S5PV210 显示控制器及framebuffer驱动s3c-fb.c中probe函数分析
三星SOC芯片上集成了显示控制器（有称作fimd的，Fully Interactive Mobile Display）。它的驱动分为mainline版本的和legacy版本的，mainline版本的是通用的，由Ben Dooks <[email protected]> 管理着的，代码比较规范。下面我们来分析一下这个驱动，这个驱动在driver/video/里，文件名是s3c-fb.c 与其相关的，主要还有arch/arm/plat-s5p/dev-fimd0.c和arch/arm/mach-XXXX/setup-fimd0.c 。 前者是定义platform device的，后者是定义一些比较depend on 具体芯片的东西，例如GPIO。
我们这里主要分析s3c-fb.c中的probe函数， probe函数里最重要的是s3c_fb_probe_win函数，一会也一并分析。
首先解释一个概念，很多书中有framebuffer这个概念，但是在三星的显示控制器文档或代码中，常出现win或window的概念，显示控制器可以控制0~5个windows，代码中分给它们分别编号win0, win1,win2......这里一张win或window就对应一个framebuffer, 每个framebuffer有自己的一个FBI（fb_info）结构。
代码中， 显示控制器是s3c_fb结构体， window是s3c_fb_win结构体。
代码中有两种data，一种是platform data（在板文件中定义），另一种是driver data(在驱动文件中定义)，在它们各自的结构体里面，又可以分为两部份，一是用于sfb的data, 另一是用于win的data。
framebuffer是fb_info结构体，里面主要存储设置参数的数据结构有两个，fb_var_screeninfo和fb_fix_screeninfo结构体。
************************************************ platform data***************************************************
static struct s3c_fb_platdata smdkv210_lcd0_pdata __initdata = {
.win[0] = &smdkv210_fb_win0, -------->用于win的部分，下文称作“platform data中win的部分”
.vidcon0 = VIDCON0_VIDOUT_RGB | VIDCON0_PNRMODE_RGB, -------->下面开始是sfb的部分，
.vidcon1 = VIDCON1_INV_HSYNC | VIDCON1_INV_VSYNC,
.setup_gpio = s5pv210_fb_gpio_setup_24bpp,
};
************************************************ driver data***************************************************
static struct s3c_fb_driverdata s3c_fb_data_s5pv210 = {
.variant = { ---------->用于sfb的driverdata
.nr_windows = 5,
.vidtcon = VIDTCON0,
.wincon = WINCON(0),
.winmap = WINxMAP(0),
.keycon = WKEYCON,
.osd = VIDOSD_BASE,
.osd_stride = 16,
.buf_start = VIDW_BUF_START(0),
.buf_size = VIDW_BUF_SIZE(0),
.buf_end = VIDW_BUF_END(0),
.palette = {
[0] = 0x2400,
[1] = 0x2800,
[2] = 0x2c00,
[3] = 0x3000,
[4] = 0x3400,
},
.has_shadowcon= 1,
.has_blendcon = 1,
.has_alphacon = 1,
.has_clksel = 1,
.has_fixvclk = 1,
},
.win[0] = &s3c_fb_data_s5p_wins[0], ---------->用于各个win的部分，下文称作“driver data中win的部份”
.win[1] = &s3c_fb_data_s5p_wins[1],
.win[2] = &s3c_fb_data_s5p_wins[2],
.win[3] = &s3c_fb_data_s5p_wins[3],
.win[4] = &s3c_fb_data_s5p_wins[4],
};
************************************************ s3c_fb_probe() ***************************************************
static int __devinit s3c_fb_probe(struct platform_device *pdev)
{
const struct platform_device_id *platid; -------> 因为一个驱动要适合很多版本的设备，每个版本的设备的设置 参数都不一样，所以要用到platid来选择哪个版本的设备，像“s5pv210-fb”, "s3c2443-fb"..., 这些就是platid(也在s3c-fb.c中定义了)， 也表明了，这个驱动能适合于这些设备。
struct s3c_fb_driverdata *fbdrv; ----> driver data
struct device *dev = &pdev->dev;
struct s3c_fb_platdata *pd; ----> platform data
struct s3c_fb *sfb; -----> 一个最重要的数据结据， 它代表了一个显示控制器，显示控制器的所有东东都放在这里了。但这里把它做成一个局部变量了。
struct resource *res; -----> 资源
int win;
int default_win;
...
platid = platform_get_device_id(pdev); ----> 从platform device 里 的id_entry 变量中获取platid，由一个宏实现
fbdrv = (struct s3c_fb_driverdata *)platid->driver_data; ---> 获取platid对应的driver data，driver data在s3c-fb.c中定义，主要是一定设置参数
...
pd = pdev->dev.platform_data; --> 获取platform data，它在板文件中定义，这个data里包含了关于显示控制器的数据，也包含了win的数据。
...
sfb = kzalloc(sizeof(struct s3c_fb), GFP_KERNEL); ------> 给这个最重要的结构分配内存空间
...
sfb->dev = dev; ---> 向sfb 填入 显示控制器的 device 结构体
sfb->pdata = pd; ---> 向sfb 填入 显示控制器的 platform data 结构体
sfb->variant = fbdrv->variant; ---> driver data结构体里 有 variant成员， 具体variant可以看下面s3c_fb_variant结构。
...
sfb->bus_clk = clk_get(dev, "lcd"); -->用"lcd"这个名字，去clock文件中找到自己的bus clock
...
clk_enable(sfb->bus_clk); ---> bus clock有什么用，我还不太清楚
...
if (!sfb->variant.has_clksel) {
sfb->lcd_clk = clk_get(dev, "sclk_fimd"); --> 如果driver data里没定义 源时钟， 就用“sclk_fimd”此名字去clock文件找到自己的源时钟
...
clk_enable(sfb->lcd_clk);
....
res = platform_get_resource(pdev, IORESOURCE_MEM, 0); --> 获取资源的物理起始地址，终地址，大小，类型等，放在res结构中。实际上是寄存器们的物理起，终地址。
...
sfb->regs_res = request_mem_region(res->start, resource_size(res), dev_name(dev)); ---> 分配内存
...
sfb->regs = ioremap(res->start, resource_size(res)); ----> 内存映射， 将寄存器的访问地址映射到刚才分配的内存上， sfb->regs为起始地址。
... // 中断的请求略
platform_set_drvdata(pdev, sfb); ---> 将sfb 填入pdev->dev->p->driverdata 结构体中
...
pd->setup_gpio(); --> 执行setup_gpio函数，此函数在上面说的 setup_fimd0.c 中定义了。用来配置GPIO端口给FIMD使用。
...
writel(pd->vidcon1, sfb->regs + VIDCON1); -->设置VIDCON1 寄存器
/* set video clock running at under-run */
if (sfb->variant.has_fixvclk) { --> run vclk
reg = readl(sfb->regs + VIDCON1);
reg &= ~VIDCON1_VCLK_MASK;
reg |= VIDCON1_VCLK_RUN;
writel(reg, sfb->regs + VIDCON1);
}
for (win = 0; win < fbdrv->variant.nr_windows; win++)
s3c_fb_clear_win(sfb, win); ---> 将各个window的wincon寄存器清0，VIDOSDxA, VIDOSDxB, VIDOSDxC清0，禁止update各个window的shadow
/* initialise colour key controls */
for (win = 0; win < (fbdrv->variant.nr_windows - 1); win++) {
void __iomem *regs = sfb->regs + sfb->variant.keycon;
regs += (win * 8);
writel(0xffffff, regs + WKEYCON0);
writel(0xffffff, regs + WKEYCON1);
}
/* we have the register setup, start allocating framebuffers */
default_win = sfb->pdata->default_win; ---> platform data 在板文件中定义了
for (i = 0; i < fbdrv->variant.nr_windows; i++) {
win = i;
if (i == 0)
win = default_win;
if (i == default_win)
win = 0;
if (!pd->win[win])
continue;
if (!pd->win[win]->win_mode.pixclock)-----> 像素时钟
s3c_fb_missing_pixclock(&pd->win[win]->win_mode);----->如果像素时钟没预先定义，则由预先设定的刷新率和LCD参数来计算像素时钟
ret = s3c_fb_probe_win(sfb, win, fbdrv->win[win], &sfb->windows[win]); ----->分配 及 注册framebuffer的重要函数，下面会详细说
if (ret < 0) {
dev_err(dev, "failed to create window %d\n", win);
for (; win >= 0; win--)
s3c_fb_release_win(sfb, sfb->windows[win]); ----> 注册不成功的话就释放之前注册成功过的window
goto err_irq;
}
}
}
...
platform_set_drvdata(pdev, sfb);---> 再一次将sfb 填入pdev->dev->p->driverdata 结构体中，之前曾经这样操作过一次，现在再来一次，是因为sfb里的数据更新了很多
...
#ifdef CONFIG_HAS_EARLYSUSPEND--> 如果有定义earlysuspend的话， 则注册early suspend函数
sfb->early_suspend.suspend = s3c_fb_early_suspend;
sfb->early_suspend.resume = s3c_fb_late_resume;
sfb->early_suspend.level = EARLY_SUSPEND_LEVEL_DISABLE_FB;
register_early_suspend(&sfb->early_suspend);
#endif
return 0;
...
还有一些错训处理在此略过
} ---- > probe函数完成
************************************************ s3c_fb_probe_win() *************************************************************
static int __devinit s3c_fb_probe_win(struct s3c_fb *sfb, unsigned int win_no, --->将显示控制器的结构体作为参数传进来，它有寄存器起始地址等丰富信息；还将win的号码也作为参数传进来
struct s3c_fb_win_variant *variant, ----> driver data中win的部份, 它是由fbdrv->win[win]作参数传过来的。
struct s3c_fb_win **res) ---> per window private data for each framebuffer，它里面含有指向FBI(fb_info)结构体的针指
{
struct fb_var_screeninfo *var;
struct fb_videomode *initmode;
struct s3c_fb_pd_win *windata; -->per window setup data, 也就是platform data中win的部份
struct s3c_fb_win *win;
struct fb_info *fbinfo;
int palette_size;
int ret;
init_waitqueue_head(&sfb->vsync_info.wait); ---> 初始化等待队列头
palette_size = variant->palette_sz * 4; ---> 调色板大小 ， 这方面内容我还不了解，为什么乘以4？
fbinfo = framebuffer_alloc(sizeof(struct s3c_fb_win) + palette_size * sizeof(u32), sfb->dev); ---> 重头戏来了， 分配fb_info结构体，返回一个fb_info结构体地址，这个结构体现在没什么内容，只赋值了par(win的起始地址)和device (父设备)两个变量，
windata = sfb->pdata->win[win_no]; --->windata指向 platform data中win的部份
initmode = &windata->win_mode;
...
win = fbinfo->par;
*res = win; --->par就是win的起始地址，现在把起始地址给*res，那么*res就是指向s3c_fb_win的指针
var = &fbinfo->var; ---> 现在fbinfo->var还是空的， 只是将地址给var而已
win->variant = *variant; --->将win的参数填进win->variant里
win->fbinfo = fbinfo; ---让win->fbinfo指向这个FBI结构实体
win->parent = sfb; ---win的parent是显示控制器，所以它指向sfb结构体>
win->windata = windata; --->让win->windata指向 platform data中win的部分
win->index = win_no;
win->palette_buffer = (u32 *)(win + 1); --->这个也不太理解?
ret = s3c_fb_alloc_memory(sfb, win); ----> 下面详解
...
/* setup the r/b/g positions for the window's palette */ --->设置调色板， 未理解
if (win->variant.palette_16bpp) {
/* Set RGB 5:6:5 as default */
win->palette.r.offset = 11;
win->palette.r.length = 5;
win->palette.g.offset = 5;
win->palette.g.length = 6;
win->palette.b.offset = 0;
win->palette.b.length = 5;
} else {
/* Set 8bpp or 8bpp and 1bit alpha */
win->palette.r.offset = 16;
win->palette.r.length = 8;
win->palette.g.offset = 8;
win->palette.g.length = 8;
win->palette.b.offset = 0;
win->palette.b.length = 8;
}
/* setup the initial video mode from the window */
fb_videomode_to_var(&fbinfo->var, initmode); --> 给FBI填上各个参数，此函数详见appendix
fbinfo->fix.type
= FB_TYPE_PACKED_PIXELS;
fbinfo->fix.accel= FB_ACCEL_NONE;
fbinfo->var.activate= FB_ACTIVATE_NOW;
fbinfo->var.vmode= FB_VMODE_NONINTERLACED;
fbinfo->var.bits_per_pixel = windata->default_bpp;
fbinfo->var.width= windata->width;
fbinfo->var.height= windata->height;
fbinfo->fbops
= &s3c_fb_ops; ---->对framebuffer的操作， 详见appendix
fbinfo->flags
= FBINFO_FLAG_DEFAULT;
fbinfo->pseudo_palette = &win->pseudo_palette;
/* prepare to actually start the framebuffer */
ret = s3c_fb_check_var(&fbinfo->var, fbinfo); -->检查可变参数 Framebuffer layer call to verify the given information and allow us to update various information depending on the hardware capabilities.
...
ret = fb_alloc_cmap(&fbinfo->cmap, win->variant.palette_sz, 1);
if (ret == 0)
fb_set_cmap(&fbinfo->cmap, fbinfo);
else
dev_err(sfb->dev, "failed to allocate fb cmap\n");
s3c_fb_set_par(fbinfo);
...
ret = register_framebuffer(fbinfo);
...
return 0;
} s3c_fb_probe_win结束
************************************************ s3c_fb_alloc_memory() ************************************************
static int __devinit s3c_fb_alloc_memory(struct s3c_fb *sfb,
struct s3c_fb_win *win)
{
struct s3c_fb_pd_win *windata = win->windata; ---> platform data中win的部分
unsigned int real_size, virt_size, size;
struct fb_info *fbi = win->fbinfo; ---> 让fbi指向FBI结构体
dma_addr_t map_dma;
...
real_size = windata->win_mode.xres * windata->win_mode.yres;
virt_size = windata->virtual_x * windata->virtual_y; ---> 虚拟size
size = (real_size > virt_size) ? real_size : virt_size; 一张framebuffer的大小，是按虚拟分辨率和实际分辨率两者中较大的来算的
size *= (windata->max_bpp > 16) ? 32 : windata->max_bpp;
size /= 8;
fbi->fix.smem_len = size;-----> 要分配的内存大小，
size = PAGE_ALIGN(size); ---- 页对齐
... 关于CMA 与ION部分省略
fbi->screen_base = dma_alloc_writecombine(sfb->dev, size, &map_dma, GFP_KERNEL); -->分配framebuffer的内存
memset(fbi->screen_base, 0x0, size); -->将framebuffer的内存清空为0
fbi->fix.smem_start = map_dma;
return 0;
} ---->结束
*********************************************************Appendix******************************************************
struct s3c_fb_variant {
unsigned int is_2443:1;
unsigned shortnr_windows;
unsigned int vidtcon;
unsigned shortwincon;
unsigned shortwinmap;
unsigned shortkeycon;
unsigned shortbuf_start;
unsigned shortbuf_end;
unsigned shortbuf_size;
unsigned shortosd;
unsigned shortosd_stride;
unsigned shortpalette[S3C_FB_MAX_WIN];
unsigned int has_prtcon:1;
unsigned int has_shadowcon:1;
unsigned int has_blendcon:1;
unsigned int has_alphacon:1;
unsigned int has_clksel:1;
unsigned int has_fixvclk:1;
}
/**
* fb_videomode_to_var - convert fb_videomode to fb_var_screeninfo
* @var: pointer to struct fb_var_screeninfo
* @mode: pointer to struct fb_videomode
*/
void fb_videomode_to_var(struct fb_var_screeninfo *var,
const struct fb_videomode *mode)
{
var->xres = mode->xres;
var->yres = mode->yres;
var->xres_virtual = mode->xres;
var->yres_virtual = mode->yres;
var->xoffset = 0;
var->yoffset = 0;
var->pixclock = mode->pixclock;
var->left_margin = mode->left_margin;
var->right_margin = mode->right_margin;
var->upper_margin = mode->upper_margin;
var->lower_margin = mode->lower_margin;
var->hsync_len = mode->hsync_len;
var->vsync_len = mode->vsync_len;
var->sync = mode->sync;
var->vmode = mode->vmode & FB_VMODE_MASK;
}
static struct fb_ops s3c_fb_ops = {
.owner = THIS_MODULE,
.fb_open = s3c_fb_open,
.fb_release = s3c_fb_release,
.fb_check_var = s3c_fb_check_var,
.fb_set_par = s3c_fb_set_par,
.fb_blank = s3c_fb_blank,
.fb_setcolreg = s3c_fb_setcolreg,
.fb_fillrect = cfb_fillrect,
.fb_copyarea = cfb_copyarea,
.fb_imageblit = cfb_imageblit,
.fb_pan_display= s3c_fb_pan_display,
.fb_ioctl = s3c_fb_ioctl,
};
/**
* struct s3c_fb_win - per window private data for each framebuffer.
* @windata: The platform data supplied for the window configuration.
* @parent: The hardware that this window is part of.
* @fbinfo: Pointer pack to the framebuffer info for this window.
* @varint: The variant information for this window.
* @palette_buffer: Buffer/cache to hold palette entries.
* @pseudo_palette: For use in TRUECOLOUR modes for entries 0..15/
* @index: The window number of this window.
* @palette: The bitfields for changing r/g/b into a hardware palette entry.
*/
struct s3c_fb_win {
struct s3c_fb_pd_win*windata;
struct s3c_fb *parent;
struct fb_info*fbinfo;
struct s3c_fb_palettepalette;
struct s3c_fb_win_variant variant;
u32 *palette_buffer;
u32 pseudo_palette[16];
unsigned int index;
#ifdef CONFIG_ION_EXYNOS
struct ion_handle *fb_ion_handle;
#endif
};
转载自：http://blog.csdn.net/lihaoweiV/article/details/6988718