11.LCD drive

1.LCD display principle

2.LCD drive frame:

1. Allocate fb_info
2. Set
3. Register register_framebuffer
4. hardware-specific operations

3. About fb_info

Linux Kernel Framebuffer all the abstract structure called the fb_info, fb_info structure contains a complete property Framebuffer device and set of operations, so that each device must have a Framebuffer fb_info. In other words, LCD driver fb_info is constructed, and the registration process fb_info system. fb_info structure is defined in include / linux / fb.h file inside
a lot of focus on the following fb_info structure member variables: var, fix, fbops, screen_size , screen_base

The main steps of the procedure are as follows:

1. Assign a fb_info

static struct fb_info *s3c_lcd;
s3c_lcd = framebuffer_alloc(0, NULL);

2. Set

 2.1 fixed parameters set
 reference fb.h

	strcpy(s3c_lcd->fix.id, "mylcd");
	s3c_lcd->fix.smem_len = 480*272*16/8;/*显存长度 565 */
	s3c_lcd->fix.type     = FB_TYPE_PACKED_PIXELS;
	s3c_lcd->fix.visual   = FB_VISUAL_TRUECOLOR; /* TFT */
	s3c_lcd->fix.line_length = 480*2;/*1行480像素，每个像素 16/8=2字节*/

  2.2 provided with a variable parameter

	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;//起始地址 
	s3c_lcd->var.red.length     = 5;//总共位数
	
	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;

/ * The RGB: 565 * /
  2.3 setting operation function

static struct fb_ops s3c_lcdfb_ops = {
	.owner		= THIS_MODULE,
	.fb_setcolreg	= s3c_lcdfb_setcolreg,
	/*下面三个函数 每个ops都有*/
	.fb_fillrect	= cfb_fillrect,
	.fb_copyarea	= cfb_copyarea,
	.fb_imageblit	= cfb_imageblit,
};
s3c_lcd->fbops              = &s3c_lcdfb_ops;

  2.4 Other settings

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. Hardware related operations

  3.1 GPIO configured for 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;     /* 输出低电平背光 */

	*gpgcon |= (3<<8); /* GPG4用作LCD_PWREN */

  3.2 The LCD controller provided LCD Manual, such as frequency of VCLK



VSPW = Tl +. 1. 1 = 0 = VSPW
the VBPD. 1 + T2 = T0-Tl-377-322-1 = = = the VBPD. 4. 3
LINEVAL. 1 = + T5 = = 319 LINEVAL 320.
VFPD. 1 = + = 322-320 = T2-T5 = 2. 1 VFPD
figure above VSYNC pins polarity inversion


HSPW the T7 +. 1 = = =. 5. 4 HSPW
HbpD +. 1 = the T7-T8-T6 = = = 16. 17 HbpD 273-25-251
the HOZVAL + T11. 1 = 239 = 240 = the HOZVAL
HFPD + T8-T11. 1 = = = 251-240 = 10. 11 HFPD
HSYNC same polarity to reverse

	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);


	/* 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);

	/* 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;

#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 高低位反转下  方便操作
	 * bit[0] : 1 = HWSWP 2440手册P413
	 */
	lcd_regs->lcdcon5 = (1<<11) | (0<<10) | (1<<9) | (1<<8) | (1<<0);

  3.3 assignment memory (framebuffer), and the address to the LCD controller
  reference memory allocated by the kernel

	s3c_lcd->screen_base = dma_alloc_writecombine(NULL, s3c_lcd->fix.smem_len, 	&s3c_lcd->fix.smem_start, GFP_KERNEL);
	/*把显存地址告诉LCD控制器*/
	/*最低1位和最高两位都不要*/
	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);  /* 一行的长度(单位: 2字节) */	
		/* 启动LCD */
	lcd_regs->lcdcon1 |= (1<<0); /* 使能LCD控制器 */
	lcd_regs->lcdcon5 |= (1<<3); /* 使能LCD本身 */
	*gpbdat |= 1;     /* 输出高电平, 使能背光 */

4. Register

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

5. Exit logout

static void lcd_exit(void)
{
	unregister_framebuffer(s3c_lcd);
	lcd_regs->lcdcon1 &= ~(1<<0); /* 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);
}

6. Register

module_init(lcd_init);
module_exit(lcd_exit);

MODULE_LICENSE("GPL");

7. complementary palette

Reference kernel atmel_lcdfb.c

/* from pxafb.c */
static inline unsigned int chan_to_field(unsigned int chan, struct fb_bitfield *bf)
{
	chan &= 0xffff;//保留低16位
	chan >>= 16 - bf->length;//右移位数，保留16-位数
	return chan << bf->offset;//把16-位数 左移 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;

}

8. Test:

1. In the make menuconfig /work/system/linux-2.6.22.6 remove the original driver
-> the Drivers Device
-> Graphics Support
S3C2410 the LCD the framebuffer Support

2.在/work/system/linux-2.6.22.6 make uImage
在/work/system/linux-2.6.22.6 make modules

3. The new start uImage Development Board:
load driving three

4.insmod cfbcopyarea.ko
insmod cfbfillrect.ko
insmod cfbimgblt.ko
insmod lcd.ko

echo hello> / dev / tty1 // hello can be seen on the LCD
CAT lcd.ko> / dev / FB0 // all matter thrown so the video memory
5. Modify / etc / inittab
tty1 :: askfirst: - / bin / SH
reboot with the new kernel development board

cfbcopyarea.ko insmod
insmod cfbfillrect.ko
insmod cfbimgblt.ko
insmod lcd.ko
insmod buttons.ko