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SPI

Testing SPI from user space require some changes.

  • Configure your kernel (using "make menuconfig", for example) and make sure the spidev driver (SPI_SPIDEV) is included: Device Drivers -> SPI support -> <*> User mode SPI device driver support
  • Add spidev and pinctrl to your device tree

For VAR-SOM-MX6, edit arch/arm/boot/dts/imx6qdl-var-som.dtsi
For DART-MX6, edit arch/arm/boot/dts/imx6qdl-var-dart.dtsi

&ecspi1 {
    fsl,spi-num-chipselects = <1>;
    cs-gpios = <&gpio4 9 0>;
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_ecspi1_1>;
    status = "okay";

        chip1: spidev@0 {
               compatible = "spidev";
               spi-max-frequency = <12000000>;
               reg = <0>;
        };
/*
        chip2: spidev@1 {
               compatible = "spidev";
               spi-max-frequency = <20000000>;
               reg = <1>;
    };
*/
};

pinctrl_ecspi1_1: ecspi1grp {
    fsl,pins = <
        MX6QDL_PAD_KEY_COL1__ECSPI1_MISO    0x100b1
        MX6QDL_PAD_KEY_ROW0__ECSPI1_MOSI    0x100b1
        MX6QDL_PAD_KEY_COL0__ECSPI1_SCLK    0x100b1
        MX6QDL_PAD_KEY_ROW1__GPIO4_IO09      0x80000000
    >;
};

Choose the right chip select (you can also have multiple chip selects).

  • Continue following the "Customizing the Linux kernel" guide to build the kernel and device trees.
  • For testing use the SPI testing utility in the tools folder of the kernel source tree: tools/spi/spidev_test.c (in older kernels: Documentation/spi/spidev_test.c)