Lcd驅動程序
怎麼寫LCD驅動程序？
1. 分配一個fb_info結構體: framebuffer_alloc
2. 設置
3. 註冊: register_framebuffer
4. 硬件相關的操作
#include <linux/module.h>
#include <linux/kernel.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_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三原色構造出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 s3c_lcdfb_ops = {
.owner
= THIS_MODULE,
.fb_setcolreg
= s3c_lcdfb_setcolreg,
.fb_fillrect
= cfb_fillrect,
.fb_copyarea
= cfb_copyarea,
.fb_imageblit
= cfb_imageblit,
};
static int lcd_init(void)
{
/* 1. 分配一個fb_info */
s3c_lcd = framebuffer_alloc(0, NULL);
/* 2. 設置 */
/* 2.1 設置固定的參數 */
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 設置可變的參數 */
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 設置操作函數 */
s3c_lcd->fbops = &s3c_lcdfb_ops;
/* 2.4 其他的設置 */
s3c_lcd->pseudo_palette = pseudo_palette;
//s3c_lcd->screen_base = ; /* 顯存的虛擬地址 */
s3c_lcd->screen_size = 480*272*16/8;
/* 3. 硬件相關的操作 */
/* 3.1 配置GPIO用於LCD */
gpbcon = ioremap(0x56000010, 8);
gpbdat = gpbcon+1;
gpccon = ioremap(0x56000020, 4);
gpdcon = ioremap(0x56000030, 4);
gpgcon = ioremap(0x56000060, 4);
*gpccon = 0xaaaaaaaa; /* GPIO管腳用於VD[7:0],LCDVF[2:0],VM,VFRAME,VLINE,VCLK,LEND */
*gpdcon = 0xaaaaaaaa; /* GPIO管腳用於VD[23:8] */
*gpbcon &= ~(3); /* GPB0設置爲輸出引腳 */
*gpbcon |= 1;
*gpbdat &= ~1; /* 輸出低電平 */
*gpgcon |= (3<<8); /* GPG4用作LCD_PWREN */
/* 3.2 根據LCD手冊設置LCD控制器, 比如VCLK的頻率等 */
lcd_regs = ioremap(0x4D000000, sizeof(struct lcd_regs));
/* bit[17:8]: VCLK = HCLK / [(CLKVAL+1) x 2], LCD手冊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
/* 垂直方向的時間參數
* bit[31:24]: VBPD, VSYNC之後再過多長時間才能發出第1行數據
* LCD手冊 T0-T2-T1=4
* VBPD=3
* bit[23:14]: 多少行, 320, 所以LINEVAL=320-1=319
* bit[13:6] : VFPD, 發出最後一行數據之後，再過多長時間才發出VSYNC
* LCD手冊T2-T5=322-320=2, 所以VFPD=2-1=1
* bit[5:0] : VSPW, VSYNC信號的脈衝寬度, LCD手冊T1=1, 所以VSPW=1-1=0
*/
lcd_regs->lcdcon2 = (1<<24) | (271<<14) | (1<<6) | (9);
/* 水平方向的時間參數
* bit[25:19]: HBPD, VSYNC之後再過多長時間才能發出第1行數據
* LCD手冊 T6-T7-T8=17
* HBPD=16
* bit[18:8]: 多少列, 240, 所以HOZVAL=240-1=239
* bit[7:0] : HFPD, 發出最後一行裏最後一個象素數據之後，再過多長時間才發出HSYNC
* LCD手冊T8-T11=251-240=11, 所以HFPD=11-1=10
*/
lcd_regs->lcdcon3 = (1<<19) | (479<<8) | (1);
/* 水平方向的同步信號
* bit[7:0]
: HSPW, HSYNC信號的脈衝寬度, LCD手冊T7=5, 所以HSPW=5-1=4
*/
lcd_regs->lcdcon4 = 40;
#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
/* 信號的極性
* bit[11]: 1=565 format
* bit[10]: 0 = The video data is fetched at VCLK falling edge
* bit[9] : 1 = HSYNC信號要反轉,即低電平有效
* bit[8] : 1 = VSYNC信號要反轉,即低電平有效
* bit[6] : 0 = VDEN不用反轉
* bit[3] : 0 = PWREN輸出0
* bit[1] : 0 = BSWP
* bit[0] : 1 = HWSWP 2440手冊P413
*/
lcd_regs->lcdcon5 = (1<<11) | (0<<10) | (1<<9) | (1<<8) | (1<<0);
/* 3.3 分配顯存(framebuffer), 並把地址告訴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 = (480*16/16); /* 一行的長度(單位: 2字節) */
//s3c_lcd->fix.smem_start = xxx; /* 顯存的物理地址 */
/* 啓動LCD */
lcd_regs->lcdcon1 |= (1<<0); /* 使能LCD控制器 */
lcd_regs->lcdcon5 |= (1<<3); /* 使能LCD本身 */
*gpbdat |= 1; /* 輸出高電平, 使能背光 */
/* 4. 註冊 */
register_framebuffer(s3c_lcd);
return 0;
}
static void lcd_exit(void)
{
unregister_framebuffer(s3c_lcd);
lcd_regs->lcdcon1 &= ~(1<<0); /* 關閉LCD本身 */
*gpbdat &= ~1; /* 關閉背光 */
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");
測試：
1. make menuconfig去掉原來的驅動程序
-> Device Drivers
-> Graphics support
<M> S3C2410 LCD framebuffer support
2. make uImage
make modules
3. 使用新的uImage啓動開發板:
4. insmod cfbcopyarea.ko
insmod cfbfillrect.ko
insmod cfbimgblt.ko
insmod lcd.ko
echo hello > /dev/tty1 // 可以在LCD上看見hello
cat lcd.ko > /dev/fb0 // 花屏
5. 修改 /etc/inittab\
tty1::askfirst:-/bin/sh
用新內核重啓開發板
insmod cfbcopyarea.ko
insmod cfbfillrect.ko
insmod cfbimgblt.ko
insmod lcd.ko
insmod buttons.ko