设备树规范学习

2023-12-18 20:04:33

1、设备树概述:

DTSpec指定了一个称为设备树(device tree)的树状结构来描述系统的硬件信息。Bootloader将设备树文件加载到内存中,并将指向设备树文件地址的指针通过参数R2传递给kernel。
设备树是一个树形的数据结构,它的节点描述了系统中对应的设备。每个结点用属性-值(key-value)来描述设备的特征,除了root根节点以外,每个结点都有唯一的父节点。
以V3s为例:

#include <dt-bindings/interrupt-controller/arm-gic.h>
#include <dt-bindings/clock/sun8i-v3s-ccu.h>
#include <dt-bindings/reset/sun8i-v3s-ccu.h>

/ {
	#address-cells = <1>;
	#size-cells = <1>;
	interrupt-parent = <&gic>;

	chosen {
		#address-cells = <1>;
		#size-cells = <1>;
		ranges;

		simplefb_lcd: framebuffer@0 {
			compatible = "allwinner,simple-framebuffer",
				     "simple-framebuffer";
			allwinner,pipeline = "de0-lcd0";
			clocks = <&ccu CLK_BUS_TCON0>, <&display_clocks 0>,
				 <&display_clocks 6>, <&ccu CLK_TCON0>;
			status = "disabled";
		};
	};

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

		cpu@0 {
			compatible = "arm,cortex-a7";
			device_type = "cpu";
			reg = <0>;
			clocks = <&ccu CLK_CPU>;
		};
	};

	de: display-engine {
		compatible = "allwinner,sun8i-v3s-display-engine";
		allwinner,pipelines = <&mixer0>;
		status = "disabled";
	};

	timer {
		compatible = "arm,armv7-timer";
		interrupts = <GIC_PPI 13 (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_LOW)>,
			     <GIC_PPI 14 (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_LOW)>,
			     <GIC_PPI 11 (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_LOW)>,
			     <GIC_PPI 10 (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_LOW)>;
	};

	clocks {
		#address-cells = <1>;
		#size-cells = <1>;
		ranges;

		osc24M: osc24M_clk {
			#clock-cells = <0>;
			compatible = "fixed-clock";
			clock-frequency = <24000000>;
			clock-output-names = "osc24M";
		};

		osc32k: osc32k_clk {
			#clock-cells = <0>;
			compatible = "fixed-clock";
			clock-frequency = <32768>;
			clock-output-names = "osc32k";
		};
	};

	soc {
		compatible = "simple-bus";
		#address-cells = <1>;
		#size-cells = <1>;
		ranges;

		display_clocks: clock@1000000 {
			compatible = "allwinner,sun8i-v3s-de2-clk";
			reg = <0x01000000 0x100000>;
			clocks = <&ccu CLK_DE>,
				 <&ccu CLK_BUS_DE>;
			clock-names = "mod",
				      "bus";
			resets = <&ccu RST_BUS_DE>;
			#clock-cells = <1>;
			#reset-cells = <1>;
		};

		mixer0: mixer@1100000 {
			compatible = "allwinner,sun8i-v3s-de2-mixer";
			reg = <0x01100000 0x100000>;
			clocks = <&display_clocks 0>,
				 <&display_clocks 6>;
			clock-names = "bus",
				      "mod";
			resets = <&display_clocks 0>;
			assigned-clocks = <&display_clocks 6>;
			assigned-clock-rates = <150000000>;

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

				mixer0_out: port@1 {
					reg = <1>;

					mixer0_out_tcon0: endpoint {
						remote-endpoint = <&tcon0_in_mixer0>;
					};
				};
			};
		};

		syscon: syscon@1c00000 {
			compatible = "allwinner,sun8i-v3s-system-controller",
				"syscon";
			reg = <0x01c00000 0x1000>;
		};

		tcon0: lcd-controller@1c0c000 {
			compatible = "allwinner,sun8i-v3s-tcon";
			reg = <0x01c0c000 0x1000>;
			interrupts = <GIC_SPI 86 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&ccu CLK_BUS_TCON0>,
				 <&ccu CLK_TCON0>;
			clock-names = "ahb",
				      "tcon-ch0";
			clock-output-names = "tcon-pixel-clock";
			#clock-cells = <0>;
			resets = <&ccu RST_BUS_TCON0>;
			reset-names = "lcd";
			status = "disabled";

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

				tcon0_in: port@0 {
					reg = <0>;

					tcon0_in_mixer0: endpoint {
						remote-endpoint = <&mixer0_out_tcon0>;
					};
				};

				tcon0_out: port@1 {
					#address-cells = <1>;
					#size-cells = <0>;
					reg = <1>;
				};
			};
		};

		dma: dma-controller@01c02000 {
			compatible = "allwinner,sun8i-v3s-dma";
			reg = <0x01c02000 0x1000>;
			interrupts = <GIC_SPI 50 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&ccu CLK_BUS_DMA>;
			resets = <&ccu RST_BUS_DMA>;
			#dma-cells = <1>;
		};

		mmc0: mmc@1c0f000 {
			compatible = "allwinner,sun7i-a20-mmc";
			reg = <0x01c0f000 0x1000>;
			clocks = <&ccu CLK_BUS_MMC0>,
				 <&ccu CLK_MMC0>,
				 <&ccu CLK_MMC0_OUTPUT>,
				 <&ccu CLK_MMC0_SAMPLE>;
			clock-names = "ahb",
				      "mmc",
				      "output",
				      "sample";
			resets = <&ccu RST_BUS_MMC0>;
			reset-names = "ahb";
			interrupts = <GIC_SPI 60 IRQ_TYPE_LEVEL_HIGH>;
			pinctrl-names = "default";
			pinctrl-0 = <&mmc0_pins>;
			status = "disabled";
			#address-cells = <1>;
			#size-cells = <0>;
		};

		mmc1: mmc@1c10000 {
			compatible = "allwinner,sun7i-a20-mmc";
			reg = <0x01c10000 0x1000>;
			clocks = <&ccu CLK_BUS_MMC1>,
				 <&ccu CLK_MMC1>,
				 <&ccu CLK_MMC1_OUTPUT>,
				 <&ccu CLK_MMC1_SAMPLE>;
			clock-names = "ahb",
				      "mmc",
				      "output",
				      "sample";
			resets = <&ccu RST_BUS_MMC1>;
			reset-names = "ahb";
			interrupts = <GIC_SPI 61 IRQ_TYPE_LEVEL_HIGH>;
			pinctrl-names = "default";
			pinctrl-0 = <&mmc1_pins>;
			status = "disabled";
			#address-cells = <1>;
			#size-cells = <0>;
		};

		mmc2: mmc@1c11000 {
			compatible = "allwinner,sun7i-a20-mmc";
			reg = <0x01c11000 0x1000>;
			clocks = <&ccu CLK_BUS_MMC2>,
				 <&ccu CLK_MMC2>,
				 <&ccu CLK_MMC2_OUTPUT>,
				 <&ccu CLK_MMC2_SAMPLE>;
			clock-names = "ahb",
				      "mmc",
				      "output",
				      "sample";
			resets = <&ccu RST_BUS_MMC2>;
			reset-names = "ahb";
			interrupts = <GIC_SPI 62 IRQ_TYPE_LEVEL_HIGH>;
			status = "disabled";
			#address-cells = <1>;
			#size-cells = <0>;
		};

		usb_otg: usb@1c19000 {
			compatible = "allwinner,sun8i-h3-musb";
			reg = <0x01c19000 0x0400>;
			clocks = <&ccu CLK_BUS_OTG>;
			resets = <&ccu RST_BUS_OTG>;
			interrupts = <GIC_SPI 71 IRQ_TYPE_LEVEL_HIGH>;
			interrupt-names = "mc";
			phys = <&usbphy 0>;
			phy-names = "usb";
			extcon = <&usbphy 0>;
			status = "disabled";
		};

		usbphy: phy@1c19400 {
			compatible = "allwinner,sun8i-v3s-usb-phy";
			reg = <0x01c19400 0x2c>,
			      <0x01c1a800 0x4>;
			reg-names = "phy_ctrl",
				    "pmu0";
			clocks = <&ccu CLK_USB_PHY0>;
			clock-names = "usb0_phy";
			resets = <&ccu RST_USB_PHY0>;
			reset-names = "usb0_reset";
			status = "disabled";
			#phy-cells = <1>;
		};

		ehci0: usb@01c1a000 {
			compatible = "allwinner,sun8i-v3s-ehci", "generic-ehci";
			reg = <0x01c1a000 0x100>;
			interrupts = <GIC_SPI 72 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&ccu CLK_BUS_EHCI0>, <&ccu CLK_BUS_OHCI0>;
			resets = <&ccu RST_BUS_EHCI0>, <&ccu RST_BUS_OHCI0>;
			status = "disabled";
		};

		ohci0: usb@01c1a400 {
			compatible = "allwinner,sun8i-v3s-ohci", "generic-ohci";
			reg = <0x01c1a400 0x100>;
			interrupts = <GIC_SPI 73 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&ccu CLK_BUS_EHCI0>, <&ccu CLK_BUS_OHCI0>,
				 <&ccu CLK_USB_OHCI0>;
			resets = <&ccu RST_BUS_EHCI0>, <&ccu RST_BUS_OHCI0>;
			status = "disabled";
		};

		ccu: clock@1c20000 {
			compatible = "allwinner,sun8i-v3s-ccu";
			reg = <0x01c20000 0x400>;
			clocks = <&osc24M>, <&osc32k>;
			clock-names = "hosc", "losc";
			#clock-cells = <1>;
			#reset-cells = <1>;
		};

		rtc: rtc@1c20400 {
			compatible = "allwinner,sun6i-a31-rtc";
			reg = <0x01c20400 0x54>;
			interrupts = <GIC_SPI 40 IRQ_TYPE_LEVEL_HIGH>,
				     <GIC_SPI 41 IRQ_TYPE_LEVEL_HIGH>;
		};

		pio: pinctrl@1c20800 {
			compatible = "allwinner,sun8i-v3s-pinctrl";
			reg = <0x01c20800 0x400>;
			interrupts = <GIC_SPI 15 IRQ_TYPE_LEVEL_HIGH>,
				     <GIC_SPI 17 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&ccu CLK_BUS_PIO>, <&osc24M>, <&osc32k>;
			clock-names = "apb", "hosc", "losc";
			gpio-controller;
			#gpio-cells = <3>;
			interrupt-controller;
			#interrupt-cells = <3>;

			emac_rgmii_pins: emac-rgmii-pins {
				pins = "PD0", "PD1", "PD2", "PD3", "PD4",
				       "PD5", "PD7", "PD8", "PD9", "PD10",
				       "PD12", "PD13", "PD15", "PD16", "PD17";
				function = "emac";
				drive-strength = <40>;
			};

			i2c0_pins: i2c0-pins {
				pins = "PB6", "PB7";
				function = "i2c0";
			};

			pwm0_pins: pwm0 {
				pins = "PB4";
				function = "pwm0";
			};

			uart0_pb_pins: uart0-pb-pins {
				pins = "PB8", "PB9";
				function = "uart0";
			};

			lcd_rgb666_pins_a: lcd-rgb666-pe {
				pins = "PE0", "PE1", "PE2", "PE3", "PE4", "PE5",
				       "PE6", "PE7", "PE8", "PE9", "PE10", "PE11",
				       "PE12", "PE13", "PE14", "PE15", "PE16", "PE17",
				       "PE18", "PE19", "PE23", "PE24";
				function = "lcd";
			};

			mmc0_pins: mmc0-pins {
				pins = "PF0", "PF1", "PF2", "PF3",
				       "PF4", "PF5";
				function = "mmc0";
				drive-strength = <30>;
				bias-pull-up;
			};

			mmc1_pins: mmc1-pins {
				pins = "PG0", "PG1", "PG2", "PG3",
				       "PG4", "PG5";
				function = "mmc1";
				drive-strength = <30>;
				bias-pull-up;
			};

			spi0_pins: spi0-pins {
				pins = "PC0", "PC1", "PC2", "PC3";
				function = "spi0";
			};
		};

		timer@1c20c00 {
			compatible = "allwinner,sun4i-a10-timer";
			reg = <0x01c20c00 0xa0>;
			interrupts = <GIC_SPI 18 IRQ_TYPE_LEVEL_HIGH>,
				     <GIC_SPI 19 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&osc24M>;
		};

		wdt0: watchdog@1c20ca0 {
			compatible = "allwinner,sun6i-a31-wdt";
			reg = <0x01c20ca0 0x20>;
			interrupts = <GIC_SPI 25 IRQ_TYPE_LEVEL_HIGH>;
		};

		pwm: pwm@1c21400 {
			compatible = "allwinner,sun8i-v3s-pwm",
				     "allwinner,sun7i-a20-pwm";
			reg = <0x01c21400 0x400>;
			clocks = <&osc24M>;
			#pwm-cells = <3>;
			status = "disabled";
		};

		lradc: lradc@1c22800 {
			compatible = "allwinner,sun4i-a10-lradc-keys";
			reg = <0x01c22800 0x400>;
			interrupts = <GIC_SPI 30 IRQ_TYPE_LEVEL_HIGH>;
			status = "disabled";
		};

		codec: codec@01c22c00 {
			#sound-dai-cells = <0>;
			compatible = "allwinner,sun8i-v3s-codec";
			reg = <0x01c22c00 0x400>;
			interrupts = <GIC_SPI 29 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&ccu CLK_BUS_CODEC>, <&ccu CLK_AC_DIG>;
			clock-names = "apb", "codec";
			resets = <&ccu RST_BUS_CODEC>;
			dmas = <&dma 15>, <&dma 15>;
			dma-names = "rx", "tx";
			allwinner,codec-analog-controls = <&codec_analog>;
			status = "disabled";
		};

		codec_analog: codec-analog@01c23000 {
			compatible = "allwinner,sun8i-v3s-codec-analog";
			reg = <0x01c23000 0x4>;
		};

		uart0: serial@1c28000 {
			compatible = "snps,dw-apb-uart";
			reg = <0x01c28000 0x400>;
			interrupts = <GIC_SPI 0 IRQ_TYPE_LEVEL_HIGH>;
			reg-shift = <2>;
			reg-io-width = <4>;
			clocks = <&ccu CLK_BUS_UART0>;
			resets = <&ccu RST_BUS_UART0>;
			status = "disabled";
		};

		uart1: serial@1c28400 {
			compatible = "snps,dw-apb-uart";
			reg = <0x01c28400 0x400>;
			interrupts = <GIC_SPI 1 IRQ_TYPE_LEVEL_HIGH>;
			reg-shift = <2>;
			reg-io-width = <4>;
			clocks = <&ccu CLK_BUS_UART1>;
			resets = <&ccu RST_BUS_UART1>;
			status = "disabled";
		};

		uart2: serial@1c28800 {
			compatible = "snps,dw-apb-uart";
			reg = <0x01c28800 0x400>;
			interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>;
			reg-shift = <2>;
			reg-io-width = <4>;
			clocks = <&ccu CLK_BUS_UART2>;
			resets = <&ccu RST_BUS_UART2>;
			status = "disabled";
		};

		i2c0: i2c@1c2ac00 {
			compatible = "allwinner,sun6i-a31-i2c";
			reg = <0x01c2ac00 0x400>;
			interrupts = <GIC_SPI 6 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&ccu CLK_BUS_I2C0>;
			resets = <&ccu RST_BUS_I2C0>;
			pinctrl-names = "default";
			pinctrl-0 = <&i2c0_pins>;
			status = "disabled";
			#address-cells = <1>;
			#size-cells = <0>;
		};

		i2c1: i2c@1c2b000 {
			compatible = "allwinner,sun6i-a31-i2c";
			reg = <0x01c2b000 0x400>;
			interrupts = <GIC_SPI 7 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&ccu CLK_BUS_I2C1>;
			resets = <&ccu RST_BUS_I2C1>;
			status = "disabled";
			#address-cells = <1>;
			#size-cells = <0>;
		};

		emac: ethernet@1c30000 {
			compatible = "allwinner,sun8i-h3-emac";
			syscon = <&syscon>;
			reg = <0x01c30000 0x10000>;
			interrupts = <GIC_SPI 82 IRQ_TYPE_LEVEL_HIGH>;
			interrupt-names = "macirq";
			resets = <&ccu RST_BUS_EMAC>;
			reset-names = "stmmaceth";
			clocks = <&ccu CLK_BUS_EMAC>;
			clock-names = "stmmaceth";
			status = "disabled";

			mdio: mdio {
				#address-cells = <1>;
				#size-cells = <0>;
				compatible = "snps,dwmac-mdio";
			};

			mdio-mux {
				compatible = "allwinner,sun8i-h3-mdio-mux";
				#address-cells = <1>;
				#size-cells = <0>;

				mdio-parent-bus = <&mdio>;
				/* Only one MDIO is usable at the time */
				internal_mdio: mdio@1 {
					compatible = "allwinner,sun8i-h3-mdio-internal";
					reg = <1>;
					#address-cells = <1>;
					#size-cells = <0>;

					int_mii_phy: ethernet-phy@1 {
						compatible = "ethernet-phy-ieee802.3-c22";
						reg = <1>;
						clocks = <&ccu CLK_BUS_EPHY>;
						resets = <&ccu RST_BUS_EPHY>;
					};
				};

				external_mdio: mdio@2 {
					reg = <2>;
					#address-cells = <1>;
					#size-cells = <0>;
				};
			};
		};

		spi0: spi@1c68000 {
			compatible = "allwinner,sun8i-h3-spi";
			reg = <0x01c68000 0x1000>;
			interrupts = <GIC_SPI 65 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&ccu CLK_BUS_SPI0>, <&ccu CLK_SPI0>;
			clock-names = "ahb", "mod";
			pinctrl-names = "default";
			pinctrl-0 = <&spi0_pins>;
			resets = <&ccu RST_BUS_SPI0>;
			status = "disabled";
			#address-cells = <1>;
			#size-cells = <0>;
		};

		gic: interrupt-controller@1c81000 {
			compatible = "arm,gic-400";
			reg = <0x01c81000 0x1000>,
			      <0x01c82000 0x1000>,
			      <0x01c84000 0x2000>,
			      <0x01c86000 0x2000>;
			interrupt-controller;
			#interrupt-cells = <3>;
			interrupts = <GIC_PPI 9 (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_HIGH)>;
		};
	};
};

2、设备树的约定:

a、节点名称:

设备树中的每个节点都应该遵循以下的约定:

node-name@unit-address

node-name指定节点的名称。它的长度应为1到31个字符,并且应该只包含表中所示的字符。

字符描述
0-9数字
a-z小写字母
A-Z大写字母
,逗号
.句号
_下划线
+加号
-短斜杠

节点名称应以小写或大写字符开头,并应描述设备的常规类型。名称中的单元地址组件特定于节点所在的总线类型。unit-address必须与节点的reg属性中指定的第一个地址匹配。如果节点没有reg属性,则必须省略@unit-address,并且节点名称将节点与树中同一级别的其他节点区分开来。特定总线的绑定可以为reg属性unit-address的格式指定更多,更具体的要求。根节点没有节点名和unit-address。它由正斜杠/标识。

b、路径名:

设备树中的一个结点能够被从根结点开始的绝对路径所唯一标识,能逐层查找到所描述的结点。制定一个设备路径的规则是:

/node-name-1/node-name-2/node-name-N

例如,访问CPU0的路径是:

/cpus/cpu@0

路径的根节点是/,如果根节点的绝对路径没问题,那么unit-address可以被省略。

c、属性:

设备树中的每个结点都有属性来描述结点的特性。属性由键值对名字和值组成。

i、属性名:

由表中的字符组成:

字符描述
0-9数字
a-z小写字符
A-Z大写字符
,逗号
.句号
_下划线
+加号
?问号
##号

ii、属性值:

属性值是一个包含属性相关信息的数组。如果它表达的是true-false信息,那么它可能是一个空值。
表描述了 DTSpec 定义的一组基本值类型。

描述
值是empty。用来表示这个属性它自己是否存在的真假(true-false)信息。
big-endian格式的32位整数。例如32位值 0x11223344 在内存中的形式为:
address 11
address+1 22
address+2 33
address+3 44
big-endian格式的64位整数,它由两个组成。例如0x1122334455667788将被表示为2个单元:<0x11223344 0x4455667788> 它在内存中的形式为:
address 11
address+1 22
address+2 33
address+3 44
address+4 55
address+5 66
address+6 77
address+7 88
< string >字符串是可打印的字符(不能是空格等)。例如"hello"它在内存中的形式为:
address ‘h’
address+1 ‘e’
address+2 ‘l’
address+3 ‘l’
address+4 ‘o’
address+5 ‘\0’
< stringlist >由多个组成的字符串列表。如"hello",“world”,他在内存中的形式为:
address ‘h’
address+1 ‘e’
address+2 ‘l’
address+3 ‘l’
address+4 ‘o’
address+5 ‘\0’
address+6 ‘w’
address+7 ‘o’
address+8 ‘r’
address+9 ‘l’
address+10 ‘d’
address+11 ‘\0’

文章来源:https://blog.csdn.net/a_qwq_a/article/details/135066612
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