当使能一个I2C或者UART功能导致系统开不起机的情况，一般有两点原因：

1、Pin脚被占用

2、在TZ那边，Pin脚给的权限不够

以SDM660平台的I2C_3为例：

我在sdm660-mtp.dtsi文件中使能了i2_3:

&i2c_3 {
	status = "ok";
};

结果原本能开机的系统开不起来了……

i2c的配置在sdm660-blsp.dtsi文件中，我们一起来看一下：

i2c_3: [email protected] { /* BLSP1 QUP3 */
	compatible = "qcom,i2c-msm-v2";
	#address-cells = <1>;
	#size-cells = <0>;
	reg = <0xc177000  0x600>;
	reg-names = "qup_phys_addr";
	interrupt-names = "qup_irq";
	interrupts = <0 97 0>;
	dmas = <&dma_blsp1 8 64 0x20000020 0x20>,
		<&dma_blsp1 9 32 0x20000020 0x20>;
	dma-names = "tx", "rx";
	qcom,master-id = <86>;
	qcom,clk-freq-out = <400000>;
	qcom,clk-freq-in  = <19200000>;
	clock-names = "iface_clk", "core_clk";
	clocks = <&clock_gcc GCC_BLSP1_AHB_CLK>,
		 <&clock_gcc GCC_BLSP1_QUP3_I2C_APPS_CLK>;
	qcom,i2c-dat = <&tlmm 10 0x00>;
	qcom,i2c-clk = <&tlmm 11 0x00>;
	pinctrl-names = "i2c_active", "i2c_sleep", "i2c_bitbang";
	pinctrl-0 = <&i2c_3_active>;
	pinctrl-1 = <&i2c_3_sleep>;
	pinctrl-2 = <&i2c_3_bitbang>;
	status = "disabled";
};

嗯……以上，似乎没什么问题，好吧，看高通给的SDM660 的GPIO CONFIG文件找对应的pin脚号：

1、检查kernel里pin脚有没有被占用，看sdm660-pinctrl.dtsi文件发现在SPI3的配置中有占用，嗯！果断屏蔽掉！

gpio10和gpio11的占用通通/**/屏蔽掉！

spi_3 {
	spi_3_active: spi_3_active {
		mux {
			pins = "gpio8", "gpio9"/*,
					"gpio10", "gpio11"*/;
			function = "blsp_spi3";
		};

		config {
			pins = "gpio8", "gpio9"/*,
					"gpio10", "gpio11"*/;
			drive-strength = <6>;
			bias-disable;
		};
	};

	spi_3_sleep: spi_3_sleep {
		mux {
			pins = "gpio8", "gpio9"/*,
					"gpio10", "gpio11"*/;
			function = "blsp_spi3";
		};

		config {
			pins = "gpio8", "gpio9"/*,
					"gpio10", "gpio11"*/;
			drive-strength = <6>;
			bias-disable;
		};
	};
};

更改dtsi后单编的命令为：在LA.UM.7.2\LINUX\android目录下执行 m dtboimage -jx 和 m bootimage -jx

编译出来的文件路径：

LA.UM.7.2\LINUX\android\out\target\product\sdm660_64\dtbo.img

LA.UM.7.2\LINUX\android\out\target\product\sdm660_64\boot.img

adb单刷dtbo和boot的命令：

fastboot flash dtbo dtbo.img

fastboot flash boot boot.img

2、检查TZ端pin脚的权限给的够不够

TZ.BF.4.0.7\trustzone_images\core\buses\qup_accesscontrol\honeybadger\config\QUPAC_660_Access.xml

果然，不仅多配了俩口，连权限给的也只有TZ能用，嗯，改！

<device id=BLSP_QUP3_DEV_ACCESS>
  <props name="PERIPH ID"           type=DALPROP_ATTR_TYPE_UINT32>     BLSP_QUP3         </props>
  <props name="GPIO range"          type=DALPROP_ATTR_TYPE_BYTE_SEQ>   10, 11, end       </props> 
  <props name="IS_GPIO_PROTECTED"   type=DALPROP_ATTR_TYPE_UINT32>     1                 </props>
  <props name="RW_ACCESS_LIST"      type=DALPROP_ATTR_TYPE_BYTE_SEQ>   AC_HLOS, end      </props>
  <props name="IS_PERSISTENT"       type=DALPROP_ATTR_TYPE_UINT32>     0                 </props>		
</device>

更改TZ后单编的命令为：在TZ.BF.4.0.7\trustzone_images目录下执行 ./build_target_sdm660.sh

编译出来的文件路径：TZ.BF.4.0.7\trustzone_images\build\ms\bin\KAJAANAA\devcfg.mbn

adb单刷devcfg.mbn的命令：

fastboot flash devcfg_a   devcfg.mbn
fastboot flash devcfg_b   devcfg.mbn