開發板：tiny4412SDK + S702 + 4GB Flash
要移植的核心版本：Linux-4.4.0 （支援device tree）
u-boot版本：友善之臂自帶的 U-Boot 2010.12
busybox版本：busybox 1.25

1、背光
　　友善之臂的該款LCD採用了一線觸控技術，包括背光控制也整合在一線觸控之中，關於背光的控制，在前一篇文章中已經提及，本文重點在於LCD驅動。

2、LCD介面

• 1)Tiny 4412 使用的lcd介面為LCD1
• 2)圖片資料訊號介面
  
  • B[0:7] : 藍色資料訊號線
  • G[0:7] : 綠色資料訊號線
  • R[0:7] : 紅色資料訊號線
• 3)時序訊號介面
  
  • DEN 資料允許訊號
  • VSYNC 垂直同步訊號
  • HSYNC 水平同步訊號
  • VLCK LCD時鐘訊號
• 4)一線觸控
  
  • XEINT10_OUT

3、影象的構成

• 幀：一幅影象被稱為一幀,每幀有多行組成，每行有多個畫素點組成
• 畫素：
  
  • 1)顯示的最小單位
  • 2)由若干位的顏色資料來構成,畫素越高，則一個畫素點所需要的顏色資料越多，能夠顯示的顏色更廣
  • 3)一個畫素點構成的顏色位數稱為畫素深度，單位為1BPP 常見的有16BPP/24BPP

4、顏色的量化(顏色<—–>數字)
顏色一般採用RGB標準,通過對紅（R）、綠（GREEN），藍（B）三個顏色以及相互疊加獲取各種不同的顏色

• 1）通過對顏色的編碼來對顏色進行量化（即轉換成數字量，RGB是一種編碼方式）
• 2）每種顏色根據RGB格式不同，每種顏色的量化位不相同
• 3) 常見的RGB格式有RGB565/RGB888
  
  • RGB565: red :5 green : 6 blue:5
  • RGB888: red :8 green : 8 blue:8

5、顯示影象與LCD時序

• 1)使用HSYNC訊號來控制一行的顯示
• 2)使用VSYNC訊號來控制一幀的顯示
• 3)使用VCLK訊號來控制一個畫素的顯示
• 4)使用VDEN訊號來控制資料的輸出

6、Exyons 4412 display 控制器

• 1)alpha,alpha操作用於實現圖形漸變效果，以及半透明效果
  
  • 0xfff == 全透明
  • 0x0 == 不透明
• 2)colorkey,colorkey操作在融合兩個視窗時過慮掉其中一個視窗的某一種特定顏色
• 3)HOZVAL與LINEVAL
  
  • HOZVAL = (Horizontal display size) - 1
  • LINEVAL = (Vertical display size) - 1
• 4)LCD時序圖
  notes:
  .Using the display controller data, you can select one of the above data paths by setting LCDBLK_CFG Register(0x1001_0210). For more information, refer to the “System Others” manual
  
  
  
  
  

7、Exyons 4412 display 控制器配置

• 1)gpio配置,檢視原理圖 ,獲取LCD介面的對應的gpio
  
  • LCD_HSYNC:GPF0_0
  • LCD_VSYNC:GPF0_1
  • LCD_VDEV: GPF0_2
  • LCD_VCLK: GPF0_3
  • VD[23:0]:GPF1_0 - GPF1_5 / GPF2_0 - GPF2_7 / GPF3_0 - GPF3_3
• 2)時鐘配置
  
  • (1)檢視Exyons 4412 手冊 獲取LCD時鐘源
    LCD 時鐘源為SCLKmpll_user_t:800Mhz
  • (2)配置相關的暫存器得到LCD所需要的時鐘 (見07lcd_clock)
• 3)系統配置
  LCDBLK_CFG : 配置成FIMD介面
  

一、裝置樹

&pinctrl_0 {
        lcd_demo: lcd{
                samsung,pins = "gpf0-0", "gpf0-1", "gpf0-2", "gpf0-3", "gpf0-4", "gpf0-5", "gpf0-6","gpf0-7", "gpf1-0", "gpf1-1", "gpf1-2", "gpf1-3", "gpf1-4", "gpf1-5", "gpf1-6","gpf1-7", "gpf2-0", "gpf2-1", "gpf2-2", "gpf2-3", "gpf2-4", "gpf2-5", "gpf2-6","gpf2-7", "gpf3-0", "gpf3-1", "gpf3-2", "gpf3-3";
                samsung,pin-function = <2>;
                samsung,pin-pud = <0>;
                samsung,pin-drv = <0>;
        };
};

        [email protected]11C00000{
                compatible         = "tiny4412,lcd_demo";
                reg = <0x11C00000  0x20c0 0x10010210 0x08 0x10023c80 0x04 0x1003c000 0x1000>;
                pinctrl-names = "default";
                pinctrl-0 = <&lcd_demo>;
                clocks = <&clock CLK_FIMD0 &clock CLK_ACLK160>;
                clock-names = "fimd0","aclk160";
        };

二、驅動程式碼

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/fb.h>
#include <linux/init.h>
#include <linux/dma-mapping.h>
#include <linux/interrupt.h>
#include <linux/workqueue.h>
#include <linux/wait.h>
#include <linux/platform_device.h>
#include <linux/clk.h>

#include <asm/io.h>
#include <asm/uaccess.h>
#include <asm/div64.h>

#include <asm/mach/map.h>
#include <linux/fb.h>
#include <asm/types.h>

#define     VIDCON0         0x00
#define     VIDCON1         0x04
#define     VIDTCON0        0x10
#define     VIDTCON1        0x14
#define     VIDTCON2        0x18
#define     WINCON0         0x20
#define     VIDOSD0C        0x48
#define     SHADOWCON       0x34
#define     WINCHMAP2       0x3c
#define     VIDOSD0A        0x40
#define     VIDOSD0B        0x44
#define     VIDW00ADD0B0    0xA0
#define     VIDW00ADD1B0    0xD0

#define     CLK_SRC_LCD0        0x234
#define     CLK_SRC_MASK_LCD    0x334
#define     CLK_DIV_LCD         0x534
#define     CLK_GATE_IP_LCD     0x934

#define     LCDBLK_CFG      0x00
#define     LCDBLK_CFG2     0x04

static int s3c_lcdfb_setcolreg(unsigned int regno, unsigned int red,
                               unsigned int green, unsigned int blue,
                               unsigned int transp, struct fb_info *info);


static struct fb_ops s3c_lcdfb_ops =
{
    .owner      = THIS_MODULE,
    .fb_setcolreg   = s3c_lcdfb_setcolreg,
    .fb_fillrect    = cfb_fillrect,
    .fb_copyarea    = cfb_copyarea,
    .fb_imageblit   = cfb_imageblit,
};


static struct fb_info *s3c_lcd;
static volatile void __iomem *lcd_regs_base;
static volatile void __iomem *clk_regs_base;
static volatile void __iomem *lcdblk_regs_base;
static volatile void __iomem *lcd0_configuration;
static u32 pseudo_palette[16];
static struct resource *res1, *res2, *res3, *res4;

/* from pxafb.c */
static inline unsigned int chan_to_field(unsigned int chan, struct fb_bitfield *bf)
{
    chan &= 0xffff;
    chan >>= 16 - bf->length;
    return chan << bf->offset;
}


static int s3c_lcdfb_setcolreg(unsigned int regno, unsigned int red,
                               unsigned int green, unsigned int blue,
                               unsigned int transp, struct fb_info *info)
{
    unsigned int val;

    if (regno > 16)
        { return 1; }

    /* 用red,green,blue三原色構造出val */
    val  = chan_to_field(red,   &info->var.red);
    val |= chan_to_field(green, &info->var.green);
    val |= chan_to_field(blue,  &info->var.blue);
    //((u32 *)(info->pseudo_palette))[regno] = val;
    pseudo_palette[regno] = val;
    return 0;
}

static int lcd_probe(struct platform_device *pdev)
{
    int ret;
    unsigned int temp;
    /* 1. 分配一個fb_info */
    s3c_lcd = framebuffer_alloc(0, NULL);
    /* 2. 設定 */
    /* 2.1 設定 fix 固定的引數 */
    strcpy(s3c_lcd->fix.id, "mylcd");
    s3c_lcd->fix.smem_len = 480 * 800 * 16 / 8;     //視訊記憶體的長度
    s3c_lcd->fix.type     = FB_TYPE_PACKED_PIXELS;  //型別
    s3c_lcd->fix.visual   = FB_VISUAL_TRUECOLOR;    //TFT 真彩色
    s3c_lcd->fix.line_length = 800 * 2;             //一行的長度
    /* 2.2 設定 var 可變的引數 */
    s3c_lcd->var.xres           = 800;  //x方向解析度
    s3c_lcd->var.yres           = 480;  //y方向解析度
    s3c_lcd->var.xres_virtual   = 800;  //x方向虛擬解析度
    s3c_lcd->var.yres_virtual   = 480;  //y方向虛擬解析度
    s3c_lcd->var.bits_per_pixel = 16;   //每個畫素佔的bit
    /* RGB:565 */
    s3c_lcd->var.red.offset     = 11;   //紅
    s3c_lcd->var.red.length     = 5;
    s3c_lcd->var.green.offset   = 5;    //綠
    s3c_lcd->var.green.length   = 6;
    s3c_lcd->var.blue.offset    = 0;    //藍
    s3c_lcd->var.blue.length    = 5;
    s3c_lcd->var.activate       = FB_ACTIVATE_NOW;
    /* 2.3 設定操作函式 */
    s3c_lcd->fbops              = &s3c_lcdfb_ops;
    /* 2.4 其他的設定 */
    s3c_lcd->pseudo_palette = pseudo_palette;       //調色盤
    //s3c_lcd->screen_base  = ;                     //視訊記憶體的虛擬地址,分配視訊記憶體時填充
    s3c_lcd->screen_size    = 480 * 800 * 16 / 8;   //視訊記憶體大小
    /* 3. 硬體相關的操作 */
    /* 3.1 配置GPIO用於LCD */
    //裝置樹中使用"default"
    /* 3.2 根據LCD手冊設定LCD控制器, 比如VCLK的頻率等 */
    //暫存器對映
    res1 = platform_get_resource(pdev, IORESOURCE_MEM, 0);

    if (res1 == NULL)
    {
        printk("platform_get_resource error\n");
        return -EINVAL;
    }

    lcd_regs_base = devm_ioremap_resource(&pdev->dev, res1);

    if (lcd_regs_base == NULL)
    {
        printk("devm_ioremap_resource error\n");
        return -EINVAL;
    }

    res2 = platform_get_resource(pdev, IORESOURCE_MEM, 1);

    if (res2 == NULL)
    {
        printk("platform_get_resource error\n");
        return -EINVAL;
    }

    lcdblk_regs_base = devm_ioremap_resource(&pdev->dev, res2);

    if (lcdblk_regs_base == NULL)
    {
        printk("devm_ioremap_resource error\n");
        return -EINVAL;
    }

    res3 = platform_get_resource(pdev, IORESOURCE_MEM, 2);

    if (res3 == NULL)
    {
        printk("platform_get_resource error\n");
        return -EINVAL;
    }

    lcd0_configuration = ioremap(res3->start, 0x04);
    *lcd0_configuration = 0x07;

    res4 = platform_get_resource(pdev, IORESOURCE_MEM, 3);

    if (res4 == NULL)
    {
        printk("platform_get_resource error\n");
        return -EINVAL;
    }

    clk_regs_base = ioremap(res4->start, 0x1000);

    if (clk_regs_base == NULL)
    {
        printk("devm_ioremap_resource error\n");
        return -EINVAL;
    }

    //使能時鐘
    //時鐘源選擇 0110  SCLKMPLL_USER_T 800M
    temp = readl(clk_regs_base + CLK_SRC_LCD0);
    temp &= ~0x0f;
    temp |= 0x06;
    writel(temp, clk_regs_base + CLK_SRC_LCD0);

    //FIMD0_MASK
    temp = readl(clk_regs_base + CLK_SRC_MASK_LCD);
    temp |= 0x01;
    writel(temp, clk_regs_base + CLK_SRC_MASK_LCD);

    //SCLK_FIMD0 = MOUTFIMD0/(FIMD0_RATIO + 1),分頻 1/1
    temp = readl(clk_regs_base + CLK_DIV_LCD);
    temp &= ~0x0f;
    writel(temp, clk_regs_base + CLK_DIV_LCD);

    //CLK_FIMD0 Pass
    temp = readl(clk_regs_base + CLK_GATE_IP_LCD);
    temp |= 0x01;
    writel(temp, clk_regs_base + CLK_GATE_IP_LCD);

    //FIMDBYPASS_LBLK0 FIMD Bypass
    temp = readl(lcdblk_regs_base + LCDBLK_CFG);
    temp |= 1 << 1;
    writel(temp, lcdblk_regs_base + LCDBLK_CFG);
    temp = readl(lcdblk_regs_base + LCDBLK_CFG2);
    temp |= 1 << 0;
    writel(temp, lcdblk_regs_base + LCDBLK_CFG2);
    mdelay(1000);

    //分頻    800/(23 +1 ) == 33M
    temp = readl(lcd_regs_base + VIDCON0);
    temp |= (23 << 6);
    writel(temp, lcd_regs_base + VIDCON0);

    /*
     * VIDTCON1:
     * [5]:IVSYNC  ===> 1 : Inverted(反轉)
     * [6]:IHSYNC  ===> 1 : Inverted(反轉)
     * [7]:IVCLK   ===> 1 : Fetches video data at VCLK rising edge (下降沿觸發)
     * [10:9]:FIXVCLK  ====> 01 : VCLK running
     */
    temp = readl(lcd_regs_base + VIDCON1);
    temp |= (1 << 9) | (1 << 7) | (1 << 5) | (1 << 6);
    writel(temp, lcd_regs_base + VIDCON1);

    /*
     * VIDTCON0:
     * [23:16]:  VBPD + 1  <------> tvpw (1 - 20)  13
     * [15:8] :  VFPD + 1  <------> tvfp 22
     * [7:0]  :  VSPW  + 1 <------> tvb - tvpw = 23 - 13 = 10
     */
    temp = readl(lcd_regs_base + VIDTCON0);
    temp |= (12 << 16) | (21 << 8) | (9);
    writel(temp, lcd_regs_base + VIDTCON0);

    /*
     * VIDTCON1:
     * [23:16]:  HBPD + 1  <------> thpw (1 - 40)  36
     * [15:8] :  HFPD + 1  <------> thfp 210
     * [7:0]  :  HSPW  + 1 <------> thb - thpw = 46 - 36 = 10
     */
    temp = readl(lcd_regs_base + VIDTCON1);
    temp |= (35 << 16) | (209 << 8)  | (9);
    writel(temp, lcd_regs_base + VIDTCON1);

    /*
     * HOZVAL = (Horizontal display size) - 1 and LINEVAL = (Vertical display size) - 1.
     * Horizontal(水平) display size : 800
     * Vertical(垂直) display size : 480
     */
    temp = (479 << 11) | 799;
    writel(temp, lcd_regs_base + VIDTCON2);

    /*
     * WINCON0:
     * [16]:Specifies Half-Word swap control bit.  1 = Enables swap P1779 低位畫素存放在低位元組
     * [5:2]: Selects Bits Per Pixel (BPP) mode for Window image : 0101 ===> 16BPP RGB565
     * [1]:Enables/disables video output   1 = Enables
     */
    temp = readl(lcd_regs_base + WINCON0);
    temp |= (1 << 16) | (5 << 2) | 1;
    writel(temp, lcd_regs_base + WINCON0);

    temp = readl(lcd_regs_base + SHADOWCON);
    writel(temp | 0x01, lcd_regs_base + SHADOWCON);

    //p1769
    temp = readl(lcd_regs_base + WINCHMAP2);
    temp &= ~(7 << 16);
    temp |= 1 << 16;
    temp &= ~7;
    temp |= 1;
    writel(temp, lcd_regs_base + WINCHMAP2);

    /*
     * bit0-10 : 指定OSD影象左上畫素的垂直螢幕座標
     * bit11-21: 指定OSD影象左上畫素的水平螢幕座標
     */
    writel(0, lcd_regs_base + VIDOSD0A);

    /*
     * bit0-10 : 指定OSD影象右下畫素的垂直螢幕座標
     * bit11-21: 指定OSD影象右下畫素的水平螢幕座標
     */
    writel((799 << 11) | 479, lcd_regs_base + VIDOSD0B);

    //Window Size For example, Height ? Width (number of word)
    temp = 480 * 800 >> 1;
    writel(temp, lcd_regs_base + VIDOSD0C);

    /* 3.3 分配視訊記憶體(framebuffer), 並把地址告訴LCD控制器 */
    // s3c_lcd->screen_base     視訊記憶體虛擬地址
    // s3c_lcd->fix.smem_len    視訊記憶體大小，前面計算的
    // s3c_lcd->fix.smem_start  視訊記憶體實體地址
    s3c_lcd->screen_base = dma_alloc_writecombine(NULL, s3c_lcd->fix.smem_len, (dma_addr_t *)&s3c_lcd->fix.smem_start, GFP_KERNEL);

    //視訊記憶體起始地址
    writel(s3c_lcd->fix.smem_start, lcd_regs_base + VIDW00ADD0B0);

    //視訊記憶體結束地址
    writel(s3c_lcd->fix.smem_start + s3c_lcd->fix.smem_len, lcd_regs_base + VIDW00ADD1B0);
    //Enables video output and logic immediately
    temp = readl(lcd_regs_base + VIDCON0);
    writel(temp | 0x03, lcd_regs_base + VIDCON0);

    /* 4. 註冊 */
    ret = register_framebuffer(s3c_lcd);
    return ret;
}

static int lcd_remove(struct platform_device *pdev)
{
    printk("%s enter.\n", __func__);
    unregister_framebuffer(s3c_lcd);
    dma_free_writecombine(NULL, s3c_lcd->fix.smem_len, s3c_lcd->screen_base, s3c_lcd->fix.smem_start);
    framebuffer_release(s3c_lcd);
    iounmap(lcd0_configuration);
    iounmap(clk_regs_base);
    return 0;
}

static const struct of_device_id lcd_dt_ids[] =
{
    { .compatible = "tiny4412,lcd_demo", },
    {},
};

MODULE_DEVICE_TABLE(of, lcd_dt_ids);

static struct platform_driver lcd_driver =
{
    .driver        = {
        .name      = "lcd_demo",
        .of_match_table    = of_match_ptr(lcd_dt_ids),
    },
    .probe         = lcd_probe,
    .remove        = lcd_remove,
};

static int lcd_init(void)
{
    int ret;
    printk("enter %s\n", __func__);
    ret = platform_driver_register(&lcd_driver);

    if (ret)
    {
        printk(KERN_ERR "pwm demo: probe faipwm: %d\n", ret);
    }

    return ret;
}

static void lcd_exit(void)
{
    printk("enter %s\n", __func__);
    platform_driver_unregister(&lcd_driver);
}

module_init(lcd_init);
module_exit(lcd_exit);

MODULE_LICENSE("GPL");