Uboot : parse info from dts to control gpio

README.md

@@ -20,6 +20,10 @@
 
 [Regmap 驱动实例](./debug/regmap/README.md)
 
+## Uboot中驱动开发
+
+[GPIO驱动](./uboot/README.md)
+
 ## 烧写
 
 ### 分区和对应文件

uboot/README.md

@@ -0,0 +1,82 @@
+# Uboot
+
+## 在uboot中控制gpio操作led实例
+
+![leds](./leds.png)
+
+对于上图的Q23三极管,只要拉高WORK_LED管脚,三级管导通,led被点亮
+
+在设备树中leds描述如下
+
+```c
+leds {
+   compatible = "gpio-leds";
+   power {
+	   label = "firefly:blue:power";
+	   linux,default-trigger = "ir-power-click";
+	   default-state = "on";
+	   gpios = <&gpio2 D3 GPIO_ACTIVE_HIGH>;
+	   pinctrl-names = "default";
+	   pinctrl-0 = <&led_power>;
+   };
+   user {
+	   label = "firefly:yellow:user";
+	   linux,default-trigger = "ir-user-click";
+	   default-state = "off";
+	   gpios = <&gpio0 B5 GPIO_ACTIVE_HIGH>;
+	   pinctrl-names = "default";
+	   pinctrl-0 = <&led_user>;
+   };
+};
+ ```
+
+其中注意两个宏设置,和名字意思相反
+
+	#define GPIO_ACTIVE_HIGH 0
+	#define GPIO_ACTIVE_LOW 1
+
+在uboot的板级驱动文件rk33xx.c中添加如下代码,
+后在board_late_init函数中调用power_led_init即可
+
+```c
+static struct fdt_gpio_state power_led_gpio;
+static struct fdt_gpio_state user_led_gpio;
+int power_led_parse_dt(const void *blob)
+{
+	int power_node = 0;
+	int user_node = 0;
+	int node = 0;
+
+	/* 通过compatible获取leds的node */
+	node = fdt_node_offset_by_compatible(blob, 0, "gpio-leds");
+	if (node < 0) {
+		printf("can't find dts node for led\n");
+		return -ENODEV;
+	}
+
+	/* 获取leds下power和user的node */
+	power_node = fdt_subnode_offset(blob, node, "power");
+	user_node = fdt_subnode_offset(blob, node, "user");
+
+	/* 获取power和user里管脚配置 */
+	fdtdec_decode_gpio(blob, power_node, "gpios", &power_led_gpio);
+	fdtdec_decode_gpio(blob, user_node, "gpios", &user_led_gpio);
+
+	/* 打印出相关信息 */
+	printf("power_led_gpio: %s,%d-%d\n", power_led_gpio.name, power_led_gpio.gpio, power_led_gpio.flags);
+	printf("user_led_gpio: %s,%d-%d\n", user_led_gpio.name, user_led_gpio.gpio, user_led_gpio.flags);
+
+	return 0;
+}
+
+void power_led_init(void)
+{
+	power_led_parse_dt(gd->fdt_blob);
+	if (power_led_gpio.name != NULL)
+	{
+		/* 由于GPIO_ACTIVE_HIGH宏定义反了,所以这里需要取反flags */
+		gpio_direction_output(power_led_gpio.gpio, !power_led_gpio.flags);
+		gpio_direction_output(user_led_gpio.gpio, !user_led_gpio.flags);
+	}
+}
+```