DESK-MX6-L/Peripherals/PCI express

History
Issue Date	Notes
2021/07/16	First DESK-MX6-L release
2022/03/03	DESK-MX6-L 3.0.0 release
2023/04/11	DESK-MX6-L 4.0.0 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:

...
...
[    0.158611] PCI: CLS 0 bytes, default 64
[    0.265640] imx6q-pcie 1ffc000.pcie: supply epdev_on not found, using dummy regulator
[    0.306554] imx6q-pcie 1ffc000.pcie: iATU unroll: disabled
[    0.306566] imx6q-pcie 1ffc000.pcie: Detected iATU regions: 4 outbound, 4 inbound
[    0.306592] imx6q-pcie 1ffc000.pcie: host bridge /soc/pcie@1ffc000 ranges:
[    0.306654] imx6q-pcie 1ffc000.pcie:       IO 0x0001f80000..0x0001f8ffff -> 0x0000000000
[    0.306685] imx6q-pcie 1ffc000.pcie:      MEM 0x0001000000..0x0001efffff -> 0x0001000000
[    0.306809] imx6q-pcie 1ffc000.pcie: iATU unroll: disabled
[    0.306819] imx6q-pcie 1ffc000.pcie: Detected iATU regions: 4 outbound, 4 inbound
[    0.405002] imx6q-pcie 1ffc000.pcie: Link up
[    0.405013] imx6q-pcie 1ffc000.pcie: Link: Gen2 disabled
[    0.405022] imx6q-pcie 1ffc000.pcie: Link up, Gen1
[    0.528786] imx6q-pcie 1ffc000.pcie: Link up
[    0.528968] imx6q-pcie 1ffc000.pcie: PCI host bridge to bus 0000:00
...
...
[    3.472568] 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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