dt-bindings: PCI: dwc: Add Baikal-T1 PCIe Root Port bindings

Baikal-T1 SoC is equipped with DWC PCIe v4.60a Root Port controller, which
link can be trained to work on up to Gen.3 speed over up to x4 lanes. The
controller is supposed to be fed up with four clock sources: DBI
peripheral clock, AXI application Tx/Rx clocks and external PHY/core
reference clock generating the 100MHz signal. In addition to that the
platform provide a way to reset each part of the controller:
sticky/non-sticky bits, host controller core, PIPE interface, PCS/PHY and
Hot/Power reset signal. The Root Port controller is equipped with multiple
IRQ lines like MSI, system AER, PME, HP, Bandwidth change, Link
equalization request and eDMA ones. The registers space is accessed over
the DBI interface. There can be no more than four inbound or outbound iATU
windows configured.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Serge Semin <[e-mail]>
Signed-off-by: Lorenzo Pieralisi <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/pci/baikal,bt1-pcie.yaml

···
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pci/baikal,bt1-pcie.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Baikal-T1 PCIe Root Port Controller
+
+maintainers:
+  - Serge Semin <[e-mail]>
+
+description:
+  Embedded into Baikal-T1 SoC Root Complex controller with a single port
+  activated. It's based on the DWC RC PCIe v4.60a IP-core, which is configured
+  to have just a single Root Port function and is capable of establishing the
+  link up to Gen.3 speed on x4 lanes. It doesn't have embedded clock and reset
+  control module, so the proper interface initialization is supposed to be
+  performed by software. There four in- and four outbound iATU regions
+  which can be used to emit all required TLP types on the PCIe bus.
+
+allOf:
+  - $ref: /schemas/pci/snps,dw-pcie.yaml#
+
+properties:
+  compatible:
+    const: baikal,bt1-pcie
+
+  reg:
+    description:
+      DBI, DBI2 and at least 4KB outbound iATU-capable region for the
+      peripheral devices CFG-space access.
+    maxItems: 3
+
+  reg-names:
+    items:
+      - const: dbi
+      - const: dbi2
+      - const: config
+
+  interrupts:
+    description:
+      MSI, AER, PME, Hot-plug, Link Bandwidth Management, Link Equalization
+      request and eight Read/Write eDMA IRQ lines are available.
+    maxItems: 14
+
+  interrupt-names:
+    items:
+      - const: dma0
+      - const: dma1
+      - const: dma2
+      - const: dma3
+      - const: dma4
+      - const: dma5
+      - const: dma6
+      - const: dma7
+      - const: msi
+      - const: aer
+      - const: pme
+      - const: hp
+      - const: bw_mg
+      - const: l_eq
+
+  clocks:
+    description:
+      DBI (attached to the APB bus), AXI-bus master and slave interfaces
+      are fed up by the dedicated application clocks. A common reference
+      clock signal is supposed to be attached to the corresponding Ref-pad
+      of the SoC. It will be redistributed amongst the controller core
+      sub-modules (pipe, core, aux, etc).
+    maxItems: 4
+
+  clock-names:
+    items:
+      - const: dbi
+      - const: mstr
+      - const: slv
+      - const: ref
+
+  resets:
+    description:
+      A comprehensive controller reset logic is supposed to be implemented
+      by software, so almost all the possible application and core reset
+      signals are exposed via the system CCU module.
+    maxItems: 9
+
+  reset-names:
+    items:
+      - const: mstr
+      - const: slv
+      - const: pwr
+      - const: hot
+      - const: phy
+      - const: core
+      - const: pipe
+      - const: sticky
+      - const: non-sticky
+
+  baikal,bt1-syscon:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      Phandle to the Baikal-T1 System Controller DT node. It's required to
+      access some additional PM, Reset-related and LTSSM signals.
+
+  num-lanes:
+    maximum: 4
+
+  max-link-speed:
+    maximum: 3
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - interrupts
+  - interrupt-names
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/mips-gic.h>
+    #include <dt-bindings/gpio/gpio.h>
+
+    pcie@1f052000 {
+      compatible = "baikal,bt1-pcie";
+      device_type = "pci";
+      reg = <0x1f052000 0x1000>, <0x1f053000 0x1000>, <0x1bdbf000 0x1000>;
+      reg-names = "dbi", "dbi2", "config";
+      #address-cells = <3>;
+      #size-cells = <2>;
+      ranges = <0x81000000 0 0x00000000 0x1bdb0000 0 0x00008000>,
+               <0x82000000 0 0x20000000 0x08000000 0 0x13db0000>;
+      bus-range = <0x0 0xff>;
+
+      interrupts = <GIC_SHARED 80 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 81 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 82 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 83 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 84 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 85 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 86 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 87 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 88 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 89 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 90 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 91 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 92 IRQ_TYPE_LEVEL_HIGH>,
+                   <GIC_SHARED 93 IRQ_TYPE_LEVEL_HIGH>;
+      interrupt-names = "dma0", "dma1", "dma2", "dma3",
+                        "dma4", "dma5", "dma6", "dma7",
+                        "msi", "aer", "pme", "hp", "bw_mg",
+                        "l_eq";
+
+      clocks = <&ccu_sys 1>, <&ccu_axi 6>, <&ccu_axi 7>, <&clk_pcie>;
+      clock-names = "dbi", "mstr", "slv", "ref";
+
+      resets = <&ccu_axi 6>, <&ccu_axi 7>, <&ccu_sys 7>, <&ccu_sys 10>,
+               <&ccu_sys 4>, <&ccu_sys 6>, <&ccu_sys 5>, <&ccu_sys 8>,
+               <&ccu_sys 9>;
+      reset-names = "mstr", "slv", "pwr", "hot", "phy", "core", "pipe",
+                    "sticky", "non-sticky";
+
+      reset-gpios = <&port0 0 GPIO_ACTIVE_LOW>;
+
+      num-lanes = <4>;
+      max-link-speed = <3>;
+    };
+...