linux下LCD驱动程序

定义LCD相应寄存器的结构体

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;
};

定义调色板，假的调色板，如果framebuffer中的数据足够用的话，就不需要调色板，这里只是为了兼容。

u32 pseudo_palette[16];

定义LCD寄存器结构体变量

volatile struct lcd_regs* lcd_regs;

其他定义

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;

构造fb_ops结构体

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 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;
}

1.分配fb_info结构体

struct fb_info *s3c_lcd = framebuffer_alloc(0, NULL);

2.设置fb_info结构体

2.1设置固定参数

strcpy(s3c_lcd->fix.id, "mylcd");
s3c_lcd->fix.smem_len = 480*272*32/8;/* 单位字节 */
s3c_lcd->fix.type = FB_TYPE_PACKED_PIXELS;
s3c_lcd->fix.visual = FB_VISUAL_TRUECOLOR;
s3c_lcd->fix.line_length = 480*4;/* 单位字节 */

2.2设置可变参数

s3c_lcd->var.xres = 480;
s3c_lcd->var.yres = 272;
s3c_lcd->var.xres_virtual = 480;
s3c_lcd->var.yres_virtual = 272;
s3c_lcd->var.bit_per_pixel = 32;
/* RGB */
s3c_lcd->var.red.offset = 16;
s3c_lcd->var.red.lenght = 8;
s3c_lcd->var.green.offset = 8;
s3c_lcd->var.green.length = 8;
s3c_lcd->var.blue.offset = 0;
s3c_lcd->var.blue.length = 8;
s3c_lcd->var.activate = FB_ACTIVATE_NOW;

2.3设置操作函数

s3c_lcd->fbops = &s3c_lcdfb_ops;

2.4其他设置

s3c_lcd->pseudo_palette = pseudo_palette;
s3c_lcd->screen_size = 480*270*32/8;

3.硬件相关的设置

3.1配置GPIO管脚用于LCD

gpbcon = ioremap(0x56000010, 8);
gpbdat = gpbcon+1;
gpccon = ioremap(0x56000020, 4);
gpdcon = ioremap(0x56000030, 4);
gpgcon = ioremap(0x56000060, 4);
*gpccon = 0xaaaaaaaa;
*gpdcon = 0xaaaaaaaa;
*gpbcon |= (3<<8);/* 使能LCD_PWREN */

3.2映射LCD寄存器并设置

lcd_regs = ioremap(0x4D000000, sizeof(struct lcd_regs));
lcd_regs->lcdcon1 = (4<<8) | (3<<5) | (0x0d<<1);/* 设置CLKVAL，VCLK = HCLK / [(CLKVAL+1) x 2], LCD手册P22 (Dclk=9MHz~15MHz) */
/* 垂直方向的时间参数 */
/*VBPD VSYNC之后再过多长时间发出第一行数据*/
/* VFPD 发出最后一行后再过多长时间发出VSYNC */
/* VSPW VSYNC信号的脉冲宽度 */
lcd_regs->lcdcon2 = (1<<24) | (271<<14) | (1<<6) | (9<<0);
/* 水平方向的时间参数 */
/* HBPD HSYNC之后再过多长时间才能发出这一行数据 */
/* HFPD 发出一行最后一个像素数据之后，再过多长时间才能发出HSYNC */
lcd_regs->lcdcon3 = (1<<19) | (479<<8) | (1<<0);
/* HSPW HSYNC信号的脉冲宽度 */
lcd_regs->lcdcon4 = 40;
/* 信号极性、字节序 */
lcd_regs->lcdcon5 = (0<<10) | (1<<9) | (1<<8) | (0<<12) | (0<<1) | (0<<0);

3.3分配显存，并把地址告诉LCD控制器

/* s3c_lcd->fix.smem_start为显存的物理地址 */
s3c_lcd->screen_base = dma_alloc_writecombine(NULL, s3c_lcd->fix.smem_len, &s3c_lcd->fix.smem_start, GFP_KERNEL);
lcd_regs->lcdaddr1 = (s3c_lcd->fix.smem_start >> 1) & ~(3<<30);
lcd_regs->lcdaddr2 = ((s3c_lcd->fix.smem_start + s3c_lcd->fix.smem_len) >> 1) & 0x1fffff;
lcd_regs->lcdaddr3 = (480*32/16);  /* 一行的长度(单位: 2字节) */

3.4启动LCD

lcd_regs->lcdcon1 |= (1<<0); /* 使能LCD控制器 */
lcd_regs->lcdcon5 |= (1<<3); /* 使能LCD器件: LCD_PWREN */

4.注册

register_framebuffer(s3c_lcd);/* /dev/fb0 */

5.测试LCD驱动

5.1配置内核，去掉原来的驱动程序

-> Device Drivers
  -> Graphics support
<M> S3C2410 LCD framebuffer support

5.2编译内核

make zImage

make modules

将编译出来的cfbcopyarea.ko、cfbfillrect.ko、cfbimgblt.ko模块拷贝到文件系统

5.3使用新内核启动开发板

insmod cfbcopyarea.ko

insmod cfbfillrect.ko
insmod cfbimgblt.ko
insmod lcd.ko

5.4测试

echo hello > /dev/tty1  // 可以在LCD上看见hello。

echo hello起作用的前提是要配置：CONFIG_FRAMEBUFFER_CONSOLE

cat lcd.ko > /dev/fb0   // 花屏