作者：刘昊昱
博客：http://blog.csdn.net/liuhaoyutz
内核版本：2.6.36
源码路径：drivers/video/s3c2410fb.c
本文分析S3C2410的LCD驱动,该驱动程序基于Framebuffer机制。
一、相关数据结构
首先，我们来介绍一下基于Framebuffer的S3C2410 LCD驱动涉及的几个重要数据结构：
Framebuffer的核心数据结构是fb_info，该结构体定义在include/linux/fb.h文件中：
832struct fb_info { 833 int node; 834 int flags; 835 struct mutex lock; /* Lock for open/release/ioctl funcs */ 836 struct mutex mm_lock; /* Lock for fb_mmap and smem_* fields */ 837 struct fb_var_screeninfo var; /* Current var */ 838 struct fb_fix_screeninfo fix; /* Current fix */ 839 struct fb_monspecs monspecs; /* Current Monitor specs */ 840 struct work_struct queue; /* Framebuffer event queue */ 841 struct fb_pixmap pixmap; /* Image hardware mapper */ 842 struct fb_pixmap sprite; /* Cursor hardware mapper */ 843 struct fb_cmap cmap; /* Current cmap */ 844 struct list_head modelist; /* mode list */ 845 struct fb_videomode *mode; /* current mode */ 846 847#ifdef CONFIG_FB_BACKLIGHT 848 /* assigned backlight device */ 849 /* set before framebuffer registration, 850 remove after unregister */ 851 struct backlight_device *bl_dev; 852 853 /* Backlight level curve */ 854 struct mutex bl_curve_mutex; 855 u8 bl_curve[FB_BACKLIGHT_LEVELS]; 856#endif 857#ifdef CONFIG_FB_DEFERRED_IO 858 struct delayed_work deferred_work; 859 struct fb_deferred_io *fbdefio; 860#endif 861 862 struct fb_ops *fbops; 863 struct device *device; /* This is the parent */ 864 struct device *dev; /* This is this fb device */ 865 int class_flag; /* private sysfs flags */ 866#ifdef CONFIG_FB_TILEBLITTING 867 struct fb_tile_ops *tileops; /* Tile Blitting */ 868#endif 869 char __iomem *screen_base; /* Virtual address */ 870 unsigned long screen_size; /* Amount of ioremapped VRAM or 0 */ 871 void *pseudo_palette; /* Fake palette of 16 colors */ 872#define FBINFO_STATE_RUNNING 0 873#define FBINFO_STATE_SUSPENDED 1 874 u32 state; /* Hardware state i.e suspend */ 875 void *fbcon_par; /* fbcon use-only private area */ 876 /* From here on everything is device dependent */ 877 void *par; 878 /* we need the PCI or similiar aperture base/size not 879 smem_start/size as smem_start may just be an object 880 allocated inside the aperture so may not actually overlap */ 881 struct apertures_struct { 882 unsigned int count; 883 struct aperture { 884 resource_size_t base; 885 resource_size_t size; 886 } ranges[0]; 887 } *apertures; 888};
fb_info结构体中，最重要的三个成员是var，fix，fbops，分别代表LCD可变参数，固定参数和对底层硬件的操作函数集。
837行，fb_var_screeninfo结构体变量var代表LCD的可变参数。该结构体定义如下：
238struct fb_var_screeninfo { 239 __u32 xres; /* visible resolution */ 240 __u32 yres; 241 __u32 xres_virtual; /* virtual resolution */ 242 __u32 yres_virtual; 243 __u32 xoffset; /* offset from virtual to visible */ 244 __u32 yoffset; /* resolution */ 245 246 __u32 bits_per_pixel; /* guess what */ 247 __u32 grayscale; /* != 0 Graylevels instead of colors */ 248 249 struct fb_bitfield red; /* bitfield in fb mem if true color, */ 250 struct fb_bitfield green; /* else only length is significant */ 251 struct fb_bitfield blue; 252 struct fb_bitfield transp; /* transparency */ 253 254 __u32 nonstd; /* != 0 Non standard pixel format */ 255 256 __u32 activate; /* see FB_ACTIVATE_* */ 257 258 __u32 height; /* height of picture in mm */ 259 __u32 width; /* width of picture in mm */ 260 261 __u32 accel_flags; /* (OBSOLETE) see fb_info.flags */ 262 263 /* Timing: All values in pixclocks, except pixclock (of course) */ 264 __u32 pixclock; /* pixel clock in ps (pico seconds) */ 265 __u32 left_margin; /* time from sync to picture */ 266 __u32 right_margin; /* time from picture to sync */ 267 __u32 upper_margin; /* time from sync to picture */ 268 __u32 lower_margin; 269 __u32 hsync_len; /* length of horizontal sync */ 270 __u32 vsync_len; /* length of vertical sync */ 271 __u32 sync; /* see FB_SYNC_* */ 272 __u32 vmode; /* see FB_VMODE_* */ 273 __u32 rotate; /* angle we rotate counter clockwise */ 274 __u32 reserved[5]; /* Reserved for future compatibility */ 275};
838行，fb_fix_screeninfo结构体变量fix代表LCD的固定参数，该结构体定义如下：
155struct fb_fix_screeninfo { 156 char id[16]; /* identification string eg "TT Builtin" */ 157 unsigned long smem_start; /* Start of frame buffer mem */ 158 /* (physical address) */ 159 __u32 smem_len; /* Length of frame buffer mem */ 160 __u32 type; /* see FB_TYPE_* */ 161 __u32 type_aux; /* Interleave for interleaved Planes */ 162 __u32 visual; /* see FB_VISUAL_* */ 163 __u16 xpanstep; /* zero if no hardware panning */ 164 __u16 ypanstep; /* zero if no hardware panning */ 165 __u16 ywrapstep; /* zero if no hardware ywrap */ 166 __u32 line_length; /* length of a line in bytes */ 167 unsigned long mmio_start; /* Start of Memory Mapped I/O */ 168 /* (physical address) */ 169 __u32 mmio_len; /* Length of Memory Mapped I/O */ 170 __u32 accel; /* Indicate to driver which */ 171 /* specific chip/card we have */ 172 __u16 reserved[3]; /* Reserved for future compatibility */ 173};
862行，fb_ops结构体变量fbops代表对底层硬件操作的函数集，该结构体定义如下：
621struct fb_ops { 622 /* open/release and usage marking */ 623 struct module *owner; 624 int (*fb_open)(struct fb_info *info, int user); 625 int (*fb_release)(struct fb_info *info, int user); 626 627 /* For framebuffers with strange non linear layouts or that do not 628 * work with normal memory mapped access 629 */ 630 ssize_t (*fb_read)(struct fb_info *info, char __user *buf, 631 size_t count, loff_t *ppos); 632 ssize_t (*fb_write)(struct fb_info *info, const char __user *buf, 633 size_t count, loff_t *ppos); 634 635 /* checks var and eventually tweaks it to something supported, 636 * DO NOT MODIFY PAR */ 637 int (*fb_check_var)(struct fb_var_screeninfo *var, struct fb_info *info); 638 639 /* set the video mode according to info->var */ 640 int (*fb_set_par)(struct fb_info *info); 641 642 /* set color register */ 643 int (*fb_setcolreg)(unsigned regno, unsigned red, unsigned green, 644 unsigned blue, unsigned transp, struct fb_info *info); 645 646 /* set color registers in batch */ 647 int (*fb_setcmap)(struct fb_cmap *cmap, struct fb_info *info); 648 649 /* blank display */ 650 int (*fb_blank)(int blank, struct fb_info *info); 651 652 /* pan display */ 653 int (*fb_pan_display)(struct fb_var_screeninfo *var, struct fb_info *info); 654 655 /* Draws a rectangle */ 656 void (*fb_fillrect) (struct fb_info *info, const struct fb_fillrect *rect); 657 /* Copy data from area to another */ 658 void (*fb_copyarea) (struct fb_info *info, const struct fb_copyarea *region); 659 /* Draws a image to the display */ 660 void (*fb_imageblit) (struct fb_info *info, const struct fb_image *image); 661 662 /* Draws cursor */ 663 int (*fb_cursor) (struct fb_info *info, struct fb_cursor *cursor); 664 665 /* Rotates the display */ 666 void (*fb_rotate)(struct fb_info *info, int angle); 667 668 /* wait for blit idle, optional */ 669 int (*fb_sync)(struct fb_info *info); 670 671 /* perform fb specific ioctl (optional) */ 672 int (*fb_ioctl)(struct fb_info *info, unsigned int cmd, 673 unsigned long arg); 674 675 /* Handle 32bit compat ioctl (optional) */ 676 int (*fb_compat_ioctl)(struct fb_info *info, unsigned cmd, 677 unsigned long arg); 678 679 /* perform fb specific mmap */ 680 int (*fb_mmap)(struct fb_info *info, struct vm_area_struct *vma); 681 682 /* get capability given var */ 683 void (*fb_get_caps)(struct fb_info *info, struct fb_blit_caps *caps, 684 struct fb_var_screeninfo *var); 685 686 /* teardown any resources to do with this framebuffer */ 687 void (*fb_destroy)(struct fb_info *info); 688 689 /* called at KDB enter and leave time to prepare the console */ 690 int (*fb_debug_enter)(struct fb_info *info); 691 int (*fb_debug_leave)(struct fb_info *info); 692};
S3C2410驱动还定义了几个专用结构体：
在drivers/video/s3c2410fb.h文件中定义了s3c2410fb_info结构体：
21struct s3c2410fb_info { 22 struct device *dev; 23 struct clk *clk; 24 25 struct resource *mem; 26 void __iomem *io; 27 void __iomem *irq_base; 28 29 enum s3c_drv_type drv_type; 30 struct s3c2410fb_hw regs; 31 32 unsigned long clk_rate; 33 unsigned int palette_ready; 34 35#ifdef CONFIG_CPU_FREQ 36 struct notifier_block freq_transition; 37#endif 38 39 /* keep these registers in case we need to re-write palette */ 40 u32 palette_buffer[256]; 41 u32 pseudo_pal[16]; 42};
在arch/arm/mach-s3c2410/include/mach/fb.h文件中定义了s3c2410fb_display和s3c2410fb_mach_info结构体：
25/* LCD description */ 26struct s3c2410fb_display { 27 /* LCD type */ 28 unsigned type; 29 30 /* Screen size */ 31 unsigned short width; 32 unsigned short height; 33 34 /* Screen info */ 35 unsigned short xres; 36 unsigned short yres; 37 unsigned short bpp; 38 39 unsigned pixclock; /* pixclock in picoseconds */ 40 unsigned short left_margin; /* value in pixels (TFT) or HCLKs (STN) */ 41 unsigned short right_margin; /* value in pixels (TFT) or HCLKs (STN) */ 42 unsigned short hsync_len; /* value in pixels (TFT) or HCLKs (STN) */ 43 unsigned short upper_margin; /* value in lines (TFT) or 0 (STN) */ 44 unsigned short lower_margin; /* value in lines (TFT) or 0 (STN) */ 45 unsigned short vsync_len; /* value in lines (TFT) or 0 (STN) */ 46 47 /* lcd configuration registers */ 48 unsigned long lcdcon5; 49}; 50 51struct s3c2410fb_mach_info { 52 53 struct s3c2410fb_display *displays; /* attached diplays info */ 54 unsigned num_displays; /* number of defined displays */ 55 unsigned default_display; 56 57 /* GPIOs */ 58 59 unsigned long gpcup; 60 unsigned long gpcup_mask; 61 unsigned long gpccon; 62 unsigned long gpccon_mask; 63 unsigned long gpdup; 64 unsigned long gpdup_mask; 65 unsigned long gpdcon; 66 unsigned long gpdcon_mask; 67 68 /* lpc3600 control register */ 69 unsigned long lpcsel; 70};
二、platform_driver probe函数分析
下面我们来看模块初始化函数s3c2410fb_init：
1119int __init s3c2410fb_init(void) 1120{ 1121 int ret = platform_driver_register(&s3c2410fb_driver); 1122 1123 if (ret == 0) 1124 ret = platform_driver_register(&s3c2412fb_driver); 1125 1126 return ret; 1127}
我们只关注S3C2410，1121行，注册platform_drivers 3c2410fb_driver，定义如下：
1097static struct platform_driver s3c2410fb_driver = { 1098 .probe = s3c2410fb_probe, 1099 .remove = __devexit_p(s3c2410fb_remove), 1100 .suspend = s3c2410fb_suspend, 1101 .resume = s3c2410fb_resume, 1102 .driver = { 1103 .name = "s3c2410-lcd", 1104 .owner = THIS_MODULE, 1105 }, 1106};
当模块被装载时，会调用s3c2410fb_probe函数，该函数定义如下：
1007static int __devinit s3c2410fb_probe(struct platform_device *pdev) 1008{ 1009 return s3c24xxfb_probe(pdev, DRV_S3C2410); 1010}
实际上s3c2410fb_probe直接调用了s3c24xxfb_probe，并传递参数DVR_S3C2410，表明是S3C2410平台。下面看s3c24xxfb_probe函数：
817static int __devinit s3c24xxfb_probe(struct platform_device *pdev, 818 enum s3c_drv_type drv_type) 819{ 820 struct s3c2410fb_info *info; 821 struct s3c2410fb_display *display; 822 struct fb_info *fbinfo; 823 struct s3c2410fb_mach_info *mach_info; 824 struct resource *res; 825 int ret; 826 int irq; 827 int i; 828 int size; 829 u32 lcdcon1; 830 831 mach_info = pdev->dev.platform_data; 832 if (mach_info == NULL) { 833 dev_err(&pdev->dev, 834 "no platform data for lcd, cannot attach\n"); 835 return -EINVAL; 836 } 837 838 if (mach_info->default_display >= mach_info->num_displays) { 839 dev_err(&pdev->dev, "default is %d but only %d displays\n", 840 mach_info->default_display, mach_info->num_displays); 841 return -EINVAL; 842 } 843 844 display = mach_info->displays + mach_info->default_display; 845 846 irq = platform_get_irq(pdev, 0); 847 if (irq < 0) { 848 dev_err(&pdev->dev, "no irq for device\n"); 849 return -ENOENT; 850 } 851 852 fbinfo = framebuffer_alloc(sizeof(struct s3c2410fb_info), &pdev->dev); 853 if (!fbinfo) 854 return -ENOMEM; 855 856 platform_set_drvdata(pdev, fbinfo); 857 858 info = fbinfo->par; 859 info->dev = &pdev->dev; 860 info->drv_type = drv_type; 861 862 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 863 if (res == NULL) { 864 dev_err(&pdev->dev, "failed to get memory registers\n"); 865 ret = -ENXIO; 866 goto dealloc_fb; 867 } 868 869 size = (res->end - res->start) + 1; 870 info->mem = request_mem_region(res->start, size, pdev->name); 871 if (info->mem == NULL) { 872 dev_err(&pdev->dev, "failed to get memory region\n"); 873 ret = -ENOENT; 874 goto dealloc_fb; 875 } 876 877 info->io = ioremap(res->start, size); 878 if (info->io == NULL) { 879 dev_err(&pdev->dev, "ioremap() of registers failed\n"); 880 ret = -ENXIO; 881 goto release_mem; 882 } 883 884 info->irq_base = info->io + ((drv_type == DRV_S3C2412) ? S3C2412_LCDINTBASE : S3C2410_LCDINTBASE); 885 886 dprintk("devinit\n"); 887 888 strcpy(fbinfo->fix.id, driver_name); 889 890 /* Stop the video */ 891 lcdcon1 = readl(info->io + S3C2410_LCDCON1); 892 writel(lcdcon1 & ~S3C2410_LCDCON1_ENVID, info->io + S3C2410_LCDCON1); 893 894 fbinfo->fix.type = FB_TYPE_PACKED_PIXELS; 895 fbinfo->fix.type_aux = 0; 896 fbinfo->fix.xpanstep = 0; 897 fbinfo->fix.ypanstep = 0; 898 fbinfo->fix.ywrapstep = 0; 899 fbinfo->fix.accel = FB_ACCEL_NONE; 900 901 fbinfo->var.nonstd = 0; 902 fbinfo->var.activate = FB_ACTIVATE_NOW; 903 fbinfo->var.accel_flags = 0; 904 fbinfo->var.vmode = FB_VMODE_NONINTERLACED; 905 906 fbinfo->fbops = &s3c2410fb_ops; 907 fbinfo->flags = FBINFO_FLAG_DEFAULT; 908 fbinfo->pseudo_palette = &info->pseudo_pal; 909 910 for (i = 0; i < 256; i++) 911 info->palette_buffer[i] = PALETTE_BUFF_CLEAR; 912 913 ret = request_irq(irq, s3c2410fb_irq, IRQF_DISABLED, pdev->name, info); 914 if (ret) { 915 dev_err(&pdev->dev, "cannot get irq %d - err %d\n", irq, ret); 916 ret = -EBUSY; 917 goto release_regs; 918 } 919 920 info->clk = clk_get(NULL, "lcd"); 921 if (!info->clk || IS_ERR(info->clk)) { 922 printk(KERN_ERR "failed to get lcd clock source\n"); 923 ret = -ENOENT; 924 goto release_irq; 925 } 926 927 clk_enable(info->clk); 928 dprintk("got and enabled clock\n"); 929 930 msleep(1); 931 932 info->clk_rate = clk_get_rate(info->clk); 933 934 /* find maximum required memory size for display */ 935 for (i = 0; i < mach_info->num_displays; i++) { 936 unsigned long smem_len = mach_info->displays[i].xres; 937 938 smem_len *= mach_info->displays[i].yres; 939 smem_len *= mach_info->displays[i].bpp; 940 smem_len >>= 3; 941 if (fbinfo->fix.smem_len < smem_len) 942 fbinfo->fix.smem_len = smem_len; 943 } 944 945 /* Initialize video memory */ 946 ret = s3c2410fb_map_video_memory(fbinfo); 947 if (ret) { 948 printk(KERN_ERR "Failed to allocate video RAM: %d\n", ret); 949 ret = -ENOMEM; 950 goto release_clock; 951 } 952 953 dprintk("got video memory\n"); 954 955 fbinfo->var.xres = display->xres; 956 fbinfo->var.yres = display->yres; 957 fbinfo->var.bits_per_pixel = display->bpp; 958 959 s3c2410fb_init_registers(fbinfo); 960 961 s3c2410fb_check_var(&fbinfo->var, fbinfo); 962 963 ret = s3c2410fb_cpufreq_register(info); 964 if (ret < 0) { 965 dev_err(&pdev->dev, "Failed to register cpufreq\n"); 966 goto free_video_memory; 967 } 968 969 ret = register_framebuffer(fbinfo); 970 if (ret < 0) { 971 printk(KERN_ERR "Failed to register framebuffer device: %d\n", 972 ret); 973 goto free_cpufreq; 974 } 975 976 /* create device files */ 977 ret = device_create_file(&pdev->dev, &dev_attr_debug); 978 if (ret) { 979 printk(KERN_ERR "failed to add debug attribute\n"); 980 } 981 982 printk(KERN_INFO "fb%d: %s frame buffer device\n", 983 fbinfo->node, fbinfo->fix.id); 984 985 return 0; 986 987 free_cpufreq: 988 s3c2410fb_cpufreq_deregister(info); 989free_video_memory: 990 s3c2410fb_unmap_video_memory(fbinfo); 991release_clock: 992 clk_disable(info->clk); 993 clk_put(info->clk); 994release_irq: 995 free_irq(irq, info); 996release_regs: 997 iounmap(info->io); 998release_mem: 999 release_resource(info->mem); 1000 kfree(info->mem); 1001dealloc_fb: 1002 platform_set_drvdata(pdev, NULL); 1003 framebuffer_release(fbinfo); 1004 return ret; 1005}
820行，定义了s3c2410fb_info结构体指针变量info。
821行，定义了s3c2410fb_display结构体指针变量display。
822行，定义了fb_info结构体指针变量fbinfo。
823行，定义了s3c2410fb_mach_info结构体指针变量mach_info。
831行，由platform数据取得mach_info。
844行，由match_info得到display。
846行，取得中断号。
852行，调用framebuffer_alloc创建fb_info结构体变量fbinfo。fb_info结构体体是LCD驱动的核心数据结构。注意传递给framebuffer_alloc函数的第一个参数是sizeof(struct s3c2410fb_info)，即s3c2410fb_info结构体的大小，通过分析framebuffer_alloc函数的源码，可知，该函数除了为fb_info分配的内存空间，还多分配了第二个参数指定大小的空间，并将fb_info.par指定多分配出来的这个空间。
856行，将fbinfo保存在驱动私有数据中，以方便以后使用。
858行，将fbinfo->par指向的s3c2410fb_info结构体空间赋值给info变量。
862行，取得LCD控制器的I/O内存资源信息。
870行，调用request_mem_region取得I/O内存,这个I/O内存对应LCD控制器的寄存器集,而不是Framebuffer。
877行，通过ioremap 函数得到I/O内存的虚拟地址空间，起始地址保存在fbinfo->io中。
884行，取得LCD Interrupt Pending Register寄存器的地址保存在info->irq_base中。
891 - 892行，通过将LCDCON1寄存器的第0位设置为0，禁用LCD。
894 - 908行，初始化fbinfo。其中，特别需要注意的是906行，设置fbinfo->fbops为3c2410fb_ops
910 - 911行，将info->palette_buffer清0，info->palette_buffer对应S3C2410内部的256*16的调色板内存。
913行，申请中断，设置中断处理函数为s3c2410fb_irq。
920行，取得LCD时钟。
927行，使能LCD时钟。
932行，取得LCD时钟频率。
935 - 943行，计算需要的最大显存大小。
946行，调用s3c2410fb_map_video_memory函数申请以DMA方式访问的帧缓冲区(Framebuffer)空间。这个函数我们在后面再仔细分析。
959行，调用s3c2410fb_init_registers函数初始化LCD控制器的各个寄存器，这个函数我们在后面再仔细分析。
961行，调用s3c2410fb_check_var函数检查相关变量是否符合要求。这是framebuffer驱动要求必须进行的一个检查。这个函数我们在后面再仔细分析。
963行,s3c2410fb_cpufreq_register这个函数实现变频功能，涉及Linux cupfreq(变频)机制。根据宏CONFIG_CPU_FREQ是否被定义，可以直接返回0，也可以具体实现变频功能。
969行，调用register_framebuffer注册fb_info结构。
977行，调用device_create_file创建/sys系统文件。
s3c2410fb_map_video_memory函数定义如下：
626/* 627 * s3c2410fb_map_video_memory(): 628 * Allocates the DRAM memory for the frame buffer. This buffer is 629 * remapped into a non-cached, non-buffered, memory region to 630 * allow palette and pixel writes to occur without flushing the 631 * cache. Once this area is remapped, all virtual memory 632 * access to the video memory should occur at the new region. 633 */ 634837837static int __devinit s3c2410fb_map_video_memory(struct fb_info *info) 635{ 636 struct s3c2410fb_info *fbi = info->par; 637 dma_addr_t map_dma; 638 unsigned map_size = PAGE_ALIGN(info->fix.smem_len); 639 640 dprintk("map_video_memory(fbi=%p) map_size %u\n", fbi, map_size); 641 642 info->screen_base = dma_alloc_writecombine(fbi->dev, map_size, 643 &map_dma, GFP_KERNEL); 644 645 if (info->screen_base) { 646 /* prevent initial garbage on screen */ 647 dprintk("map_video_memory: clear %p:%08x\n", 648 info->screen_base, map_size); 649 memset(info->screen_base, 0x00, map_size); 650 651 info->fix.smem_start = map_dma; 652 653 dprintk("map_video_memory: dma=%08lx cpu=%p size=%08x\n", 654 info->fix.smem_start, info->screen_base, map_size); 655 } 656 657 return info->screen_base ? 0 : -ENOMEM; 658}
s3c2410fb_map_video_memory函数的作用是申请以DMA方式访问的帧缓冲区(Framebuffer)地址空间。
638行，从fb_info.fb_fix_screeninfo.smem_len的注释＂Length of frame buffer mem＂可以看出,这里是取得以页对齐的帧缓冲区的大小保存在map_size变量中。
642行，从fb_info->screen_base的注释＂Virtual address＂可以看出，这里是通过调用dma_alloc_writecombine函数，分配以DMA方式访问的帧缓冲区空间(Framebuffer)，并将帧缓冲区的虚拟地址起始值返回保存在fb_info->screen_base中。
649行，将帧缓冲区清0。
651行，从fb_info.fb_fix_screeninfo.smem_start的注释＂Start of frame buffer mem (physical address)＂可以看出，这里是把帧缓冲区的物理地址起始地址map_dma赋值给info->fix.smem_start。
下面看s3c2410fb_init_registers函数，该函数用于初始化LCD控制器：
677/* 678 * s3c2410fb_init_registers - Initialise all LCD-related registers 679 */ 680static int s3c2410fb_init_registers(struct fb_info *info) 681{ 682 struct s3c2410fb_info *fbi = info->par; 683 struct s3c2410fb_mach_info *mach_info = fbi->dev->platform_data; 684 unsigned long flags; 685 void __iomem *regs = fbi->io; 686 void __iomem *tpal; 687 void __iomem *lpcsel; 688 689 if (is_s3c2412(fbi)) { 690 tpal = regs + S3C2412_TPAL; 691 lpcsel = regs + S3C2412_TCONSEL; 692 } else { 693 tpal = regs + S3C2410_TPAL; 694 lpcsel = regs + S3C2410_LPCSEL; 695 } 696 697 /* Initialise LCD with values from haret */ 698 699 local_irq_save(flags); 700 701 /* modify the gpio(s) with interrupts set (bjd) */ 702 703 modify_gpio(S3C2410_GPCUP, mach_info->gpcup, mach_info->gpcup_mask); 704 modify_gpio(S3C2410_GPCCON, mach_info->gpccon, mach_info->gpccon_mask); 705 modify_gpio(S3C2410_GPDUP, mach_info->gpdup, mach_info->gpdup_mask); 706 modify_gpio(S3C2410_GPDCON, mach_info->gpdcon, mach_info->gpdcon_mask); 707 708 local_irq_restore(flags); 709 710 dprintk("LPCSEL = 0x%08lx\n", mach_info->lpcsel); 711 writel(mach_info->lpcsel, lpcsel); 712 713 dprintk("replacing TPAL %08x\n", readl(tpal)); 714 715 /* ensure temporary palette disabled */ 716 writel(0x00, tpal); 717 718 return 0; 719}
685行，取得LCD控制器寄存器虚拟地址的起始地址，保存在regs变量中。
693行，取得临时调色板寄存器(Temp Palette Register)的虚拟地址保存在tpal变量中。
694行，取得LPCSEL寄存器的地址，该寄存器用于控制中是否启动LPC3600模式。LPC3600是专用于三星LTS350Q1-PD1/2液晶屏的控制器。
699行，修改寄存器的值之前，先调用local_irq_save屏蔽中断，并将中断状态保存到flags变量中。
703 - 706行，调用modify_gpio函数设置GPC和GPD寄存器为LCD模式。
modify_gpio函数用于设置GPIO寄存器，注意第三个参数mask的作用是把要设置的位先清0。
668static inline void modify_gpio(void __iomem *reg, 669 unsigned long set, unsigned long mask) 670{ 671 unsigned long tmp; 672 673 tmp = readl(reg) & ~mask; 674 writel(tmp | set, reg); 675}
708行，调用local_irq_restore恢复被屏蔽的中断。
711行，设置LPCSEL寄存器。
716行，清0并禁用临时调色板寄存器。
下面我们来看s3c2410fb_check_var函数，该函数用于对LCD可变参数进行检查，其定义如下：
109/* 110 * s3c2410fb_check_var(): 111 * Get the video params out of 'var'. If a value doesn't fit, round it up, 112 * if it's too big, return -EINVAL. 113 * 114 */ 115static int s3c2410fb_check_var(struct fb_var_screeninfo *var, 116 struct fb_info *info) 117{ 118 struct s3c2410fb_info *fbi = info->par; 119 struct s3c2410fb_mach_info *mach_info = fbi->dev->platform_data; 120 struct s3c2410fb_display *display = NULL; 121 struct s3c2410fb_display *default_display = mach_info->displays + 122 mach_info->default_display; 123 int type = default_display->type; 124 unsigned i; 125 126 dprintk("check_var(var=%p, info=%p)\n", var, info); 127 128 /* validate x/y resolution */ 129 /* choose default mode if possible */ 130 if (var->yres == default_display->yres && 131 var->xres == default_display->xres && 132 var->bits_per_pixel == default_display->bpp) 133 display = default_display; 134 else 135 for (i = 0; i < mach_info->num_displays; i++) 136 if (type == mach_info->displays[i].type && 137 var->yres == mach_info->displays[i].yres && 138 var->xres == mach_info->displays[i].xres && 139 var->bits_per_pixel == mach_info->displays[i].bpp) { 140 display = mach_info->displays + i; 141 break; 142 } 143 144 if (!display) { 145 dprintk("wrong resolution or depth %dx%d at %d bpp\n", 146 var->xres, var->yres, var->bits_per_pixel); 147 return -EINVAL; 148 } 149 150 /* it is always the size as the display */ 151 var->xres_virtual = display->xres; 152 var->yres_virtual = display->yres; 153 var->height = display->height; 154 var->width = display->width; 155 156 /* copy lcd settings */ 157 var->pixclock = display->pixclock; 158 var->left_margin = display->left_margin; 159 var->right_margin = display->right_margin; 160 var->upper_margin = display->upper_margin; 161 var->lower_margin = display->lower_margin; 162 var->vsync_len = display->vsync_len; 163 var->hsync_len = display->hsync_len; 164 165 fbi->regs.lcdcon5 = display->lcdcon5; 166 /* set display type */ 167 fbi->regs.lcdcon1 = display->type; 168 169 var->transp.offset = 0; 170 var->transp.length = 0; 171 /* set r/g/b positions */ 172 switch (var->bits_per_pixel) { 173 case 1: 174 case 2: 175 case 4: 176 var->red.offset = 0; 177 var->red.length = var->bits_per_pixel; 178 var->green = var->red; 179 var->blue = var->red; 180 break; 181 case 8: 182 if (display->type != S3C2410_LCDCON1_TFT) { 183 /* 8 bpp 332 */ 184 var->red.length = 3; 185 var->red.offset = 5; 186 var->green.length = 3; 187 var->green.offset = 2; 188 var->blue.length = 2; 189 var->blue.offset = 0; 190 } else { 191 var->red.offset = 0; 192 var->red.length = 8; 193 var->green = var->red; 194 var->blue = var->red; 195 } 196 break; 197 case 12: 198 /* 12 bpp 444 */ 199 var->red.length = 4; 200 var->red.offset = 8; 201 var->green.length = 4; 202 var->green.offset = 4; 203 var->blue.length = 4; 204 var->blue.offset = 0; 205 break; 206 207 default: 208 case 16: 209 if (display->lcdcon5 & S3C2410_LCDCON5_FRM565) { 210 /* 16 bpp, 565 format */ 211 var->red.offset = 11; 212 var->green.offset = 5; 213 var->blue.offset = 0; 214 var->red.length = 5; 215 var->green.length = 6; 216 var->blue.length = 5; 217 } else { 218 /* 16 bpp, 5551 format */ 219 var->red.offset = 11; 220 var->green.offset = 6; 221 var->blue.offset = 1; 222 var->red.length = 5; 223 var->green.length = 5; 224 var->blue.length = 5; 225 } 226 break; 227 case 32: 228 /* 24 bpp 888 and 8 dummy */ 229 var->red.length = 8; 230 var->red.offset = 16; 231 var->green.length = 8; 232 var->green.offset = 8; 233 var->blue.length = 8; 234 var->blue.offset = 0; 235 break; 236 } 237 return 0; 238}
128 - 148行，验证x/y解析度。如果没有正好匹配的设置，则返回错误。
151 - 154行，设置屏幕的虚拟解析像素和高度宽度。
157 - 163行，设置时钟像素，行、帧切换值，水平同步和垂直同步长度值。
165行，配置LCDCON5寄存器。
167行，通过LCDCON1配置LCD类型。
169 - 170行，设置透明度。
172 - 236行，根据色位模式(BPP)来设置可变参数中R、G、B的颜色位域。
s3c24xxfb_probe函数的第963行,调用s3c2410fb_cpufreq_register函数实现变频功能。根据宏CONFIG_CPU_FREQ是否被定义，可以直接返回0，也可以具体实现变频功能。
下面我们要分析的中LCD中断处理函数s3c2410fb_irq：
747static irqreturn_t s3c2410fb_irq(int irq, void *dev_id) 748{ 749 struct s3c2410fb_info *fbi = dev_id; 750 void __iomem *irq_base = fbi->irq_base; 751 unsigned long lcdirq = readl(irq_base + S3C24XX_LCDINTPND); 752 753 if (lcdirq & S3C2410_LCDINT_FRSYNC) { 754 if (fbi->palette_ready) 755 s3c2410fb_write_palette(fbi); 756 757 writel(S3C2410_LCDINT_FRSYNC, irq_base + S3C24XX_LCDINTPND); 758 writel(S3C2410_LCDINT_FRSYNC, irq_base + S3C24XX_LCDSRCPND); 759 } 760 761 return IRQ_HANDLED; 762}
749行，注意s3c2410fb_info实例以dev_id参数的形式传递进来，注意理解dev_id的用法。
751行，读取LCDINTPND寄存器(LCD Interrupt Pending Register)的值到lcdirq中。
753行，如果LCDINTPND寄存器的第1位为1，说明LCD触发了中断。
754行，如果fbi->palette_ready等于1，表明需要更新fbi->palette_buffer中的调色板信息到LCD控制器的调色板内存区。相反，如果fbi->palette_ready等于0，则表明不需要更新调色板内存区。
755行，调用s3c2410fb_write_palette函数将fbi->palette_buffer中的信息写入LCD控制器的调色板内存空间中。
757行，设置LCDINTPND寄存器，表明已插入中断请求，这里不理解经过了753行的判断，应该已经设置好了，这里为什么再设置一遍？
758行，设置LCDSRCPND寄存器，表明已插入中断请求。
s3c2410fb_write_palette函数用于填充调色板，其定义如下：
721static void s3c2410fb_write_palette(struct s3c2410fb_info *fbi) 722{ 723 unsigned int i; 724 void __iomem *regs = fbi->io; 725 726 fbi->palette_ready = 0; 727 728 for (i = 0; i < 256; i++) { 729 unsigned long ent = fbi->palette_buffer[i]; 730 if (ent == PALETTE_BUFF_CLEAR) 731 continue; 732 733 writel(ent, regs + S3C2410_TFTPAL(i)); 734 735 /* it seems the only way to know exactly 736 * if the palette wrote ok, is to check 737 * to see if the value verifies ok 738 */ 739 740 if (readw(regs + S3C2410_TFTPAL(i)) == ent) 741 fbi->palette_buffer[i] = PALETTE_BUFF_CLEAR; 742 else 743 fbi->palette_ready = 1; /* retry */ 744 } 745}
728 - 744行，将fbi->palette_buffer中的调色板信息写到LCD控制器的调色板内存区。
三、platform_driver remove函数分析
s3c2410fb_remove函数定义如下：
1021static int __devexit s3c2410fb_remove(struct platform_device *pdev) 1022{ 1023 struct fb_info *fbinfo = platform_get_drvdata(pdev); 1024 struct s3c2410fb_info *info = fbinfo->par; 1025 int irq; 1026 1027 unregister_framebuffer(fbinfo); 1028 s3c2410fb_cpufreq_deregister(info); 1029 1030 s3c2410fb_lcd_enable(info, 0); 1031 msleep(1); 1032 1033 s3c2410fb_unmap_video_memory(fbinfo); 1034 1035 if (info->clk) { 1036 clk_disable(info->clk); 1037 clk_put(info->clk); 1038 info->clk = NULL; 1039 } 1040 1041 irq = platform_get_irq(pdev, 0); 1042 free_irq(irq, info); 1043 1044 iounmap(info->io); 1045 1046 release_resource(info->mem); 1047 kfree(info->mem); 1048 1049 platform_set_drvdata(pdev, NULL); 1050 framebuffer_release(fbinfo); 1051 1052 return 0; 1053}
1027行，调用unregister_framebuffer，注销fb_info结构实例。
1028行，注销变频。
1030行，停止LCD控制器的工作。
1031行，延迟1毫秒，因为停止LCD控制器的工作需要一定时间。
1033行，释放帧缓冲区。
1035 - 1039，释放时钟资源。
1042行，释放中断号。
1044行，取消对LCD I/O内存的映射。
1046 - 1047，释放LCD I/O内存。
1050行，释放fb_info空间。
s3c2410fb_lcd_enable函数定义如下：
530static void s3c2410fb_lcd_enable(struct s3c2410fb_info *fbi, int enable) 531{ 532 unsigned long flags; 533 534 local_irq_save(flags); 535 536 if (enable) 537 fbi->regs.lcdcon1 |= S3C2410_LCDCON1_ENVID; 538 else 539 fbi->regs.lcdcon1 &= ~S3C2410_LCDCON1_ENVID; 540 541 writel(fbi->regs.lcdcon1, fbi->io + S3C2410_LCDCON1); 542 543 local_irq_restore(flags); 544}
536 - 537行，将LCDCON1寄存器的第0位设置为1，使能LCD控制器。
538 - 539行，将LCDCON1寄存器的第0位设置为0，禁用LCD控制器。
四、platform_driver的电源管理支持
如果定义了CONFIG_PM宏，则需要platform_driver提供suspend和resume函数以支持电源管理功能。
1057/* suspend and resume support for the lcd controller */ 1058static int s3c2410fb_suspend(struct platform_device *dev, pm_message_t state) 1059{ 1060 struct fb_info *fbinfo = platform_get_drvdata(dev); 1061 struct s3c2410fb_info *info = fbinfo->par; 1062 1063 s3c2410fb_lcd_enable(info, 0); 1064 1065 /* sleep before disabling the clock, we need to ensure 1066 * the LCD DMA engine is not going to get back on the bus 1067 * before the clock goes off again (bjd) */ 1068 1069 msleep(1); 1070 clk_disable(info->clk); 1071 1072 return 0; 1073}
1063行，禁用LCD控制器。
1070行，关闭时钟。
s3c2410fb_resume函数定义如下：
1075static int s3c2410fb_resume(struct platform_device *dev) 1076{ 1077 struct fb_info *fbinfo = platform_get_drvdata(dev); 1078 struct s3c2410fb_info *info = fbinfo->par; 1079 1080 clk_enable(info->clk); 1081 msleep(1); 1082 1083 s3c2410fb_init_registers(fbinfo); 1084 1085 /* re-activate our display after resume */ 1086 s3c2410fb_activate_var(fbinfo); 1087 s3c2410fb_blank(FB_BLANK_UNBLANK, fbinfo); 1088 1089 return 0; 1090}
1080行，使能时钟。
1083行，重新初始化LCD寄存器。
1086行，重新激活fb_info的所有参数配置，这个函数在第五部分分析。
1087行，让LCD显示空白，这个函数在第五部分分析。
五、fb_ops函数集的实现
S3C2410 LCD驱动程序的fb_ops函数集定义如下：
615static struct fb_ops s3c2410fb_ops = { 616 .owner = THIS_MODULE, 617 .fb_check_var = s3c2410fb_check_var, 618 .fb_set_par = s3c2410fb_set_par, 619 .fb_blank = s3c2410fb_blank, 620 .fb_setcolreg = s3c2410fb_setcolreg, 621 .fb_fillrect = cfb_fillrect, 622 .fb_copyarea = cfb_copyarea, 623 .fb_imageblit = cfb_imageblit, 624};
617行，s3c2410fb_check_var函数我们前面已经分析过了。
下面看s3c2410fb_set_par函数的实现：
416/* 417 * s3c2410fb_set_par - Alters the hardware state. 418 * @info: frame buffer structure that represents a single frame buffer 419 * 420 */ 421static int s3c2410fb_set_par(struct fb_info *info) 422{ 423 struct fb_var_screeninfo *var = &info->var; 424 425 switch (var->bits_per_pixel) { 426 case 32: 427 case 16: 428 case 12: 429 info->fix.visual = FB_VISUAL_TRUECOLOR; 430 break; 431 case 1: 432 info->fix.visual = FB_VISUAL_MONO01; 433 break; 434 default: 435 info->fix.visual = FB_VISUAL_PSEUDOCOLOR; 436 break; 437 } 438 439 info->fix.line_length = (var->xres_virtual * var->bits_per_pixel) / 8; 440 441 /* activate this new configuration */ 442 443 s3c2410fb_activate_var(info); 444 return 0; 445}
425 - 439行，根据info->var调整info->fix的值。
443行，调用s3c2410fb_activate_var函数激活info->var指定的配置。
361/* s3c2410fb_activate_var 362 * 363 * activate (set) the controller from the given framebuffer 364 * information 365 */ 366static void s3c2410fb_activate_var(struct fb_info *info) 367{ 368 struct s3c2410fb_info *fbi = info->par; 369 void __iomem *regs = fbi->io; 370 int type = fbi->regs.lcdcon1 & S3C2410_LCDCON1_TFT; 371 struct fb_var_screeninfo *var = &info->var; 372 int clkdiv; 373 374 clkdiv = DIV_ROUND_UP(s3c2410fb_calc_pixclk(fbi, var->pixclock), 2); 375 376 dprintk("%s: var->xres = %d\n", __func__, var->xres); 377 dprintk("%s: var->yres = %d\n", __func__, var->yres); 378 dprintk("%s: var->bpp = %d\n", __func__, var->bits_per_pixel); 379 380 if (type == S3C2410_LCDCON1_TFT) { 381 s3c2410fb_calculate_tft_lcd_regs(info, &fbi->regs); 382 --clkdiv; 383 if (clkdiv < 0) 384 clkdiv = 0; 385 } else { 386 s3c2410fb_calculate_stn_lcd_regs(info, &fbi->regs); 387 if (clkdiv < 2) 388 clkdiv = 2; 389 } 390 391 fbi->regs.lcdcon1 |= S3C2410_LCDCON1_CLKVAL(clkdiv); 392 393 /* write new registers */ 394 395 dprintk("new register set:\n"); 396 dprintk("lcdcon[1] = 0x%08lx\n", fbi->regs.lcdcon1); 397 dprintk("lcdcon[2] = 0x%08lx\n", fbi->regs.lcdcon2); 398 dprintk("lcdcon[3] = 0x%08lx\n", fbi->regs.lcdcon3); 399 dprintk("lcdcon[4] = 0x%08lx\n", fbi->regs.lcdcon4); 400 dprintk("lcdcon[5] = 0x%08lx\n", fbi->regs.lcdcon5); 401 402 writel(fbi->regs.lcdcon1 & ~S3C2410_LCDCON1_ENVID, 403 regs + S3C2410_LCDCON1); 404 writel(fbi->regs.lcdcon2, regs + S3C2410_LCDCON2); 405 writel(fbi->regs.lcdcon3, regs + S3C2410_LCDCON3); 406 writel(fbi->regs.lcdcon4, regs + S3C2410_LCDCON4); 407 writel(fbi->regs.lcdcon5, regs + S3C2410_LCDCON5); 408 409 /* set lcd address pointers */ 410 s3c2410fb_set_lcdaddr(info); 411 412 fbi->regs.lcdcon1 |= S3C2410_LCDCON1_ENVID, 413 writel(fbi->regs.lcdcon1, regs + S3C2410_LCDCON1); 414}
370行，获取液晶屏类型。
374行，计算LCDCON1寄存器用到的CLKVAL值(从391行可以看出)。根据S3C2410 Datasheet，计算公式如下：
STN: VCLK = HCLK / ( CLKVAL x 2 ) ( CLKVAL >= 2 )
TFT: VCLK = HCLK / [(CLKVAL + 1) x 2 ] (CLKVAL >= 0 )
DIV_ROUND_UP 宏定义在include/linux/kernel.h文件中，其定义如下：
#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
s3c2410fb_calc_pixclk函数定义如下：
86/* s3c2410fb_calc_pixclk() 87 * 88 * calculate divisor for clk->pixclk 89 */ 90static unsigned int s3c2410fb_calc_pixclk(struct s3c2410fb_info *fbi, 91 unsigned long pixclk) 92{ 93 unsigned long clk = fbi->clk_rate; 94 unsigned long long div; 95 96 /* pixclk is in picoseconds, our clock is in Hz 97 * 98 * Hz -> picoseconds is / 10^-12 99 */ 100 101 div = (unsigned long long)clk * pixclk; 102 div >>= 12; /* div / 2^12 */ 103 do_div(div, 625 * 625UL * 625); /* div / 5^12 */ 104 105 dprintk("pixclk %ld, divisor is %ld\n", pixclk, (long)div); 106 return div; 107}
pixclk的单位是皮秒，皮秒是天文学名词，是目前最小的时间单位，一皮秒等于10的12次方分之一秒。
do_div宏的定义在arch/arm/include/asm/div64.h文件中。看注释其作用是div/5^12，但是为什么这样做，还不清楚。
回到s3c2410fb_activate_var函数，
381行，如果是TFT屏，调用s3c2410fb_calculate_tft_lcd_regs函数：
300/* s3c2410fb_calculate_tft_lcd_regs 301 * 302 * calculate register values from var settings 303 */ 304static void s3c2410fb_calculate_tft_lcd_regs(const struct fb_info *info, 305 struct s3c2410fb_hw *regs) 306{ 307 const struct s3c2410fb_info *fbi = info->par; 308 const struct fb_var_screeninfo *var = &info->var; 309 310 switch (var->bits_per_pixel) { 311 case 1: 312 regs->lcdcon1 |= S3C2410_LCDCON1_TFT1BPP; 313 break; 314 case 2: 315 regs->lcdcon1 |= S3C2410_LCDCON1_TFT2BPP; 316 break; 317 case 4: 318 regs->lcdcon1 |= S3C2410_LCDCON1_TFT4BPP; 319 break; 320 case 8: 321 regs->lcdcon1 |= S3C2410_LCDCON1_TFT8BPP; 322 regs->lcdcon5 |= S3C2410_LCDCON5_BSWP | 323 S3C2410_LCDCON5_FRM565; 324 regs->lcdcon5 &= ~S3C2410_LCDCON5_HWSWP; 325 break; 326 case 16: 327 regs->lcdcon1 |= S3C2410_LCDCON1_TFT16BPP; 328 regs->lcdcon5 &= ~S3C2410_LCDCON5_BSWP; 329 regs->lcdcon5 |= S3C2410_LCDCON5_HWSWP; 330 break; 331 case 32: 332 regs->lcdcon1 |= S3C2410_LCDCON1_TFT24BPP; 333 regs->lcdcon5 &= ~(S3C2410_LCDCON5_BSWP | 334 S3C2410_LCDCON5_HWSWP | 335 S3C2410_LCDCON5_BPP24BL); 336 break; 337 default: 338 /* invalid pixel depth */ 339 dev_err(fbi->dev, "invalid bpp %d\n", 340 var->bits_per_pixel); 341 } 342 /* update X/Y info */ 343 dprintk("setting vert: up=%d, low=%d, sync=%d\n", 344 var->upper_margin, var->lower_margin, var->vsync_len); 345 346 dprintk("setting horz: lft=%d, rt=%d, sync=%d\n", 347 var->left_margin, var->right_margin, var->hsync_len); 348 349 regs->lcdcon2 = S3C2410_LCDCON2_LINEVAL(var->yres - 1) | 350 S3C2410_LCDCON2_VBPD(var->upper_margin - 1) | 351 S3C2410_LCDCON2_VFPD(var->lower_margin - 1) | 352 S3C2410_LCDCON2_VSPW(var->vsync_len - 1); 353 354 regs->lcdcon3 = S3C2410_LCDCON3_HBPD(var->right_margin - 1) | 355 S3C2410_LCDCON3_HFPD(var->left_margin - 1) | 356 S3C2410_LCDCON3_HOZVAL(var->xres - 1); 357 358 regs->lcdcon4 = S3C2410_LCDCON4_HSPW(var->hsync_len - 1); 359}
针对TFT屏，这个函数通过info->var的成员变量值计算各个LCD Control寄存器的值。参考Datasheet很容易理解这个函数。
386行，如果是STN屏，则调用s3c2410fb_calculate_stn_lcd_regs函数：
240/* s3c2410fb_calculate_stn_lcd_regs 241 * 242 * calculate register values from var settings 243 */ 244static void s3c2410fb_calculate_stn_lcd_regs(const struct fb_info *info, 245 struct s3c2410fb_hw *regs) 246{ 247 const struct s3c2410fb_info *fbi = info->par; 248 const struct fb_var_screeninfo *var = &info->var; 249 int type = regs->lcdcon1 & ~S3C2410_LCDCON1_TFT; 250 int hs = var->xres >> 2; 251 unsigned wdly = (var->left_margin >> 4) - 1; 252 unsigned wlh = (var->hsync_len >> 4) - 1; 253 254 if (type != S3C2410_LCDCON1_STN4) 255 hs >>= 1; 256 257 switch (var->bits_per_pixel) { 258 case 1: 259 regs->lcdcon1 |= S3C2410_LCDCON1_STN1BPP; 260 break; 261 case 2: 262 regs->lcdcon1 |= S3C2410_LCDCON1_STN2GREY; 263 break; 264 case 4: 265 regs->lcdcon1 |= S3C2410_LCDCON1_STN4GREY; 266 break; 267 case 8: 268 regs->lcdcon1 |= S3C2410_LCDCON1_STN8BPP; 269 hs *= 3; 270 break; 271 case 12: 272 regs->lcdcon1 |= S3C2410_LCDCON1_STN12BPP; 273 hs *= 3; 274 break; 275 276 default: 277 /* invalid pixel depth */ 278 dev_err(fbi->dev, "invalid bpp %d\n", 279 var->bits_per_pixel); 280 } 281 /* update X/Y info */ 282 dprintk("setting horz: lft=%d, rt=%d, sync=%d\n", 283 var->left_margin, var->right_margin, var->hsync_len); 284 285 regs->lcdcon2 = S3C2410_LCDCON2_LINEVAL(var->yres - 1); 286 287 if (wdly > 3) 288 wdly = 3; 289 290 if (wlh > 3) 291 wlh = 3; 292 293 regs->lcdcon3 = S3C2410_LCDCON3_WDLY(wdly) | 294 S3C2410_LCDCON3_LINEBLANK(var->right_margin / 8) | 295 S3C2410_LCDCON3_HOZVAL(hs - 1); 296 297 regs->lcdcon4 = S3C2410_LCDCON4_WLH(wlh); 298}
针对STN屏，这个函数通过info->var的成员变量值计算各个LCD Control寄存器的值。参考Datasheet理解这个函数。
回到s3c2410fb_activate_var函数，
391行，设置LCDCON1的CLKVAL。
402 - 407行，把相关设置写入LCD控制寄存器。
410行，调用s3c2410fb_set_lcdaddr函数设置帧缓冲区的地址，寄存器LCDSADDR1、LCDSADDR2、LCDSADDR3的含义参考Datasheet：
59/* s3c2410fb_set_lcdaddr 60 * 61 * initialise lcd controller address pointers 62 */ 63static void s3c2410fb_set_lcdaddr(struct fb_info *info) 64{ 65 unsigned long saddr1, saddr2, saddr3; 66 struct s3c2410fb_info *fbi = info->par; 67 void __iomem *regs = fbi->io; 68 69 saddr1 = info->fix.smem_start >> 1; 70 saddr2 = info->fix.smem_start; 71 saddr2 += info->fix.line_length * info->var.yres; 72 saddr2 >>= 1; 73 74 saddr3 = S3C2410_OFFSIZE(0) | 75 S3C2410_PAGEWIDTH((info->fix.line_length / 2) & 0x3ff); 76 77 dprintk("LCDSADDR1 = 0x%08lx\n", saddr1); 78 dprintk("LCDSADDR2 = 0x%08lx\n", saddr2); 79 dprintk("LCDSADDR3 = 0x%08lx\n", saddr3); 80 81 writel(saddr1, regs + S3C2410_LCDSADDR1); 82 writel(saddr2, regs + S3C2410_LCDSADDR2); 83 writel(saddr3, regs + S3C2410_LCDSADDR3); 84}
回忆一下在s3c2410fb_map_video_memory函数的651行,帧缓冲区Framebuffer的物理地址首地址保存在fb_info.fix.smem_start中。LCDADDR1寄存器的值怎样计算呢？其实就是把Framebuffer物理地址值右移1位(因为是16位BPP)，写到LCDADDR1寄存器就可以了。
LCDADDR2寄存器保存Framebuffer的结束地址，在s3c2410fb_set_par函数中，439行，将每行占用的字节数保存在fb_info.fix.line_length变量中。屏幕共有多少行,保存在fb_info.var.yres中。所以，71行得到Framebuffer的结束位置，72行将结束位置右移1位(因为是16位BPP)。
74行，S3C2410_OFFSIZE 宏定义如下：
#define S3C2410_OFFSIZE(x) ((x) << 11)
75行，S3C2410_PAGEWIDTH宏定义如下：
#define S3C2410_PAGEWIDTH(x) (x)
回到s3c2410fb_activate_var函数，
413行，使能LCD控制器。
至此，s3c2410fb_activate_var函数就全部分析完了。
同时，s3c2410fb_set_par函数也就全部分析完了。
下面来分析fb_ops.fb_bank函数s3c2410fb_blank的实现：
547/* 548 * s3c2410fb_blank 549 * @blank_mode: the blank mode we want. 550 * @info: frame buffer structure that represents a single frame buffer 551 * 552 * Blank the screen if blank_mode != 0, else unblank. Return 0 if 553 * blanking succeeded, != 0 if un-/blanking failed due to e.g. a 554 * video mode which doesn't support it. Implements VESA suspend 555 * and powerdown modes on hardware that supports disabling hsync/vsync: 556 * 557 * Returns negative errno on error, or zero on success. 558 * 559 */ 560static int s3c2410fb_blank(int blank_mode, struct fb_info *info) 561{ 562 struct s3c2410fb_info *fbi = info->par; 563 void __iomem *tpal_reg = fbi->io; 564 565 dprintk("blank(mode=%d, info=%p)\n", blank_mode, info); 566 567 tpal_reg += is_s3c2412(fbi) ? S3C2412_TPAL : S3C2410_TPAL; 568 569 if (blank_mode == FB_BLANK_POWERDOWN) { 570 s3c2410fb_lcd_enable(fbi, 0); 571 } else { 572 s3c2410fb_lcd_enable(fbi, 1); 573 } 574 575 if (blank_mode == FB_BLANK_UNBLANK) 576 writel(0x0, tpal_reg); 577 else { 578 dprintk("setting TPAL to output 0x000000\n"); 579 writel(S3C2410_TPAL_EN, tpal_reg); 580 } 581 582 return 0; 583}
如果要输出一帧单色图像，可以在TPAL寄存器中设定这个颜色值，然后使能TPAL寄存器，这种方法可以避免修改整个调色板或帧缓冲区。
579行，使能TPAL，同时显示让屏幕清屏，S3C2410_TPAL_EN宏定义如下：
#define S3C2410_TPAL_EN (1<<24)
下面来分析fb_ops.fb_setcolreg函数s3c2410fb_setcolreg：
479static int s3c2410fb_setcolreg(unsigned regno, 480 unsigned red, unsigned green, unsigned blue, 481 unsigned transp, struct fb_info *info) 482{ 483 struct s3c2410fb_info *fbi = info->par; 484 void __iomem *regs = fbi->io; 485 unsigned int val; 486 487 /* dprintk("setcol: regno=%d, rgb=%d,%d,%d\n", 488 regno, red, green, blue); */ 489 490 switch (info->fix.visual) { 491 case FB_VISUAL_TRUECOLOR: 492 /* true-colour, use pseudo-palette */ 493 494 if (regno < 16) { 495 u32 *pal = info->pseudo_palette; 496 497 val = chan_to_field(red, &info->var.red); 498 val |= chan_to_field(green, &info->var.green); 499 val |= chan_to_field(blue, &info->var.blue); 500 501 pal[regno] = val; 502 } 503 break; 504 505 case FB_VISUAL_PSEUDOCOLOR: 506 if (regno < 256) { 507 /* currently assume RGB 5-6-5 mode */ 508 509 val = (red >> 0) & 0xf800; 510 val |= (green >> 5) & 0x07e0; 511 val |= (blue >> 11) & 0x001f; 512 513 writel(val, regs + S3C2410_TFTPAL(regno)); 514 schedule_palette_update(fbi, regno, val); 515 } 516 517 break; 518 519 default: 520 return 1; /* unknown type */ 521 } 522 523 return 0; 524}
该函数的作用是将颜色值写入调色板（或伪调色板）的指定位置。
501行，将颜色值写入伪调色板。
513行，将颜色值写入调色板。
chan_to_field函数定义如下：
471static inline unsigned int chan_to_field(unsigned int chan, 472 struct fb_bitfield *bf) 473{ 474 chan &= 0xffff; 475 chan >>= 16 - bf->length; 476 return chan << bf->offset; 477}
schedule_palette_update函数定义如下：447static void schedule_palette_update(struct s3c2410fb_info *fbi, 448 unsigned int regno, unsigned int val) 449{ 450 unsigned long flags; 451 unsigned long irqen; 452 void __iomem *irq_base = fbi->irq_base; 453 454 local_irq_save(flags); 455 456 fbi->palette_buffer[regno] = val; 457 458 if (!fbi->palette_ready) { 459 fbi->palette_ready = 1; 460 461 /* enable IRQ */ 462 irqen = readl(irq_base + S3C24XX_LCDINTMSK); 463 irqen &= ~S3C2410_LCDINT_FRSYNC; 464 writel(irqen, irq_base + S3C24XX_LCDINTMSK); 465 } 466 467 local_irq_restore(flags); 468}
