增加 1.9inch LCD Module fbtft 驱动 for RK356x。
Signed-off-by: rick.chan <cy@haoan119.com>
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# 1.9inch LCD Module fbtft 驱动 for RK356x
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由于需要在 RK356x 平台下驱动 SPI 显示屏，因此做了一下技术调查。这种屏的驱动主要使用 fbtft，这一种 framebuffer 驱动。另一说可以使用基于 DRM 技术的 [TinyDRM](https://github.com/notro/tinydrm) 驱动。
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framebuffer 的缺点在于，使用非桌面环境的 Qt 图形程序时不支持视频播放。但是 Qt 的 Animation（AnimatedImage、PropertyAnimation 等） 是可以正常使用的。
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我对 TinyDRM 的框架存有许多疑问，但时间有限，不能仔细阅读其框架代码，只好先使用 fbtft 来驱动。
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我所使用的 SPI 显示屏是 微雪 的 1.9inch LCD 模块，其控制芯片为 ST7789V2，对于这款芯片，内核是有类似驱动的，参考微雪官方示例代码对此文件和设备树进行修改即可。
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Linux 内核版本为 4.9。
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## 1. 显示屏信息
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本驱动对应 微雪 1.9inch SPI 显示屏，该显示屏参数如下：
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- 工作电压： 3.3V/5V
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- 通信接口：SPI
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- 屏幕类型：IPS
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- 控制芯片：ST7789V2
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- 分辨率：170(H)RGB × 320(V)
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- 显示尺寸：22.70 × 42.72mm
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- 像素间距：0.1335 × 0.1335mm
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- 产品尺寸：27.3 × 51.2mm
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- 像素格式：RGB444、RGB565、RGB666
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官方资料及参考代码下载见：[微雪 1.9inch LCD Module 资料连接](https://www.waveshare.net/wiki/1.9inch_LCD_Module)
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## 2. 接线方式
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| LCD Module | RK356x |
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|------------|--------|
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| VCC | V3.3 |
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| GND | GND |
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| DIN | SPI3_MOSI_M1 |
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| CLK | SPI3_CLK_M1 |
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| CS | GPIO4_C4 |
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| DC | GPIO3_A6 |
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| RST | GPIO1_A4 |
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| BL | GPIO3_A5 |
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注意 SPI 通讯使用 Mode 0。
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## 3. 内核驱动及设备树
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Linux 在 /drivers/staging/fbtft 下有 fb_st7789v.c 文件，直接在此文件基础上进行修改，内容如下：
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```cpp
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// SPDX-License-Identifier: GPL-2.0+
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/*
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* FB driver for the ST7789V LCD Controller
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*
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* Copyright (C) 2015 Dennis Menschel
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*/
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#include <linux/bitops.h>
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#include <linux/delay.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <video/mipi_display.h>
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#include "fbtft.h"
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#define DRVNAME "fb_st7789v"
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#define DEFAULT_GAMMA \
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"70 2C 2E 15 10 09 48 33 53 0B 19 18 20 25\n" \
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"70 2C 2E 15 10 09 48 33 53 0B 19 18 20 25"
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/**
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* enum st7789v_command - ST7789V display controller commands
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*
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* @PORCTRL: porch setting
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* @GCTRL: gate control
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* @VCOMS: VCOM setting
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* @VDVVRHEN: VDV and VRH command enable
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* @VRHS: VRH set
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* @VDVS: VDV set
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* @VCMOFSET: VCOM offset set
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* @PWCTRL1: power control 1
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* @PVGAMCTRL: positive voltage gamma control
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* @NVGAMCTRL: negative voltage gamma control
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*
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* The command names are the same as those found in the datasheet to ease
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* looking up their semantics and usage.
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*
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* Note that the ST7789V display controller offers quite a few more commands
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* which have been omitted from this list as they are not used at the moment.
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* Furthermore, commands that are compliant with the MIPI DCS have been left
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* out as well to avoid duplicate entries.
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*/
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enum st7789v_command {
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PORCTRL = 0xB2,
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GCTRL = 0xB7,
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VCOMS = 0xBB,
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VDVVRHEN = 0xC2,
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VRHS = 0xC3,
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VDVS = 0xC4,
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VCMOFSET = 0xC5,
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PWCTRL1 = 0xD0,
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PVGAMCTRL = 0xE0,
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NVGAMCTRL = 0xE1,
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};
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#define MADCTL_BGR BIT(3) /* bitmask for RGB/BGR order */
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#define MADCTL_MV BIT(5) /* bitmask for page/column order */
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#define MADCTL_MX BIT(6) /* bitmask for column address order */
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#define MADCTL_MY BIT(7) /* bitmask for page address order */
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/**
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* init_display() - initialize the display controller
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*
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* @par: FBTFT parameter object
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*
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* Most of the commands in this init function set their parameters to the
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* same default values which are already in place after the display has been
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* powered up. (The main exception to this rule is the pixel format which
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* would default to 18 instead of 16 bit per pixel.)
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* Nonetheless, this sequence can be used as a template for concrete
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* displays which usually need some adjustments.
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*
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* Return: 0 on success, < 0 if error occurred.
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*/
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static int init_display(struct fbtft_par *par)
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{
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par->fbtftops.reset(par);
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/* turn off sleep mode */
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// write_reg(par, MIPI_DCS_EXIT_SLEEP_MODE); // 0x11
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// mdelay(120);
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write_reg(par, MIPI_DCS_SET_ADDRESS_MODE, 0x70); // 0x36, 0x00-HORIZONTAL, 0x70-VERTICAL
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/* set pixel format to RGB-565 */
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write_reg(par, MIPI_DCS_SET_PIXEL_FORMAT, 0x55); // 0x3A
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// write_reg(par, MIPI_DCS_ENTER_INVERT_MODE); // 0x21
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// write_reg(par, MIPI_DCS_SET_COLUMN_ADDRESS, 0x00, 0x00, 0x01, 0x3F); // 0x2A
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// write_reg(par, MIPI_DCS_SET_PAGE_ADDRESS, 0x00, 0x00, 0x00, 0xEF); // 0x2B
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write_reg(par, PORCTRL, 0x0C, 0x0C, 0x00, 0x33, 0x33); // 0xB2
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// VGH VGL
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write_reg(par, GCTRL, 0x35); // 0xB7
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// VCOM
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write_reg(par, VCOMS, 0x13); // 0xBB
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write_reg(par, 0xC0, 0x2C);
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/*
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* VDV and VRH register values come from command write
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* (instead of NVM)
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*/
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write_reg(par, VDVVRHEN, 0x01); // 0xC2
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// VAP VAN
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write_reg(par, VRHS, 0x0B); // 0xC3
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// VDV
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write_reg(par, VDVS, 0x20); // 0xC4
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write_reg(par, 0xC6, 0x0F);
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// AVDD AVCL VDS
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write_reg(par, PWCTRL1, 0xA4, 0xA1); // 0xD0
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// write_reg(par, PVGAMCTRL, 0x00, 0x03, 0x07, 0x08, 0x07, 0x15, 0x2A, 0x44, 0x42, 0x0A, 0x17, 0x18, 0x25, 0x27); // 0xE0
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// write_reg(par, NVGAMCTRL, 0x00, 0x03, 0x08, 0x07, 0x07, 0x23, 0x2A, 0x43, 0x42, 0x09, 0x18, 0x17, 0x25, 0x27); // 0xE1
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write_reg(par, MIPI_DCS_ENTER_INVERT_MODE); // 0x21
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write_reg(par, MIPI_DCS_EXIT_SLEEP_MODE); // 0x11
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/* VCOM offset = 0V */
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// write_reg(par, VCMOFSET, 0x20);
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mdelay(50);
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write_reg(par, MIPI_DCS_SET_DISPLAY_ON); // 0x29
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return 0;
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}
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/**
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* set_var() - apply LCD properties like rotation and BGR mode
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*
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* @par: FBTFT parameter object
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*
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* Return: 0 on success, < 0 if error occurred.
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*/
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static int set_var(struct fbtft_par *par)
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{
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switch (par->info->var.rotate) {
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case 0:
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write_reg(par, MIPI_DCS_SET_ADDRESS_MODE, 0x00); // 0x36, 0x00-HORIZONTAL, 0x70-VERTICAL
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break;
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default:
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write_reg(par, MIPI_DCS_SET_ADDRESS_MODE, 0x70); // 0x36, 0x00-HORIZONTAL, 0x70-VERTICAL
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break;
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}
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return 0;
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}
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/**
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* set_gamma() - set gamma curves
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*
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* @par: FBTFT parameter object
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* @curves: gamma curves
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*
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* Before the gamma curves are applied, they are preprocessed with a bitmask
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* to ensure syntactically correct input for the display controller.
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* This implies that the curves input parameter might be changed by this
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* function and that illegal gamma values are auto-corrected and not
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* reported as errors.
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*
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* Return: 0 on success, < 0 if error occurred.
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*/
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static int set_gamma(struct fbtft_par *par, u32 *curves)
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{
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int i;
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int c;
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for (i = 0; i < par->gamma.num_curves; i++) {
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c = i * par->gamma.num_values;
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write_reg(par, PVGAMCTRL+i,
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curves[c+0], curves[c+1], curves[c+2],
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curves[c+3], curves[c+4], curves[c+5],
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curves[c+6], curves[c+7], curves[c+8],
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curves[c+9], curves[c+10], curves[c+11],
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curves[c+12], curves[c+13]);
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}
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return 0;
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}
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/**
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* blank() - blank the display
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*
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* @par: FBTFT parameter object
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* @on: whether to enable or disable blanking the display
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*
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* Return: 0 on success, < 0 if error occurred.
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*/
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static int blank(struct fbtft_par *par, bool on)
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{
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if (on)
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write_reg(par, MIPI_DCS_SET_DISPLAY_OFF);
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else
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write_reg(par, MIPI_DCS_SET_DISPLAY_ON);
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return 0;
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}
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static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe,
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int ye)
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{
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switch (par->info->var.rotate) {
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case 0:
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xs += 0x23;
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xe += 0x23;
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ys += 0x00;
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ye += 0x00;
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break;
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default:
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xs += 0x00;
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xe += 0x00;
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ys += 0x23;
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ye += 0x23;
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break;
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}
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write_reg(par, MIPI_DCS_SET_COLUMN_ADDRESS,
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(xs >> 8) & 0xFF, xs & 0xFF, (xe >> 8) & 0xFF, xe & 0xFF); // 0x2A
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write_reg(par, MIPI_DCS_SET_PAGE_ADDRESS,
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(ys >> 8) & 0xFF, ys & 0xFF, (ye >> 8) & 0xFF, ye & 0xFF); // 0x2B
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write_reg(par, MIPI_DCS_WRITE_MEMORY_START); // 0x2C
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}
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static struct fbtft_display display = {
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.regwidth = 8,
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.width = 170,
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.height = 320,
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.gamma_num = 2,
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.gamma_len = 14,
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.gamma = DEFAULT_GAMMA,
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.fbtftops = {
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.init_display = init_display,
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.set_var = set_var,
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.set_gamma = set_gamma,
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.blank = blank,
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.set_addr_win = set_addr_win
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},
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};
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FBTFT_REGISTER_DRIVER(DRVNAME, "sitronix,st7789v", &display);
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MODULE_ALIAS("spi:" DRVNAME);
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MODULE_ALIAS("platform:" DRVNAME);
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MODULE_ALIAS("spi:st7789v");
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MODULE_ALIAS("platform:st7789v");
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MODULE_DESCRIPTION("FB driver for the ST7789V LCD Controller");
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MODULE_AUTHOR("Dennis Menschel");
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MODULE_LICENSE("GPL");
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```
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主要的修改是参考示例编写 init_display() 函数中的初始化序列。
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其次是 set_addr_win() 函数，xs 等有个偏移，每个屏厂参数都不同。如果你的屏显示出现 **撕裂，错位倾斜** 或者 **偏移**，可能就是这个参数有问题。微雪官方给的参考中，xe 和 ye 进行了 减1 处理，但 Linux 驱动**不需要 减1**，否则显示的图像/文字就会因为减 1 的偏移导致错位倾斜。
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这个驱动的显示方向可以由设备树中的 rotate 参数配置，gamma 也可以通过设备树配置。
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我所使用的 鲁班猫 1N，设备树配置比较清晰，很容易的在 arch/arm64/boot/dts/rockchip/overlay/rk356x-lubancat-spi3-m1-gpio-cs-overlay.dts 文件中找到了 SPI3 设备，注释掉其中的 spi_dev 并修改如下：
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```dts
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/dts-v1/;
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/plugin/;
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#include <dt-bindings/gpio/gpio.h>
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#include <dt-bindings/pinctrl/rockchip.h>
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/ {
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compatible = "rockchip,rk3568";
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fragment@0 {
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target = <&spi3>;
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__overlay__ {
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status = "okay";
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#address-cells = <1>;
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#size-cells = <0>;
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// SPI gpio 模拟多个 cs 信号
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pinctrl-names = "default", "high_speed";
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pinctrl-0 = <&spi3_cs0 &spi3_cs1 &spi3m1_pins>;
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pinctrl-1 = <&spi3_cs0 &spi3_cs1 &spi3m1_pins_hs>;
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cs-gpios = <&gpio4 RK_PC4 GPIO_ACTIVE_LOW>;
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// spi_dev@00 {
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// compatible = "rockchip,spidev";
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// reg = <0>; //chip select 0:cs0 1:cs1
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// spi-max-frequency = <24000000>; //spi output clock
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// };
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// spi_dev@01 {
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// compatible = "rockchip,spidev";
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// reg = <1>;
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// spi-max-frequency = <24000000>;
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// };
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st7789v@00 {
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status = "okay";
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compatible = "sitronix,st7789v";
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reg = <0>;
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spi-max-frequency = <24000000>;
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rotate = <90>;
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rgb;
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fps = <30>;
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buswidth = <8>;
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gamma = "0x00 0x03 0x07 0x08 0x07 0x15 0x2A 0x44 0x42 0x0A 0x17 0x18 0x25 0x27\n0x00 0x03 0x08 0x07 0x07 0x23 0x2A 0x43 0x42 0x09 0x18 0x17 0x25 0x27";
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reset-gpios = <&gpio1 RK_PA4 GPIO_ACTIVE_LOW>;
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dc-gpios = <&gpio3 RK_PA6 GPIO_ACTIVE_LOW>;
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led-gpios = <&gpio3 RK_PA5 GPIO_ACTIVE_HIGH>;
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pinctrl-names = "default";
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pinctrl-0 = <&st7789v_cmd_pin &st7789v_reset_pin &st7789v_light_pin>;
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debug = <1>;
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};
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};
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};
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fragment@1 {
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target = <&pinctrl>;
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__overlay__ {
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st7789v {
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// 配置指定引脚的 复用/上下拉/驱动能力 等
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st7789v_cmd_pin: st7789v_cmd_pin {
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rockchip,pins = <3 RK_PA6 RK_FUNC_GPIO &pcfg_pull_up_drv_level_1>;
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};
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st7789v_reset_pin: st7789v_reset_pin {
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rockchip,pins = <1 RK_PA4 RK_FUNC_GPIO &pcfg_pull_up_drv_level_1>;
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};
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st7789v_light_pin: st7789v_light_pin {
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rockchip,pins = <3 RK_PA5 RK_FUNC_GPIO &pcfg_pull_up_drv_level_1>;
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};
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};
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};
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};
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// 关 hdmi 等，否则默认显示设备不是 SPI 屏
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fragment@2 {
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target = <&route_hdmi>;
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__overlay__ {
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status = "disabled";
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};
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};
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fragment@3 {
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target = <&hdmi_in_vp0>;
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__overlay__ {
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status = "disabled";
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};
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};
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fragment@4 {
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target = <&hdmi_in_vp1>;
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__overlay__ {
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status = "disabled";
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};
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};
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fragment@5 {
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target = <&hdmi>;
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__overlay__ {
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status = "disabled";
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};
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};
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};
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```
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需要注意的是，设备树 overlay 加载时间会比较晚，使用 overlay 驱动显示屏将导致无法在上电时立刻 probe 到设备，显示屏会延迟点亮。如果需要上电立刻亮屏，可以将以上设备树配置固定到设备树文件中。
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Reference in New Issue