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0045_SoC_Device_Tree.md

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SoC Device Tree

proc file

  • cat /proc/device-tree/compatible 
    raspberrypi,4-model-bbrcm,bcm2838
  • cat /proc/device-tree/model 
    Raspberry Pi 4 Model B Rev 1.1r

compile dts

  • KERNEL=kernel7l
  • make bcm2711_defconfig
  • make -j4 dtbs
  • sudo cp arch/arm/boot/dts/bcm2711-rpi-4-b.dtb /boot/bcm2711-rpi-4-b.dtb

default dts

  • cat arch/arm64/boot/dts/broadcom/bcm2711-rpi-4-b.dts 
    #define RPI364

#include "../../../../arm/boot/dts/bcm2711-rpi-4-b.dts"
  • cat arch/arm/boot/dts/bcm2711-rpi-4-b.dts 
    /dts-v1/;

#include "bcm2711.dtsi"
#include "bcm2711-rpi.dtsi"
#include "bcm283x-rpi-csi1-2lane.dtsi"

/ {
    compatible = "raspberrypi,4-model-b", "brcm,bcm2838";
    model = "Raspberry Pi 4 Model B";

    memory {
        device_type = "memory";
        reg = <0x0 0x0 0x0>;
    };

    chosen {
        bootargs = "coherent_pool=1M 8250.nr_uarts=1 cma=64M zengjf ";
    };

    aliases {
        serial0 = &uart1;
        serial1 = &uart0;
        mmc0 = &emmc2;
        mmc1 = &mmcnr;
        mmc2 = &sdhost;
        i2c3 = &i2c3;
        i2c4 = &i2c4;
        i2c5 = &i2c5;
        i2c6 = &i2c6;
        /delete-property/ ethernet;
        /delete-property/ intc;
        ethernet0 = &genet;
    };
};

[...省略]
  • 添加zengjf节点进行调试确认 
    /dts-v1/;

#include "bcm2711.dtsi"
#include "bcm2711-rpi.dtsi"
#include "bcm283x-rpi-csi1-2lane.dtsi"

/ {
    compatible = "raspberrypi,4-model-b", "brcm,bcm2838";
    model = "Raspberry Pi zengjf 4 Model B ";

    memory {
        device_type = "memory";
        reg = <0x0 0x0 0x0>;
    };

    zengjf{                           /* 添加节点 */
        name = "zengjf";
    };

    chosen {
        bootargs = "coherent_pool=1M 8250.nr_uarts=1 cma=64M";
    };

    aliases {
        serial0 = &uart1;
        serial1 = &uart0;
        mmc0 = &emmc2;
        mmc1 = &mmcnr;
        mmc2 = &sdhost;
        i2c3 = &i2c3;
        i2c4 = &i2c4;
        i2c5 = &i2c5;
        i2c6 = &i2c6;
        /delete-property/ ethernet;
        /delete-property/ intc;
        ethernet0 = &genet;
    };
};
  • ls /proc/device-tree 
    '#address-cells'   fixedregulator_3v3   name            __symbols__
 aliases           fixedregulator_5v0   __overrides__   system
 arm-pmu           hat                  phy             thermal-zones
 axi               interrupt-parent     scb             timer
 chosen            leds                 sd_io_1v8_reg   v3dbus
 clocks            memory               serial-number   zengjf   <--------添加的节点
 compatible        memreserve          '#size-cells'
 cpus              model                soc
  • cat /proc/cmdline 
    coherent_pool=1M 8250.nr_uarts=0 cma=64M zengjf  bcm2708_fb.fbwidth=1280 bcm2708_fb.fbheight=720 bcm2708_fb.fbswap=1 smsc95xx.macaddr=DC:A6:32:17:47:91 vc_mem.mem_base=0x3ec00000 vc_mem.mem_size=0x40000000  dwc_otg.lpm_enable=1 console=ttyS0,115200 console=tty1 root=PARTUUID=48597d87-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait quiet splash plymouth.ignore-serial-consoles modules-load=dwc2,g_ether

i2c1 dts

  • i2c1控制器注册
    • bcm2711-rpi-4-b.dts
      • bcm2711.dtsi
        • bcm2838.dtsi
          • bcm283x.dtsi 
            i2c1: i2c@7e804000 {
    compatible = "brcm,bcm2835-i2c";
    reg = <0x7e804000 0x1000>;
    interrupts = <2 21>;
    clocks = <&clocks BCM2835_CLOCK_VPU>;
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};
  • 添加默认设备，默认是没有添加设备的
    • bcm2711-rpi-4-b.dts
      • bcm2711-rpi.dtsi
        • bcm2708-rpi.dtsi 
          &i2c1 {
    status = "disabled";

    eeprom@50 {
        compatible = "24c02";
        reg = <0x50>;
        status = "okay";
    };
};
  • 编译拷贝覆盖boot分区dts：sudo cp arch/arm/boot/dts/bcm2711-rpi-4-b.dtb /boot/bcm2711-rpi-4-b.dtb
  • 运行时查看设备树情况 
    root@raspberrypi:/proc/device-tree/soc/i2c@7e804000# pwd
/proc/device-tree/soc/i2c@7e804000
root@raspberrypi:/proc/device-tree/soc/i2c@7e804000# ls
'#address-cells'   eeprom@50         lsm9ds1-accel6a   pinctrl-0      '#size-cells'
 clock-frequency   hts221-humid@5f   lsm9ds1-magn@1c   pinctrl-names   status
 clocks            interrupts        name              reg
 compatible        lps25h-press@5c   phandle           rpi-sense@46

overrides

  • "bcm2708-rpi.dtsi"
    • "bcm2711-rpi.dtsi"
      • "bcm2708-rpi.dtsi" 
        __overrides__ {
    cache_line_size;

    uart0 = <&uart0>,"status";
    uart1 = <&uart1>,"status";
    i2s = <&i2s>,"status";
    spi = <&spi0>,"status";
    i2c0 = <&i2c0>,"status";
    i2c1 = <&i2c1>,"status";
    i2c2_iknowwhatimdoing = <&i2c2>,"status";
    i2c0_baudrate = <&i2c0>,"clock-frequency:0";
    i2c1_baudrate = <&i2c1>,"clock-frequency:0";
    i2c2_baudrate = <&i2c2>,"clock-frequency:0";

    audio = <&audio>,"status";
    watchdog = <&watchdog>,"status";
    random = <&random>,"status";
    sd_overclock = <&sdhost>,"brcm,overclock-50:0";
    sd_force_pio = <&sdhost>,"brcm,force-pio?";
    sd_pio_limit = <&sdhost>,"brcm,pio-limit:0";
    sd_debug     = <&sdhost>,"brcm,debug";
    sdio_overclock = <&mmc>,"brcm,overclock-50:0",
             <&mmcnr>,"brcm,overclock-50:0";
    axiperf      = <&axiperf>,"status";
};
  • What does raspi-config do when you enable i2c?: /boot/config.txt 
    # Uncomment some or all of these to enable the optional hardware interfaces
dtparam=i2c_arm=on
#dtparam=i2s=on
dtparam=spi=on
  • cat /proc/device-tree/soc/i2c@7e804000/status 
    okay
  • https://github.com/raspberrypi/userland
    • host_applications/linux/apps/dtoverlay
      • dtoverlay是覆盖整体dts；
      • dtparam主要是处理__overrides__中的部分；
    • Linux Kenrel Driver: OF_CONFIGFS