Linux学习: LCD驱动
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LCD驱动框架：
1.分配一个fb_info结构体：s3c_lcd = framebuffer_alloc(0,NULL);
2.设置fb_info（s3c_lcd）: ID、固定参数、可变参数、设置操作函数 及 其他设置
3.注册：register_framebuffer(s3c_lcd);
4.硬件相关的操作： ①分配引脚用于LCD
②根据LCD手册设置控制器参数
③分配显存并将地址告诉LCD控制器
显存分配：在嵌入式系统中一般没有专门的显存，而仅仅是从RAM(SDRAM)空间中分配一段显示缓冲区，LCD也可说是一个frame buffer 设备
lcdc.palette_virt = dma_alloc_writecombine(lcdc.fbdev->dev,MAX_PALETTE_SIZE, &lcdc.palette_phys, GFP_KERNEL);
硬件时序：
VCLK:每来一个时钟就向下移动一个像素。
VD0~VD23：数据宽度，但是我们只用了16位。
VLINE:(HYSNC，行同步型号，水平方向的，从上一行的行尾调到下一行的行首)，
VSYNC:(垂直同步信号，从最后一行行尾跳转到第一行的行首)
VDEN:有效才打印颜色
调色板：存储256种颜色的RGB值，每种颜色的RGB值是16位。用这256种颜色编制索引，从OOH～FFH只需 要8位数据宽度，而每个索引所对应的颜色却是16位宽度的颜色信息，
通过调色板的转换可以减少显存的开销。
LCD驱动代码示例：#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> 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; };
static struct fb_ops s3c_lcdfb_ops = { .owner = THIS_MODULE, .fb_setcolreg = s3c_lcdfb_setcolreg, //设置调色板 .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 = 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 设置可变的参数 */ 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 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; //s3c_lcd->screen_base = ; /* 显存的虚拟地址 */ s3c_lcd->screen_size = 480*272*16/8; /* 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，默认关闭背光 */ *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)); /* 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 = (1<<24) | (271<<14) | (1<<6) | (9); /* 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 = (1<<19) | (479<<8) | (1); /* 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 = 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); 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) */ //s3c_lcd->fix.smem_start = xxx; /* 分配到的显存物理地址 */ /* 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");
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