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Linux设备树学习1 - DTS文件格式

作者：很楠不爱3 | 2024-06-13 12:20:44

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dts文件

一. 设备树简介

        Linux设备树，英文称为Devicetree，设备树的源文件称为DTS。设备树是用于描述系统的硬件资源。例如在Linux2.x时，我们写驱动程序需要在代码中写死我们需要使用的GPIO等资源，但是当硬件改板或是开发另一款设备时，GPIO有所改动时，我们就要修改驱动源码了，这样修改有可能会遗漏，特别GPIO改动太大时。Linux3.x内核出现设备树时，我们就可以在可以在一个设备树文件中把GPIO资源都修改好，不仅提高了效率，而且也避免了出错。

二. DTS文件

1. DTS文件类型

        设备树文件有两种文件，以.dts和.dtsi结尾的文件。dtsi文件通常是用来描述CPU所支持的外设 ，dts文件通常是用来描述具体单板的硬件资源使用。所以dtsi文件是用来被dts文件包含的。它们的关系类似于C语言中的.c和.h文件的关系。

2. DTS文件布局

  1. [label:] node-name[@unit-address] {
  2.     [properties definitions]
  3.     [child nodes]
  4. };

dtsi示例代码：

  1. / {
  2. 	#address-cells = <1>;
  3. 	#size-cells = <1>;
  4. 	compatible = "ralink,mtk7620n-soc";
  5.  
  6. 	cpus {
  7. 		cpu@0 {
  8. 			compatible = "mips,mips24KEc";
  9. 		};
  10. 	};
  11.  
  12. 	chosen {
  13. 		bootargs = "console=ttyS0,57600";
  14. 	};
  15.  
  16. 	cpuintc: cpuintc@0 {
  17. 		#address-cells = <0>;
  18. 		#interrupt-cells = <1>;
  19. 		interrupt-controller;
  20. 		compatible = "mti,cpu-interrupt-controller";
  21. 	};
  22.  
  23. 	palmbus@10000000 {
  24. 		compatible = "palmbus";
  25. 		reg = <0x10000000 0x200000>;
  26.                 ranges = <0x0 0x10000000 0x1FFFFF>;
  27.  
  28. 		#address-cells = <1>;
  29. 		#size-cells = <1>;
  30.  
  31. 		sysc@0 {
  32. 			compatible = "ralink,mt7620a-sysc", "ralink,rt3050-sysc";
  33. 			reg = <0x0 0x100>;
  34. 		};
  35.  
  36. 		timer@100 {
  37. 			compatible = "ralink,mt7620a-timer", "ralink,rt2880-timer";
  38. 			reg = <0x100 0x20>;
  39.  
  40. 			interrupt-parent = <&intc>;
  41. 			interrupts = <1>;
  42. 		};
  43.  
  44. 		watchdog@120 {
  45. 			compatible = "ralink,mt7620a-wdt", "ralink,rt2880-wdt";
  46. 			reg = <0x120 0x10>;
  47.  
  48. 			resets = <&rstctrl 8>;
  49. 			reset-names = "wdt";
  50.  
  51. 			interrupt-parent = <&intc>;
  52. 			interrupts = <1>;
  53. 		};
  54.  
  55. 		intc: intc@200 {
  56. 			compatible = "ralink,mt7620a-intc", "ralink,rt2880-intc";
  57. 			reg = <0x200 0x100>;
  58.  
  59. 			resets = <&rstctrl 19>;
  60. 			reset-names = "intc";
  61.  
  62. 			interrupt-controller;
  63. 			#interrupt-cells = <1>;
  64.  
  65. 			interrupt-parent = <&cpuintc>;
  66. 			interrupts = <2>;
  67. 		};
  68.  
  69. 		memc@300 {
  70. 			compatible = "ralink,mt7620a-memc", "ralink,rt3050-memc";
  71. 			reg = <0x300 0x100>;
  72.  
  73. 			resets = <&rstctrl 20>;
  74. 			reset-names = "mc";
  75.  
  76. 			interrupt-parent = <&intc>;
  77. 			interrupts = <3>;
  78. 		};
  79.  
  80. 		gpio0: gpio@600 {
  81. 			compatible = "ralink,mt7620a-gpio", "ralink,rt2880-gpio";
  82. 			reg = <0x600 0x34>;
  83.  
  84. 			resets = <&rstctrl 13>;
  85. 			reset-names = "pio";
  86.  
  87. 			interrupt-parent = <&intc>;
  88. 			interrupts = <6>;
  89.  
  90. 			gpio-controller;
  91. 			#gpio-cells = <2>;
  92.  
  93. 			ralink,gpio-base = <0>;
  94. 			ralink,num-gpios = <24>;
  95. 			ralink,register-map = [ 00 04 08 0c
  96. 						20 24 28 2c
  97. 						30 34 ];
  98. 		};
  99.  
  100. 		gpio1: gpio@638 {
  101. 			compatible = "ralink,mt7620a-gpio", "ralink,rt2880-gpio";
  102. 			reg = <0x638 0x24>;
  103.  
  104. 			interrupt-parent = <&intc>;
  105. 			interrupts = <6>;
  106.  
  107. 			gpio-controller;
  108. 			#gpio-cells = <2>;
  109.  
  110. 			ralink,gpio-base = <24>;
  111. 			ralink,num-gpios = <16>;
  112. 			ralink,register-map = [ 00 04 08 0c
  113. 						10 14 18 1c
  114. 						20 24 ];
  115.  
  116. 			#status = "disabled";
  117. 			status = "okay";
  118. 		};
  119.  
  120. 		gpio2: gpio@660 {
  121. 			compatible = "ralink,mt7620a-gpio", "ralink,rt2880-gpio";
  122. 			reg = <0x660 0x24>;
  123.  
  124. 			interrupt-parent = <&intc>;
  125. 			interrupts = <6>;
  126.  
  127. 			gpio-controller;
  128. 			#gpio-cells = <2>;
  129.  
  130. 			ralink,gpio-base = <40>;
  131. 			ralink,num-gpios = <32>;
  132. 			ralink,register-map = [ 00 04 08 0c
  133. 						10 14 18 1c
  134. 						20 24 ];
  135.  
  136. 			status = "disabled";
  137. 		};
  138.  
  139. 		gpio3: gpio@688 {
  140. 			compatible = "ralink,mt7620a-gpio", "ralink,rt2880-gpio";
  141. 			reg = <0x688 0x24>;
  142.  
  143. 			interrupt-parent = <&intc>;
  144. 			interrupts = <6>;
  145.  
  146. 			gpio-controller;
  147. 			#gpio-cells = <2>;
  148.  
  149. 			ralink,gpio-base = <72>;
  150. 			ralink,num-gpios = <1>;
  151. 			ralink,register-map = [ 00 04 08 0c
  152. 						10 14 18 1c
  153. 						20 24 ];
  154.  
  155. 			status = "disabled";
  156. 		};
  157.         
  158.         i2c: i2c@900 {
  159.             compatible = "ralink,rt2880-i2c";
  160.             reg = <0x900 0x100>;
  161.  
  162.             resets = <&rstctrl 16>;
  163.             reset-names = "i2c";
  164.  
  165.             #address-cells = <1>;
  166.             #size-cells = <0>;
  167.  
  168.             pinctrl-names = "default";
  169.             pinctrl-0 = <&i2c_pins>;
  170.         };
  171.  
  172. 		spi@b00 {
  173. 			compatible = "ralink,mt7620a-spi", "ralink,rt2880-spi";
  174. 			reg = <0xb00 0x100>;
  175.  
  176. 			resets = <&rstctrl 18>;
  177. 			reset-names = "spi";
  178.  
  179. 			#address-cells = <1>;
  180. 			#size-cells = <1>;
  181.  
  182. 			pinctrl-names = "default";
  183. 			pinctrl-0 = <&spi_pins>;
  184. 		};
  185.  
  186. 		uartlite@c00 {
  187. 			compatible = "ralink,mt7620a-uart", "ralink,rt2880-uart", "ns16550a";
  188. 			reg = <0xc00 0x100>;
  189.  
  190. 			resets = <&rstctrl 19>;
  191. 			reset-names = "uartl";
  192.  
  193. 			interrupt-parent = <&intc>;
  194. 			interrupts = <12>;
  195.  
  196. 			reg-shift = <2>;
  197.  
  198. 			pinctrl-names = "default";
  199. 			pinctrl-0 = <&uartlite_pins>;
  200. 		};
  201.  
  202. 		systick@d00 {
  203. 			compatible = "ralink,mt7620a-systick", "ralink,cevt-systick";
  204. 			reg = <0xd00 0x10>;
  205.  
  206. 			resets = <&rstctrl 28>;
  207. 			reset-names = "intc";
  208.  
  209. 			interrupt-parent = <&cpuintc>;
  210. 			interrupts = <7>;
  211. 		};
  212. 	};
  213.  
  214. 	pinctrl {
  215. 		compatible = "ralink,rt2880-pinmux";
  216. 		pinctrl-names = "default";
  217. 		pinctrl-0 = <&state_default>;
  218. 		state_default: pinctrl0 {
  219. 		};
  220. 		spi_pins: spi {
  221. 			spi {
  222. 				ralink,group = "spi";
  223. 				ralink,function = "spi";
  224. 			};
  225. 		};
  226. 		uartlite_pins: uartlite {
  227. 			uart {
  228. 				ralink,group = "uartlite";
  229. 				ralink,function = "uartlite";
  230. 			};
  231. 		};
  232. 	};
  233.  
  234. 	rstctrl: rstctrl {
  235. 		compatible = "ralink,mt7620a-reset", "ralink,rt2880-reset";
  236. 		#reset-cells = <1>;
  237. 	};
  238.  
  239. 	usbphy: usbphy {
  240. 		compatible = "ralink,mt7620a-usbphy";
  241. 		#phy-cells = <1>;
  242.  
  243. 		resets = <&rstctrl 22 &rstctrl 25>;
  244. 		reset-names = "host", "device";
  245. 	};
  246.  
  247. 	ethernet@10100000 {
  248. 		compatible = "ralink,mt7620a-eth";
  249. 		reg = <0x10100000 10000>;
  250.  
  251. 		#address-cells = <1>;
  252. 		#size-cells = <0>;
  253.  
  254. 		interrupt-parent = <&cpuintc>;
  255. 		interrupts = <5>;
  256.  
  257. 		resets = <&rstctrl 21 &rstctrl 23>;
  258. 		reset-names = "fe", "esw";
  259.  
  260. 		mdio-bus {
  261. 			#address-cells = <1>;
  262. 			#size-cells = <0>;
  263.  
  264. 			status = "disabled";
  265. 		};
  266. 	};
  267.  
  268. 	gsw@10110000 {
  269. 		compatible = "ralink,mt7620a-gsw";
  270. 		reg = <0x10110000 8000>;
  271.  
  272. 		resets = <&rstctrl 23>;
  273. 		reset-names = "esw";
  274.  
  275. 		interrupt-parent = <&intc>;
  276. 		interrupts = <17>;
  277. 		ralink,port4 = "gmac";
  278. 	};
  279.  
  280. 	ehci@101c0000 {
  281. 		compatible = "ralink,rt3xxx-ehci";
  282. 		reg = <0x101c0000 0x1000>;
  283.  
  284. 		interrupt-parent = <&intc>;
  285. 		interrupts = <18>;
  286.  
  287. 		phys = <&usbphy 1>;
  288. 		phy-names = "usb";
  289.  
  290. 		status = "disabled";
  291. 	};
  292.  
  293. 	ohci@101c1000 {
  294. 		compatible = "ralink,rt3xxx-ohci";
  295. 		reg = <0x101c1000 0x1000>;
  296.  
  297. 		phys = <&usbphy 1>;
  298. 		phy-names = "usb";
  299.  
  300. 		interrupt-parent = <&intc>;
  301. 		interrupts = <18>;
  302.  
  303. 		status = "disabled";
  304. 	};
  305.  
  306. 	wmac@10180000 {
  307. 		compatible = "ralink,rt7620-wmac", "ralink,rt2880-wmac";
  308. 		reg = <0x10180000 40000>;
  309.  
  310. 		interrupt-parent = <&cpuintc>;
  311. 		interrupts = <6>;
  312.  
  313. 		ralink,eeprom = "soc_wmac.eeprom";
  314. 	};
  315. };

dts文件示例：

  1. /dts-v1/;
  2.  
  3. /include/ "mt7620n.dtsi"
  4.  
  5. / {
  6. 	compatible = "mediatek,hiwooya", "ralink,mt7620n-soc";
  7. 	model = "Wooya IOT Smart 7620";
  8.  
  9. 	palmbus@10000000 {
  10. 		gpio0: gpio@600 {
  11. 			status = "okay";
  12. 		};
  13. 	
  14. 		gpio2: gpio@660 {
  15. 			status = "okay";
  16. 		};
  17.  
  18. 		gpio3: gpio@688 {
  19. 			status = "okay";
  20. 		};
  21.  
  22. 		spi@b00 {
  23. 			status = "okay";
  24.  
  25. 			m25p80@0 {
  26. 				#address-cells = <1>;
  27. 				#size-cells = <1>;
  28. 				compatible = "mx25l12805d";
  29. 				reg = <0 0>;
  30. 				linux,modalias = "m25p80", "w25q128";
  31. 				spi-max-frequency = <10000000>;
  32.  
  33. 				partition@0 {
  34. 					label = "u-boot";
  35. 					reg = <0x0 0x30000>;
  36. 					read-only;
  37. 				};
  38.  
  39. 				partition@30000 {
  40. 					label = "u-boot-env";
  41. 					reg = <0x30000 0x10000>;
  42. 					read-only;
  43. 				};
  44.  
  45. 				factory: partition@40000 {
  46. 					label = "factory";
  47. 					reg = <0x40000 0x10000>;
  48. 					read-only;
  49. 				};
  50.  
  51. 				partition@50000 {
  52. 					label = "firmware";
  53. 					reg = <0x50000 0xdb0000>;
  54. 				};
  55. 				
  56. 				partition@ff0000 {
  57. 					label = "config";
  58. 					reg = <0xe00000 0x100000>;
  59. 				};
  60. 			};
  61. 		};
  62. 	};
  63. 	
  64. 	lte-leds {
  65. 		compatible = "gpio-leds";
  66. 		red-led {
  67. 			label = "red";
  68. 			gpios = <&gpio0 7 1>;
  69. 			linux,default-trigger = "none";
  70. 		};
  71. 		
  72. 		green-led {
  73. 			label = "green";
  74. 			gpios = <&gpio0 1 1>;
  75. 		};
  76. 		
  77. 		blue-led {
  78. 			label = "blue";
  79. 			gpios = <&gpio1 14 1>;
  80. 			linux,default-trigger = "none";
  81. 		};
  82. 		l1 {
  83. 			label = "led1";
  84. 			gpios = <&gpio2 6 1>;
  85. 			linux,default-trigger = "none";
  86. 		};
  87. 		l2 {
  88. 			label = "led2";
  89. 			gpios = <&gpio2 11 1>;
  90. 			linux,default-trigger = "none";
  91. 		};
  92. 		l3 {
  93. 			label = "led3";
  94. 			gpios = <&gpio2 10 1>;
  95. 			linux,default-trigger = "none";
  96. 		};
  97. 		l4 {
  98. 			label = "led4";
  99. 			gpios = <&gpio2 19 1>;
  100. 			linux,default-trigger = "none";
  101. 		};
  102.  
  103. 	};
  104. 	
  105. 	gpio-keys-polled {
  106.     compatible = "gpio-keys-polled";
  107. 	#address-cells = <1>;
  108. 	#size-cells = <0>;
  109. 	poll-interval = <20>;
  110. 	reset {
  111. 			label = "reset";
  112. 			gpios = <&gpio1 13 1>;
  113. 			linux,code = <0x198>;
  114. 		  };
  115. 	}; 
  116.  
  117. 	ehci@101c0000 {
  118. 		status = "okay";
  119. 	};
  120.  
  121. 	ohci@101c1000 {
  122. 		status = "okay";
  123. 	};
  124.  
  125. 	ethernet@10100000 {
  126. 		mtd-mac-address = <&factory 0x4>;
  127. 		ralink,port-map = "llllw";
  128. 	};
  129.  
  130. 	wmac@10180000 {
  131. 		ralink,mtd-eeprom = <&factory 0>;
  132. 	};
  133.  
  134. 	pinctrl {
  135. 		state_default: pinctrl0 {
  136. 			default {
  137. 				ralink,group = "pa", "spi refclk", "wdt", "uartf", "nd_sd";
  138. 				ralink,function = "gpio";
  139. 			};
  140.             
  141.             i2c_pins: i2c_pins {
  142.                 i2c_pins {
  143.                         ralink,group = "i2c";
  144.                         ralink,function = "i2c";
  145.                 };
  146.             };
  147. 		};
  148. 	};
  149.     
  150.     
  151. };

        从上面设备的设备树代码来看，设备树dts文件需要指定dts的版本号（/dts-v1/;），包含了什么dtsi文件（/include/ "mt7620n.dtsi"），以/开始的根节点和节点名开始的子节点。简化代码如下

  1. /dts-v1/;
  2.  
  3. /include/ "mt7620n.dtsi"
  4.  
  5. / {
  6. 	compatible = "mediatek,hiwooya", "ralink,mt7620n-soc";
  7. 	model = "Wooya IOT Smart 7620";
  8.  
  9. 	palmbus@10000000 {
  10.         ........
  11. 	};
  12. 	
  13. 	lte-leds {
  14. 		compatible = "gpio-leds";
  15. 		red-led {
  16.             ........
  17. 		};
  18.  
  19. 	};
  20. 	
  21. 	gpio-keys-polled {
  22.         compatible = "gpio-keys-polled";
  23.         ........
  24. 	}; 
  25.  
  26. 	ohci@101c1000 {
  27. 		status = "okay";
  28. 	};
  29. };

        从上面代码可以看出设备树的节点是以node-name@unit-address { }组成，node-name一般以字母数字等ASCII码组成，根节点是一种特殊节点。有些节点带有unit-address，而有些没有，节点都有一个compatible属性等。接下来详细介绍。        

三. DTS设备节点属性介绍

1. compatible

        compatible可以包含一个或者多个字符串，中间以逗号隔开。主要用来指定驱动代码设备的型号名称。当驱动代码中的名称和设备树的某个节点compatible属性名称一样，驱动代码则调用probe函数。示例如下：

compatible = "fsl,mpc8641", "ns16550";

2. model

        主要用来指定产商的设备型号。示例如下

model = "fsl,MPC8349EMITX";

3. phandle

        phandle属性指定一个设备树中唯一的数字标识。带有phandle属性的节点可以被其他节点引用，示例如下

  1. pic@10000000 {
  2.     phandle = <1>;
  3.     interrupt-controller;
  4. };
  5.  
  6. another-device-node {
  7.     interrupt-parent = <1>;
  8. };

4. status

        status属性指示设备的可操作的状态，可用的状态如下：

okay ：表示设备可以操作

disabled ：表示设备当前不可操作，但未来可能可以操作

fail ：表示设备不可操作，检测到严重的错误，如果不修复无法操作。

fail-sss ：和fail的含义类型

5. #address-cells和#size-cells

        #address-cells和#size-cells属性可用于任何在设备树层次结构中拥有子节点的设备节点，并描述子设备节点应该如何被寻址。#address-cells属性定义了该节点的子节点中的reg属性该用几个u32类型的数字编码其地址字段。#size-cells则定义了reg属性的size字段需要使用的u32类型的数字的数量。#address-cells和#size-cells都不从父节点那继承，需要明确的定义。示例如下

  1. soc {
  2.     #address-cells = <1>;
  3.     #size-cells = <1>;
  4.     serial {
  5.         compatible = "ns16550";
  6.         reg = <0x4600 0x100>;
  7.         clock-frequency = <0>;
  8.         interrupts = <0xA 0x8>;
  9.         interrupt-parent = <&ipic>;
  10.     };
  11. };

6. reg

        reg属性描述了在父总线定义的地址空间中设备资源的地址。通常表示寄存器映射在内存中的起始地址和长度，或者CPU寄存器地址的真实地址。

        当寄存器在内存中有两段地址时，reg需要指定两对#address-cells和#size-cells，示例如下

reg = <0x3000 0x20 0xFE00 0x100>;

7. ranges

        以后补充

8. dma-ranges

        以后补充

四. DTS设备节点类型介绍

1. 根节点（/）

        设备树有一个根节点，其余节点都是子节点，根节点使用/表示，示意代码如下

  1. / {
  2.  
  3. };

2. /aliases

        aliases节点是用来定义一个设备节点的别名的，aliases节点应该在设备树的根节点中使用。

aliases的属性名是需要指定的别名，属性值是设备树中某个节点的完整路径，示例如下

  1. aliases {
  2.     serial0 = "/simple-bus@fe000000/serial@llc500";
  3.     ethernet0 = "/simple-bus@fe000000/ethernet@31c000";
  4. };

3. /memory

       memory节点是用于描述系统的物理内存的的布局的，如果系统有多个地址范围的内存，则多个memory节点需要创建，或者在reg节点中指定多个范围。示例如下

  1. memory@0 {
  2.     device_type = "memory";
  3.     reg = <0x000000000 0x00000000 0x00000000 0x80000000
  4.            0x000000001 0x00000000 0x00000001 0x00000000>;
  5. };
  1. memory@0 {
  2.     device_type = "memory";
  3.     reg = <0x000000000 0x00000000 0x00000000 0x80000000>;
  4. };
  5. memory@100000000 {
  6.     device_type = "memory";
  7.     reg = <0x000000001 0x00000000 0x00000001 0x00000000>;
  8. };

4. /chosen

        chosen节点不用来描述一个真实的设备，而是描述设备的启动和运行参数，例如bootargs，示例如下

  1. chosen {
  2.     bootargs = "root=/dev/nfs rw nfsroot=192.168.1.1 console=ttyS0,115200";
  3. };

5. /cpus

        后面补充

6. /cpus/cpu*

        后面补充

五. 总结

        本文主要介绍了设备树的格式布局，属性名，设备节点名的使用。

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