linux驱动摸索-- LCD显示（mini2440_T35)
内核版本：linux-2.6.32.2
开发板：mini2440
TFT屏：统宝3.5寸屏
LCD内核框架：
内核自带的LCD驱动程序：drivers/video/S3c2410fb.c
这个驱动程序通过提供最底层的操作来被核心层调用，这个核心层提供了应用程序所需 open/close，read/write 其中drivers/video/fbmem.c提供了对LCD的所有抽象操作。
LCD硬件原理简介：
• VD3-VD23: video data引脚，lcd控制器发的数据在这几根线上
• VLINE: 能发出HSYNC信号，用于切换到下一行扫描
• VFRAME: 能发出VSYNC信号，用于返回到最开始行的扫描
• VCLK：控制器发给lcd的时钟引脚，根据lcd手册设置
• VM／VDEN: video data 使能引脚
LCD驱动编写步骤
1.分配一个fb_info结构
mini2440fb = framebuffer_alloc(0, NULL);注意：每一个lcd驱动程序都要分配一个fb_info结构体,framebuffer_alloc的用法可以参考其他lcd驱动，第一个参数0表示只需要分配本结构体的长度，
第二个NULL，表示无device结构，返回值为fb_info结构体。
2.设置fb_info的fix，val等相关参数,例如：
mini2440fb->fix.smem_len = MINI2440_LCD_WIDTH*MINI2440_LCD_LENGTH*MINI2440_LCD_DEEPTH/8; /* Length of frame buffer mem */ mini2440fb->fix.type = FB_TYPE_PACKED_PIXELS; /* see FB_TYPE_**/ mini2440fb->fix.visual = FB_VISUAL_TRUECOLOR; /* see FB_VISUAL_**/ mini2440fb->fix.line_length = MINI2440_LCD_WIDTH*MINI2440_LCD_DEEPTH/8; /* length of a line in bytes */注意：在设置操作函数中这个操作函数是必须的，具体可参考 S3c2410fb.c中的相关配置，还有在mini2440中LCD位宽是24,但是2440里会分配4字节即32位(浪费1字节)即设置 MINI2440_LCD_DEEPTH 为32.
3.硬件相关的操作：
参考s3c2440手册和lcd手册，配置相关参数，在mini2440开发板中。背光控制引脚是GPG4.
4.注册
register_framebuffer(mini2440fb);
mini2440 LCD驱动程序，源码如下：
#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/platform_device.h>
#include <linux/clk.h>
#include <linux/cpufreq.h>
#include <asm/io.h>
#include <asm/div64.h>
#include <asm/mach/map.h>
#include <mach/regs-lcd.h>
#include <mach/regs-gpio.h>
#include <mach/fb.h>
#define MINI2440_LCD_WIDTH 240
#define MINI2440_LCD_LENGTH 320
#define MINI2440_LCD_DEEPTH 32
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 volatile unsigned long *gpccon;
static volatile unsigned long *gpdcon;
static volatile unsigned long *gpgcon;
static volatile unsigned long *gpgdat;
static u32 pseudo_palette[16];
static struct fb_info *mini2440fb;
static volatile struct lcd_regs *s3c_lcd_regs;
/* 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 mini2440fb_setcolreg(unsigned regno,
unsigned red, unsigned green, unsigned blue,
unsigned 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 struct fb_ops mini2440fb_ops = {
.owner = THIS_MODULE,
.fb_setcolreg = mini2440fb_setcolreg,
.fb_fillrect = cfb_fillrect,
.fb_copyarea = cfb_copyarea,
.fb_imageblit = cfb_imageblit,
};
static int mini2440_tft_t35_init(void)
{
/*1.分配一个fb_info结构体*/
mini2440fb = framebuffer_alloc(0, NULL); //不需要额外的私有空间，设为0
if (!mini2440fb)
{
printk("framebuffer_alloc filed\n");
return -ENOMEM;
}
/*2.设置*/
/*set fix param*/
strcpy(mini2440fb->fix.id, "mytft");
mini2440fb->fix.smem_len = MINI2440_LCD_WIDTH*MINI2440_LCD_LENGTH*MINI2440_LCD_DEEPTH/8; /* Length of frame buffer mem */
mini2440fb->fix.type = FB_TYPE_PACKED_PIXELS; /* see FB_TYPE_**/
mini2440fb->fix.visual = FB_VISUAL_TRUECOLOR; /* see FB_VISUAL_**/
mini2440fb->fix.line_length = MINI2440_LCD_WIDTH*MINI2440_LCD_DEEPTH/8; /* length of a line in bytes */
/*set var param*/
mini2440fb->var.xres = MINI2440_LCD_WIDTH; /* visible resolution*/
mini2440fb->var.yres = MINI2440_LCD_LENGTH;
mini2440fb->var.xres_virtual = MINI2440_LCD_WIDTH; /* virtual resolution*/
mini2440fb->var.yres_virtual = MINI2440_LCD_LENGTH;
mini2440fb->var.bits_per_pixel = MINI2440_LCD_DEEPTH; /* guess what */
mini2440fb->var.red.offset = 16; /* bitfield in fb mem if true color, */
mini2440fb->var.red.length = 8;
mini2440fb->var.green.offset = 8;
mini2440fb->var.green.length = 8 ;
mini2440fb->var.blue.offset = 0;
mini2440fb->var.blue.length = 8;
mini2440fb->var.activate = FB_ACTIVATE_NOW; /* see FB_ACTIVATE_**/
mini2440fb->fbops = &mini2440fb_ops;
mini2440fb->pseudo_palette = pseudo_palette;
mini2440fb->screen_size = MINI2440_LCD_WIDTH*MINI2440_LCD_LENGTH*MINI2440_LCD_DEEPTH/8;
/*3.硬件相关的配置*/
gpccon = ioremap(0x56000020,4);
gpdcon = ioremap(0x56000030,4);
gpgcon = ioremap(0x56000060,4);
gpgdat = gpgcon + 1;
/*3.1将GPIOC,GPIOD配成VD模式*/
*gpccon = 0xaaaaaaaa;
*gpdcon = 0xaaaaaaaa;
/*3.2配置背光GPIOG4,低电平，关闭*/
*gpgcon &= ~(3<<8);
*gpgcon |= (1<<8);
*gpgdat &= ~(1<<4);
//*gpgcon |= (3<<8);
/*3.3配置lcd相关寄存器*/
s3c_lcd_regs = ioremap(0X4D000000,sizeof(struct lcd_regs));
/* LCDCON1 :
* CLKVAL [17:8]:VCLK = HCLK / [(CLKVAL+1) x 2] HCLK=100Mhz,VCLK=6400000
* CLKVAL = 7
* PNRMODE [6:5]:11 = TFT LCD panel
* BPPMODE [4:1]:1100 = 16 bpp for TFT
* ENVID [0]:0 = Disable the video output and the LCD control signal.
* 1 = Enable the video output and the LCD control signal.
*/
s3c_lcd_regs->lcdcon1 = (7<<8)|(3<<5)|(0x0d<<1);
/* LCDCON2 :
* VBPD [31:24]:VBPD+1 = 4
* LINEVAL [23:14] : LINEVAL+1=320
* VFPD [13:6]:VFPD+1=2
* VSPW [5:0]:VSPW+1 =2
*/
s3c_lcd_regs->lcdcon2 = (3<<24)|(319<<14)|(1<<6)|(1<<0);
/* LCDCON3 :
* HBPD (TFT) [25:19]: HBPD+1=30
* HOZVAL [18:8] : HOZVAL+1=240
* HFPD (TFT) [7:0]:HFPD+1=10
*/
s3c_lcd_regs->lcdcon3 = (29<<19)|(239<<8)|(9<<0);
/* LCDCON4 :
* HSPW(TFT) [7:0]:HSPW+1=10
*/
s3c_lcd_regs->lcdcon4 = 0;
/* LCDCON5 :
* FRM565 [11]: 1 = 5:6:5 Format
* INVVCLK [10]:1 = The video data is fetched at VCLK rising edge
* INVVLINE [9] 1 = Inverted
* INVVFRAME [8] 1 = Inverted
* INVVDEN [6] 0 = normal
* PWREN [3]: 0 = Disable PWREN signal 1 = Enable PWREN signal
* BSWP [1]: 0 见2440手册 413页
HWSWP [0]: 0
*/
s3c_lcd_regs->lcdcon5 = (1<<10) | (1<<9) | (1<<8) | (0<<12) | (0<<1) | (0<<0);
/*分配显存(framebuffer), 并把地址告诉LCD控制器*/
mini2440fb->screen_base =dma_alloc_writecombine(NULL,mini2440fb->fix.smem_len,\
&mini2440fb->fix.smem_start,GFP_KERNEL);
s3c_lcd_regs->lcdsaddr1 = (mini2440fb->fix.smem_start>>1)&(~(3<<30));
s3c_lcd_regs->lcdsaddr2 = ((mini2440fb->fix.smem_start+mini2440fb->fix.smem_len)>>1)&\
(0x1fffff);
s3c_lcd_regs->lcdsaddr3 =(240*MINI2440_LCD_DEEPTH/16); /* 一行的长度(单位: 2字节) */
/*使能LCD*/
s3c_lcd_regs->lcdcon1 |= 1;
s3c_lcd_regs->lcdcon5 |=(1<<3);
*gpgdat |= (1<<4);
/*注册*/
register_framebuffer(mini2440fb);
return 0;
}
static void mini2440_tft_t35_exit(void)
{
unregister_framebuffer(mini2440fb);
s3c_lcd_regs->lcdcon1 &= ~1;
s3c_lcd_regs->lcdcon5 &=~(1<<3);
*gpgdat &= ~(1<<4);
dma_free_writecombine(NULL, mini2440fb->fix.smem_len, mini2440fb->screen_base,\
mini2440fb->fix.smem_start);
iounmap(gpccon);
iounmap(gpdcon);
iounmap(gpgcon);
iounmap(s3c_lcd_regs);
framebuffer_release(mini2440fb);
}
/* 这两行指定驱动程序的初始化函数和卸载函数 */
module_init(mini2440_tft_t35_init);
module_exit(mini2440_tft_t35_exit);
/* 描述驱动程序的一些信息*/
MODULE_LICENSE("GPL");
测试：
1. make menuconfig去掉原来的驱动程序，mini2440开发板提供的内核时，需要把相关的LCD驱动去掉。
-> 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 tft.ko
echo hello > /dev/tty1 // 可以在LCD上看见hello
