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  • devicetree -- SPI

    SPI (Serial Peripheral Interface) busses

    SPI busses can be described with a node for the SPI master device
    and a set of child nodes for each SPI slave on the bus.  For this
    discussion, it is assumed that the system's SPI controller is in
    SPI master mode.  This binding does not describe SPI controllers
    in slave mode.

    The SPI master node requires the following properties:
    - #address-cells  - number of cells required to define a chip select
                address on the SPI bus.
    - #size-cells     - should be zero.
    - compatible      - name of SPI bus controller following generic names
                recommended practice.
    - cs-gpios      - (optional) gpios chip select.
    No other properties are required in the SPI bus node.  It is assumed
    that a driver for an SPI bus device will understand that it is an SPI bus.
    However, the binding does not attempt to define the specific method for
    assigning chip select numbers.  Since SPI chip select configuration is
    flexible and non-standardized, it is left out of this binding with the
    assumption that board specific platform code will be used to manage
    chip selects.  Individual drivers can define additional properties to
    support describing the chip select layout.

    Optional property:
    - num-cs : total number of chipselects

    If cs-gpios is used the number of chip select will automatically increased
    with max(cs-gpios > hw cs)

    So if for example the controller has 2 CS lines, and the cs-gpios
    property looks like this:

    cs-gpios = <&gpio1 0 0> <0> <&gpio1 1 0> <&gpio1 2 0>;

    Then it should be configured so that num_chipselect = 4 with the
    following mapping:

    cs0 : &gpio1 0 0
    cs1 : native
    cs2 : &gpio1 1 0
    cs3 : &gpio1 2 0

    SPI slave nodes must be children of the SPI master node and can
    contain the following properties.
    - reg             - (required) chip select address of device.
    - compatible      - (required) name of SPI device following generic names
                recommended practice
    - spi-max-frequency - (required) Maximum SPI clocking speed of device in Hz
    - spi-cpol        - (optional) Empty property indicating device requires
                inverse clock polarity (CPOL) mode
    - spi-cpha        - (optional) Empty property indicating device requires
                shifted clock phase (CPHA) mode
    - spi-cs-high     - (optional) Empty property indicating device requires
                chip select active high
    - spi-3wire       - (optional) Empty property indicating device requires
                    3-wire mode.

    If a gpio chipselect is used for the SPI slave the gpio number will be passed
    via the cs_gpio

    SPI example for an MPC5200 SPI bus:
        spi@f00 {
            #address-cells = <1>;
            #size-cells = <0>;
            compatible = "fsl,mpc5200b-spi","fsl,mpc5200-spi";
            reg = <0xf00 0x20>;
            interrupts = <2 13 0 2 14 0>;
            interrupt-parent = <&mpc5200_pic>;

            ethernet-switch@0 {
                compatible = "micrel,ks8995m";
                spi-max-frequency = <1000000>;
                reg = <0>;
            };

            codec@1 {
                compatible = "ti,tlv320aic26";
                spi-max-frequency = <100000>;
                reg = <1>;
            };
        };

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  • 原文地址:https://www.cnblogs.com/zym0805/p/4277208.html
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