S3C2440上LCD驱动(FrameBuffer)实例开发讲解（二）
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/*最后，注册这个帧缓冲设备fb_info到系统中, register_framebuffer定义在fb.h中在fbmem.c中实现*/
本文引用地址：https://www.eepw.com.cn/article/201608/295509.htmret = register_framebuffer(fbinfo);
if (ret < 0)
{
dev_err(&pdev->dev, "failed to register framebuffer device: %dn", ret);
goto err_video_nomem;
}
/*对设备文件系统的支持(对设备文件系统的理解请参阅：嵌入式Linux之我行——设备文件系统剖析与使用)
创建frambuffer设备文件，device_create_file定义在linux/device.h中*/
ret = device_create_file(&pdev->dev, &dev_attr_debug);
if (ret)
{
dev_err(&pdev->dev, "failed to add debug attributen");
}
return 0;
/*以下是上面错误处理的跳转点*/
err_nomem:
release_resource(fbvar->lcd_mem);
kfree(fbvar->lcd_mem);
err_nomap:
iounmap(fbvar->lcd_base);
err_noclk:
clk_disable(fbvar->lcd_clock);
clk_put(fbvar->lcd_clock);
err_noirq:
free_irq(fbvar->lcd_irq_no, fbvar);
err_nofb:
platform_set_drvdata(pdev, NULL);
framebuffer_release(fbinfo);
err_video_nomem:
my2440fb_unmap_video_memory(fbinfo);
return ret;
}
/*LCD中断服务程序*/
static irqreturn_t lcd_fb_irq(int irq, void *dev_id)
{
struct my2440fb_var *fbvar = dev_id;
void __iomem *lcd_irq_base;
unsigned long lcdirq;
/*LCD中断挂起寄存器基地址*/
lcd_irq_base = fbvar->lcd_base + S3C2410_LCDINTBASE;
/*读取LCD中断挂起寄存器的值*/
lcdirq = readl(lcd_irq_base + S3C24XX_LCDINTPND);
/*判断是否为中断挂起状态*/
if(lcdirq & S3C2410_LCDINT_FRSYNC)
{
/*填充调色板*/
if (fbvar->palette_ready)
{
my2440fb_write_palette(fbvar);
}
/*设置帧已插入中断请求*/
writel(S3C2410_LCDINT_FRSYNC, lcd_irq_base + S3C24XX_LCDINTPND);
writel(S3C2410_LCDINT_FRSYNC, lcd_irq_base + S3C24XX_LCDSRCPND);
}
return IRQ_HANDLED;
}
/*填充调色板*/
static void my2440fb_write_palette(struct my2440fb_var *fbvar)
{
unsigned int i;
void __iomem *regs = fbvar->lcd_base;
fbvar->palette_ready = 0;
for (i = 0; i < 256; i++)
{
unsigned long ent = fbvar->palette_buffer[i];
if (ent == PALETTE_BUFF_CLEAR)
{
continue;
}
writel(ent, regs + S3C2410_TFTPAL(i));
if (readw(regs + S3C2410_TFTPAL(i)) == ent)
{
fbvar->palette_buffer[i] = PALETTE_BUFF_CLEAR;
}
else
{
fbvar->palette_ready = 1;
}
}
}
/*LCD各寄存器进行初始化*/
static int my2440fb_init_registers(struct fb_info *fbinfo)
{
unsigned long flags;
void __iomem *tpal;
void __iomem *lpcsel;
/*从lcd_fb_probe探测函数设置的私有变量结构体中再获得LCD相关信息的数据*/
struct my2440fb_var *fbvar = fbinfo->par;
struct s3c2410fb_mach_info *mach_info = fbvar->dev->platform_data;
/*获得临时调色板寄存器基地址，S3C2410_TPAL宏定义在mach-s3c2410/include/mach/regs-lcd.h中。
注意对于lpcsel这是一个针对三星TFT屏的一个专用寄存器，如果用的不是三星的TFT屏应该不用管它。*/
tpal = fbvar->lcd_base + S3C2410_TPAL;
lpcsel = fbvar->lcd_base + S3C2410_LPCSEL;
/*在修改下面寄存器值之前先屏蔽中断，将中断状态保存到flags中*/
local_irq_save(flags);
/*这里就是在上一篇章中讲到的把IO端口C和D配置成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);
/*恢复被屏蔽的中断*/
local_irq_restore(flags);
writel(0x00, tpal);/*临时调色板寄存器使能禁止*/
writel(mach_info->lpcsel, lpcsel);/*在上一篇中讲到过，它是三星TFT屏的一个寄存器，这里可以不管*/
return 0;
}
/*该函数实现修改GPIO端口的值，注意第三个参数mask的作用是将要设置的寄存器值先清零*/
static inline void modify_gpio(void __iomem *reg, unsigned long set, unsigned long mask)
{
unsigned long tmp;
tmp = readl(reg) & ~mask;
writel(tmp | set, reg);
}
/*检查fb_info中的可变参数*/
static int my2440fb_check_var(struct fb_info *fbinfo)
{
unsigned i;
/*从lcd_fb_probe探测函数设置的平台数据中再获得LCD相关信息的数据*/
struct fb_var_screeninfo *var = &fbinfo->var;/*fb_info中的可变参数*/
struct my2440fb_var *fbvar = fbinfo->par;/*在lcd_fb_probe探测函数中设置的私有结构体数据*/
struct s3c2410fb_mach_info *mach_info = fbvar->dev->platform_data;/*LCD的配置结构体数据，这个配置结构体的赋值在上一篇章的"3. 帧缓冲设备作为平台设备"中*/
struct s3c2410fb_display *display = NULL;
struct s3c2410fb_display *default_display = mach_info->displays + mach_info->default_display;
int type = default_display->type;/*LCD的类型，看上一篇章的"3. 帧缓冲设备作为平台设备"中的type赋值是TFT类型*/
/*验证X/Y解析度*/
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)
{
return -EINVAL;
}
/*配置LCD配置寄存器1中的5-6位(配置成TFT类型)和配置LCD配置寄存器5*/
fbvar->regs.lcdcon1 = display->type;
fbvar->regs.lcdcon5 = display->lcdcon5;
/* 设置屏幕的虚拟解析像素和高度宽度 */
var->xres_virtual = display->xres;
var->yres_virtual = display->yres;
var->height = display->height;
var->width = display->width;
/* 设置时钟像素，行、帧切换值，水平同步、垂直同步长度值 */
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;
/*设置透明度*/
var->transp.offset = 0;
var->transp.length = 0;
/*根据色位模式(BPP)来设置可变参数中R、G、B的颜色位域。对于这些参数值的设置请参考CPU数据
手册中"显示缓冲区与显示点对应关系图"，例如在上一篇章中我就画出了8BPP和16BPP时的对应关系图*/
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:/* 8 bpp 332 */
if (display->type != S3C2410_LCDCON1_TFT)
{
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;
case 16:/* 16 bpp */
if (display->lcdcon5 & S3C2410_LCDCON5_FRM565)
{
/* 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 {
/* 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;
}
/*申请帧缓冲设备fb_info的显示缓冲区空间*/
static int __init my2440fb_map_video_memory(struct fb_info *fbinfo)
{
dma_addr_t map_dma;/*用于保存DMA缓冲区总线地址*/
struct my2440fb_var *fbvar = fbinfo->par;/*获得在lcd_fb_probe探测函数中设置的私有结构体数据*/
unsigned map_size = PAGE_ALIGN(fbinfo->fix.smem_len);/*获得FrameBuffer缓存的大小, PAGE_ALIGN定义在mm.h中*/
/*将分配的一个写合并DMA缓存区设置为LCD屏幕的虚拟地址(对于DMA请参考DMA相关知识)
dma_alloc_writecombine定义在arch/arm/mm/dma-mapping.c中*/
fbinfo->screen_base = dma_alloc_writecombine(fbvar->dev, map_size, &map_dma, GFP_KERNEL);
if (fbinfo->screen_base)
{
/*设置这片DMA缓存区的内容为空*/
memset(fbinfo->screen_base, 0x00, map_size);
/*将DMA缓冲区总线地址设成fb_info不可变参数中framebuffer缓存的开始位置*/
fbinfo->fix.smem_start = map_dma;
}
return fbinfo->screen_base ? 0 : -ENOMEM;
}
/*释放帧缓冲设备fb_info的显示缓冲区空间*/
static inline void my2440fb_unmap_video_memory(struct fb_info *fbinfo)
{
struct my2440fb_var *fbvar = fbinfo->par;
unsigned map_size = PAGE_ALIGN(fbinfo->fix.smem_len);
/*跟申请DMA的地方想对应*/
dma_free_writecombine(fbvar->dev, map_size, fbinfo->screen_base, fbinfo->fix.smem_start);
}
/*LCD FrameBuffer设备移除的实现，注意这里使用一个__devexit宏，和lcd_fb_probe接口函数相对应。
在Linux内核中，使用了大量不同的宏来标记具有不同作用的函数和数据结构，这些宏在include/linux/init.h
头文件中定义，编译器通过这些宏可以把代码优化放到合适的内存位置，以减少内存占用和提高内核效率。
__devinit、__devexit就是这些宏之一，在probe()和remove()函数中应该使用__devinit和__devexit宏。
又当remove()函数使用了__devexit宏时，则在驱动结构体中一定要使用__devexit_p宏来引用remove()，
所以在第①步中就用__devexit_p来引用lcd_fb_remove接口函数。*/
static int __devexit lcd_fb_remove(struct platform_device *pdev)
{
struct fb_info *fbinfo = platform_get_drvdata(pdev);
struct my2440fb_var *fbvar = fbinfo->par;
/*从系统中注销帧缓冲设备*/
unregister_framebuffer(fbinfo);
/*停止LCD控制器的工作*/
my2440fb_lcd_enable(fbvar, 0);
/*延迟一段时间，因为停止LCD控制器需要一点时间 */
msleep(1);
/*释放帧缓冲设备fb_info的显示缓冲区空间*/
my2440fb_unmap_video_memory(fbinfo);
/*将LCD平台数据清空和释放fb_info空间资源*/
platform_set_drvdata(pdev, NULL);
framebuffer_release(fbinfo);
/*释放中断资源*/
free_irq(fbvar->lcd_irq_no, fbvar);
/*释放时钟资源*/
if (fbvar->lcd_clock)
{
clk_disable(fbvar->lcd_clock);
clk_put(fbvar->lcd_clock);
fbvar->lcd_clock = NULL;
}
/*释放LCD IO空间映射的虚拟内存空间*/
iounmap(fbvar->lcd_base);
/*释放申请的LCD IO端口所占用的IO空间*/
release_resource(fbvar->lcd_mem);
kfree(fbvar->lcd_mem);
return 0;
}
/*停止LCD控制器的工作*/
static void my2440fb_lcd_enable(struct my2440fb_var *fbvar, int enable)
{
unsigned long flags;
/*在修改下面寄存器值之前先屏蔽中断，将中断状态保存到flags中*/
local_irq_save(flags);
if (enable)
{
fbvar->regs.lcdcon1 |= S3C2410_LCDCON1_ENVID;
}
else
{
fbvar->regs.lcdcon1 &= ~S3C2410_LCDCON1_ENVID;
}
writel(fbvar->regs.lcdcon1, fbvar->lcd_base + S3C2410_LCDCON1);
/*恢复被屏蔽的中断*/
local_irq_restore(flags);
}
/*对LCD FrameBuffer平台设备驱动电源管理的支持,CONFIG_PM这个宏定义在内核中*/
#ifdef CONFIG_PM
/*当配置内核时选上电源管理，则平台设备的驱动就支持挂起和恢复功能*/
static int lcd_fb_suspend(struct platform_device *pdev, pm_message_t state)
{
/*挂起LCD设备，注意这里挂起LCD时并没有保存LCD控制器的各种状态，所以在恢复后LCD不会继续显示挂起前的内容
若要继续显示挂起前的内容，则要在这里保存LCD控制器的各种状态，这里就不讲这个了，以后讲到电源管理再讲*/
struct fb_info *fbinfo = platform_get_drvdata(pdev);
struct my2440fb_var *fbvar = fbinfo->par;
/*停止LCD控制器的工作*/
my2440fb_lcd_enable(fbvar, 0);
msleep(1);
/*停止时钟*/
clk_disable(fbvar->lcd_clock);
return 0;
}
staticint lcd_fb_resume(struct platform_device *pdev)
{
/*恢复挂起的LCD设备*/
struct fb_info *fbinfo = platform_get_drvdata(pdev);
struct my2440fb_var *fbvar = fbinfo->par;
/*开启时钟*/
clk_enable(fbvar->lcd_clock);
/*初始化LCD控制器之前要延迟一段时间*/
msleep(1);
/*恢复时重新初始化LCD各寄存器*/
my2440fb_init_registers(fbinfo);
/*重新激活fb_info中所有的参数配置，该函数定义在第③步中再讲*/
my2440fb_activate_var(fbinfo);
/*正与挂起时讲到的那样，因为没保存挂起时LCD控制器的各种状态，
所以恢复后就让LCD显示空白，该函数定义也在第③步中再讲*/
my2440fb_blank(FB_BLANK_UNBLANK, fbinfo);
return 0;
}
#else
/*如果配置内核时没选上电源管理,则平台设备的驱动就不支持挂起和恢复功能,这两个函数也就无需实现了*/
#define lcd_fb_suspend NULL
#define lcd_fb_resume NULL
#endif
③、帧缓冲设备驱动对底层硬件操作的函数接口实现(即：my2440fb_ops的实现)：
/*Framebuffer底层硬件操作各接口函数*/
static struct fb_ops my2440fb_ops =
{
.owner = THIS_MODULE,
.fb_check_var = my2440fb_check_var,/*第②步中已实现*/
.fb_set_par = my2440fb_set_par,/*设置fb_info中的参数，主要是LCD的显示模式*/
.fb_blank = my2440fb_blank,/*显示空白(即：LCD开关控制)*/
.fb_setcolreg = my2440fb_setcolreg,/*设置颜色表*/
/*以下三个函数是可选的，主要是提供fb_console的支持，在内核中已经实现，这里直接调用即可*/
.fb_fillrect = cfb_fillrect,/*定义在drivers/video/cfbfillrect.c中*/
.fb_copyarea = cfb_copyarea,/*定义在drivers/video/cfbcopyarea.c中*/
.fb_imageblit = cfb_imageblit,/*定义在drivers/video/cfbimgblt.c中*/
};
/*设置fb_info中的参数，这里根据用户设置的可变参数var调整固定参数fix*/
static int my2440fb_set_par(struct fb_info *fbinfo)
{
/*获得fb_info中的可变参数*/
struct fb_var_screeninfo *var = &fbinfo->var;
/*判断可变参数中的色位模式，根据色位模式来设置色彩模式*/
switch (var->bits_per_pixel)
{
case 32:
case 16:
case 12:/*12BPP时，设置为真彩色(分成红、绿、蓝三基色)*/
fbinfo->fix.visual = FB_VISUAL_TRUECOLOR;
break;
case 1:/*1BPP时，设置为黑白色(分黑、白两种色，FB_VISUAL_MONO01代表黑，FB_VISUAL_MONO10代表白)*/
fbinfo->fix.visual = FB_VISUAL_MONO01;
break;
default:/*默认设置为伪彩色，采用索引颜色显示*/
fbinfo->fix.visual = FB_VISUAL_PSEUDOCOLOR;
break;
}
/*设置fb_info中固定参数中一行的字节数，公式：1行字节数=(1行像素个数*每像素位数BPP)/8 */
fbinfo->fix.line_length = (var->xres_virtual * var->bits_per_pixel) / 8;
/*修改以上参数后，重新激活fb_info中的参数配置(即：使修改后的参数在硬件上生效)*/
my2440fb_activate_var(fbinfo);
return 0;
}
/*重新激活fb_info中的参数配置*/
static void my2440fb_activate_var(struct fb_info *fbinfo)
{
/*获得结构体变量*/
struct my2440fb_var *fbvar = fbinfo->par;
void __iomem *regs = fbvar->lcd_base;
/*获得fb_info可变参数*/
struct fb_var_screeninfo *var = &fbinfo->var;
/*计算LCD控制寄存器1中的CLKVAL值, 根据数据手册中该寄存器的描述，计算公式如下：
* STN屏：VCLK = HCLK / (CLKVAL * 2), CLKVAL要求>= 2
* TFT屏：VCLK = HCLK / [(CLKVAL + 1) * 2], CLKVAL要求>= 0*/
int clkdiv = my2440fb_calc_pixclk(fbvar, var->pixclock) / 2;
/*获得屏幕的类型*/
int type = fbvar->regs.lcdcon1 & S3C2410_LCDCON1_TFT;
if (type == S3C2410_LCDCON1_TFT)
{
/*根据数据手册按照TFT屏的要求配置LCD控制寄存器1-5*/
my2440fb_config_tft_lcd_regs(fbinfo, &fbvar->regs);
--clkdiv;
if (clkdiv < 0)
{
clkdiv = 0;
}
}
else
{
/*根据数据手册按照STN屏的要求配置LCD控制寄存器1-5*/
my2440fb_config_stn_lcd_regs(fbinfo, &fbvar->regs);
if (clkdiv < 2)
{
clkdiv = 2;
}
}
/*设置计算的LCD控制寄存器1中的CLKVAL值*/
fbvar->regs.lcdcon1 |= S3C2410_LCDCON1_CLKVAL(clkdiv);
/*将各参数值写入LCD控制寄存器1-5中*/
writel(fbvar->regs.lcdcon1 & ~S3C2410_LCDCON1_ENVID, regs + S3C2410_LCDCON1);
writel(fbvar->regs.lcdcon2, regs + S3C2410_LCDCON2);
writel(fbvar->regs.lcdcon3, regs + S3C2410_LCDCON3);
writel(fbvar->regs.lcdcon4, regs + S3C2410_LCDCON4);
writel(fbvar->regs.lcdcon5, regs + S3C2410_LCDCON5);
/*配置帧缓冲起始地址寄存器1-3*/
my2440fb_set_lcdaddr(fbinfo);
fbvar->regs.lcdcon1 |= S3C2410_LCDCON1_ENVID,
writel(fbvar->regs.lcdcon1, regs + S3C2410_LCDCON1);
}
/*计算LCD控制寄存器1中的CLKVAL值*/
static unsigned int my2440fb_calc_pixclk(struct my2440fb_var *fbvar, unsigned long pixclk)
{
/*获得LCD的时钟*/
unsigned long clk = clk_get_rate(fbvar->lcd_clock);
/* 像素时钟单位是皮秒，而时钟的单位是赫兹，所以计算公式为：
* Hz -> picoseconds is / 10^-12
*/
unsigned long long div = (unsigned long long)clk * pixclk;
div >>= 12;/* div / 2^12 */
do_div(div, 625 * 625UL * 625); /* div / 5^12, do_div宏定义在asm/div64.h中*/
return div;
}
/*根据数据手册按照TFT屏的要求配置LCD控制寄存器1-5*/
static void my2440fb_config_tft_lcd_regs(const struct fb_info *fbinfo, struct s3c2410fb_hw *regs)
{
const struct my2440fb_var *fbvar = fbinfo->par;
const struct fb_var_screeninfo *var = &fbinfo->var;
/*根据色位模式设置LCD控制寄存器1和5，参考数据手册*/
switch (var->bits_per_pixel)
{
case 1:/*1BPP*/
regs->lcdcon1 |= S3C2410_LCDCON1_TFT1BPP;
break;
case 2:/*2BPP*/
regs->lcdcon1 |= S3C2410_LCDCON1_TFT2BPP;
break;
case 4:/*4BPP*/
regs->lcdcon1 |= S3C2410_LCDCON1_TFT4BPP;
break;
case 8:/*8BPP*/
regs->lcdcon1 |= S3C2410_LCDCON1_TFT8BPP;
regs->lcdcon5 |= S3C2410_LCDCON5_BSWP | S3C2410_LCDCON5_FRM565;
regs->lcdcon5 &= ~S3C2410_LCDCON5_HWSWP;
break;
case 16:/*16BPP*/
regs->lcdcon1 |= S3C2410_LCDCON1_TFT16BPP;
regs->lcdcon5 &= ~S3C2410_LCDCON5_BSWP;
regs->lcdcon5 |= S3C2410_LCDCON5_HWSWP;
break;
case 32:/*32BPP*/
regs->lcdcon1 |= S3C2410_LCDCON1_TFT24BPP;
regs->lcdcon5 &= ~(S3C2410_LCDCON5_BSWP | S3C2410_LCDCON5_HWSWP | S3C2410_LCDCON5_BPP24BL);
break;
default:/*无效的BPP*/
dev_err(fbvar->dev, "invalid bpp %dn", var->bits_per_pixel);
}
/*设置LCD配置寄存器2、3、4*/
regs->lcdcon2 = S3C2410_LCDCON2_LINEVAL(var->yres - 1) |
S3C2410_LCDCON2_VBPD(var->upper_margin - 1) |
S3C2410_LCDCON2_VFPD(var->lower_margin - 1) |
S3C2410_LCDCON2_VSPW(var->vsync_len - 1);
regs->lcdcon3 = S3C2410_LCDCON3_HBPD(var->right_margin - 1) |
S3C2410_LCDCON3_HFPD(var->left_margin - 1) |
S3C2410_LCDCON3_HOZVAL(var->xres - 1);
regs->lcdcon4 = S3C2410_LCDCON4_HSPW(var->hsync_len - 1);
}
/*根据数据手册按照STN屏的要求配置LCD控制寄存器1-5*/
static void my2440fb_config_stn_lcd_regs(const struct fb_info *fbinfo, struct s3c2410fb_hw *regs)
{
const struct my2440fb_var *fbvar = fbinfo->par;
const struct fb_var_screeninfo *var = &fbinfo->var;
int type = regs->lcdcon1 & ~S3C2410_LCDCON1_TFT;
int hs = var->xres >> 2;
unsigned wdly = (var->left_margin >> 4) - 1;
unsigned wlh = (var->hsync_len >> 4) - 1;
if (type != S3C2410_LCDCON1_STN4)
{
hs >>= 1;
}
/*根据色位模式设置LCD控制寄存器1，参考数据手册*/
switch (var->bits_per_pixel)
{
case 1:/*1BPP*/
regs->lcdcon1 |= S3C2410_LCDCON1_STN1BPP;
break;
case 2:/*2BPP*/
regs->lcdcon1 |= S3C2410_LCDCON1_STN2GREY;
break;
case 4:/*4BPP*/
regs->lcdcon1 |= S3C2410_LCDCON1_STN4GREY;
break;
case 8:/*8BPP*/
regs->lcdcon1 |= S3C2410_LCDCON1_STN8BPP;
hs *= 3;
break;
case 12:/*12BPP*/
regs->lcdcon1 |= S3C2410_LCDCON1_STN12BPP;
hs *= 3;
break;
default:/*无效的BPP*/
dev_err(fbvar->dev, "invalid bpp %dn", var->bits_per_pixel);
}
/*设置LCD配置寄存器2、3、4, 参考数据手册*/
if (wdly > 3) wdly = 3;
if (wlh > 3) wlh = 3;
regs->lcdcon2 = S3C2410_LCDCON2_LINEVAL(var->yres - 1);
regs->lcdcon3 = S3C2410_LCDCON3_WDLY(wdly) |
S3C2410_LCDCON3_LINEBLANK(var->right_margin / 8) |
S3C2410_LCDCON3_HOZVAL(hs - 1);
regs->lcdcon4 = S3C2410_LCDCON4_WLH(wlh);
}
/*配置帧缓冲起始地址寄存器1-3，参考数据手册*/
static void my2440fb_set_lcdaddr(struct fb_info *fbinfo)
{
unsigned long saddr1, saddr2, saddr3;
struct my2440fb_var *fbvar = fbinfo->par;
void __iomem *regs = fbvar->lcd_base;
saddr1 = fbinfo->fix.smem_start >> 1;
saddr2 = fbinfo->fix.smem_start;
saddr2 += fbinfo->fix.line_length * fbinfo->var.yres;
saddr2 >>= 1;
saddr3 = S3C2410_OFFSIZE(0) | S3C2410_PAGEWIDTH((fbinfo->fix.line_length / 2) & 0x3ff);
writel(saddr1, regs + S3C2410_LCDSADDR1);
writel(saddr2, regs + S3C2410_LCDSADDR2);
writel(saddr3, regs + S3C2410_LCDSADDR3);
}
/*显示空白，blank mode有5种模式，定义在fb.h中，是一个枚举*/
static int my2440fb_blank(int blank_mode, struct fb_info *fbinfo)
{
struct my2440fb_var *fbvar = fbinfo->par;
void __iomem *regs = fbvar->lcd_base;
/*根据显示空白的模式来设置LCD是开启还是停止*/
if (blank_mode == FB_BLANK_POWERDOWN)
{
my2440fb_lcd_enable(fbvar, 0);/*在第②步中定义*/
}
else
{
my2440fb_lcd_enable(fbvar, 1);/*在第②步中定义*/
}
/*根据显示空白的模式来控制临时调色板寄存器*/
if (blank_mode == FB_BLANK_UNBLANK)
{
/*临时调色板寄存器无效*/
writel(0x0, regs + S3C2410_TPAL);
}
else
{
/*临时调色板寄存器有效*/
writel(S3C2410_TPAL_EN, regs + S3C2410_TPAL);
}
return 0;
}
/*设置颜色表*/
static int my2440fb_setcolreg(unsigned regno,unsigned red,unsigned green,unsigned blue,unsigned transp,struct fb_info *fbinfo)
{
unsigned int val;
struct my2440fb_var *fbvar = fbinfo->par;
void __iomem *regs = fbvar->lcd_base;
switch (fbinfo->fix.visual)
{
case FB_VISUAL_TRUECOLOR:
/*真彩色*/
if (regno < 16)
{
u32 *pal = fbinfo->pseudo_palette;
val = chan_to_field(red, &fbinfo->var.red);
val |= chan_to_field(green, &fbinfo->var.green);
val |= chan_to_field(blue, &fbinfo->var.blue);
pal[regno] = val;
}
break;
case FB_VISUAL_PSEUDOCOLOR:
/*伪彩色*/
if (regno < 256)
{
val = (red >> 0) & 0xf800;
val |= (green >> 5) & 0x07e0;
val |= (blue >> 11) & 0x001f;
writel(val, regs + S3C2410_TFTPAL(regno));
/*修改调色板*/
schedule_palette_update(fbvar, regno, val);
}
break;
default:
return 1;
}
return 0;
}
static inline unsigned int chan_to_field(unsigned int chan, struct fb_bitfield *bf)
{
chan &= 0xffff;
chan >>= 16 - bf->length;
return chan << bf->offset;
}
/*修改调色板*/
static void schedule_palette_update(struct my2440fb_var *fbvar, unsigned int regno, unsigned int val)
{
unsigned long flags;
unsigned long irqen;
/*LCD中断挂起寄存器基地址*/
void __iomem *lcd_irq_base = fbvar->lcd_base + S3C2410_LCDINTBASE;
/*在修改中断寄存器值之前先屏蔽中断，将中断状态保存到flags中*/
local_irq_save(flags);
fbvar->palette_buffer[regno] = val;
/*判断调色板是否准备就像*/
if (!fbvar->palette_ready)
{
fbvar->palette_ready = 1;
/*使能中断屏蔽寄存器*/
irqen = readl(lcd_irq_base + S3C24XX_LCDINTMSK);
irqen &= ~S3C2410_LCDINT_FRSYNC;
writel(irqen, lcd_irq_base + S3C24XX_LCDINTMSK);
}
/*恢复被屏蔽的中断*/
local_irq_restore(flags);
}
五、从整体上再描述一下FrameBuffer设备驱动实例代码的结构：
1、在第①部分代码中主要做的事情有：
a.将LCD设备注册到系统平台设备中;
b.定义LCD平台设备结构体lcd_fb_driver。
2、在第②部分代码中主要做的事情有：
a.获取和设置LCD平台设备的各种资源;
b.分配fb_info结构体空间;
c.初始化fb_info结构体中的各参数;
d.初始化LCD控制器;
e.检查fb_info中可变参数;
f.申请帧缓冲设备的显示缓冲区空间;
g.注册fb_info。
a.实现对fb_info相关参数进行检查的硬件接口函数;
b.实现对LCD显示模式进行设定的硬件接口函数;
c.实现对LCD显示开关(空白)的硬件接口函数等。
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