怎样写LCD驱动程序

1、分配一个fb_info结构体，使用framebuffer_alloc（）函数

2、设置fb_info中的参数，

1)固定参数(fix)

2)可变参数(var)

3)设置操作函数 fbops

4）其他设置 如调色板pseudo_palette和屏幕尺寸screen_size

5)分配显存 dma_alloc_writecombine（）,返回的是虚拟地址

3、注册fb_info 使用register_framebuffer

4、硬件相关操作，LCD寄存器等

测试方法：

虚拟机：

1、make menuconfig去掉原来的驱动程序

->Device Drivers

->Graphics support

S3c2410 LCD framebuffer support

2、make uImage

   make modules

cp arch/arm/boot/uImage /work/nfs_root/mydriver/uImage_nolcd

cp drivers/video/cfb*.ko /work/nfs_root/mydriver/

开发板：

3、使用新的uImage启动开发板

   nfs 30000000 192.168.34.251:/work/nfs_root/uImage_nolcd

   bootm 30000000

4、加载驱动

    insmod cfbfillrect.ko 

insmod cfbimgblt.ko 

insmod cfbcopyarea.ko 

insmod lcd.ko 

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

cat lcd.ko > /dev/fb0 //花屏

5、修改inittab

vi /etc/inittab

增加一行

tty1::askfirst:-/bin/sh

重启reboot

insmod cfbfillrect.ko 

insmod cfbimgblt.ko 

insmod cfbcopyarea.ko 

insmod lcd.ko 

insmod buttons.ko //输入子系统中的驱动

函数说明：

s3c_lcd->screen_base = dma_alloc_writecombine(NULL, s3c_lcd->fix.smem_len, &s3c_lcd->fix.smem_start, GFP_KERNEL);

含义：

s3c_lcd->screen_base : 内存的虚拟起始地址，在内核要用此地址来操作所分配的内存

NULL : 可以平台初始化里指定，主要是用到dma_mask之类参数，可参考framebuffer

s3c_lcd->fix.smem_len : 实际分配大小，传入dma_map_size即可

&s3c_lcd->fix.smem_start ：返回的内存物理地址，dma就可以用。

s3c_lcd->screen_base 和  s3c_lcd->fix.smem_start是一一对应的，

s3c_lcd->screen_base 是虚拟地址，

而s3c_lcd->fix.smem_start是总线地址。对任意一个操作都将改变写缓冲区内容。

lcd.c

#include

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static int s3c_lcdfb_setcolreg(unsigned int regno, unsigned int red,

     unsigned int green, unsigned int blue,

     unsigned int transp, struct fb_info *info);

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_setcolreg = s3c_lcdfb_setcolreg,

.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];

/* 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 **************************************************/

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 = 480*272*16/8;

s3c_lcd->fix.type     = FB_TYPE_PACKED_PIXELS;

s3c_lcd->fix.visual   = FB_VISUAL_TRUECOLOR; /* TFT */

s3c_lcd->fix.line_length = 480*2;

/* 2.2 设置可变的参数 */

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.bits_per_pixel = 16;

/* RGB:565 */

s3c_lcd->var.red.offset     = 11;

s3c_lcd->var.red.length     = 5;

s3c_lcd->var.green.offset   = 5;

s3c_lcd->var.green.length   = 6;

s3c_lcd->var.blue.offset    = 0;

s3c_lcd->var.blue.length    = 5;

s3c_lcd->var.activate       = FB_ACTIVATE_NOW;

/* 2.3 设置操作函数 */

s3c_lcd->fbops              = &s3c_lcdfb_ops;

/* 2.4 其他的设置 */

s3c_lcd->pseudo_palette = pseudo_palette;

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

s3c_lcd->screen_size   = 480*272*16/8;

/* 3. 硬件相关的操作 */

/* 3.1 配置GPIO用于LCD */

gpbcon = ioremap(0x56000010, 8);//ioremap功能：将一个IO地址空间映射到内核的虚拟地址空间上去，便于访问；

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));

/* bit[17:8]: VCLK = HCLK / [(CLKVAL+1) x 2], LCD手册P14

*            10MHz(100ns) = 100MHz / [(CLKVAL+1) x 2]

*            CLKVAL = 4

* bit[6:5]: 0b11, TFT LCD

* bit[4:1]: 0b1100, 16 bpp for TFT

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

*/

lcd_regs->lcdcon1  = (4<<8) | (3<<5) | (0x0c<<1);

#if 1

/* 垂直方向的时间参数

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

*             LCD手册 T0-T2-T1=4

*             VBPD=3

* bit[23:14]: 多少行, 320, 所以LINEVAL=320-1=319

* bit[13:6] : VFPD, 发出最后一行数据之后，再过多长时间才发出VSYNC

*             LCD手册T2-T5=322-320=2, 所以VFPD=2-1=1

* bit[5:0]  : VSPW, VSYNC信号的脉冲宽度, LCD手册T1=1, 所以VSPW=1-1=0

*/

//lcd_regs->lcdcon2  = (3<<24) | (319<<14) | (1<<6) | (0<<0);

lcd_regs->lcdcon2  = (1<<24) | (271<<14) | (1<<6) | 9; //同一厂家同一型号的led屏 某些位的值是一样的，查手册获得

/* 水平方向的时间参数

* bit[25:19]: HBPD, VSYNC之后再过多长时间才能发出第1行数据

*             LCD手册 T6-T7-T8=17

*             HBPD=16

* bit[18:8]: 多少列, 240, 所以HOZVAL=240-1=239

* bit[7:0] : HFPD, 发出最后一行里最后一个象素数据之后，再过多长时间才发出HSYNC

*             LCD手册T8-T11=251-240=11, 所以HFPD=11-1=10

*/

//lcd_regs->lcdcon3 = (16<<19) | (239<<8) | (10<<0);

    lcd_regs->lcdcon3 = (1<<19) | (479<<8) | (1);

/* 水平方向的同步信号

* bit[7:0] : HSPW, HSYNC信号的脉冲宽度, LCD手册T7=5, 所以HSPW=5-1=4

*/

//lcd_regs->lcdcon4 = 4;

lcd_regs->lcdcon4 = 40;

       lcd_regs->lcdcon5 =1<<11|1<<9|1<<8|1<<1;

#else

lcd_regs->lcdcon2 = S3C2410_LCDCON2_VBPD(5) |

S3C2410_LCDCON2_LINEVAL(319) |

S3C2410_LCDCON2_VFPD(3) |

S3C2410_LCDCON2_VSPW(1);

lcd_regs->lcdcon3 = S3C2410_LCDCON3_HBPD(10) |

S3C2410_LCDCON3_HOZVAL(239) |

S3C2410_LCDCON3_HFPD(1);

lcd_regs->lcdcon4 = S3C2410_LCDCON4_MVAL(13) |

S3C2410_LCDCON4_HSPW(0);

#endif

/* 信号的极性 

* bit[11]: 1=565 format

* bit[10]: 0 = The video data is fetched at VCLK falling edge

* bit[9] : 1 = HSYNC信号要反转,即低电平有效 

* bit[8] : 1 = VSYNC信号要反转,即低电平有效 

* bit[6] : 0 = VDEN不用反转

* bit[3] : 0 = PWREN输出0

* bit[1] : 0 = BSWP

* bit[0] : 1 = HWSWP 2440手册P413

*/

// lcd_regs->lcd