DESK-MX6-L/Pheripherals/PCI express

History
Version	Issue Date	Notes
1.0.0	Oct 2020	First DESK release

Peripheral PCI express

Device tree configuration

Here below an example of device tree configuration used on standard DAVE's kit for the AXELLite SOM:

From imx6qdl-sbcx-revb-common.dtsi:

&pcie {
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_pci_axel_sbc>;
    reset-gpio = <&gpio5 27 0>;
    wake-up-gpio = <&gpio5 20 0>;
    disable-gpio = <&gpio5 26 0>;
    status = "okay";
};

From imx6qdl-axelcommon.dtsi:

&iomuxc {
...
...
    pcie {
        pinctrl_pci_axel_sbc: pci_grp-1 {
            fsl,pins = <
                MX6QDL_PAD_CSI0_DATA_EN__GPIO5_IO20     0x1b0b0 /* PCIE_WAKE_B */
                MX6QDL_PAD_CSI0_DAT9__GPIO5_IO27        0x1b0b0 /* PCIE_RST_B */
                MX6QDL_PAD_CSI0_DAT8__GPIO5_IO26        0x1b0b0 /* PCIE_DIS_B */
            >;
        };
    };
...
...
};

Accessing the peripheral

Linux messages at boot time

PCIe driver initialized:

...
...
[    0.443763] PCI: CLS 0 bytes, default 64
[    0.459987] imx6q-pcie 1ffc000.pcie: no reserved region node.
[    0.460090] imx6q-pcie 1ffc000.pcie: 1ffc000.pcie supply epdev_on not found, using dummy regulator
[    0.460415] OF: PCI: host bridge /soc/pcie@1ffc000 ranges:
[    0.460451] OF: PCI:    IO 0x01f80000..0x01f8ffff -> 0x00000000
[    0.460470] OF: PCI:   MEM 0x01000000..0x01efffff -> 0x01000000
[    0.709248] imx6q-pcie 1ffc000.pcie: phy link never came up
[    0.712328] imx6q-pcie 1ffc000.pcie: failed to initialize host
[    0.712343] imx6q-pcie 1ffc000.pcie: unable to add pcie port.
[    0.712571] imx6q-pcie: probe of 1ffc000.pcie failed with error -110
...
...
[    2.459055] ehci-pci: EHCI PCI platform driver
...
...

The PCIe usage is strictly related to the peripheral type connected to the PCIe slot. Then, the peripheral type defines the linux commands used for the accessing (hiding the PCIe bus commands)

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