linux之lcd驱动程序总结

大家看完lcd驱动模块系列头晕了吧，下面看看 韦东山老师写的一个简单的lcd驱动程序，大家可以参考下：



假设

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

--------------------------------------------------------------

kernel:

         fb_open

          int fbidx = iminor(inode);

          struct fb_info *info = = registered_fb[0];

app:  read()

---------------------------------------------------------------

kernel:
fb_read
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)        

问1. registered_fb在哪里被设置？

答1. register_framebuffer

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

测试：

1. make menuconfig去掉原来的驱动程序

-> Device Drivers

  -> Graphics support

<M> S3C2410 LCD framebuffer support

2. make uImage

   make modules  

3. 使用新的uImage启动开发板:

4. 

insmod cfbcopyarea.ko 

insmod cfbfillrect.ko 

insmod cfbimgblt.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 /etc/inittab

tty1::askfirst:-/bin/sh

用新内核重启开发板

insmod cfbcopyarea.ko 

insmod cfbfillrect.ko 

insmod cfbimgblt.ko 

insmod lcd.ko

insmod buttons.ko

LCD驱动程序

#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 <asm/arch/regs-lcd.h>
#include <asm/arch/regs-gpio.h>
#include <asm/arch/fb.h>

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 = 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; /* TFT */
s3c_lcd->fix.line_length = 320*4;

/* 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;

/* 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    = 8;

s3c_lcd->var.activate       = FB_ACTIVATE_NOW;

/* 2.3 设置操作函数 */
s3c_lcd->fbops              = &s3c_lcdfb_ops;

/* 2.4 其他的设置 */
s3c_lcd->pseudo_palette = 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
*             LCD手册 tvb=18
*             VBPD=17
* bit[23:14]: 多少行, 240, 所以LINEVAL=240-1=239
* 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tvf=4, 所以VFPD=4-1=3
* bit[5:0]  : VSPW, VSYNC信号的脉冲宽度, LCD手册tvp=1, 所以VSPW=1-1=0
*/

/* 使用这些数值, 图像有下移的现象, 应该是数据手册过时了
* 自己微调一下, 上下移动调VBPD和VFPD
* 保持(VBPD+VFPD)不变, 减小VBPD图像上移, 取VBPD=11, VFPD=9
* 多试几次, 我试了10多次
*/
//lcd_regs->lcdcon2  = (17<<24) | (239<<14) | (3<<6) | (0<<0);
lcd_regs->lcdcon2  = (11<<24) | (239<<14) | (9<<6) | (0<<0);

/* 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 thb=38
*             HBPD=37
* bit[18:8]: 多少列, 320, 所以HOZVAL=320-1=319
* 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thf>=2, th=408=thp+thb+320+thf, thf=49, HFPD=49-1=48
*/

/* 使用这些数值, 图像有左移的现象, 应该是数据手册过时了
* 自己微调一下, 左右移动调HBPD和HFPD
* 保持(HBPD+HFPD)不变, 增加HBPD图像右移, 取HBPD=69, HFPD=16
* 多试几次, 我试了10多次
*/

//	lcd_regs->lcdcon3 = (37<<19) | (319<<8) | (48<<0);
lcd_regs->lcdcon3 = (69<<19) | (319<<8) | (16<<0);

/* 水平方向的同步信号
* bit[7:0]	: HSPW, HSYNC信号的脉冲宽度, LCD手册Thp=1, 所以HSPW=1-1=0
*/
lcd_regs->lcdcon4 = 0;

/* 信号的极性
* bit[11]: 1=565 format, 对于24bpp这个不用设
* 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
*
* BSWP = 0, HWSWP = 0, BPP24BL = 0 : 当bpp=24时,2440会给每一个象素分配32位即4字节,哪一个字节是不使用的? 看2440手册P412
* bit[12]: 0, LSB valid, 即最高字节不使用
* bit[1] : 0 = BSWP
* bit[0] : 0 = HWSWP
*/
lcd_regs->lcdcon5 = (0<<10) | (1<<9) | (1<<8) | (0<<12) | (0<<1) | (0<<0);

/* 3.3 分配显存(framebuffer), 并把地址告诉LCD控制器 */
s3c_lcd->screen_base = dma_alloc_writecombine(NULL, s3c_lcd->fix.smem_len, &s3c_lcd->fix.smem_start, GFP_KERNEL);

lcd_regs->lcdsaddr1  = (s3c_lcd->fix.smem_start >> 1) & ~(3<<30);
lcd_regs->lcdsaddr2  = ((s3c_lcd->fix.smem_start + s3c_lcd->fix.smem_len) >> 1) & 0x1fffff;
lcd_regs->lcdsaddr3  = (320*32/16);  /* 一行的长度(单位: 2字节) */

//s3c_lcd->fix.smem_start = xxx;  /* 显存的物理地址 */
/* 启动LCD */
lcd_regs->lcdcon1 |= (1<<0); /* 使能LCD控制器 */
lcd_regs->lcdcon5 |= (1<<3); /* 使能LCD本身: LCD_PWREN */
//	*gpbdat |= 1;     /* MINI2440的背光电路也是通过LCD_PWREN来控制的, 不需要单独的背光引脚 */

/* 4. 注册 */
register_framebuffer(s3c_lcd);

return 0;
}

static void lcd_exit(void)
{
unregister_framebuffer(s3c_lcd);
lcd_regs->lcdcon1 &= ~(1<<0); /* 关闭LCD控制器 */
lcd_regs->lcdcon1 &= ~(1<<3); /* 关闭LCD本身 */
//	*gpbdat &= ~1;     /* 关闭背光 */
dma_free_writecombine(NULL, s3c_lcd->fix.smem_len, s3c_lcd->screen_base, s3c_lcd->fix.smem_start);
iounmap(lcd_regs);
iounmap(gpbcon);
iounmap(gpccon);
iounmap(gpdcon);
iounmap(gpgcon);
framebuffer_release(s3c_lcd);
}

module_init(lcd_init);
module_exit(lcd_exit);

MODULE_LICENSE("GPL");

主要步骤套路：

1. 分配一个fb_info

2. 设置

3. 硬件相关的操作

4. 注册

其实驱动不难，抓住思路,框架很重要!!!