设备树DTS 学习：2-设备树语法

四、设备树语法

1.节点node

节点名称：每个节点必须有一个“ <名称> [@ <设备地址> ]”形式的名字：
<名称> 就是一个不超过31位的简单 ascii 字符串，节点的命名应该根据它所体现的是什么样的设备。
<设备地址> 用来访问该设备的主地址，并且该地址也在节点的 reg 属性中列出，同级节点命名必须是唯一的，但只要地址不同，多个节点也可以使用一样的通用名称，当然设备地址也是可选的，可以有也可以没有
树中每个表示一个设备的节点都需要一个 compatible 属性

1）节点名称name

name描述设备类型，比如网口宜用ethernet；如果有地址，则用@指定地址

<name>[@<unit-address>]

举例：

cpus {}
serial@101F2000 { }
ethernet@0,0 {}

2.属性property

简单的键－值对，它的值可以为空或者包含一个任意字节流。虽然数据类型并没有编码进数据结构，但在设备树源文件中任有几个基本的

数据表示形式

:
- 文本字符串（无结束符）可以用双引号表示：
  string-property = "a string"
- Cells是 32 位无符号整数，用尖括号限定：
  cell-property = <0xbeef 123 0xabcd1234>
- 二进制数据用方括号限定：
  binary-property = [01 23 45 67];
- 不同表示形式的数据可以使用逗号连在一起：
  mixed-property = "a string", [01 23 45 67], <0x12345678>;
- 逗号也可用于创建字符串列表：
  string-list = "red fish", "blue fish";

1）compatible属性

指定了系统的名称，是一个字符串列表，它包含了一个“ <制造商> , <型号> ”形式的字符串。重要的是要指定一个确切的设备，并且包括制造商的名字，以避免命名空间冲突。

compatible = "<manufacturer>,<model>" [, "model"]
#manufacturer指定厂家名，model指定特定设备型号，后续的model指定兼容的设备型号。

对应到具体的驱动文件定义的设备，如spidev 对应于openwrt/build_dir/target-mipsel_24kc_glibc-2.24/linux-ramips_mt7688/linux-4.4.167/drivers/spi/spidev.c的spidev_spi_driver的name。

举例：

compatible = "smc, smc91c11";
compatible = "samsung,k8f1315ebm", "cfi-flash";

2）#address-cells和#size-cells属性

#address-cells = <1>: 基地址、片选号等绝对起始地址所占字长，单位uint32
#size-cells = <1>: 长度所占字长，单位uint32

external-bus {  
    #address-cells = <2>  
    #size-cells = <1>;  

    ethernet@0,0 {  
        compatible = "smc,smc91c111";  
        reg = <0 0 0x1000>;   // 地址占两个cells， 长度占1个cells
        nterrupts = < 5 2 >;  
     };  
}

3）reg属性

reg = ...: addr表明基址，len表明长度，addr由#address-cells个uint32值组成，len由#size-cells个uint32值组成。表明了设备使用的一个地址范围。

/{
compatible = "acme,coyotes-revenge";
#address-cells = <1>;
#size-cells = <1>;
serial@101f2000 {  
        compatible = "arm,pl011";  
        reg = <0x101f2000 0x1000 >;  

    interrupts = < 2 0 >;  
    };
｝

4）中断属性

interrupt-parent - 设备结点透过它来指定它所依附的中断控制器的phandle，当结点没有指定interrupt-parent时，则从父级结点继承。
interrupt-controller - 一个空的属性定义该节点作为一个接收中断信号的设备
#interrupt-cells - 表明连接此中断控制器的设备的interrupts属性的cell大小（个数）
interrupts - 一个中断指示符的列表，对应于该设备上的每个中断输出信号，在ARM GIC中：
- 当#interrupt-cells为3时，interrupts包含三个cells，如interrupts = <0 168 4> [, <0 169 4>]
  - 第一个cell代表中断类型：0 表示SPI中断，1 表示PPI中断
  - 第二个cell代表具体的中断类型：、
    - PPI中断：私有外设中断(Private Peripheral Interrupt)，是每个CPU私有的中断。最多支持16个PPI中断，范围【0 - 15】。
    - SPI中断类型：公用外设中断(Shared Peripheral Interrupt)，最多可以支持988个外设中断，范围【0 - 987】。
  - 第三个cell代表中断触发标志：
    - bits [ 3 ：0 ] 触发类型和级别标志：
      1 = 低- 至- 高边沿触发
      2 = 高- 到- 低边沿触发
      4 = 活跃的高水平- 敏感
      8 = 低电平有效- 敏感
    - bits [ 15 ：8 ] PPI中断cpu掩码。每个位对应于每个位附加到GIC的8个可能的cpu。指示设置为“1”的位中断被连接到该CPU 。只有有效的PPI中断。
- 当#interrupt-cells为2时，interrupts包含2个cells，如interrupts = <2 4>
  - 第一个cell代表具体的中断类型：
    - SGI中断：软件触发中断(Software Generated Interrupt)，通常用于多核间通讯，最多支持16个SGI中断，硬件中断号从ID0~ID15。
    - PPI中断：私有外设中断(Private Peripheral Interrupt)，是每个CPU私有的中断。最多支持16个PPI中断，硬件中断号从ID16~ID31。
    - SPI中断类型：公用外设中断(Shared Peripheral Interrupt)，最多可以支持988个外设中断，硬件中断号从ID32~ID1019。
  - 第二个cell代表中断触发标志：
    - bits [ 3 ：0 ] 触发类型和级别标志：
      1 = 低- 至- 高边沿触发
      2 = 高- 到- 低边沿触发
      4 = 活跃的高水平- 敏感
      8 = 低电平有效- 敏感
    - bits [ 15 ：8 ] PPI中断cpu掩码。每个位对应于每个位附加到GIC的8个可能的cpu。指示设置为“1”的位中断被连接到该CPU 。只有有效的PPI中断。
  备注：ARM GIC V3说明：kernel/Documentation/devicetree/bindings/arm/gic.txt
reg - 指定基物理地址和所述GIC寄存器的大小
- 第一个区域是GIC分销商的注册基数和规模。
- 第二个区域是GIC cpu 接口寄存器的基数和大小。

/ {
    compatible = "acme,coyotes-revenge";
    #address-cells = <1>;
    #size-cells = <1>;
    interrupt-parent = <&intc>;//指定依附的中断控制器是intc

    serial@101f0000 {   //子节点：串口设备
        compatible = "arm,pl011";
        reg = <0x101f0000 0x1000 >;
        interrupts = < 1 0 >;
    };

    intc: interrupt-controller@10140000 { //intc中断控制器
        compatible = "arm,pl190";
        reg = <0x10140000 0x1000 >;
        interrupt-controller;//定义为中断控制器设备
        #interrupt-cells = <2>;
    };
｝

四、设备树文件分析

mt7628/mt7688的设备树管脚配置参考openwrt/build_dir/target-mipsel_24kc_glibc-2.24/linux-ramips_mt7688/linux-4.4.167/arch/mips/ralink/mt7620.c文件

//mt7628an.dtsi文件
/ {
    #address-cells = <1>;
    #size-cells = <1>;
    compatible = "ralink,mtk7628an-soc";

    cpus {
        cpu@0 {
            compatible = "mips,mips24KEc";
        };
    };

    chosen {
        bootargs = "console=ttyS0,57600";
    };

    aliases {
        serial0 = &uartlite;
    };

    cpuintc: cpuintc@0 {
        #address-cells = <0>;
        #interrupt-cells = <1>;
        interrupt-controller;
        compatible = "mti,cpu-interrupt-controller";
    };

    palmbus: palmbus@10000000 {
        compatible = "palmbus";
        reg = <0x10000000 0x200000>;
        ranges = <0x0 0x10000000 0x1FFFFF>;

        #address-cells = <1>;
        #size-cells = <1>;

        sysc: sysc@0 {
            compatible = "ralink,mt7620a-sysc";
            reg = <0x0 0x100>;
        };

        watchdog: watchdog@120 {
            compatible = "ralink,mt7628an-wdt", "mtk,mt7621-wdt";
            reg = <0x120 0x10>;

            resets = <&rstctrl 8>;
            reset-names = "wdt";

            interrupt-parent = <&intc>;
            interrupts = <24>;
        };

        intc: intc@200 {
            compatible = "ralink,mt7628an-intc", "ralink,rt2880-intc";
            reg = <0x200 0x100>;

            resets = <&rstctrl 9>;
            reset-names = "intc";

            interrupt-controller;
            #interrupt-cells = <1>;

            interrupt-parent = <&cpuintc>;
            interrupts = <2>;

            ralink,intc-registers = <0x9c 0xa0
                         0x6c 0xa4
                         0x80 0x78>;
        };

        memc: memc@300 {
            compatible = "ralink,mt7620a-memc", "ralink,rt3050-memc";
            reg = <0x300 0x100>;

            resets = <&rstctrl 20>;
            reset-names = "mc";

            interrupt-parent = <&intc>;
            interrupts = <3>;
        };

        gpio@600 {
            #address-cells = <1>;
            #size-cells = <0>;

            compatible = "mtk,mt7628-gpio", "mtk,mt7621-gpio";
            reg = <0x600 0x100>;

            interrupt-parent = <&intc>;
            interrupts = <6>;

            gpio0: bank@0 {
                reg = <0>;
                compatible = "mtk,mt7621-gpio-bank";
                gpio-controller;
                #gpio-cells = <2>;
            };

            gpio1: bank@1 {
                reg = <1>;
                compatible = "mtk,mt7621-gpio-bank";
                gpio-controller;
                #gpio-cells = <2>;
            };

            gpio2: bank@2 {
                reg = <2>;
                compatible = "mtk,mt7621-gpio-bank";
                gpio-controller;
                #gpio-cells = <2>;
            };
        };

        i2c: i2c@900 {
            compatible = "mediatek,mt7621-i2c";
            reg = <0x900 0x100>;

            resets = <&rstctrl 16>;
            reset-names = "i2c";

            #address-cells = <1>;
            #size-cells = <0>;

            status = "disabled";

            pinctrl-names = "default";
            pinctrl-0 = <&i2c_pins>;
        };

        i2s: i2s@a00 {
            compatible = "mediatek,mt7628-i2s";
            reg = <0xa00 0x100>;

            resets = <&rstctrl 17>;
            reset-names = "i2s";

            interrupt-parent = <&intc>;
            interrupts = <10>;

            txdma-req = <2>;
            rxdma-req = <3>;

            dmas = <&gdma 4>,
                <&gdma 6>;
            dma-names = "tx", "rx";

            status = "disabled";
        };

        spi0: spi@b00 {
            compatible = "ralink,mt7621-spi";
            reg = <0xb00 0x100>;

            resets = <&rstctrl 18>;
            reset-names = "spi";

            #address-cells = <1>;
            #size-cells = <0>;

            pinctrl-names = "default";
            pinctrl-0 = <&spi_pins>;

            status = "disabled";
        };

        uartlite: uartlite@c00 {
            compatible = "ns16550a";
            reg = <0xc00 0x100>;

            reg-shift = <2>;
            reg-io-width = <4>;
            no-loopback-test;

            clock-frequency = <40000000>;

            resets = <&rstctrl 12>;
            reset-names = "uartl";

            interrupt-parent = <&intc>;
            interrupts = <20>;

            pinctrl-names = "default";
            pinctrl-0 = <&uart0_pins>;
        };

        uart1: uart1@d00 {
            compatible = "ns16550a";
            reg = <0xd00 0x100>;

            reg-shift = <2>;
            reg-io-width = <4>;
            no-loopback-test;

            clock-frequency = <40000000>;

            resets = <&rstctrl 19>;
            reset-names = "uart1";

            interrupt-parent = <&intc>;
            interrupts = <21>;

            pinctrl-names = "default";
            pinctrl-0 = <&uart1_pins>;

            status = "disabled";
        };

        uart2: uart2@e00 {
            compatible = "ns16550a";
            reg = <0xe00 0x100>;

            reg-shift = <2>;
            reg-io-width = <4>;
            no-loopback-test;

            clock-frequency = <40000000>;

            resets = <&rstctrl 20>;
            reset-names = "uart2";

            interrupt-parent = <&intc>;
            interrupts = <22>;

            pinctrl-names = "default";
            pinctrl-0 = <&uart2_pins>;

            status = "disabled";
        };

        pwm: pwm@5000 {
            compatible = "mediatek,mt7628-pwm";
            reg = <0x5000 0x1000>;

            resets = <&rstctrl 31>;
            reset-names = "pwm";

            pinctrl-names = "default";
            pinctrl-0 = <&pwm0_pins>, <&pwm1_pins>;

            status = "disabled";
        };

        pcm: pcm@2000 {
            compatible = "ralink,mt7620a-pcm";
            reg = <0x2000 0x800>;

            resets = <&rstctrl 11>;
            reset-names = "pcm";

            interrupt-parent = <&intc>;
            interrupts = <4>;

            status = "disabled";
        };

        gdma: gdma@2800 {
            compatible = "ralink,rt3883-gdma";
            reg = <0x2800 0x800>;

            resets = <&rstctrl 14>;
            reset-names = "dma";

            interrupt-parent = <&intc>;
            interrupts = <7>;

            #dma-cells = <1>;
            #dma-channels = <16>;
            #dma-requests = <16>;

            status = "disabled";
        };
    };

    pinctrl: pinctrl {
        compatible = "ralink,rt2880-pinmux";
        pinctrl-names = "default";
        pinctrl-0 = <&state_default>;

        state_default: pinctrl0 {
        };

        spi_pins: spi {
            spi {
                ralink,group = "spi";
                ralink,function = "spi";
            };
        };

        spi_cs1_pins: spi_cs1 {
            spi_cs1 {
                ralink,group = "spi cs1";
                ralink,function = "spi cs1";
            };
        };

        i2c_pins: i2c {
            i2c {
                ralink,group = "i2c";
                ralink,function = "i2c";
            };
        };

        uart0_pins: uartlite {
            uartlite {
                ralink,group = "uart0";
                ralink,function = "uart0";
            };
        };

        uart1_pins: uart1 {
            uart1 {
                ralink,group = "uart1";
                ralink,function = "uart1";
            };
        };

        uart2_pins: uart2 {
            uart2 {
                ralink,group = "uart2";
                ralink,function = "uart2";
            };
        };

        sdxc_pins: sdxc {
            sdxc {
                ralink,group = "sdmode";
                ralink,function = "sdxc";
            };
        };

        pwm0_pins: pwm0 {
            pwm0 {
                ralink,group = "pwm0";
                ralink,function = "pwm0";
            };
        };

        pwm1_pins: pwm1 {
            pwm1 {
                ralink,group = "pwm1";
                ralink,function = "pwm1";
            };
        };

        pcm_i2s_pins: i2s {
            i2s {
                ralink,group = "i2s";
                ralink,function = "pcm";
            };
        };
    };

    rstctrl: rstctrl {
        compatible = "ralink,mt7620a-reset", "ralink,rt2880-reset";
        #reset-cells = <1>;
    };

    clkctrl: clkctrl {
        compatible = "ralink,rt2880-clock";
        #clock-cells = <1>;
    };

    usbphy: usbphy@10120000 {
        compatible = "ralink,mt7628an-usbphy", "mediatek,mt7620-usbphy";
        reg = <0x10120000 0x1000>;
        #phy-cells = <1>;

        resets = <&rstctrl 22 &rstctrl 25>;
        reset-names = "host", "device";
        clocks = <&clkctrl 22 &clkctrl 25>;
        clock-names = "host", "device";
    };

    sdhci: sdhci@10130000 {
        compatible = "ralink,mt7620-sdhci";
        reg = <0x10130000 0x4000>;

        interrupt-parent = <&intc>;
        interrupts = <14>;

        pinctrl-names = "default";
        pinctrl-0 = <&sdxc_pins>;

        status = "disabled";
    };

    ehci: ehci@101c0000 {
        compatible = "generic-ehci";
        reg = <0x101c0000 0x1000>;

        phys = <&usbphy 1>;
        phy-names = "usb";

        interrupt-parent = <&intc>;
        interrupts = <18>;
    };

    ohci: ohci@101c1000 {
        compatible = "generic-ohci";
        reg = <0x101c1000 0x1000>;

        phys = <&usbphy 1>;
        phy-names = "usb";

        interrupt-parent = <&intc>;
        interrupts = <18>;
    };

    ethernet: ethernet@10100000 {
        compatible = "ralink,rt5350-eth";
        reg = <0x10100000 0x10000>;

        interrupt-parent = <&cpuintc>;
        interrupts = <5>;

        resets = <&rstctrl 21 &rstctrl 23>;
        reset-names = "fe", "esw";

        mediatek,switch = <&esw>;
    };

    esw: esw@10110000 {
        compatible = "mediatek,mt7628-esw", "ralink,rt3050-esw";
        reg = <0x10110000 0x8000>;

        resets = <&rstctrl 23>;
        reset-names = "esw";

        interrupt-parent = <&intc>;
        interrupts = <17>;
    };

    pcie: pcie@10140000 {
        compatible = "mediatek,mt7620-pci";
        reg = <0x10140000 0x100
            0x10142000 0x100>;

        #address-cells = <3>;
        #size-cells = <2>;

        interrupt-parent = <&cpuintc>;
        interrupts = <4>;

        resets = <&rstctrl 26 &rstctrl 27>;
        reset-names = "pcie0", "pcie1";
        clocks = <&clkctrl 26 &clkctrl 27>;
        clock-names = "pcie0", "pcie1";

        status = "disabled";

        device_type = "pci";

        bus-range = <0 255>;
        ranges = <
            0x02000000 0 0x00000000 0x20000000 0 0x10000000 /* pci memory */
            0x01000000 0 0x00000000 0x10160000 0 0x00010000 /* io space */
        >;

        pcie-bridge {
            reg = <0x0000 0 0 0 0>;

            #address-cells = <3>;
            #size-cells = <2>;

            device_type = "pci";
        };
    };

    wmac: wmac@10300000 {
        compatible = "mediatek,mt7628-wmac";
        reg = <0x10300000 0x100000>;

        interrupt-parent = <&cpuintc>;
        interrupts = <6>;

        status = "disabled";

        mediatek,mtd-eeprom = <&factory 0x0000>;
    };
};