The NXP i.MX6 CPU has one PCI Express (PCIe) hardware module that can either be configured to act as a root complex or a PCIe endpoint. PCI Express (PCIe) is a third-generation I/O interconnect targeting low-cost, high-volume, multi-platform interconnection.

PCI Express includes the following cores:

  • PCI Express dual mode (DM) core

  • PCI Express root complex (RC) core

  • PCI Express endpoint (EP) core

The Linux BSP only supports the PCIe port acting as root complex.

Kernel configuration

You can manage the PCIe driver support through the kernel configuration option

  • PCI host controller drivers (CONFIG_PCI_IMX6)

This option is enabled as built-in on the ConnectCore 6 Plus SBC kernel configuration file.

Kernel driver

The PCIe bus driver for the ConnectCore 6 Plus is located at drivers/pci/host/pci-imx6.c.

Device tree bindings and customization

The i.MX6 PCIe interface device tree binding is documented at Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt.

The PCIe interface is defined in the i.MX6 CPU, ConnectCore 6 Plus, and ConnectCore 6 Plus SBC device tree files.

Example: PCIe

Definition of the bus

Common ConnectCore 6 Plus device tree
pcie: pcie@0x01000000 {
    compatible = "fsl,imx6q-pcie", "snps,dw-pcie";
    reg = <0x01ffc000 0x04000>,
          <0x01f00000 0x80000>;
    reg-names = "dbi", "config";
    #address-cells = <3>;
    #size-cells = <2>;
    device_type = "pci";
    ranges = <0x00000800 0 0x01f00000 0x01f00000 0 0x00080000 /* configuration space */
          0x81000000 0 0          0x01f80000 0 0x00010000 /* downstream I/O */
          0x82000000 0 0x01000000 0x01000000 0 0x00f00000>; /* non-prefetchable memory */
    num-lanes = <1>;
    interrupts = <GIC_SPI 120 IRQ_TYPE_LEVEL_HIGH>;
    interrupt-names = "msi";
    #interrupt-cells = <1>;
    interrupt-map-mask = <0 0 0 0x7>;
    interrupt-map = <0 0 0 1 &gpc GIC_SPI 123 IRQ_TYPE_LEVEL_HIGH>,
                    <0 0 0 2 &gpc GIC_SPI 122 IRQ_TYPE_LEVEL_HIGH>,
                    <0 0 0 3 &gpc GIC_SPI 121 IRQ_TYPE_LEVEL_HIGH>,
                    <0 0 0 4 &gpc GIC_SPI 120 IRQ_TYPE_LEVEL_HIGH>;
    clocks = <&clks IMX6QDL_CLK_PCIE_AXI>,
         <&clks IMX6QDL_CLK_LVDS1_GATE>,
         <&clks IMX6QDL_CLK_PCIE_REF_125M>;
    clock-names = "pcie", "pcie_bus", "pcie_phy";
    status = "disabled";
};

IOMUX configuration

The ConnectCore 6 Plus SBC assembles a PCIe connector. Three GPIOs of the i.MX6 system-on-chip are routed to the PCIe connector:

  • GPIO1_4: PCIe disable line

  • GPIO7_7: PCIe wake line

  • GPIO7_8: PCIe reset line

The ConnectCore 6 Plus SBC configures the IOMUX for these three GPIOs.

ConnectCore 6 Plus SBC device tree
pcie {
    pinctrl_pcie: pcie {
        fsl,pins = <
            MX6QDL_PAD_SD3_DAT3__GPIO7_IO07 0x80000000
            MX6QDL_PAD_GPIO_4__GPIO1_IO04   0x80000000
            MX6QDL_PAD_SD3_RST__GPIO7_IO08 0x80000000
            MX6QDL_PAD_NANDF_RB0__GPIO6_IO10 0x80000000
        >;
    };
};

Bus enabling and customization

ConnectCore 6 Plus SBC device tree
&pcie {
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_pcie>;
    reset-gpio = <&gpio7 8 GPIO_ACTIVE_HIGH>;
    wake-up-gpio = <&gpio7 7 GPIO_ACTIVE_HIGH>;
    disable-gpio = <&gpio1 4 GPIO_ACTIVE_HIGH>;
    power-on-gpio = <&gpio6 10 GPIO_ACTIVE_HIGH>;
    power-on-delay-ms = <10>;
    vin-supply = <&ldo6>;
};