查看“Linux内核-5寸触摸屏驱动移植”的源代码

==实验原理==
FS-MP1A使用的是GT911触摸芯片，通过I2C2总线与SoC进行数据交互。

[[Image:54-1-1-1.png]] <br>

查看原理图确认I2C2管脚对应关系：

[[Image:54-1-1-2.png]] <br>

查看原理图确认中断管脚TP_IRQ和复位管脚TP_RST管脚对应关系：

[[Image:54-1-1-3.png]] <br>

{|class="wikitable"
|-
! 原理图网络编号 !! 对应管脚 !! 管脚功能 !! 管脚功能码
|-
| I2C2_SCL
| PH4
| I2C2_SCL
| AF4
|-
| I2C2_SDA
| PH5 
| I2C2_SDA
| AF4
|-
| TP_RST
| PG8 
| GPIO
| 
|-
| TP_INT
| PG7 
| INT
| 
|}
<ol>
<li>I2C2设备树节点</li>

I2C节点添加与HDMI中对应I2C的内容一致，本节不再重复。

<li>触摸屏设备树节点</li>

参考文档：
 devicetree/bindings/input/touchscreen/goodix.txt
参考goodix.txt及ST提供的I2C相关设备树文档，触摸屏节点内容如下：
<pre><nowiki>
touchscreen@5d {
	compatible = "goodix,gt911";
	reg = <0x5d>;
	irq-gpios = <&gpiog 7 (GPIO_ACTIVE_HIGH | GPIO_PULL_UP)>;
	reset-gpios = <&gpiog 8	GPIO_ACTIVE_HIGH>;
	interrupt-parent = <&gpiog>;
	interrupts = <7 IRQ_TYPE_EDGE_FALLING>;
	status = "okay";

	// touchscreen-inverted-x;
	touchscreen-inverted-y;
	// touchscreen-swapped-x-y;
};
</nowiki></pre>
</ol>

==实验目的==
熟悉基于Linux操作系统下的MIPI 触摸屏设备驱动移植配置过程。
==实验平台==
华清远见开发环境，FS-MP1A平台；

==实验步骤==
<ol>
<li>导入交叉编译工具链</li>
 linux@ubuntu:$ source /opt/st/stm32mp1/3.1-openstlinux-5.4-dunfell-mp1-20-06-24/environment-setup-cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi
<li>修改设备树</li>

修改arch/arm/boot/dts/stm32mp157a-fsmp1a-mipi050.dts文件，在文件末尾增加如下内容：
<pre><nowiki>
&i2c2 {
	pinctrl-names = "default", "sleep";
	pinctrl-0 = <&i2c2_pins_a>;
	pinctrl-1 = <&i2c2_pins_sleep_a>;
	i2c-scl-rising-time-ns = <100>;
	i2c-scl-falling-time-ns = <7>;
	status = "okay";
	/delete-property/dmas;
	/delete-property/dma-names;

	touchscreen@5d {
		compatible = "goodix,gt911";
		reg = <0x5d>;
		irq-gpios = <&gpiog 7 (GPIO_ACTIVE_HIGH | GPIO_PULL_UP)>;
		reset-gpios = <&gpiog 8	GPIO_ACTIVE_HIGH>;
		interrupt-parent = <&gpiog>;
		interrupts = <7 IRQ_TYPE_EDGE_FALLING>;
		status = "okay";

		// touchscreen-inverted-x;
		touchscreen-inverted-y;
		// touchscreen-swapped-x-y;
	};
};
</nowiki></pre>
<li>配置内核</li>

由于内核源码默认配置以及支持sii902x，本节列出主要选项，如下：
<pre><nowiki>
linux@ubuntu:$ make menuconfig
Device Drivers  --->
	Graphics support  --->
		<*> Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)  --->
		<*> DRM Support for STMicroelectronics SoC Series
			Display Interface Bridges  --->
				<*> Silicon Image sii902x RGB/HDMI bridge
</nowiki></pre>
<li>编译内核级设备树：</li>
 linux@ubuntu:$ make -j4 uImage dtbs LOADADDR=0xC2000040
<li>重启测试</li>

将编译好的设备树和内核镜像拷贝到/tftpboot目录下，通过tftp引导内核，设备连接MIPI屏幕，重启设备后查看/dev会多出event0的信息，这是点击屏幕会的到反馈。
 root@fsmp1a:# ls /dev/input
[[Image:54-1-4-1.png]] <br>

</ol>