android lcd 屏 测试

1. LCD设备驱动相关的数据结构

struct fb_info {
	atomic_t count;
	int node;
	int flags;
	struct mutex lock;		/* Lock for open/release/ioctl funcs */
	struct mutex mm_lock;		/* Lock for fb_mmap and smem_* fields */
	struct fb_var_screeninfo var;	/* Current var */		//可变参数
	struct fb_fix_screeninfo fix;	/* Current fix */		//固定参数
	struct fb_monspecs monspecs;	/* Current Monitor specs */		//显示器标志
	struct work_struct queue;	/* Framebuffer event queue */
	struct fb_pixmap pixmap;	/* Image hardware mapper */		//图像硬件映射
	struct fb_pixmap sprite;	/* Cursor hardware mapper */	//光标硬件映射
	struct fb_cmap cmap;		/* Current cmap */		//调色板
	struct list_head modelist;      /* mode list */
	struct fb_videomode *mode;	/* current mode */		//视频模式

#ifdef CONFIG_FB_BACKLIGHT
	/* assigned backlight device */
	/* set before framebuffer registration, 
	   remove after unregister */
	struct backlight_device *bl_dev;

	/* Backlight level curve */
	struct mutex bl_curve_mutex;	
	u8 bl_curve[FB_BACKLIGHT_LEVELS];
#endif
#ifdef CONFIG_FB_DEFERRED_IO
	struct delayed_work deferred_work;
	struct fb_deferred_io *fbdefio;
#endif

	struct fb_ops *fbops;			//帧缓冲操作函数集
	struct device *device;		/* This is the parent */
	struct device *dev;		/* This is this fb device */
	int class_flag;                    /* private sysfs flags */
#ifdef CONFIG_FB_TILEBLITTING
	struct fb_tile_ops *tileops;    /* Tile Blitting */
#endif
	char __iomem *screen_base;	/* Virtual address */	//虚拟基地址
	unsigned long screen_size;	/* Amount of ioremapped VRAM or 0 */ 	//ioremap的虚拟内存大小
	void *pseudo_palette;		/* Fake palette of 16 colors */ 
#define FBINFO_STATE_RUNNING	0
#define FBINFO_STATE_SUSPENDED	1
	u32 state;			/* Hardware state i.e suspend */
	void *fbcon_par;                /* fbcon use-only private area */
	/* From here on everything is device dependent */
	void *par;
	/* we need the PCI or similar aperture base/size not
	   smem_start/size as smem_start may just be an object
	   allocated inside the aperture so may not actually overlap */
	struct apertures_struct {
		unsigned int count;
		struct aperture {
			resource_size_t base;
			resource_size_t size;
		} ranges[0];
	} *apertures;
};
struct fb_var_screeninfo {
	__u32 xres;			/* visible resolution		*/	//x方向可见解析度
	__u32 yres;
	__u32 xres_virtual;		/* virtual resolution		*/	//x方向虚拟解析度
	__u32 yres_virtual;
	__u32 xoffset;			/* offset from virtual to visible */	//可见和不可见部分的偏移
	__u32 yoffset;			/* resolution			*/

	__u32 bits_per_pixel;		/* guess what			*/	//每一个像素的位数
	__u32 grayscale;		/* != 0 Graylevels instead of colors */

	struct fb_bitfield red;		/* bitfield in fb mem if true color, */
	struct fb_bitfield green;	/* else only length is significant */
	struct fb_bitfield blue;
	struct fb_bitfield transp;	/* transparency			*/	

	__u32 nonstd;			/* != 0 Non standard pixel format */

	__u32 activate;			/* see FB_ACTIVATE_*		*/

	__u32 height;			/* height of picture in mm    */	//屏幕的高度
	__u32 width;			/* width of picture in mm     */	//屏幕的宽度

	__u32 accel_flags;		/* (OBSOLETE) see fb_info.flags */

	/* Timing: All values in pixclocks, except pixclock (of course) */
	__u32 pixclock;			/* pixel clock in ps (pico seconds) */	//像素时钟
	__u32 left_margin;		/* time from sync to picture	*/	//行切换时间，行同步与开始绘图之间的延迟
	__u32 right_margin;		/* time from picture to sync	*/	//行切换时间，绘图结束与行同步之间的延迟
	__u32 upper_margin;		/* time from sync to picture	*/	//帧切换，从同步到开始绘图之间的延迟
	__u32 lower_margin;							//帧切换，从绘图结束到同步之间的延迟
	__u32 hsync_len;		/* length of horizontal sync	*/	//水平同步的长度
	__u32 vsync_len;		/* length of vertical sync	*/	//垂直同步的长度
	__u32 sync;			/* see FB_SYNC_*		*/
	__u32 vmode;			/* see FB_VMODE_*		*/
	__u32 rotate;			/* angle we rotate counter clockwise */
	__u32 reserved[5];		/* Reserved for future compatibility */
};
struct fb_fix_screeninfo {
	char id[16];			/* identification string eg "TT Builtin" */
	unsigned long smem_start;	/* Start of frame buffer mem */		//fb缓冲区的开始位置
					/* (physical address) */<span style="white-space:pre">	</span>
	__u32 smem_len;			/* Length of frame buffer mem */	//fb缓冲区的长度
	__u32 type;			/* see FB_TYPE_*		*/
	__u32 type_aux;			/* Interleave for interleaved Planes */
	__u32 visual;			/* see FB_VISUAL_*		*/ 
	__u16 xpanstep;			/* zero if no hardware panning  */
	__u16 ypanstep;			/* zero if no hardware panning  */
	__u16 ywrapstep;		/* zero if no hardware ywrap    */
	__u32 line_length;		/* length of a line in bytes    */	//1行的字节数
	unsigned long mmio_start;	/* Start of Memory Mapped I/O   */	//内存映射IO的开始位置
					/* (physical address) */
	__u32 mmio_len;			/* Length of Memory Mapped I/O  */	//内存映射IO的长度
	__u32 accel;			/* Indicate to driver which	*/
					/*  specific chip/card we have	*/
	__u16 reserved[3];		/* Reserved for future compatibility */
};

2. s3c2440 lcd控制器的结构

我们根据数据手册来描述一下这个集成在S3C2440内部的LCD控制器
LCD控制器由REGBANK、LCDCDMA、TIMEGEN、VIDPRCS寄存器组成；
REGBANK由17个可编程的寄存器组和一块256*16的调色板内存组成，它们用来配置LCD控制器的；
LCDCDMA是一个专用的DMA，它能自动地把在侦内存中的视频数据传送到LCD驱动器，通过使用这个DMA通道，视频数据在不需要CPU的干预的情况下显示在LCD屏上；
VIDPRCS接收来自LCDCDMA的数据，将数据转换为合适的数据格式，比如说4/8位单扫，4位双扫显示模式，然后通过数据端口VD[23:0]传送视频数据到LCD驱动器；
TIMEGEN由可编程的逻辑组成，他生成LCD驱动器需要的控制信号，比如VSYNC、HSYNC、VCLK和LEND等等，而这些控制信号又与REGBANK寄存器组中的LCDCON1/2/3/4/5的配置密切相关，通过不同的配置，TIMEGEN就能产生这些信号的不同形态，从而支持不同的LCD驱动器(即不同的STN/TFT屏)。

常见的TFT屏工作时序分析：

VSYNC：垂直同步信号
HSYNC：水平同步信号 
VCLK：像素时钟信号
VD:像素数据输出端口
VDEN：数据使能信号
LEND：行结束信号

VBPD(vertical back porch)：表示在一帧图像开始时，垂直同步信号以后的无效的行数，对应驱动中的upper_margin；   
VFBD(vertical front porch)：表示在一帧图像结束后，垂直同步信号以前的无效的行数，对应驱动中的lower_margin；   
VSPW(vertical sync pulse width)：表示垂直同步脉冲的宽度，用行数计算，对应驱动中的vsync_len；   
HBPD(horizontal back porch)：表示从水平同步信号开始到一行的有效数据开始之间的VCLK的个数，对应驱动中的left_margin；   
HFPD(horizontal front porth)：表示一行的有效数据结束到下一个水平同步信号开始之间的VCLK的个数，对应驱动中的right_margin；   
HSPW(horizontal sync pulse width)：表示水平同步信号的宽度，用VCLK计算，对应驱动中的hsync_len；  

3. 帧缓冲设备的注册

 首先在arch/arm/mach-xx/目录中定义一些信息
（1）LCD控制器的IO端口开始地址，结束地址，LCD中断

（2）LCD硬件参数，如LCD的屏幕尺寸，屏幕类型，像素时钟，水平可见的像素，垂直可见的像素，色位模式，以及上面介绍的6个参数。有的板子可以支持很多个尺寸的屏幕，所以要建立一个数组，default赋值相应的index。

（3）LCD引脚相关的配置，哪些配置成LEND、VCLK、HSYNC、VSYNC、VDEN。

第（1）行的信息保存在platform_device结构的resource成员。

第（2）行和第（3）行的信息保存在platform_device结构的device成员的void *platform_data指针中，在平台初始化时赋值。

接下来看下probe的过程：

static int __devinit s3c24xxfb_probe(struct platform_device *pdev,
				  enum s3c_drv_type drv_type)
{
	struct s3c2410fb_info *info;	//封装了fb_info信息的结构
	struct s3c2410fb_display *display;	//指向定义的lcd信息
	struct fb_info *fbinfo;
	struct s3c2410fb_mach_info *mach_info;	//指向平台数据
	struct resource *res;
	int ret;
	int irq;
	int i;
	int size;
	u32 lcdcon1;

	mach_info = pdev->dev.platform_data;
	if (mach_info == NULL) {
		dev_err(&pdev->dev,
			"no platform data for lcd, cannot attach\n");
		return -EINVAL;
	}

	if (mach_info->default_display >= mach_info->num_displays) {
		dev_err(&pdev->dev, "default is %d but only %d displays\n",
			mach_info->default_display, mach_info->num_displays);
		return -EINVAL;
	}

	display = mach_info->displays + mach_info->default_display;	//指向你定义的lcd信息

	irq = platform_get_irq(pdev, 0);
	if (irq < 0) {
		dev_err(&pdev->dev, "no irq for device\n");
		return -ENOENT;
	}

	fbinfo = framebuffer_alloc(sizeof(struct s3c2410fb_info), &pdev->dev);	//分配s3c2410fb_info
	if (!fbinfo)
		return -ENOMEM;

	platform_set_drvdata(pdev, fbinfo);

	info = fbinfo->par;
	info->dev = &pdev->dev;
	info->drv_type = drv_type;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (res == NULL) {
		dev_err(&pdev->dev, "failed to get memory registers\n");
		ret = -ENXIO;
		goto dealloc_fb;
	}

	size = resource_size(res);
	info->mem = request_mem_region(res->start, size, pdev->name);
	if (info->mem == NULL) {
		dev_err(&pdev->dev, "failed to get memory region\n");
		ret = -ENOENT;
		goto dealloc_fb;
	}

	info->io = ioremap(res->start, size);
	if (info->io == NULL) {
		dev_err(&pdev->dev, "ioremap() of registers failed\n");
		ret = -ENXIO;
		goto release_mem;
	}

	info->irq_base = info->io + ((drv_type == DRV_S3C2412) ? S3C2412_LCDINTBASE : S3C2410_LCDINTBASE);

	dprintk("devinit\n");

	strcpy(fbinfo->fix.id, driver_name);

	/* Stop the video */	//关闭显示器
	lcdcon1 = readl(info->io + S3C2410_LCDCON1);
	writel(lcdcon1 & ~S3C2410_LCDCON1_ENVID, info->io + S3C2410_LCDCON1);

	fbinfo->fix.type	    = FB_TYPE_PACKED_PIXELS;
	fbinfo->fix.type_aux	    = 0;
	fbinfo->fix.xpanstep	    = 0;
	fbinfo->fix.ypanstep	    = 0;
	fbinfo->fix.ywrapstep	    = 0;
	fbinfo->fix.accel	    = FB_ACCEL_NONE;

	fbinfo->var.nonstd	    = 0;
	fbinfo->var.activate	    = FB_ACTIVATE_NOW;
	fbinfo->var.accel_flags     = 0;
	fbinfo->var.vmode	    = FB_VMODE_NONINTERLACED;

	fbinfo->fbops		    = &s3c2410fb_ops;	//赋值fb操作函数集
	fbinfo->flags		    = FBINFO_FLAG_DEFAULT;
	fbinfo->pseudo_palette      = &info->pseudo_pal;

	for (i = 0; i < 256; i++)
		info->palette_buffer[i] = PALETTE_BUFF_CLEAR;

	ret = request_irq(irq, s3c2410fb_irq, IRQF_DISABLED, pdev->name, info);
	if (ret) {
		dev_err(&pdev->dev, "cannot get irq %d - err %d\n", irq, ret);
		ret = -EBUSY;
		goto release_regs;
	}

	info->clk = clk_get(NULL, "lcd");
	if (IS_ERR(info->clk)) {
		printk(KERN_ERR "failed to get lcd clock source\n");
		ret = PTR_ERR(info->clk);
		goto release_irq;
	}

	clk_enable(info->clk);	//打开LCD时钟
	dprintk("got and enabled clock\n");

	msleep(1);

	info->clk_rate = clk_get_rate(info->clk);

	/* find maximum required memory size for display */
	for (i = 0; i < mach_info->num_displays; i++) {
		unsigned long smem_len = mach_info->displays[i].xres;

		smem_len *= mach_info->displays[i].yres;
		smem_len *= mach_info->displays[i].bpp;
		smem_len >>= 3;
		if (fbinfo->fix.smem_len < smem_len)
			fbinfo->fix.smem_len = smem_len;
	}
	//计算显存大小，并映射DMA资源
	/* Initialize video memory */
	ret = s3c2410fb_map_video_memory(fbinfo);
	if (ret) {
		printk(KERN_ERR "Failed to allocate video RAM: %d\n", ret);
		ret = -ENOMEM;
		goto release_clock;
	}

	dprintk("got video memory\n");

	fbinfo->var.xres = display->xres;
	fbinfo->var.yres = display->yres;
	fbinfo->var.bits_per_pixel = display->bpp;
	//初始化LCD控制器的各个寄存器
	s3c2410fb_init_registers(fbinfo);
	//调整可变参数
	s3c2410fb_check_var(&fbinfo->var, fbinfo);

	ret = s3c2410fb_cpufreq_register(info);
	if (ret < 0) {
		dev_err(&pdev->dev, "Failed to register cpufreq\n");
		goto free_video_memory;
	}
	//注册帧缓冲结构，也就是把指针赋给一个全局index指针数组
	ret = register_framebuffer(fbinfo);
	if (ret < 0) {
		printk(KERN_ERR "Failed to register framebuffer device: %d\n",
			ret);
		goto free_cpufreq;
	}

	/* create device files */
	ret = device_create_file(&pdev->dev, &dev_attr_debug);
	if (ret) {
		printk(KERN_ERR "failed to add debug attribute\n");
	}

	printk(KERN_INFO "fb%d: %s frame buffer device\n",
		fbinfo->node, fbinfo->fix.id);

	return 0;

 free_cpufreq:
	s3c2410fb_cpufreq_deregister(info);
free_video_memory:
	s3c2410fb_unmap_video_memory(fbinfo);
release_clock:
	clk_disable(info->clk);
	clk_put(info->clk);
release_irq:
	free_irq(irq, info);
release_regs:
	iounmap(info->io);
release_mem:
	release_mem_region(res->start, size);
dealloc_fb:
	platform_set_drvdata(pdev, NULL);
	framebuffer_release(fbinfo);
	return ret;
}

static int __devinit s3c2410fb_map_video_memory(struct fb_info *info)
{
	struct s3c2410fb_info *fbi = info->par;
	dma_addr_t map_dma;
	unsigned map_size = PAGE_ALIGN(info->fix.smem_len);

	dprintk("map_video_memory(fbi=%p) map_size %u\n", fbi, map_size);
	//将分配的一个写合并DMA缓冲区设置为LCD屏幕的虚拟地址
	info->screen_base = dma_alloc_writecombine(fbi->dev, map_size,
						   &map_dma, GFP_KERNEL);

	if (info->screen_base) {
		/* prevent initial garbage on screen */
		dprintk("map_video_memory: clear %p:%08x\n",
			info->screen_base, map_size);
		memset(info->screen_base, 0x00, map_size);

		info->fix.smem_start = map_dma;

		dprintk("map_video_memory: dma=%08lx cpu=%p size=%08x\n",
			info->fix.smem_start, info->screen_base, map_size);
	}

	return info->screen_base ? 0 : -ENOMEM;
}
static int s3c2410fb_init_registers(struct fb_info *info)
{
	struct s3c2410fb_info *fbi = info->par;
	struct s3c2410fb_mach_info *mach_info = fbi->dev->platform_data;
	unsigned long flags;
	void __iomem *regs = fbi->io;
	void __iomem *tpal;
	void __iomem *lpcsel;

	if (is_s3c2412(fbi)) {
		tpal = regs + S3C2412_TPAL;
		lpcsel = regs + S3C2412_TCONSEL;
	} else {
		tpal = regs + S3C2410_TPAL;
		lpcsel = regs + S3C2410_LPCSEL;
	}

	/* Initialise LCD with values from haret */

	local_irq_save(flags);

	/* modify the gpio(s) with interrupts set (bjd) */
	//把GPIOC和GPIOD设置为LCD模式
	modify_gpio(S3C2410_GPCUP,  mach_info->gpcup,  mach_info->gpcup_mask);
	modify_gpio(S3C2410_GPCCON, mach_info->gpccon, mach_info->gpccon_mask);
	modify_gpio(S3C2410_GPDUP,  mach_info->gpdup,  mach_info->gpdup_mask);
	modify_gpio(S3C2410_GPDCON, mach_info->gpdcon, mach_info->gpdcon_mask);

	local_irq_restore(flags);

	dprintk("LPCSEL    = 0x%08lx\n", mach_info->lpcsel);
	writel(mach_info->lpcsel, lpcsel);

	dprintk("replacing TPAL %08x\n", readl(tpal));

	/* ensure temporary palette disabled */
	writel(0x00, tpal);

	return 0;
}
static int s3c2410fb_check_var(struct fb_var_screeninfo *var,
			       struct fb_info *info)
{
	struct s3c2410fb_info *fbi = info->par;
	struct s3c2410fb_mach_info *mach_info = fbi->dev->platform_data;
	struct s3c2410fb_display *display = NULL;
	struct s3c2410fb_display *default_display = mach_info->displays +
						    mach_info->default_display;
	int type = default_display->type;
	unsigned i;

	dprintk("check_var(var=%p, info=%p)\n", var, info);

	/* validate x/y resolution */
	/* choose default mode if possible */
	if (var->yres == default_display->yres &&
	    var->xres == default_display->xres &&
	    var->bits_per_pixel == default_display->bpp)
		display = default_display;
	else
		for (i = 0; i < mach_info->num_displays; i++)
			if (type == mach_info->displays[i].type &&
			    var->yres == mach_info->displays[i].yres &&
			    var->xres == mach_info->displays[i].xres &&
			    var->bits_per_pixel == mach_info->displays[i].bpp) {
				display = mach_info->displays + i;
				break;
			}

	if (!display) {
		dprintk("wrong resolution or depth %dx%d at %d bpp\n",
			var->xres, var->yres, var->bits_per_pixel);
		return -EINVAL;
	}
	//直接赋值给新分配的var
	/* it is always the size as the display */
	var->xres_virtual = display->xres;
	var->yres_virtual = display->yres;
	var->height = display->height;
	var->width = display->width;

	/* copy lcd settings */
	var->pixclock = display->pixclock;
	var->left_margin = display->left_margin;
	var->right_margin = display->right_margin;
	var->upper_margin = display->upper_margin;
	var->lower_margin = display->lower_margin;
	var->vsync_len = display->vsync_len;
	var->hsync_len = display->hsync_len;

	fbi->regs.lcdcon5 = display->lcdcon5;
	/* set display type */
	fbi->regs.lcdcon1 = display->type;

	var->transp.offset = 0;
	var->transp.length = 0;
	/* set r/g/b positions */
	//根据设置的色位模式，设置相应的参数
	switch (var->bits_per_pixel) {
	case 1:
	case 2:
	case 4:
		var->red.offset	= 0;
		var->red.length	= var->bits_per_pixel;
		var->green	= var->red;
		var->blue	= var->red;
		break;
	case 8:
		if (display->type != S3C2410_LCDCON1_TFT) {
			/* 8 bpp 332 */
			var->red.length		= 3;
			var->red.offset		= 5;
			var->green.length	= 3;
			var->green.offset	= 2;
			var->blue.length	= 2;
			var->blue.offset	= 0;
		} else {
			var->red.offset		= 0;
			var->red.length		= 8;
			var->green		= var->red;
			var->blue		= var->red;
		}
		break;
	case 12:
		/* 12 bpp 444 */
		var->red.length		= 4;
		var->red.offset		= 8;
		var->green.length	= 4;
		var->green.offset	= 4;
		var->blue.length	= 4;
		var->blue.offset	= 0;
		break;

	default:
	case 16:
		if (display->lcdcon5 & S3C2410_LCDCON5_FRM565) {
			/* 16 bpp, 565 format */
			var->red.offset		= 11;
			var->green.offset	= 5;
			var->blue.offset	= 0;
			var->red.length		= 5;
			var->green.length	= 6;
			var->blue.length	= 5;
		} else {
			/* 16 bpp, 5551 format */
			var->red.offset		= 11;
			var->green.offset	= 6;
			var->blue.offset	= 1;
			var->red.length		= 5;
			var->green.length	= 5;
			var->blue.length	= 5;
		}
		break;
	case 32:
		/* 24 bpp 888 and 8 dummy */
		var->red.length		= 8;
		var->red.offset		= 16;
		var->green.length	= 8;
		var->green.offset	= 8;
		var->blue.length	= 8;
		var->blue.offset	= 0;
		break;
	}
	return 0;
}