gpio power off

Author: FolderLevel

README.md

@@ -2,12 +2,17 @@
 
 个人认为，树莓派应该算是目前开源硬件里学习嵌入式Linux系统最好的工具，里面的设计思路和一些工具是很值得借鉴的，这里主要使用Raspberry Pi 4B进行系统架构分析。
 
+## 40 Pin引脚
+
+![Shematic_RPI_40_Pin.png](docs/images/Shematic_RPI_40_Pin.png)
+
 ## Refers
 
 ## docs
 
 NO.|文件名称|摘要
 :--:|:--|:--
+0014| [动态设备树GPIO控制LED](docs/0014_动态设备树GPIO控制LED.md) | 通过使用动态改变设备树，使用内核gpio-poweroff驱动实现LED控制
 0013| [开机自动发IP信息邮件](docs/0013_开机自动发IP信息邮件.md) | Python3自动发邮件
 0012| [dtparam_dtoverlay_DTS动态设备树](docs/0012_dtparam_dtoverlay_DTS动态设备树.md) | 分析dtparam/dtoverlay本质，为什么能够动态改变设备与驱动的match
 0011| [SoC设备树DTS分析](docs/0011_SoC设备树DTS分析.md) | 怎么分析芯片设备树

docs/0014_动态设备树GPIO控制LED.md

@@ -0,0 +1,110 @@
+# 动态设备树GPIO控制LED
+
+通过使用动态改变设备树，使用内核gpio-poweroff驱动实现LED控制
+
+## 参考文档
+
+* [Device Trees, overlays, and parameters](https://www.raspberrypi.org/documentation/configuration/device-tree.md)
+  * 2.2: Device Tree parameters
+* [Raspberry Pi overlays README](https://github.com/raspberrypi/firmware/blob/master/boot/overlays/README)
+  * gpio-poweroff
+
+## 原理图  
+
+![0014_GPIO_LED_Power_OFF.png](images/0014_GPIO_LED_Power_OFF.png)
+
+## 实践操作
+
+* sudo cat /sys/kernel/debug/gpio
+  ```
+  gpiochip0: GPIOs 0-53, parent: platform/fe200000.gpio, pinctrl-bcm2835:
+   gpio-0   (ID_SDA              )
+   gpio-1   (ID_SCL              )
+   gpio-2   (SDA1                )
+   gpio-3   (SCL1                )
+   gpio-4   (GPIO_GCLK           )
+   gpio-5   (GPIO5               )
+   gpio-6   (GPIO6               )
+   gpio-7   (SPI_CE1_N           )
+   gpio-8   (SPI_CE0_N           )
+   gpio-9   (SPI_MISO            )
+   gpio-10  (SPI_MOSI            )
+  ...省略
+  ```
+* 加载设备树及驱动：
+  * /boot/config.txt
+    * 末尾添加：`dtoverlay=gpio-poweroff,gpiopin=10,export=1`
+    * 需要重启生效
+  * sudo dtoverlay gpio-poweroff gpiopin=10 export=1
+    * 这种方式存在问题，overlay文件系统不生效以后，重启的时候，电平拉不上去，暂不深入解释，自行理解分析
+* sudo cat /sys/kernel/debug/gpio
+  ```
+  gpiochip0: GPIOs 0-53, parent: platform/fe200000.gpio, pinctrl-bcm2835:
+   gpio-0   (ID_SDA              )
+   gpio-1   (ID_SCL              )
+   gpio-2   (SDA1                )
+   gpio-3   (SCL1                )
+   gpio-4   (GPIO_GCLK           )
+   gpio-5   (GPIO5               )
+   gpio-6   (GPIO6               )
+   gpio-7   (SPI_CE1_N           )
+   gpio-8   (SPI_CE0_N           )
+   gpio-9   (SPI_MISO            )
+   gpio-10  (SPI_MOSI            |power_ctrl          ) out lo
+  ...省略
+  ```
+* sudo reboot
+* sudo shutdown now
+* sudo su
+  * cd /sys/class/gpio/gpio10
+  * echo 1 > value
+  * echo 0 > value
+  * 引出一个新的问题：用户空间原来可以这个控制GPIO口
+
+## overlay分析
+
+* arch/arm/boot/dts/overlays/gpio-poweroff-overlay.dts
+  ```dts
+  // Definitions for gpio-poweroff module
+  /dts-v1/;
+  /plugin/;
+  
+  / {
+          compatible = "brcm,bcm2835";
+  
+          fragment@0 {
+                  target-path = "/";
+                  __overlay__ {
+                          power_ctrl: power_ctrl {
+                                  compatible = "gpio-poweroff";
+                                  gpios = <&gpio 26 0>;
+                                  force;
+                          };
+                  };
+          };
+  
+          fragment@1 {
+                  target = <&gpio>;
+                  __overlay__ {
+                          power_ctrl_pins: power_ctrl_pins {
+                                  brcm,pins = <26>;
+                                  brcm,function = <1>; // out
+                          };
+                  };
+          };
+  
+          __overrides__ {
+                  gpiopin =       <&power_ctrl>,"gpios:4",
+                                  <&power_ctrl_pins>,"brcm,pins:0";
+                  active_low =    <&power_ctrl>,"gpios:8";
+                  input =         <&power_ctrl>,"input?";
+                  export =        <&power_ctrl>,"export?";
+                  timeout_ms =    <&power_ctrl>,"timeout-ms:0";
+          };
+  };
+  ```
+
+## 驱动分析
+
+* drivers/power/reset/gpio-poweroff.c
+