Changes between Version 17 and Version 18 of SPI


Ignore:
Timestamp:
11/16/2021 05:37:33 PM (13 months ago)
Author:
Tim Harvey
Comment:

added additional board examples for spidev dt configuration

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  • SPI

    v17 v18  
    169169Userspace access to SPI devices is done through the /dev/spidev<bus>.<chip-select> device interface. In order to use this you must have spidev enabled in the kernel (CONFIG_SPI_SPIDEV) and have a spidev node defined under the SPI controller in the device-tree.
    170170
    171 In order to support {{{spidev}}} a spidev child node needs to be present in the device-tree under the SPI host controller. For example, a GW54xx which brings out the ecspi2 host interface:
     171In order to support {{{spidev}}} a spidev child node needs to be present in the device-tree under the SPI host controller.
     172
     173Examples:
     174 * Venice:
     175  - GW71xx (imx8mm-venice-gw71xx.dtsi), GW72xx (imx8mm-venice-gw72xx.dtsi), and GW73xx (imx8mm-venice-gw73xx.dtsi) all provide ecspi2 to an off-board connector with GPIO5_IO13 as a chip select:
     176{{{#!c
     177/* off-board header */
     178&ecspi2 {
     179        pinctrl-names = "default";
     180        pinctrl-0 = <&pinctrl_spi2>;
     181        cs-gpios = <&gpio5 13 GPIO_ACTIVE_LOW>;
     182        status = "okay";
     183
     184        /*
     185         * SPI_CS0 goes to the off-board connector
     186         * compatible must match a string from drivers/spi/spidev.c's compatible list
     187         */
     188        spidev0: spidev0@0 {
     189                compatible = "rohm,dh2228fv";
     190                reg = <0>;
     191                spi-max-frequency = <10000000>;
     192        };
     193};
     194}}}
     195 * Newport:
     196  - GW620x/GW630x/GW640x which has a single SPI controller with 2 chip selects, with CS0 going to an off-board connector and CS1 used for a CAN controller (loaded on GW6204/GW6304/GW6404 boards). Change dts/gw620x-linux.dtsi, dts/gw630x-linux.dtsi dts/gw640x-linux.dtsi to:
     197{{{#!c
     198&spi_7_0 {
     199        /*
     200         * SPI_CS0 goes to the off-board connector
     201         * compatible must match a string from drivers/spi/spidev.c's compatible list
     202         */
     203        spidev0: spidev0@0 {
     204                compatible = "rohm,dh2228fv";
     205                reg = <0>;
     206                spi-max-frequency = <10000000>;
     207        };
     208
     209        /*
     210         * SPI_CS1 goes to the Microchip MCP2515 CAN controller (GW6204/GW6304/GW6404)
     211         */
     212        can0: can@1 {
     213                compatible = "microchip,mcp2515","linux,spidev";
     214                reg = <1>;
     215                clocks = <&can20m>;
     216                oscillator-frequency = <20000000>;
     217                interrupt-parent = <&gpio_6_0>;
     218                interrupts = <5 0x8>; /* IRQ_TYPE_LEVEL_LOW */
     219                spi-max-frequency = <10000000>;
     220        };
     221};
     222}}}
     223  - GW610x which has a single SPI controller with 2 chip selects, with CS0 going to an off-board connector. Change dts/gw610x-linux.dtsi to add the following at the end:
     224{{{#!c
     225&spi_7_0 {
     226        /*
     227         * SPI_CS0 goes to the off-board connector
     228         * compatible must match a string from drivers/spi/spidev.c's compatible list
     229         */
     230        spidev0: spidev0@0 {
     231                compatible = "rohm,dh2228fv";
     232                reg = <0>;
     233                spi-max-frequency = <10000000>;
     234        };
     235};
     236}}}
     237 * Ventana:
     238  - GW54xx (arch/arm/boot/dts/imx6qdl-gw52xx.dtsi) which brings out the ecspi2 host interface to an off-board connector with GPIO2_IO26 as a chip select:
    172239{{{#!c
    173240&ecspi2 {
     
    184251};
    185252}}}
     253  - GW52xx (arch/arm/boot/dts/imx6qdl-gw53xx.dtsi) which brings out the ecspi3 host interface to an off-board connector with GPIO4_IO24 as a chip select:
     254{{{#!c
     255&ecspi3 {
     256        cs-gpios = <&gpio4 24 GPIO_ACTIVE_HIGH>;
     257        pinctrl-names = "default";
     258        pinctrl-0 = <&pinctrl_ecspi3>;
     259        status = "okay";
     260
     261        spidev0: spidev@0 {
     262                compatible = "rohm,dh2228fv";
     263                reg = <0>;
     264                spi-max-frequency = <60000000>;
     265        };
     266};
     267}}}
     268
     269In the above examples, adjust 'spi-max-frequency' according to the max frequency your slave device can support.
    186270
    187271For instructions on compiling and updating a device-tree see [wiki:linux/devicetree linux/devicetree]