DRV_06_I2C接口触摸屏驱动分析

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I2C接口触摸屏驱动分析

参考资料：

• Linux 5.x内核

  • Documentation\devicetree\bindings\input\touchscreen\goodix.txt
  • drivers/input/touchscreen/goodix.c

• Linux 4.x内核

  • Documentation\devicetree\bindings\input\touchscreen\goodix.txt
  • drivers/input/touchscreen/gt9xx/gt9xx.c

• 设备树

  • IMX6ULL：Linux-4.9.88/arch/arm/boot/dts/100ask_imx6ull-14x14.dts
  • STM32MP157：Linux-5.4/arch/arm/boot/dts/stm32mp15xx-100ask.dtsi

1. 驱动程序框架

2. 设备树示例 2.1 设备树讲解

示例：

i2c@00000000 {
	/* ... */

	gt928@5d {
		compatible = "goodix,gt928";
		reg = ;
		interrupt-parent = ;
		interrupts = ;

		irq-gpios = ;
		reset-gpios = ;
	};

	/* ... */
};

作为一个I2C设备，在某个I2C控制器节点下创建一个子节点。 属性：

• 必备，根据这个属性找到驱动程序：compatible = "xxxx";

• 必备，I2C设备地址：reg = ;

• 可选：

  • 中断

• 复位引脚

2.2 100ASK_IMX6ULL

&i2c2 {
	gt9xx@5d {
			compatible = "goodix,gt9xx";
			reg = ;
			status = "okay";
			interrupt-parent = ;
			interrupts = ;
			pinctrl-names = "default";
			pinctrl-0 = ;
			/*pinctrl-1 = ;*/
			/*
			 pinctrl-names = "default", "int-output-low", "int-output-high", "int-input";
			 pinctrl-0 = ;
			 pinctrl-1 = ;
			 pinctrl-2 = ;
			 pinctrl-3 = ;
			*/
			reset-gpios = ;
			irq-gpios = ;
			irq-flags = ;                /*1:rising 2: falling*/

			touchscreen-max-id = ;
			touchscreen-size-x = ;
			touchscreen-size-y = ;
			touchscreen-max-w = ;
			touchscreen-max-p = ;
			/*touchscreen-key-map = , ;*/ /*KEY_HOMEPAGE, KEY_BACK*/

			goodix,type-a-report = ;
			goodix,driver-send-cfg = ;
			goodix,create-wr-node = ;
			goodix,wakeup-with-reset = ;
			goodix,resume-in-workqueue = ;
			goodix,int-sync = ;
			goodix,swap-x2y = ;
			goodix,esd-protect = ;
			goodix,pen-suppress-finger = ;
			goodix,auto-update = ;
			goodix,auto-update-cfg = ;
			goodix,power-off-sleep = ;
			/* ...... */
	};
};	

2.3 100ASK_STM32MP157

&i2c4 {
    gt911@5d {
		compatible = "goodix,gt928";
		reg = ;
		interrupt-parent = ;
		interrupts = ;
		reset-gpios = ;
		irq-gpios = ;
		irq-flags = ;                /*1:rising 2: falling*/
		touchscreen-max-id = ;
		touchscreen-size-x = ;
		touchscreen-size-y = ;
	};
};

3. 驱动程序分析 3.1 分配/设置/注册input_dev

• IMX6ULL Linux 4.x

gtp_probe
	ret = gtp_request_input_dev(ts);
			ts->input_dev = input_allocate_device();
			......
			ret = input_register_device(ts->input_dev);

	ret = gtp_request_irq(ts);			

• STM32MP157 Linux 5.x

goodix_ts_probe
		error = request_firmware_nowait(THIS_MODULE, true, ts->cfg_name,
						&client->dev, GFP_KERNEL, ts,
						goodix_config_cb);

goodix_config_cb
	goodix_configure_dev(ts);
		ts->input_dev = devm_input_allocate_device(&ts->client->dev);
		......
		error = input_register_device(ts->input_dev);
		
		error = goodix_request_irq(ts);		

3.2 注册中断处理函数

• IMX6ULL Linux 4.x

		ret = request_threaded_irq(ts->client->irq, NULL,
				gtp_irq_handler,
				ts->pdata->irq_flags | IRQF_ONESHOT,
				ts->client->name,
				ts);

• STM32MP157 Linux 5.x

static int goodix_request_irq(struct goodix_ts_data *ts)
{
	return devm_request_threaded_irq(&ts->client->dev, ts->client->irq,
					 NULL, goodix_ts_irq_handler,
					 ts->irq_flags, ts->client->name, ts);
}

3.3 中断处理函数分析

通过I2C函数读取数据、上报数据。

• IMX6ULL Linux 4.x

gtp_irq_handler
	gtp_work_func(ts);
		point_state = gtp_get_points(ts, points, &key_value);
			gtp_i2c_read
				i2c_transfer
		gtp_mt_slot_report(ts, point_state & 0x0f, points);
			input_mt_slot
			input_mt_report_slot_state
			input_report_abs

• STM32MP157 Linux 5.x

goodix_ts_irq_handler
	goodix_process_events(ts);
		touch_num = goodix_ts_read_input_report(ts, point_data);
			goodix_i2c_read
				i2c_transfer
		goodix_ts_report_touch_9b
			input_mt_slot
			input_mt_report_slot_state
			touchscreen_report_pos
			input_report_abs

	touch_num = goodix_ts_read_input_report(ts, point_data);
		goodix_i2c_read
			i2c_transfer
	goodix_ts_report_touch_9b
		input_mt_slot
		input_mt_report_slot_state
		touchscreen_report_pos
		input_report_abs