记一次移植GT9271无法正常通信

 移植汇顶的TP GT9271时，发现i2c通信不上，检查了TP的供电和复位脚及硬件连接，都没发现问题，然后发现内核有如下的报错信息。

[49533.829164] gpio-272 (goodix_ts_int): _gpiod_direction_output_raw: tried to set a GPIO tied to an IRQ as output
[49533.849418] goodix-ts 3-005d: I2c read failed,dev:5d,reg:8047,size:1
[49533.849433] goodix-ts 3-005d: GTP i2c test failed time 1
[49533.871495] goodix-ts 3-005d: I2c read failed,dev:5d,reg:8047,size:1
[49533.871510] goodix-ts 3-005d: GTP i2c test failed time 2
[49533.895621] goodix-ts 3-005d: I2c read failed,dev:5d,reg:8047,size:1
[49533.895634] goodix-ts 3-005d: GTP i2c test failed time 

但为什么设置io口为输出也报错呢 ，查看相应的代码

drivers/gpio/gpiolib.c

static int _gpiod_direction_output_raw(struct gpio_desc *desc, int value)
{
	struct gpio_chip *gc = desc->gdev->chip;
	int val = !!value;
	int ret;

	/* GPIOs used for IRQs shall not be set as output */
	if (test_bit(FLAG_USED_AS_IRQ, &desc->flags)) {
		gpiod_err(desc,
			  "%s: tried to set a GPIO tied to an IRQ as output\n",
			  __func__);
		return -EIO;
	}

	if (test_bit(FLAG_OPEN_DRAIN, &desc->flags)) {
		/* First see if we can enable open drain in hardware */
		ret = gpio_set_drive_single_ended(gc, gpio_chip_hwgpio(desc),
						  PIN_CONFIG_DRIVE_OPEN_DRAIN);
		if (!ret)
			goto set_output_value;
		/* Emulate open drain by not actively driving the line high */
		if (val)
			return gpiod_direction_input(desc);
	}
	else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags)) {
		ret = gpio_set_drive_single_ended(gc, gpio_chip_hwgpio(desc),
						  PIN_CONFIG_DRIVE_OPEN_SOURCE);
		if (!ret)
			goto set_output_value;
		/* Emulate open source by not actively driving the line low */
		if (!val)
			return gpiod_direction_input(desc);
	} else {
		gpio_set_drive_single_ended(gc, gpio_chip_hwgpio(desc),
					    PIN_CONFIG_DRIVE_PUSH_PULL);
	}

set_output_value:
	if (!gc->set || !gc->direction_output) {
		gpiod_warn(desc,
		       "%s: missing set() or direction_output() operations\n",
		       __func__);
		return -EIO;
	}

	ret = gc->direction_output(gc, gpio_chip_hwgpio(desc), val);
	if (!ret)
		set_bit(FLAG_IS_OUT, &desc->flags);
	trace_gpio_value(desc_to_gpio(desc), 0, val);
	trace_gpio_direction(desc_to_gpio(desc), 0, ret);
	return ret;
}

原来，内核默认禁止中断设置成输出，这也合理，一般设置成中断模式的引脚，只需设置成输入模式，然后读取引脚的状态即可。

但为什么代码里将中断脚设置成输出呢。

查看规格书https://github.com/hadess/gt9xx

居然用中断脚来进行通信了 ，跟普通的中断脚不一样了。

但为什么高通/MTK他们用这份驱动没有问题了，原来他们用pinctrl的方式控制引脚状态，但展讯平台还没支持pinctrl这种方式，用的是普通的gpio模式，所以有这样的问题。那要怎么修改呢。

一种方式是先释放中断，拉低或拉高gpio后，重新设置成中断模式。

第二种方式是屏蔽_gpiod_direction_output_raw的返回，让代码跑下去。