NanoPi NEO Air使用十二：使用自带的fbtft驱动点亮SPI接口TFT屏幕，ST7789V

上节自己编写spi驱动来点亮spi接口的小屏幕，其实Linux内核里已经提供spi接口小屏的设备驱动，即内核中已经自带了此类驱动，名字为fbtft。本节就来使用它。

引脚

240x240分辨率，1.3寸，主控为ST7789VW。

与开发板的引脚连接确定如下：

功能	IO
GND	Pin6
5V	Pin2
LCD_RESET	Pin7-PG11
LCD_DC	Pin22-PA1
SPICLK	Pin23-PC2
SPIMOSI	Pin19-PC0

从开发板的引脚图发现，开发板使用的SPI0。

修改设备树

打开/home/ql/linux/H3/linux/arch/arm/boot/dts/sun8i-h3-nanopi.dtsi，找到spi0节点，修改为如下：

&spi0 {
	/* needed to avoid dtc warning */
	#address-cells = <1>;
	#size-cells = <0>;

	status = "okay";
	pinctrl-names = "default";
	pinctrl-0 = <&spi0_pins &spi0_cs_pins>;
	cs-gpios = <&pio 2 3 GPIO_ACTIVE_HIGH>, <&pio 0 6 GPIO_ACTIVE_HIGH>; /*SPI-CS:PC3 and PA6*/

	pitft: pitft@0{
		compatible = "sitronix,st7789vw";
		reg = <0>;
		status = "okay";

		spi-max-frequency = <50000000>;
		rotate = <0>;
		fps = <33>;
		buswidth = <8>;
		dc-gpios = <&pio 0 1 GPIO_ACTIVE_HIGH>;	 /* PA1 */
		reset-gpios = <&pio 6 11 GPIO_ACTIVE_HIGH>; /* PG11 */
		led-gpios = <&pio 0 0 GPIO_ACTIVE_LOW>;	 /* PA0 */		
		debug = <0x0>;
	};
};

&pio {
	leds_npi: led_pins {
		pins = "PA10";
		function = "gpio_out";
	};

	pinctrl_testTFTRes: testTFTRes_pins {
		pins = "PG11";
		function = "gpio_out";
	};

	pinctrl_testTFTDc: testTFTDc_pins {
		pins = "PA1";
		function = "gpio_out";
	};

	pinctrl_testTFTBk: testTFTBk_pins {
		pins = "PA0";
		function = "gpio_out";
	};
	
	spi0_cs_pins: spi0_cs_pins {
		pins = "PC3", "PA6";
		function = "gpio_out";
	};
};

关闭HDMI，否则设备默认HDMI输出，tft黑屏

&hdmi {
	//status = "okay";
	status = "disable";
};

&hdmi_out {
	hdmi_out_con: endpoint {
		remote-endpoint = <&hdmi_con_in>;
	};
};

&sound_hdmi {
	//status = "okay";
	status = "disable";
};

修改驱动文件

打开/home/ql/linux/H3/linux/drivers/staging/fbtft/路径，看下有没有fb_st7789vw.c文件，如果有下面的步骤就可以忽略了。
如果没有，那么新建一个fb_st7789vw.c文件，把下面内容复制进去，保存。

/*
 * FB driver for the ST7789V LCD Controller
 *
 * Copyright (C) 2015 Dennis Menschel
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include "fbtft.h"

#define DRVNAME "fb_st7789vw"

#define DEFAULT_GAMMA \
	"D0 04 0D 11 13 2B 3F 54 4C 18 0D 0B 1F 23\n" \
	"D0 04 0C 11 13 2C 3F 44 51 2F 1F 1F 20 23"

/**
 * enum st7789v_command - ST7789V display controller commands
 *
 * @PORCTRL: porch setting
 * @GCTRL: gate control
 * @VCOMS: VCOM setting
 * @VDVVRHEN: VDV and VRH command enable
 * @VRHS: VRH set
 * @VDVS: VDV set
 * @VCMOFSET: VCOM offset set
 * @PWCTRL1: power control 1
 * @PVGAMCTRL: positive voltage gamma control
 * @NVGAMCTRL: negative voltage gamma control
 *
 * The command names are the same as those found in the datasheet to ease
 * looking up their semantics and usage.
 *
 * Note that the ST7789V display controller offers quite a few more commands
 * which have been omitted from this list as they are not used at the moment.
 * Furthermore, commands that are compliant with the MIPI DCS have been left
 * out as well to avoid duplicate entries.
 */
enum st7789v_command {
	PORCTRL = 0xB2,
	GCTRL = 0xB7,
	VCOMS = 0xBB,
	LCMCTRL = 0xC0,
	VDVVRHEN = 0xC2,
	VRHS = 0xC3,
	VDVS = 0xC4,
	VCMOFSET = 0xC5,
	FRCTRL2 = 0xC6,
	PWCTRL1 = 0xD0,
	PVGAMCTRL = 0xE0,
	NVGAMCTRL = 0xE1,
};

#define MADCTL_BGR BIT(3) /* bitmask for RGB/BGR order */
#define MADCTL_MV BIT(5) /* bitmask for page/column order */
#define MADCTL_MX BIT(6) /* bitmask for column address order */
#define MADCTL_MY BIT(7) /* bitmask for page address order */

/**
 * init_display() - initialize the display controller
 *
 * @par: FBTFT parameter object
 *
 * Most of the commands in this init function set their parameters to the
 * same default values which are already in place after the display has been
 * powered up. (The main exception to this rule is the pixel format which
 * would default to 18 instead of 16 bit per pixel.)
 * Nonetheless, this sequence can be used as a template for concrete
 * displays which usually need some adjustments.
 *
 * Return: 0 on success, < 0 if error occurred.
 */
static int init_display(struct fbtft_par *par)
{
	/* turn off sleep mode */
	write_reg(par, MIPI_DCS_EXIT_SLEEP_MODE);
	mdelay(120);

	write_reg(par, MIPI_DCS_SET_ADDRESS_MODE, 0x0);
	write_reg(par, MIPI_DCS_SET_PIXEL_FORMAT, MIPI_DCS_PIXEL_FMT_16BIT);
	write_reg(par, PORCTRL, 0x0C, 0x0C, 0x00, 0x33, 0x33);
	write_reg(par, GCTRL, 0x35);
	write_reg(par, VCOMS, 0x19);
	write_reg(par, LCMCTRL, 0x2C);
	write_reg(par, VDVVRHEN, 0x01);
	write_reg(par, VRHS, 0x12);
	write_reg(par, VDVS, 0x20);
	write_reg(par, FRCTRL2, 0x0F);
	write_reg(par, PWCTRL1, 0xA4, 0xA1);
	write_reg(par, MIPI_DCS_ENTER_INVERT_MODE);
	write_reg(par, MIPI_DCS_SET_DISPLAY_ON);

	return 0;
}

static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
{
	write_reg(par, MIPI_DCS_SET_COLUMN_ADDRESS,
		  xs >> 8, xs & 0xFF, xe >> 8, xe & 0xFF);

	write_reg(par, MIPI_DCS_SET_PAGE_ADDRESS,
		  ys >> 8, ys & 0xFF, ye >> 8, ye & 0xFF);

	write_reg(par, MIPI_DCS_WRITE_MEMORY_START);
}

/**
 * set_var() - apply LCD properties like rotation and BGR mode
 *
 * @par: FBTFT parameter object
 *
 * Return: 0 on success, < 0 if error occurred.
 */
static int set_var(struct fbtft_par *par)
{
	u8 madctl_par = 0;

	if (par->bgr)
		madctl_par |= MADCTL_BGR;
	switch (par->info->var.rotate) {
	case 0:
		break;
	case 90:
		madctl_par |= (MADCTL_MV | MADCTL_MY);
		break;
	case 180:
		madctl_par |= (MADCTL_MX | MADCTL_MY);
		break;
	case 270:
		madctl_par |= (MADCTL_MV | MADCTL_MX);
		break;
	default:
		return -EINVAL;
	}
	write_reg(par, MIPI_DCS_SET_ADDRESS_MODE, madctl_par);
	return 0;
}

/**
 * set_gamma() - set gamma curves
 *
 * @par: FBTFT parameter object
 * @curves: gamma curves
 *
 * Before the gamma curves are applied, they are preprocessed with a bitmask
 * to ensure syntactically correct input for the display controller.
 * This implies that the curves input parameter might be changed by this
 * function and that illegal gamma values are auto-corrected and not
 * reported as errors.
 *
 * Return: 0 on success, < 0 if error occurred.
 */
static int set_gamma(struct fbtft_par *par, u32 *curves)
{
	int i;
	int j;
	int c; /* curve index offset */

	/*
	 * Bitmasks for gamma curve command parameters.
	 * The masks are the same for both positive and negative voltage
	 * gamma curves.
	 */
	static const u8 gamma_par_mask[] = {
		0xFF, /* V63[3:0], V0[3:0]*/
		0x3F, /* V1[5:0] */
		0x3F, /* V2[5:0] */
		0x1F, /* V4[4:0] */
		0x1F, /* V6[4:0] */
		0x3F, /* J0[1:0], V13[3:0] */
		0x7F, /* V20[6:0] */
		0x77, /* V36[2:0], V27[2:0] */
		0x7F, /* V43[6:0] */
		0x3F, /* J1[1:0], V50[3:0] */
		0x1F, /* V57[4:0] */
		0x1F, /* V59[4:0] */
		0x3F, /* V61[5:0] */
		0x3F, /* V62[5:0] */
	};

	for (i = 0; i < par->gamma.num_curves; i++) {
		c = i * par->gamma.num_values;
		for (j = 0; j < par->gamma.num_values; j++)
			curves[c + j] &= gamma_par_mask[j];
		write_reg(
			par, PVGAMCTRL + i,
			curves[c + 0], curves[c + 1], curves[c + 2],
			curves[c + 3], curves[c + 4], curves[c + 5],
			curves[c + 6], curves[c + 7], curves[c + 8],
			curves[c + 9], curves[c + 10], curves[c + 11],
			curves[c + 12], curves[c + 13]);
	}
	return 0;
}

/**
 * blank() - blank the display
 *
 * @par: FBTFT parameter object
 * @on: whether to enable or disable blanking the display
 *
 * Return: 0 on success, < 0 if error occurred.
 */
static int blank(struct fbtft_par *par, bool on)
{
	if (on)
		write_reg(par, MIPI_DCS_SET_DISPLAY_OFF);
	else
		write_reg(par, MIPI_DCS_SET_DISPLAY_ON);
	return 0;
}

static struct fbtft_display display = {
	.regwidth = 8,
	.width = 240,
	.height = 240,
	.gamma_num = 2,
	.gamma_len = 14,
	.gamma = DEFAULT_GAMMA,
	.fbtftops = {
		.init_display = init_display,
		.set_addr_win = set_addr_win,
		.set_var = set_var,
		.set_gamma = set_gamma,
		.blank = blank,
	},
};

FBTFT_REGISTER_DRIVER(DRVNAME, "sitronix,st7789vw", &display);

MODULE_ALIAS("spi:" DRVNAME);
MODULE_ALIAS("platform:" DRVNAME);
MODULE_ALIAS("spi:st7789vw");
MODULE_ALIAS("platform:st7789vw");

MODULE_DESCRIPTION("FB driver for the ST7789VW LCD Controller");
MODULE_AUTHOR("FriendlyElec");
MODULE_LICENSE("GPL");

在Makefile中添加obj-$(CONFIG_FB_TFT_ST7789VW) += fb_st7789vw.o

在Kconfig中添加

config FB_TFT_ST7789VW
	tristate "FB driver for the ST7789VW LCD Controller"
	depends on FB_TFT
	help
	  This enables generic framebuffer support for the Sitronix ST7789VW
	  display controller. The controller is intended for small color
	  displays with a resolution of up to 240x240 pixels.

	  Say Y if you have such a display that utilizes this controller.

编译

到menuconfig中使能此驱动
make menuconfig ARCH=arm CROSS_COMPILE=arm-linux-

Device Drivers  --->　　
	[*] Staging drivers  --->　　
		<*>   Support for small TFT LCD display modules  --->
			<*>   FB driver for the ST7789VW LCD Controller 

# 编译内核、设备树
make zImage dtbs ARCH=arm CROSS_COMPILE=arm-linux- 

# 网络更新内核
scp arch/arm/boot/zImage [email protected]:/boot

# 网络更新设备树
scp arch/arm/boot/dts/sun8i-h3-nanopi-neo-air.dtb [email protected]:/boot

实际效果

命令行

上面的步骤做完了，重启就会有如下画面

我们一直使用SecureCRT作为Linux开发板终端，开发板通过串口和SecureCRT进行通信。现在我们已经驱动起来 LCD 了，所以可以设置 LCD 作为终端，也就是开发板使用自己的显示设备作为自己的终端，然后接上键盘就可以直接在开发板上敲命令了。

我们就拥有了两套终端，一个是基于串口的 SecureCRT，一个就是我们开发板的 LCD屏幕，但是为了方便调试，我们以后还是以 SecureCRT 为主。我们可以通过下面这一行命令向LCD 屏幕输出“hello linux！”
echo hello linux > /dev/tty1

播放视频

sudo apt install mplayer        # 安装mplayer
mplayer 1.mp4 -vo fbdev      

运行QT

下面的指令都要切换root执行

apt-get update && apt-get install git
git clone https://github.com/friendlyarm/matrix.git
cd matrix/demo/nanopi-status
./build.sh
./run.sh /dev/fb_st7789vw

轻量级界面

sudo apt install xfce4
startx

让屏幕旋转180度

如果要让屏幕旋转180度，首先修改设备树：

&spi0 {
	/* needed to avoid dtc warning */
	#address-cells = <1>;
	#size-cells = <0>;

	status = "okay";
	pinctrl-names = "default";
	pinctrl-0 = <&spi0_pins &spi0_cs_pins>;
	cs-gpios = <&pio 2 3 GPIO_ACTIVE_HIGH>, <&pio 0 6 GPIO_ACTIVE_HIGH>; /*SPI-CS:PC3 and PA6*/

	pitft: pitft@0{
		compatible = "sitronix,st7789vw";
		reg = <0>;
		status = "okay";

		spi-max-frequency = <50000000>;
		rotate = <180>;
		fps = <33>;
		buswidth = <8>;
		dc-gpios = <&pio 0 1 GPIO_ACTIVE_HIGH>;	 /* PA1 */
		reset-gpios = <&pio 6 11 GPIO_ACTIVE_HIGH>; /* PG11 */
		led-gpios = <&pio 0 0 GPIO_ACTIVE_LOW>;	 /* PA0 */		
		debug = <0x0>;
	};
};

drivers/staging/fbtft/fb_st7789vw.c驱动中的set_var函数会生效，修改相应寄存器

如果这个时候直接测试，会发现屏幕有偏移，屏幕只有上部分有显示。
因此还需要修改下面函数来纠正：

static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
{
	switch(par->info->var.rotate)
	{
		case   0: xs+=0;xe+=0;ys+=0;ye+=0;
				 break;
		// case  90: xs+=0;xe+=0;ys+=53;ye+=53;
		// 		 break;
		case 180: xs+=0;xe+=0;ys+=80;ye+=80;
				 break;
		// case 270: xs+=0;xe+=0;ys+=53;ye+=53;
		// 		 break;
		default :
				 break;
	}

	write_reg(par, MIPI_DCS_SET_COLUMN_ADDRESS,
		  xs >> 8, xs & 0xFF, xe >> 8, xe & 0xFF);

	write_reg(par, MIPI_DCS_SET_PAGE_ADDRESS,
		  ys >> 8, ys & 0xFF, ye >> 8, ye & 0xFF);

	write_reg(par, MIPI_DCS_WRITE_MEMORY_START);
}

旋转90度和270度不知道需不需要纠偏，等以后用到再说。