>   ││ CPU ├───►│          │Addr  │                ││0xA000_0000
>   ││     │CPU │          │0x8000_0000            ││
>   │└─────┘Addr└──────────┘      │                ││
>   │       0x7000_0000           └────────────────┘│
>   └───────────────────────────────────────────────┘
> 
> bus@5f000000 {
>         compatible = "simple-bus";
>         ranges = <0x80000000 0x0 0x70000000 0x10000000>;
> 
>         pcie-ep@5f010000 {
>                 reg = <0x5f010000 0x00010000>,
>                       <0x80000000 0x10000000>;
>                 reg-names = "dbi", "addr_space";
>                 ...                ^^^^
>         };
>         ...
> };
> 
> 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.
> 
> The both pave the road to eliminate ugle cpu_fixup_addr() callback function.

Applied to controller/dwc for v6.14, thank you!

	Krzysztof