LCD驱动程序架构和分析

一、LCD驱动程序架构
1.裸机驱动代码分析
①LCD初始化：控制器初始化，端口初始化，指明帧缓冲
②LCD图形显示：将图形数据写入帧缓冲

void lcd_init()
{
    lcd_port_init();     //初始化gpdcon和gpccon初始化
    lcd_control_init();   //时序初始化和帧缓冲初始化

    //打开LCD电源
    GPGCON |= 0b11<<8;
    LCDCON5 |= (1<<3);
    LCDCON1 |= 1;
}

2.帧缓冲体验
帧缓冲：内存中的一段区域，通过对内存的修改。LCD控制器从内存中获取数据，自动的控制LCD的显示。

# cat tq2440.bin > /dev/fb0

将图片显示到lcd。

3.帧缓冲架构
/dev/fb0就是帧缓冲，字符设备
fbmem_init():

static int __init
fbmem_init(void)
{
    proc_create("fb", 0, NULL, &fb_proc_fops);

    if (register_chrdev(FB_MAJOR,"fb",&fb_fops))                                                    //注册设备文件，注册帧缓冲，fp_fops是操作函数集
        printk("unable to get major %d for fb devs\n", FB_MAJOR);

    fb_class = class_create(THIS_MODULE, "graphics");
    if (IS_ERR(fb_class)) {
        printk(KERN_WARNING "Unable to create fb class; errno = %ld\n", PTR_ERR(fb_class));
        fb_class = NULL;
    }
    return 0;
}

fb_ops:

static const struct file_operations fb_fops = {
    .owner =    THIS_MODULE,
    .read =        fb_read,                                        //写入
    .write =    fb_write,
    .unlocked_ioctl = fb_ioctl,
#ifdef CONFIG_COMPAT
    .compat_ioctl = fb_compat_ioctl,
#endif
    .mmap =        fb_mmap,
    .open =        fb_open,
    .release =    fb_release,
#ifdef HAVE_ARCH_FB_UNMAPPED_AREA
    .get_unmapped_area = get_fb_unmapped_area,
#endif
#ifdef CONFIG_FB_DEFERRED_IO
    .fsync =    fb_deferred_io_fsync,
#endif
};

fb_write:

static ssize_t
fb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
    unsigned long p = *ppos;
    struct inode *inode = file->f_path.dentry->d_inode;
    int fbidx = iminor(inode);
    struct fb_info *info = registered_fb[fbidx];
    u32 *buffer, *src;
    u32 __iomem *dst;
    int c, i, cnt = 0, err = 0;
    unsigned long total_size;

    if (!info || !info->screen_base)
        return -ENODEV;

    if (info->state != FBINFO_STATE_RUNNING)
        return -EPERM;

    if (info->fbops->fb_write)
        return info->fbops->fb_write(info, buf, count, ppos);

    total_size = info->screen_size;

    if (total_size == 0)
        total_size = info->fix.smem_len;

    if (p > total_size)
        return -EFBIG;

    if (count > total_size) {
        err = -EFBIG;
        count = total_size;
    }

    if (count + p > total_size) {

    .........各种info
}

info结构：

struct fb_info {
    int node;
    int flags;
    struct mutex lock;                                //控制io操作锁
    struct fb_var_screeninfo var;/*LCD可变参数*/
    struct fb_fix_screeninfo fix;/*LCD固定参数*/
    struct fb_monspecs monspecs; /*LCD显示器标准*/
    struct work_struct queue; /*帧缓冲事件队列*/
    struct fb_pixmap pixmap; /*图像硬件mapper*/
    struct fb_pixmap sprite; /*光标硬件mapper*/
    struct fb_cmap cmap; /*当前的颜色表*/
    struct fb_videomode *mode; /*当前的显示模式*/

#ifdef CONFIG_FB_BACKLIGHT
    struct backlight_device *bl_dev;/*对应的背光设备*/
    struct mutex bl_curve_mutex;
    u8 bl_curve[FB_BACKLIGHT_LEVELS];/*背光调整*/
#endif
#ifdef CONFIG_FB_DEFERRED_IO
    struct delayed_work deferred_work;
    struct fb_deferred_io *fbdefio;
#endif

    struct fb_ops *fbops; /*对底层硬件操作的函数指针*/
    struct device *device;
    struct device *dev; /*fb设备*/
    int class_flag;
#ifdef CONFIG_FB_TILEBLITTING
    struct fb_tile_ops *tileops; /*图块Blitting*/
#endif
    char __iomem *screen_base; /*虚拟基地址*/
    unsigned long screen_size; /*LCD IO映射的虚拟内存大小*/
    void *pseudo_palette; /*伪16色颜色表*/
#define FBINFO_STATE_RUNNING    0
#define FBINFO_STATE_SUSPENDED  1
    u32 state; /*LCD的挂起或恢复状态*/
    void *fbcon_par;
    void *par;
};

主要是fb_var_screeninfo、fb_fix_screeninfo、fb_ops三个结构体：
struct fb_var_screeninfo:主要记录用户可以修改的控制器的参数。

struct fb_var_screeninfo {
    __u32 xres;            /* visible resolution        */
    __u32 yres;
    __u32 xres_virtual;        /* virtual resolution        */
    __u32 yres_virtual;
    __u32 xoffset;            /* offset from virtual to visible */
    __u32 yoffset;            /* resolution            */

    __u32 bits_per_pixel;        /* guess what            */每个像素的位数即BPP
    __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 */
    __u32 width;            /* width of picture in mm */

    __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) */
    __u32 left_margin;        /* time from sync to picture    */
    __u32 right_margin;        /* time from picture to sync    */
    __u32 upper_margin;        /* time from sync to picture    */
    __u32 lower_margin;
    __u32 hsync_len;        /* length of horizontal sync    */
    __u32 vsync_len;        /* length of vertical sync    */
    __u32 sync;            /* see FB_SYNC_*        */
    __u32 vmode;            /* see FB_VMODE_*        */
    __u32 rotate;            /* angle we rotate counter clockwise */
    __u32 reserved[5];        /* Reserved for future compatibility */
};

fb_fix_screeninfo:主要记录用户不可以修改的控制器的参数

struct fb_fix_screeninfo {
    char id[16];            /* identification string eg "TT Builtin" */
    unsigned long smem_start;    /* Start of frame buffer mem */
                    /* (physical address) */
    __u32 smem_len;            /* Length of frame buffer mem */
    __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 */
    unsigned long mmio_start;    /* Start of Memory Mapped I/O */
                    /* (physical address) */
    __u32 mmio_len;            /* Length of Memory Mapped I/O */
    __u32 accel;            /* Indicate to driver which    */
                    /* specific chip/card we have    */
    __u16 reserved[3];        /* Reserved for future compatibility */
};

fb_ops:底层硬件操作的函数指针

struct fb_ops {
    /* open/release and usage marking */
    struct module *owner;
    int (*fb_open)(struct fb_info *info, int user);
    int (*fb_release)(struct fb_info *info, int user);

    /* For framebuffers with strange non linear layouts or that do not
     * work with normal memory mapped access
     */
    ssize_t (*fb_read)(struct fb_info *info, char __user *buf,
               size_t count, loff_t *ppos);
    ssize_t (*fb_write)(struct fb_info *info, const char __user *buf,
                size_t count, loff_t *ppos);

    /* checks var and eventually tweaks it to something supported,
     * DO NOT MODIFY PAR */
    int (*fb_check_var)(struct fb_var_screeninfo *var, struct fb_info *info);

    /* set the video mode according to info->var */
    int (*fb_set_par)(struct fb_info *info);

    /* set color register */
    int (*fb_setcolreg)(unsigned regno, unsigned red, unsigned green,
                unsigned blue, unsigned transp, struct fb_info *info);

    /* set color registers in batch */
    int (*fb_setcmap)(struct fb_cmap *cmap, struct fb_info *info);

    /* blank display */
    int (*fb_blank)(int blank, struct fb_info *info);

    /* pan display */
    int (*fb_pan_display)(struct fb_var_screeninfo *var, struct fb_info *info);

    /* Draws a rectangle */
    void (*fb_fillrect) (struct fb_info *info, const struct fb_fillrect *rect);
    /* Copy data from area to another */
    void (*fb_copyarea) (struct fb_info *info, const struct fb_copyarea *region);
    /* Draws a image to the display */
    void (*fb_imageblit) (struct fb_info *info, const struct fb_image *image);

    /* Draws cursor */
    int (*fb_cursor) (struct fb_info *info, struct fb_cursor *cursor);

    /* Rotates the display */
    void (*fb_rotate)(struct fb_info *info, int angle);

    /* wait for blit idle, optional */
    int (*fb_sync)(struct fb_info *info);

    /* perform fb specific ioctl (optional) */
    int (*fb_ioctl)(struct fb_info *info, unsigned int cmd,
            unsigned long arg);

    /* Handle 32bit compat ioctl (optional) */
    int (*fb_compat_ioctl)(struct fb_info *info, unsigned cmd,
            unsigned long arg);

    /* perform fb specific mmap */
    int (*fb_mmap)(struct fb_info *info, struct vm_area_struct *vma);

    /* save current hardware state */
    void (*fb_save_state)(struct fb_info *info);

    /* restore saved state */
    void (*fb_restore_state)(struct fb_info *info);

    /* get capability given var */
    void (*fb_get_caps)(struct fb_info *info, struct fb_blit_caps *caps,
                struct fb_var_screeninfo *var);
};

http://www.cnblogs.com/lishixian/articles/2999923.html

二、LCD驱动程序分析
s3c2410fb_init:

int __init s3c2410fb_init(void)
{
    int ret = platform_driver_register(&s3c2410fb_driver);                        //注册平台驱动设备

    if (ret == 0)
        ret = platform_driver_register(&s3c2412fb_driver);;

    return ret;
}

s3c2410fb_driver:

static struct platform_driver s3c2410fb_driver = {
    .probe        = s3c2410fb_probe,                                                //probe函数，里面调用了s3c24xxfb_probe
    .remove        = s3c2410fb_remove,
    .suspend    = s3c2410fb_suspend,
    .resume        = s3c2410fb_resume,
    .driver        = {
        .name    = "s3c2410-lcd",
        .owner    = THIS_MODULE,
    },
};

s3c24xxfb_probe:

static int __init s3c24xxfb_probe(struct platform_device *pdev,
                  enum s3c_drv_type drv_type)
{
    struct s3c2410fb_info *info;
    struct s3c2410fb_display *display;
    struct fb_info *fbinfo;
    struct s3c2410fb_mach_info *mach_info;
    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;

    irq = platform_get_irq(pdev, 0);                                                       //获取中断号
    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fb_info结构
    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);                                   //获取寄存器地址
    if (res == NULL) {
        dev_err(&pdev->dev, "failed to get memory registers\n");
        ret = -ENXIO;
        goto dealloc_fb;
    }

    size = (res->end - res->start) + 1;
    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);                                                 //转化成虚拟地址
    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 */                                                                   //初始化fbinfo结构
    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;
    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);                      //注册中断函数
    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 (!info->clk || IS_ERR(info->clk)) {
        printk(KERN_ERR "failed to get lcd clock source\n");
        ret = -ENOENT;
        goto release_irq;
    }

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

    msleep(1);

    /* 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;
    }

    /* Initialize video memory */
    ret = s3c2410fb_map_video_memory(fbinfo);                                                   //为帧缓冲分配内存空间。同时使用了dma
    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;

    s3c2410fb_init_registers(fbinfo);                                                           //GPIO初始化

    s3c2410fb_check_var(&fbinfo->var, fbinfo);                                                  //设置fb_var_screeninfo

    ret = register_framebuffer(fbinfo);                                                         //注册帧缓冲-register_framebuffer
    if (ret < 0) {
        printk(KERN_ERR "Failed to register framebuffer device: %d\n",
            ret);
        goto free_video_memory;
    }

    /* 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_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_resource(info->mem);
    kfree(info->mem);
dealloc_fb:
    platform_set_drvdata(pdev, NULL);
    framebuffer_release(fbinfo);
    return ret;
}

s3c2410fb_map_vedio_memory:

static int __init 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);

    info->screen_base = dma_alloc_writecombine(fbi->dev, map_size,
                         &map_dma, GFP_KERNEL);                                                      //为帧缓冲分配内存空间。同时使用了dma

    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;
}

分析到这里发现并没有设置帧缓冲的地址：
于是可以通过搜索帧地址来辨别，在哪个函数中实现。
s3c2410fb_set_lcdaddr:

static void s3c2410fb_set_lcdaddr(struct fb_info *info)
{
    unsigned long saddr1, saddr2, saddr3;
    struct s3c2410fb_info *fbi = info->par;
    void __iomem *regs = fbi->io;

    saddr1 = info->fix.smem_start >> 1;
    saddr2 = info->fix.smem_start;
    saddr2 += info->fix.line_length * info->var.yres;
    saddr2 >>= 1;

    saddr3 = S3C2410_OFFSIZE(0) |
         S3C2410_PAGEWIDTH((info->fix.line_length / 2) & 0x3ff);

    dprintk("LCDSADDR1 = 0x%08lx\n", saddr1);
    dprintk("LCDSADDR2 = 0x%08lx\n", saddr2);
    dprintk("LCDSADDR3 = 0x%08lx\n", saddr3);

    writel(saddr1, regs + S3C2410_LCDSADDR1);                                  //这里设置了帧缓冲的地址
    writel(saddr2, regs + S3C2410_LCDSADDR2);
    writel(saddr3, regs + S3C2410_LCDSADDR3);
}

但是如何知道调用顺序呢，可以在函数中调用dump_stack()：

Backtrace:
[<c0049048>] (dump_backtrace+0x0/0x10c) from [<c0373fac>] (dump_stack+0x18/0x1c)
 r7:232f3302 r6:5bd42233 r5:00000000 r4:3a352944
[<c0373f94>] (dump_stack+0x0/0x1c) from [<c01718c8>] (s3c2410fb_set_par+0x150/0x78c)
[<c0171778>] (s3c2410fb_set_par+0x0/0x78c) from [<c016a578>] (fbcon_init+0x42c/0x4b8)
[<c016a14c>] (fbcon_init+0x0/0x4b8) from [<c0185800>] (visual_init+0xb8/0x100)
[<c0185748>] (visual_init+0x0/0x100) from [<c018a65c>] (take_over_console+0x1f4/0x3d8)
 r7:00000000 r6:c03a6c90 r5:c05a75a0 r4:00000019
[<c018a468>] (take_over_console+0x0/0x3d8) from [<c0167050>] (fbcon_takeover+0x7c/0xd4)
[<c0166fd4>] (fbcon_takeover+0x0/0xd4) from [<c016b1b0>] (fbcon_event_notify+0x768/0x7b0)
 r5:ffffffff r4:00000000
[<c016aa48>] (fbcon_event_notify+0x0/0x7b0) from [<c0070784>] (notifier_call_chain+0x54/0x94)
[<c0070730>] (notifier_call_chain+0x0/0x94) from [<c0070d08>] (__blocking_notifier_call_chain+0x54/0x6c)
 r9:c04b5008 r8:00000005 r7:ffffffff r6:c381dd98 r5:c04c5470
r4:c04c547c
[<c0070cb4>] (__blocking_notifier_call_chain+0x0/0x6c) from [<c0070d40>] (blocking_notifier_call_chain+0x20/0x28)
 r8:c3842a04 r7:00000000 r6:c0513120 r5:c3842800 r4:c381dd60
[<c0070d20>] (blocking_notifier_call_chain+0x0/0x28) from [<c015fc48>] (fb_notifier_call_chain+0x1c/0x24)
[<c015fc2c>] (fb_notifier_call_chain+0x0/0x24) from [<c0160cf0>] (register_framebuffer+0x154/0x1fc)
[<c0160b9c>] (register_framebuffer+0x0/0x1fc) from [<c0014bbc>] (s3c24xxfb_probe+0x4c4/0x6fc)
[<c00146f8>] (s3c24xxfb_probe+0x0/0x6fc) from [<c0014e20>] (s3c2410fb_probe+0x14/0x18)
[<c0014e0c>] (s3c2410fb_probe+0x0/0x18) from [<c019369c>] (platform_drv_probe+0x20/0x24)
[<c019367c>] (platform_drv_probe+0x0/0x24) from [<c0192694>] (driver_probe_device+0x8c/0x1a0)
[<c0192608>] (driver_probe_device+0x0/0x1a0) from [<c019283c>] (__driver_attach+0x94/0x98)
[<c01927a8>] (__driver_attach+0x0/0x98) from [<c0191f38>] (bus_for_each_dev+0x6c/0x98)
 r7:c01927a8 r6:c04c56b8 r5:c381de98 r4:00000000
[<c0191ecc>] (bus_for_each_dev+0x0/0x98) from [<c0192514>] (driver_attach+0x20/0x28)
 r7:c04c56b8 r6:00000000 r5:c04c56b8 r4:c001fc68
[<c01924f4>] (driver_attach+0x0/0x28) from [<c0191764>] (bus_add_driver+0xa4/0x244)
[<c01916c0>] (bus_add_driver+0x0/0x244) from [<c0192b00>] (driver_register+0x74/0x15c)
[<c0192a8c>] (driver_register+0x0/0x15c) from [<c0193a80>] (platform_driver_register+0x6c/0x88)
 r7:c381c000 r6:00000000 r5:c001fa50 r4:c001fc68
[<c0193a14>] (platform_driver_register+0x0/0x88) from [<c0014e38>] (s3c2410fb_init+0x14/0x30)
[<c0014e24>] (s3c2410fb_init+0x0/0x30) from [<c0044284>] (do_one_initcall+0x3c/0x1bc)
[<c0044248>] (do_one_initcall+0x0/0x1bc) from [<c0008438>] (kernel_init+0x88/0xf4)
[<c00083b0>] (kernel_init+0x0/0xf4) from [<c005a2e8>] (do_exit+0x0/0x620)