linux kernel - How to read STD_LOGIC_VECTOR from SPI Bus

Question

I am working on a custom PCBA and attempting to figure out how to read a defined value from the CPLD from Linux. I have an SPI bus connected between an AM335x processor and a MAX V CPLD, wherein the following is defined within the CPLD:

version : STD_LOGIC_VECTOR := x"0100");     --data width in bits
COMPONENT spi_slave
    GENERIC ( cpol : STD_LOGIC := '0'; cpha : STD_LOGIC := '1'; d_width : INTEGER := 16 );
    PORT
    (
        data        :    IN STD_LOGIC_VECTOR(d_width-1 DOWNTO 0);
        sclk        :    IN STD_LOGIC;
        ss_n        :    IN STD_LOGIC;
        mosi        :    IN STD_LOGIC;
        miso        :    OUT STD_LOGIC
    );
END COMPONENT;

And the following is the configuration in the device tree:

spi@481a0000 {
    compatible = "ti, omap4-mcspi;
    #address-cells = <0x1>;
    #size-cells = <0x0>;
    reg = <0x481a0000 0x400>;
    interrupts = <0x7d>;
    ti, spi-num-cs = <0x2>;
    ti, hwmods = "spi1";
    dmas = <0x2c 0x2a 0x0 0x2c 0x2b 0x0 0x2c 0x2c 0x0 0x2c 0x2d 0x0>;
    dma-names = "tx0", "rx0", "tx1", "rx1";
    status = "okay";
    pinctrl-names = "default";
    pinctrl-0 = <0x3c>;
    ti,pindir-d0-out-d1-in;

    cpld_spidev@0 {
        status = "okay";
        compatible = "linux,spidev";
        spi-max-frequency = <0xf4240>;
        reg = <0x0>;
     };
 };

I have been able to send messages to spidev0.0, but most of what I have been getting back is garbage. How do I get 0x0100 back from the SPI slave?

question from:https://stackoverflow.com/questions/65848327/how-to-read-std-logic-vector-from-spi-bus

Answer 1

Waitting for answers