全志V3S开发（六）-TFT屏幕适配

标签：par V3S 适配全志 dev fbtft ret gpio size

一、环境及demo目标

1. 我使用的内核版本是5.2.y。

2. 我使用的并不是Licheepi官方给出的RGB屏，而是2.4寸ST7789V-TFTLCD屏幕，分辨率为240*320。因此需要在linux Kernel中对屏幕进行适配，这个demo最终能将终端显示在屏幕上。

二、硬件连接

licheepi开发板与TFT屏幕之间按照如下线序进行连接：

硬件线序
TFT屏幕	licheepi开发板	备注
3.3V	3.3V	必须接
GND	GND	必须接
BL	PWM0	背光引脚，不需要调节的话直接接3V3
SCK	SPI-SCK	必须接
RST	U2R	必须接，可以自己改
CS	SPI-CS	必须接
DC	U2T	必须接
MOSI（SDI）	MOSI	必须接
MISO（SDO）	MISO	可不接

三、配置Linux Kernel的menuconfig

1. 进入/home/daemonchen/linux/V3S/linux_kernel/linux/linux-zero-5.2.y文件夹，在Licheepi_MY_Ethernet_defconfig的基础上进行修改。

cd /home/daemonchen/linux/V3S/linux_kernel/linux/linux-zero-5.2.y
export ARCH=arm
export CROSS_COMPILE=$CROSS_COMPILE
make Licheepi_MY_Ethernet_defconfig
make menuconfig

2. 进入menuconfig以后按照以下路径进行修改：

#使能ST7789V芯片
Device Drivers  --->
    [*] Staging drivers  --->
        <*> Support for small TFT LCD display modules  --->
            <*> FB driver for the ST7789V LCD Controller

#如有需要，使能开机企鹅logo，一般用作屏幕测试
Device Drivers  --->
    Graphics support  --->
        [*] Bootup logo  --->
            [*]   Standard black and white Linux logo (NEW)                  
            [*]   Standard 16-color Linux logo (NEW)                         
            [*]   Standard 224-color Linux logo (NEW)

3. 保存退出

4. 为了方便下次直接调用这些配置，使用下列命令将配置保存为Licheepi_MY_LCD_defconfig.

make savedefconfig
cp defconfig arch/arm/configs/Licheepi_MY_LCD_defconfig

四、更改设备树及内核文件

1. 首先打开arch/arm/boot/dts/Makefile,注释掉sun8i-v3s-licheepi-zero-with-480x272-lcd.dtb/sun8i-v3s-licheepi-zero-with-800x480-lcd.dtb/sun8i-v3s-licheepi-zero-with-1024x600-lcd.dtb，我们只编译sun8i-v3s-licheepi-zero-dock.dtb和sun8i-v3s-licheepi-zero.dtb，注意“\”后面千万不要有空格！如下图所示：

2. 打开arch/arm/boot/dts下的sun8i-v3s.dtsi，做如下更改：

注释掉57-64行（关闭默认视频输出）：

注释掉353-356行（关闭pwm0，与屏幕引脚冲突）：

注释掉 464-473行（关闭uart2，与屏幕引脚冲突）：

保存退出。

3. 打开arch/arm/boot/dts下的sun8i-v3s-licheepi-zero-dock.dts，做如下更改：

在文件末尾加上spi0的追加节点，即st7789v的设备树节点：

&spi0{
    status = "okay";
    st7789v: st7789v@0{
        compatible = "sitronix,st7789v";
        reg = <0>;
        status = "okay";
        spi-max-frequency = <36000000>;
        spi-cpol;
        spi-cpha;
        rotate = <90>;
        fps = <30>;
        buswidth = <8>;
        rgb;
        tft-dc-gpios    = <&pio 1 0 GPIO_ACTIVE_HIGH>;  // PB0 
        tft-reset-gpios = <&pio 1 1 GPIO_ACTIVE_HIGH>;  // PB1
        tft-led-gpios   = <&pio 1 4 GPIO_ACTIVE_HIGH>;  // PB4
        width = <240>;
        height= <320>;
        debug = <0>;
    };
};

如下图所示：

4. 打开drivers/staging/fbtft/fbtft-core.c文件，修改fbtft_request_one_gpio函数，注意需要在该文件上引入下面头文件，否则编译报错。

#include <linux/of_gpio.h>

static int fbtft_request_one_gpio(struct fbtft_par *par,
				  const char *name, int index,
				  struct gpio_desc **gpiop)
{
/*
	struct device *dev = par->info->device;
	struct device_node *node = dev->of_node;
	int ret = 0;

	if (of_find_property(node, name, NULL)) {
		*gpiop = devm_gpiod_get_index(dev, dev->driver->name, index,
					      GPIOD_OUT_HIGH);
		if (IS_ERR(*gpiop)) {
			ret = PTR_ERR(*gpiop);
			dev_err(dev,
				"Failed to request %s GPIO:%d\n", name, ret);
			return ret;
		}
		fbtft_par_dbg(DEBUG_REQUEST_GPIOS, par, "%s: '%s' GPIO\n",
			      __func__, name);
	}

	return ret;
*/
	struct device *dev = par->info->device;
    struct device_node *node = dev->of_node;
    int gpio, flags, ret = 0;
    enum of_gpio_flags of_flags;
    char gpio_names[32];

    //sprintf(gpio_names, "%s-gpios", name);
    sprintf(gpio_names, "%s", name);
    printk("@ gpio_names = %s\n", gpio_names);
    if (of_find_property(node, gpio_names, NULL)) {
        gpio = of_get_named_gpio_flags(node, gpio_names, index, &of_flags);
        printk ("@ gpio = %d | ENOENT = %d | EPROBE_DEFER = %d  \n", gpio, ENOENT, EPROBE_DEFER);
        if (gpio == -ENOENT)
            return 0;
        if (gpio == -EPROBE_DEFER)
            return gpio;
        if (gpio < 0) {
            dev_err(dev,
                "failed to get '%s' from DT\n", gpio_names);
            return gpio;
        }

         //active low translates to initially low 
        flags = (of_flags & OF_GPIO_ACTIVE_LOW) ? GPIOF_OUT_INIT_LOW :
                            GPIOF_OUT_INIT_HIGH;
        ret = devm_gpio_request_one(dev, gpio, flags,
                        dev->driver->name);
        if (ret) {
            dev_err(dev,
                "gpio_request_one('%s'=%d) failed with %d\n",
                gpio_names, gpio, ret);
            return ret;
        }

        *gpiop = gpio_to_desc(gpio);
        fbtft_par_dbg(DEBUG_REQUEST_GPIOS, par, "%s: '%s' = GPIO%d\n",
                            __func__, gpio_names, gpio);
    }
    return ret;
}

5. 打开drivers/staging/fbtft/fbtft-core.c文件，修改fbtft_reset函数。

static void fbtft_reset(struct fbtft_par *par)
{
	/*
	if (!par->gpio.reset)
		return;
	fbtft_par_dbg(DEBUG_RESET, par, "%s()\n", __func__);
	gpiod_set_value_cansleep(par->gpio.reset, 0);
	usleep_range(20, 40);
	gpiod_set_value_cansleep(par->gpio.reset, 1);
	msleep(120);
	*/

	if (!par->gpio.reset)
        return;
    fbtft_par_dbg(DEBUG_RESET, par, "%s()\n", __func__);
    gpiod_set_value_cansleep(par->gpio.reset, 1);
    usleep_range(20, 40);
    gpiod_set_value_cansleep(par->gpio.reset, 0);
    msleep(120);
    gpiod_set_value_cansleep(par->gpio.reset, 1);
    msleep(10);
}

6. 打开drivers/staging/fbtft/fbtft-core.c文件，修改fbtft_request_gpios_dt函数里面，reset和dc引脚名称，从reset-gpios、dc-gpios和 led-gpios 改为tft-reset-gpios 、 tft-dc-gpios 和tft-led-gpios。

7. 打开drivers/staging/fbtft/fbtft-bus.c文件，修改fbtft_write_vmem16_bus8函数，直接替换

int fbtft_write_vmem16_bus8(struct fbtft_par *par, size_t offset, size_t len)
{
	u16 *vmem16;
	__be16 *txbuf16 = par->txbuf.buf;
	size_t remain;
	size_t to_copy;
	size_t tx_array_size;
	int i;
	int ret = 0;
	size_t startbyte_size = 0;
 
	fbtft_par_dbg(DEBUG_WRITE_VMEM, par, "%s(offset=%zu, len=%zu)\n",
		      __func__, offset, len);
 
	remain = len / 2;
	vmem16 = (u16 *)(par->info->screen_buffer + offset);
 
	if (par->gpio.dc)
	{
		//printk("dc拉高！\n");
		gpiod_set_value(par->gpio.dc, 1);
	}
	/* non buffered write */
	if (!par->txbuf.buf)
		return par->fbtftops.write(par, vmem16, len);
 
	/* buffered write */
	tx_array_size = par->txbuf.len / 2;
 
	if (par->startbyte) {
		txbuf16 = par->txbuf.buf + 1;
		tx_array_size -= 2;
		*(u8 *)(par->txbuf.buf) = par->startbyte | 0x2;
		startbyte_size = 1;
	}
 
	while (remain) {
		to_copy = min(tx_array_size, remain);
		dev_dbg(par->info->device, "to_copy=%zu, remain=%zu\n",
			to_copy, remain - to_copy);
 
		for (i = 0; i < to_copy; i++)
			txbuf16[i] = cpu_to_be16(vmem16[i]);
 
		vmem16 = vmem16 + to_copy;
		ret = par->fbtftops.write(par, par->txbuf.buf,
						startbyte_size + to_copy * 2);
		if (ret < 0)
			return ret;
		remain -= to_copy;
	}
 
	return ret;
}

五、编译内核和设备树

1. 输入以下命令进行编译：

make -j16
make  -j16 modules
sudo make -j16 modules_install
make dtbs

2. 将zImage和sun8i-v3s-licheepi-zero-dock.dtb复制到nfs目录下：

cp arch/arm/boot/zImage /home/daemonchen/linux/tftpboot -f
cp arch/arm/boot/dts/sun8i-v3s-licheepi-zero-dock.dtb /home/daemonchen/linux/tftpboot -f

六、启动测试

1. 使用SecureCRT查看串口0输出的log，在uboot界面配置网络相关变量为：

setenv ipaddr 192.168.147.132
setenv gatewayip 192.168.147.2
setenv netmask 255.255.255.0
setenv serverip 192.168.147.130
saveenv

2. 将终端投射在屏幕上（即在bootargs中加入console=tty0）：

setenv bootcmd 'tftp 0x41000000 zImage; tftp 0x41800000 sun8i-v3s-licheepi-zero-dock.dtb; bootz 0x41000000 - 0x41800000'
setenv bootargs 'console=tty0 console=ttyS0,115200 root=/dev/nfs rw nfsroot=192.168.147.130:/home/daemonchen/linux/nfs/rootfs ip=192.168.147.132:192.168.147.130:192.168.147.2:255.255.255.0::eth0::off init=/linuxrc'
saveenv

3. 启动测试：