linux驱动之LCD

Posted 2020-08-25

LCD程序步骤：1. 分配一个fb_info 2. 设置 3. 硬件相关的操作4. 注册 register_framebuffer 5.入口函数 6.出口函数

#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;
};//LCD控制器的寄存器，寄存器是4字节，所以要添加unsigned long reserved[9];

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 = 240*320*16/8; 　　 //显存的长度=分辨率*每象素字节数
s3c_lcd->fix.type = FB_TYPE_PACKED_PIXELS; 　　/* Packed Pixels */
s3c_lcd->fix.visual = FB_VISUAL_TRUECOLOR;　　 /* TFT */
s3c_lcd->fix.line_length = 240*2;　　　　　　//每行的长度，以字节为单位

/* 2.2 设置可变的参数 */
s3c_lcd->var.xres = 240;　　//x方向分辨率
s3c_lcd->var.yres = 320;　　//Y方向分辨率
s3c_lcd->var.xres_virtual = 240;　　//x方向虚拟分辨率
s3c_lcd->var.yres_virtual = 320;　　//Y方向虚拟分辨率
s3c_lcd->var.bits_per_pixel = 16;　　//每个象素使用多少位

/* RGB:565 */
s3c_lcd->var.red.offset = 11; //红色偏移值为11
s3c_lcd->var.red.length = 5;//红色位长为5

s3c_lcd->var.green.offset = 5;//绿色偏移值为5
s3c_lcd->var.green.length = 6;//绿色位长为6

s3c_lcd->var.blue.offset = 0;//绿色偏移值为0
s3c_lcd->var.blue.length = 5;//蓝色位长为5

s3c_lcd->var.activate = FB_ACTIVATE_NOW;  //使设置的值立即生效


/* 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;　　//存放调色板所调颜色的数组
//s3c_lcd->screen_base = ; /* 显存的虚拟地址 */
s3c_lcd->screen_size = 240*324*16/8;//显存的大小

/* 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));　　//映射各lcd控制寄存器，

/* 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);

/* 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;

 

/* 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
* bit[0] : 1 = HWSWP 2440手册P413
*/
lcd_regs->lcdcon5 = (1<<11) | (0<<10) | (1<<9) | (1<<8) | (1<<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);//存放起始地址
lcd_regs->lcdsaddr2 = ((s3c_lcd->fix.smem_start + s3c_lcd->fix.smem_len) >> 1) & 0x1fffff;//存放结束地址
lcd_regs->lcdsaddr3 = (240*16/16); /* 一行的长度(单位: 2字节) */

//s3c_lcd->fix.smem_start  /* 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 */
*gpbdat |= 1; /* 输出高电平, 使能背光 */

/* 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");