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
#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>
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
* 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, 上下移动调HBPD和HFPD
* 保持(VBPD+VFPD)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()
{
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");
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
cp arch/arm/boot/uImage /home/null/work/yaffs/mini2440_rootfs/rootfs
make modules
3. 使用新的uImage启动开发板:
4. null@ubuntu:~/work/linux-kernel/linux-2.6.32.2/drivers/video$ cp cfb*.ko /home/null/work/yaffs/mini2440_rootfs/rootfs/wds_2
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