Device Tree资源展开过程

Device Tree就是为了取代板级信息代码而推出的。所以，大量在arch/arm/plat-xxxx, arch/arm/mach-xxxx中做的工作不再是必要的了。

A: 注册platform_device，绑定resource，即内存、IRQ等板级信息

形如： 

static struct resource xxx_resources[] = {
         [0] = {
                 .start  = …,
                 .end    = …,
                 .flags  = IORESOURCE_MEM,
         },
         [1] = {
                 .start  = …,
                 .end    = …,
                 .flags  = IORESOURCE_IRQ,
        },
 };
 static struct platform_device xxx_device = {
         .name           = "xxx",
         .id             = -1,
         .dev            = {
                                 .platform_data          = &xxx_data,
         },
         .resource       = xxx_resources,
         .num_resources  = ARRAY_SIZE(xxx_resources),
 };

 之类的platform_device代码都不再需要，其中platform_device会由kernel通过解析fdt自动展开。而这些resource实际来源于.dts中设备结点的reg、interrupts属性。典型地，大多数总线都与“simple_bus”兼容，而在SoC对应的machine的.init_machine成员函数中，调用of_platform_bus_probe(NULL, xxx_of_bus_ids, NULL);即可自动展开所有的platform_device。譬如，假设我们有个XXX SoC，则可在arch/arm/mach-xxx/的板文件中透过如下方式展开.dts中的设备结点对应的platform_device：

 static struct of_device_id xxx_of_bus_ids[] __initdata = {
         { .compatible = "simple-bus", },
         {},
 };

 void __init xxx_mach_init(void)
 {
         of_platform_bus_probe(NULL, xxx_of_bus_ids, NULL);
 }

 #ifdef CONFIG_ARCH_XXX

 DT_MACHINE_START(XXX_DT, "Generic XXX (Flattened Device Tree)")
         …
         .init_machine   = xxx_mach_init,
         …
 MACHINE_END
 #endif

 

B. 注册i2c_board_info，指定IRQ等board级别信息：

 

 

static struct i2c_board_info __initdata inv_mpu9250_i2c0_board_info[] = {
 {
  I2C_BOARD_INFO(MPU_GYRO_NAME, MPU_GYRO_ADDR),// MPU_GYRO_ADDR=0x68
  .platform_data = &mpu9250_gyro_data,
 },
 {
  I2C_BOARD_INFO(MPU_BMP_NAME, MPU_BMP_ADDR),
  .platform_data = &mpu_bmp_pdata,
 },
 {
  I2C_BOARD_INFO(MPU_COMPASS_NAME, MPU_COMPASS_ADDR),
  .platform_data = &mpu_compass_data,
 },
};

  

inv_mpu9250_i2c0_board_info[0].irq = gpio_to_irq(MPU_GYRO_IRQ_GPIO);

i2c_register_board_info(gyro_bus_num, inv_mpu9250_i2c0_board_info, ARRAY_SIZE(inv_mpu9250_i2c0_board_info));

 

可以在dtsi中修改为：

/ {
  {
   {
   compatible = "invensense,mpu6515";
   reg = <0x68>;
   interrupt-parent = <&gpio>;
   interrupts = <169 0x01>;
   invensense,int_config = <0x10>;
   invensense,level_shifter = <0>;
   invensense,orientation = [ff 00 00 00 01 00 00 00 ff];
   invensense,sec_slave_type = <0>;
   invensense,key = [4e cc 7e eb f6 1e 35 22
       00 34 0d 65 32 e9 94 89];
   vlogic-supply = <&palmas_smps8>;
   vdd-supply = <&palmas_smps9>;
  };

   {
   compatible = "ak,ak8963";
   reg = <0x0c>;
   orientation = [ff 00 00 00 01 00 00 00 ff];
   config = "mpu";
   vid-supply = <&palmas_smps8>;
   vdd-supply = <&palmas_smps9>;
  };
 };
};