《韦东山视频第二期》——LCD驱动

一、LCD驱动程序框架分析

app: open("/dev/fb0", ...)     主设备号：29， 次设备号：0

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kernel:(核心文件/drivers/video/fbmem.c)

                fb_open

                          int fbidx = iminor(inode);

                          struct fb_info *info;

                          info = registered_fb[fbidx];      //根据次设备号获得从底层注册的struct fb_info结构体中

                         file->private_data = info;

                         if (info->fbops->fb_open) {                         //调用底层struct fb_info结构体中的fb_open函数

                                 res = info->fbops->fb_open(info,1);

                                 if (res)

                                 module_put(info->fbops->owner);

                         }

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app:    read()

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kernel:

                fb_read

                            struct inode *inode = file->f_path.dentry->d_inode;

                            int fbidx = iminor(inode);

                            struct fb_info *info = registered_fb[fbidx];

                            if (info->fbops->fb_read)

                           return info->fbops->fb_read(info, buf, count, ppos);

                          src = (u32 __iomem *) (info->screen_base + p);

                          dst = buffer;

                         *dst++ = fb_readl(src++);

                         copy_to_user(buf, buffer, c)          

怎么写LCD驱动程序？

1.分配一个fb_info结构体：framebuffer_alloc()

2.设置

3.注册：register_framebuffer

4.硬件相关的操作  

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struct lcd_regs {

    unsigned long    lcdcon1;

    unsigned long    lcdcon2;

    unsigned long    lcdcon3;

    unsigned long    lcdcon4;

    unsigned long    lcdcon5;

    unsigned long    lcdsaddr1;

    unsigned long    lcdsaddr2;

    unsigned long    lcdsaddr3;

    unsigned long    redlut;

    unsigned long    greenlut;

    unsigned long    bluelut;

    unsigned long    reserved[9];

    unsigned long    dithmode;

    unsigned long    tpal;

    unsigned long    lcdintpnd;

    unsigned long    lcdsrcpnd;

    unsigned long    lcdintmsk;

    unsigned long    lpcsel;

};

static struct fb_ops* s3c_lcdfb_ops = {

    .owner          = THIS_MODULE,

//  .fb_setcplreg = atmel_lcdfb_setolreg,

    .fb_fillrect  = cfb_fillrect,

    .fb_copyarea  = cfb_copyarea,

    .fb_imageblit = cfb_imageblit,

};

static struct fb_info* s3c_lcd;

static volatile unsigned long *gpbcon;

static volatile unsigned long *gpbdat;

static volatile unsigned long *gpccon;

static volatile unsigned long *gpdcon;

static volatile unsigned long *gpgcon;

static volatile struct lcd_regs* lcd_regs;

static u32 pseudo_palette[16];    //为了兼容，设置假的调色板

/* 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三原色构造出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_init(void)

{

    /* 1. 分配一个fb_info结构体 */

    s3c_lcd = framebuffer_alloc(0, NULL);

    /* 2. 设置 */

    /* 2.1 设置固定的参数 */

    strcpy(s3c_lcd->fix.id, "mylcd");

    s3c_lcd->fix.smem_len    = 320*240*32/8; /* MINI2440的LCD位宽是24,但是2440里会分配4字节即32位(浪费1字节) */

    s3c_lcd->fix.type        = FB_TYPE_PACKED_PIXELS;

    s3c_lcd->fix.visual      = FB_VISUAL_TRUECOLOR;     /* 真彩色 */

    s3c_lcd->fix.line_length = 320 * 4;    /* 1行的字节数 */

    /* 2.2 设置可变的参数 */

    s3c_lcd->var.xres          = 320;

    s3c_lcd->var.yres          = 240;

    s3c_lcd->var.xres_virtual  = 320;

    s3c_lcd->var.yres_virtual  = 240;

    s3c_lcd->var.bits_per_pixel = 32;    /* 每个像素所占的位数 */

    /* RGB: 565 */

    s3c_lcd->var.red.offset    = 16;

    s3c_lcd->var.red.length    = 8;

    s3c_lcd->var.green.offset  = 8;

    s3c_lcd->var.green.length  = 8;

    s3c_lcd->var.blue.offset   = 0;

    s3c_lcd->var.blue.length   = 0;

    s3c_lcd->var.activate      = FB_ACTIVATE_NOW;

    /* 2.3 设置操作函数 */

    s3c_lcd->fops   = &s3c_lcdfb_ops;

    /* 2.4 其他设置 */

    //s3c_lcd->pseudo_palette =; //

    //s3c_lcd->screen_base  = ;  /* 显存的虚拟地址 */ 

    s3c_lcd->screen_size   = 320*240*32/8;

    /* 3. 硬件相关的操作 */

    /* 3.1 配置GPIO用于LCD */

    gpbcon = ioremap(0x56000010, 8);

    gpbdat = gpbcon+1;

    gpccon = ioremap(0x56000020, 4);

    gpdcon = ioremap(0x56000030, 4);

    gpgcon = ioremap(0x56000060, 4);

    *gpccon  = 0xaaaaaaaa;   /* GPIO管脚用于VD[7:0],LCDVF[2:0],VM,VFRAME,VLINE,VCLK,LEND */

    *gpdcon  = 0xaaaaaaaa;   /* GPIO管脚用于VD[23:8] */

//    *gpbcon &= ~(3);  /* GPB0设置为输出引脚 */

//    *gpbcon |= 1;

//    *gpbdat &= ~1;     /* 输出低电平 */

    *gpgcon |= (3<<8); /* GPG4用作LCD_PWREN */

    /* 3.2 根据LCD手册设置LCD控制器，比如VCLK的频率等 */

    lcd_regs = ioremap(0x4D000000, sizeof(struct lcd_regs));

    /*

     * MINI2440 LCD 3.5英寸 ZQ3506_V0 SPEC.pdf 第11、12页

     *

     * LCD手册11,12页和2440手册"Figure 15-6. TFT LCD Timing Example"一对比就知道参数含义了

     */

    /* bit[17:8]: VCLK = HCLK / [(CLKVAL+1) x 2], LCD手册11 (Dclk=6.4MHz~11MHz)

     *            7.1MHz = 100MHz / [(CLKVAL+1) x 2]

     *            CLKVAL = 6

     * bit[6:5]: 0b11, TFT LCD

     * bit[4:1]: 0b1101, 24 bpp for TFT

     * bit[0]  : 0 = Disable the video output and the LCD control signal.

     */

    lcd_regs->lcdcon1  = (6<<8) | (3<<5) | (0x0d<<1);

    /* 垂直方向的时间参数

     * 根据数据手册

     * bit[31:24]: VBPD, VSYNC之后再过多长时间才能发出第1行数据