TFT显示屏参数设置

1、在s3cfb_WXCAT43.c (linux2.6.28\drivers\video\samsung）文件中是有关具体显示器的设置。我们一段一段来看。

#include
#include
#include
#include
#include
#include
#include "s3cfb.h"

#define S3CFB_HFP 2/* front porch */
#define S3CFB_HSW 41/* hsync width */
#define S3CFB_HBP 2/* back porch */


#define S3CFB_VFP 2/* front porch */
#define S3CFB_VSW 10/* vsync width */
#define S3CFB_VBP 2/* back porch */


#define S3CFB_HRES 480/* horizon pixel  x resolition */
#define S3CFB_VRES 272/* line cnt       y resolution */


#define S3CFB_HRES_VIRTUAL 480/* horizon pixel  x resolition */
#define S3CFB_VRES_VIRTUAL 544/* line cnt       y resolution */


#define S3CFB_HRES_OSD 480/* horizon pixel  x resolition */
#define S3CFB_VRES_OSD 272/* line cnt       y resolution */


#define S3CFB_VFRAME_FREQ     60/* frame rate freq */


#define S3CFB_PIXEL_CLOCK (S3CFB_VFRAME_FREQ * (S3CFB_HFP + S3CFB_HSW + S3CFB_HBP + S3CFB_HRES) * (S3CFB_VFP + S3CFB_VSW + S3CFB_VBP + S3CFB_VRES))这个不太明白是干嘛用的？

那么上面这些参数的值是在那里得到的呢？那就要看具体的显示器的手册了。如下所示：

2、在这个文件中，还有两个函数，源码如下：

void s3cfb_init_hw(void)
{
printk(KERN_INFO "LCD TYPE :: LTE480WV will be initialized\n");


s3cfb_set_fimd_info();
s3cfb_set_gpio();
}

这个函数在s3cfb_init_fbinfo函数中被调用，其实就是在LCD对应的probe函数中被调用。

static void s3cfb_init_fbinfo(s3cfb_info_t *finfo, char *drv_name, int index)
{
int i = 0;
if (index == 0)
s3cfb_init_hw();

.........

｝

2.1、现在来分析s3cfb_set_fimd_info函数，源码如下：

static void s3cfb_set_fimd_info(void)
{
s3cfb_fimd.vidcon1 = S3C_VIDCON1_IHSYNC_INVERT | S3C_VIDCON1_IVSYNC_INVERT | S3C_VIDCON1_IVDEN_NORMAL;

其中有#define S3C_VIDCON1_IHSYNC_INVERT(1<<6)

      #define S3C_VIDCON1_IVSYNC_INVERT(1 << 5)

      #define S3C_VIDCON1_IVDEN_NORMAL(0<<4)

看下图：

         

         

       

 

        s3cfb_fimd.vidtcon0 = S3C_VIDTCON0_VBPD(S3CFB_VBP - 1) | S3C_VIDTCON0_VFPD(S3CFB_VFP - 1) | S3C_VIDTCON0_VSPW(S3CFB_VSW - 1);

        其中有： /* VIDEO Time Control 0 register - VIDTCON0 */
#define S3C_VIDTCON0_VBPDE(x) (((x)&0xFF)<<24)
#define S3C_VIDTCON0_VBPD(x) (((x)&0xFF)<<16)
#define S3C_VIDTCON0_VFPD(x) (((x)&0xFF)<<8)
#define S3C_VIDTCON0_VSPW(x) (((x)&0xFF)<<0)

 

        s3cfb_fimd.vidtcon1 = S3C_VIDTCON1_HBPD(S3CFB_HBP - 1) | S3C_VIDTCON1_HFPD(S3CFB_HFP - 1) | S3C_VIDTCON1_HSPW(S3CFB_HSW - 1);
s3cfb_fimd.vidtcon2 = S3C_VIDTCON2_LINEVAL(S3CFB_VRES - 1) | S3C_VIDTCON2_HOZVAL(S3CFB_HRES - 1);


s3cfb_fimd.vidosd0a = S3C_VIDOSDxA_OSD_LTX_F(0) | S3C_VIDOSDxA_OSD_LTY_F(0);
s3cfb_fimd.vidosd0b = S3C_VIDOSDxB_OSD_RBX_F(S3CFB_HRES - 1) | S3C_VIDOSDxB_OSD_RBY_F(S3CFB_VRES - 1);


s3cfb_fimd.vidosd1a = S3C_VIDOSDxA_OSD_LTX_F(0) | S3C_VIDOSDxA_OSD_LTY_F(0);
s3cfb_fimd.vidosd1b = S3C_VIDOSDxB_OSD_RBX_F(S3CFB_HRES_OSD - 1) | S3C_VIDOSDxB_OSD_RBY_F(S3CFB_VRES_OSD - 1);

这些也和上面一样的，对照手册，设置就可以了。


s3cfb_fimd.width = S3CFB_HRES;  屏幕的大小信息
s3cfb_fimd.height = S3CFB_VRES;
s3cfb_fimd.xres = S3CFB_HRES;
s3cfb_fimd.yres = S3CFB_VRES;


#if defined(CONFIG_FB_S3C_VIRTUAL_SCREEN)  与虚拟屏有关
s3cfb_fimd.xres_virtual = S3CFB_HRES_VIRTUAL;
s3cfb_fimd.yres_virtual = S3CFB_VRES_VIRTUAL;
#else
s3cfb_fimd.xres_virtual = S3CFB_HRES;
s3cfb_fimd.yres_virtual = S3CFB_VRES;
#endif


s3cfb_fimd.osd_width = S3CFB_HRES_OSD; 还记得上一篇中OSD的含义吗？
s3cfb_fimd.osd_height = S3CFB_VRES_OSD;
s3cfb_fimd.osd_xres = S3CFB_HRES_OSD;
s3cfb_fimd.osd_yres = S3CFB_VRES_OSD;


s3cfb_fimd.osd_xres_virtual = S3CFB_HRES_OSD;
s3cfb_fimd.osd_yres_virtual = S3CFB_VRES_OSD;


s3cfb_fimd.pixclock = S3CFB_PIXEL_CLOCK;


s3cfb_fimd.hsync_len = S3CFB_HSW;
s3cfb_fimd.vsync_len = S3CFB_VSW;
s3cfb_fimd.left_margin = S3CFB_HFP;
s3cfb_fimd.upper_margin = S3CFB_VFP;
s3cfb_fimd.right_margin = S3CFB_HBP;
s3cfb_fimd.lower_margin = S3CFB_VBP;
}

2.2、接着分析另外一个函数s3cfb_set_gpio()，这个函数的源码如下：

int s3cfb_set_gpio(void)
{
unsigned long val;
int i, err;


/* Must be '0' for Normal-path instead of By-pass */
writel(0x0, S3C_HOSTIFB_MIFPCON);

其中有：#define S3C_HOSTIFB_MIFPCONS3C_HOSTIFBREG(0x800C)

       #define S3C_HOSTIFAREG(x)((x) + S3C64XX_VA_HOSTIFA)

同时在s3c6410的手册上有这么一句话：

Caution 1: In normal display mode, SEL_BYPASS@ MIFPCON (0x7410_800C) register must be set “0”.


/* enable clock to LCD */使能LCD的时钟
val = readl(S3C_HCLK_GATE);
val |= S3C_CLKCON_HCLK_LCD;
writel(val, S3C_HCLK_GATE);


/* phantom */也和时钟有关
val = readl(S3C_SCLK_GATE);
val |= (1<<14);
writel(val, S3C_SCLK_GATE);
/* ------- */


/* select TFT LCD type (RGB I/F) */设置RGB的数据格式
val = readl(S3C64XX_SPC_BASE);
val &= ~0x3;
val |= (1 << 0);
writel(val, S3C64XX_SPC_BASE);

其中有：#define S3C64XX_SPC_BASE(S3C64XX_VA_GPIO + 0x01A0)

这个参数的设置，和具体的TFT屏有关，在TFT屏的手册中有：24bit RGB Interface

/* VD */主要是芯片引脚的设置，看下图：不过你可能对s3c_gpio_cfgpin函数不明白，它是怎样实现的，我在以前的写的一篇博客中有说明，你可以去查看，本篇后面我会给出链接地址。
for (i = 0; i < 16; i++)
s3c_gpio_cfgpin(S3C64XX_GPI(i), S3C_GPIO_SFN(2));


for (i = 0; i < 12; i++)
s3c_gpio_cfgpin(S3C64XX_GPJ(i), S3C_GPIO_SFN(2));

#ifndef CONFIG_BACKLIGHT_PWM  
/* backlight ON */
//printk("oPEN LCD BACKLIGHT1.\n");   和LCD背光灯有关，看下面的图：

 

          
 

 

        if (gpio_is_valid(S3C64XX_GPF(14))) {              //NOTE: orign GPF15 here
err = gpio_request(S3C64XX_GPF(14), "GPF");


if (err) {
printk(KERN_ERR "failed to request GPF for "
"lcd backlight control\n");
return err;
}


gpio_direction_output(S3C64XX_GPF(14), 1);
gpio_set_value(S3C64XX_GPF(14), 1);
}
#endif
//printk("oPEN LCD BACKLIGHT2.\n");
         if (gpio_is_valid(S3C64XX_GPE(0))) {
err = gpio_request(S3C64XX_GPE(0), "GPE");


if (err) {
printk(KERN_ERR "failed to request GPE for "
"lcd reset control\n");
return err;
}


gpio_direction_output(S3C64XX_GPE(0), 1);
}
gpio_set_value(S3C64XX_GPE(0), 1);
gpio_free(S3C64XX_GPE(0));


/* module reset */
/*if (gpio_is_valid(S3C64XX_GPN(5))) {
err = gpio_request(S3C64XX_GPN(5), "GPN");


if (err) {
printk(KERN_ERR "failed to request GPN for "
"lcd reset control\n");
return err;
}


gpio_direction_output(S3C64XX_GPN(5), 1);
}


mdelay(100);


gpio_set_value(S3C64XX_GPN(5), 0);
mdelay(10);


gpio_set_value(S3C64XX_GPN(5), 1);
mdelay(10);
*/
#ifndef CONFIG_BACKLIGHT_PWM
gpio_free(S3C64XX_GPF(14));
#endif

//gpio_free(S3C64XX_GPN(5));


return 0;
}
在这个函数出现了许多对GPIO操作的函数，如：s3c_gpio_cfgpin，gpio_direction_output等等，你可能不熟悉这些，下面这个地址链接对这些讲解的很详细。

http://www.linuxidc.com/Linux/2012-05/60224.htm

 

在前几篇中对LCD平台设备所对应的probe函数进行分析时，对一些函数没有进行详细的分析，因为当时主要是为了突出probe函数的整体结构，现在我们对一些函数进行再次详细点的分析。

（1）、

void s3cfb_pre_init(void)
{
/* initialize the fimd specific */
s3cfb_fimd.vidintcon0 &= ~S3C_VIDINTCON0_FRAMESEL0_MASK;
s3cfb_fimd.vidintcon0 |= S3C_VIDINTCON0_FRAMESEL0_VSYNC;
s3cfb_fimd.vidintcon0 |= S3C_VIDINTCON0_INTFRMEN_ENABLE;


writel(s3cfb_fimd.vidintcon0, S3C_VIDINTCON0);
}

这个函数主要是对VIDINTCON0寄存器的操作，这个寄存器和中断有关。具体的对那些位进行操作和怎样操作，查看手册就可以了。

（2）、

这个函数的主要作用是填充s3cfb_info_t 结构体中的成员。
static void s3cfb_init_fbinfo(s3cfb_info_t *finfo, char *drv_name, int index)
{
int i = 0;


if (index == 0)
s3cfb_init_hw();这个函数我们在上一篇博客中详细讲了，主要是根据具体TFT屏幕的参数对LCD控制寄存器的一些寄存器进行设置，还有对全局量s3cfb_fimd结构体的填充。


strcpy(finfo->fb.fix.id, drv_name);


finfo->win_id = index;  第几层窗口

下面这些代码都是填充不可变参数，这些参数的具体含义，大家可以参考另一篇博客，至于为什么要这样设置，那大家就要自己去查了。

finfo->fb.fix.type = FB_TYPE_PACKED_PIXELS;
finfo->fb.fix.type_aux = 0;
finfo->fb.fix.xpanstep = 0;
finfo->fb.fix.ypanstep = 1;
finfo->fb.fix.ywrapstep = 0;
finfo->fb.fix.accel = FB_ACCEL_NONE;


finfo->fb.fbops = &s3cfb_ops;  指向fb的操作函数集
finfo->fb.flags= FBINFO_FLAG_DEFAULT;


finfo->fb.pseudo_palette = &finfo->pseudo_pal;

填充可变参数结构，同样。
finfo->fb.var.nonstd = 0;
finfo->fb.var.activate = FB_ACTIVATE_NOW;
finfo->fb.var.accel_flags = 0;
finfo->fb.var.vmode = FB_VMODE_NONINTERLACED;


finfo->fb.var.xoffset = s3cfb_fimd.xoffset;
finfo->fb.var.yoffset = s3cfb_fimd.yoffset;


if (index == 0) {    第一层窗口时的设置
finfo->fb.var.height = s3cfb_fimd.height;
finfo->fb.var.width = s3cfb_fimd.width;


finfo->fb.var.xres = s3cfb_fimd.xres;
finfo->fb.var.yres = s3cfb_fimd.yres;


finfo->fb.var.xres_virtual = s3cfb_fimd.xres_virtual;
finfo->fb.var.yres_virtual = s3cfb_fimd.yres_virtual;
} else {    其它层窗口的设置
finfo->fb.var.height = s3cfb_fimd.osd_height;
finfo->fb.var.width = s3cfb_fimd.osd_width;


finfo->fb.var.xres = s3cfb_fimd.osd_xres;
finfo->fb.var.yres = s3cfb_fimd.osd_yres;


finfo->fb.var.xres_virtual = s3cfb_fimd.osd_xres_virtual;
finfo->fb.var.yres_virtual = s3cfb_fimd.osd_yres_virtual;
}


finfo->fb.var.bits_per_pixel = s3cfb_fimd.bpp;
        finfo->fb.var.pixclock = s3cfb_fimd.pixclock;
finfo->fb.var.hsync_len = s3cfb_fimd.hsync_len;
finfo->fb.var.left_margin = s3cfb_fimd.left_margin;
finfo->fb.var.right_margin = s3cfb_fimd.right_margin;
finfo->fb.var.vsync_len = s3cfb_fimd.vsync_len;
finfo->fb.var.upper_margin = s3cfb_fimd.upper_margin;
finfo->fb.var.lower_margin = s3cfb_fimd.lower_margin;
finfo->fb.var.sync = s3cfb_fimd.sync;
finfo->fb.var.grayscale = s3cfb_fimd.cmap_grayscale;


finfo->fb.fix.smem_len = finfo->fb.var.xres_virtual * finfo->fb.var.yres_virtual * s3cfb_fimd.bytes_per_pixel;
finfo->fb.fix.line_length = finfo->fb.var.width * s3cfb_fimd.bytes_per_pixel;


#if !defined(CONFIG_FB_S3C_VIRTUAL_SCREEN)


#if defined(CONFIG_FB_S3C_DOUBLE_BUFFERING)
if (index < 2)
finfo->fb.fix.smem_len *= 2;
#else
/*
* Some systems(ex. DirectFB) use FB0 memory as a video memory.
* You can modify the size of multiple.
*/
if (index == 0)
finfo->fb.fix.smem_len *= 5;
#endif


#endif

for (i = 0; i < 256; i++)
finfo->palette_buffer[i] = S3CFB_PALETTE_BUFF_CLEAR;  清除缓冲区
}

（3）、
这个函数用来为显存分配内存
static int __init s3cfb_map_video_memory(s3cfb_info_t *fbi)
{
DPRINTK("map_video_memory(fbi=%p)\n", fbi);


fbi->map_size_f1 = PAGE_ALIGN(fbi->fb.fix.smem_len);
fbi->map_cpu_f1 = dma_alloc_writecombine(fbi->dev, fbi->map_size_f1, &fbi->map_dma_f1, GFP_KERNEL);

    //因为系统采用DMA来搬移显示数据,所以使用dma_alloc_writecombine来分配一段内存区域
fbi->map_size_f1 = fbi->fb.fix.smem_len;


if (fbi->map_cpu_f1) {   如果分配成功，对s3cfb_info_t结构体的某些成员，进行填充
/* prevent initial garbage on screen */
printk("Window[%d] - FB1: map_video_memory: clear %p:%08x\n",
fbi->win_id, fbi->map_cpu_f1, fbi->map_size_f1);
memset(fbi->map_cpu_f1, 0xf0, fbi->map_size_f1);


fbi->screen_dma_f1 = fbi->map_dma_f1;
fbi->fb.screen_base = fbi->map_cpu_f1;
fbi->fb.fix.smem_start = fbi->screen_dma_f1;


printk("            FB1: map_video_memory: dma=%08x cpu=%p size=%08x\n",
fbi->map_dma_f1, fbi->map_cpu_f1, fbi->fb.fix.smem_len);
}


if (!fbi->map_cpu_f1)
return -ENOMEM;


#if defined(CONFIG_FB_S3C_DOUBLE_BUFFERING)
if (fbi->win_id < 2 && fbi->map_cpu_f1) {
fbi->map_size_f2 = (fbi->fb.fix.smem_len / 2);
fbi->map_cpu_f2 = fbi->map_cpu_f1 + fbi->map_size_f2;
fbi->map_dma_f2 = fbi->map_dma_f1 + fbi->map_size_f2;


/* prevent initial garbage on screen */
printk("Window[%d] - FB2: map_video_memory: clear %p:%08x\n",
fbi->win_id, fbi->map_cpu_f2, fbi->map_size_f2);


fbi->screen_dma_f2 = fbi->map_dma_f2;


printk("            FB2: map_video_memory: dma=%08x cpu=%p size=%08x\n",
fbi->map_dma_f2, fbi->map_cpu_f2, fbi->map_size_f2);
}
#endif


if (s3cfb_fimd.map_video_memory)
(s3cfb_fimd.map_video_memory)(fbi);


return 0;
}

（4）、

/*
 * s3cfb_check_var():
 * Get the video params out of 'var'. If a value doesn't fit, round it up,
 * if it's too big, return -EINVAL.
 *
 */ 此函数检查fb_info中的可变参数。
static int s3cfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
{
s3cfb_info_t *fbi = (s3cfb_info_t *) info;


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


switch (var->bits_per_pixel) {    BPP，每像素的位数
case 8:  8BPP
var->red = s3cfb_rgb_8.red;
var->green = s3cfb_rgb_8.green;
var->blue = s3cfb_rgb_8.blue;
var->transp = s3cfb_rgb_8.transp;
s3cfb_fimd.bytes_per_pixel = 1;
break;
其实上面这些red、green等都是 fb_bitfield 的结构体，这个结构体描述了每一像素显示缓冲区的组织方式，在第一篇博客说framebuffer中说过了。

struct fb_bitfield {
__u32 offset;  /* beginning of bitfield */
__u32 length;  /* length of bitfield */
__u32 msb_right;/* != 0 : Most significant bit is */ 
/* right */ 
};

其实在S3cfb.h (linux2.6.28\drivers\video\samsung)文件中还有如下定义：

typedef struct {
struct fb_bitfield red;
struct fb_bitfield green;
struct fb_bitfield blue;
struct fb_bitfield transp;
} s3cfb_rgb_t;


const static s3cfb_rgb_t s3cfb_rgb_8 = {
.red    = {.offset = 0,  .length = 8,},
.green  = {.offset = 0,  .length = 8,},
.blue   = {.offset = 0,  .length = 8,},
.transp = {.offset = 0,  .length = 0,},
};


const static s3cfb_rgb_t s3cfb_rgb_16 = {
.red    = {.offset = 11, .length = 5,},
.green  = {.offset = 5,  .length = 6,},
.blue   = {.offset = 0,  .length = 5,},
.transp = {.offset = 0,  .length = 0,},
};


const static s3cfb_rgb_t s3cfb_rgb_24 = {
.red    = {.offset = 16, .length = 8,},
.green  = {.offset = 8,  .length = 8,},
.blue   = {.offset = 0,  .length = 8,},
.transp = {.offset = 0,  .length = 0,},
};


const static s3cfb_rgb_t s3cfb_rgb_28 = {
.red    = {.offset = 16, .length = 8,},
.green  = {.offset = 8,  .length = 8,},
.blue   = {.offset = 0,  .length = 8,},
.transp = {.offset = 24,  .length = 4,},
};


const static s3cfb_rgb_t s3cfb_rgb_32 = {
.red    = {.offset = 16, .length = 8,},
.green  = {.offset = 8,  .length = 8,},
.blue   = {.offset = 0,  .length = 8,},
.transp = {.offset = 24, .length = 8,},
};
下面也是一样的，看到这些，我想一切尽在不言中了吧？
case 16:
var->red = s3cfb_rgb_16.red;
var->green = s3cfb_rgb_16.green;
var->blue = s3cfb_rgb_16.blue;
var->transp = s3cfb_rgb_16.transp;
s3cfb_fimd.bytes_per_pixel = 2;
break;


case 24:
var->red = s3cfb_rgb_24.red;
var->green = s3cfb_rgb_24.green;
var->blue = s3cfb_rgb_24.blue;
var->transp = s3cfb_rgb_24.transp;
s3cfb_fimd.bytes_per_pixel = 4;
break;


case 28:
var->red = s3cfb_rgb_28.red;
var->green = s3cfb_rgb_28.green;
var->blue = s3cfb_rgb_28.blue;
var->transp = s3cfb_rgb_28.transp;
s3cfb_fimd.bytes_per_pixel = 4;
break;


case 32:
var->red = s3cfb_rgb_32.red;
var->green = s3cfb_rgb_32.green;
var->blue = s3cfb_rgb_32.blue;
var->transp = s3cfb_rgb_32.transp;
s3cfb_fimd.bytes_per_pixel = 4;
break;
}


/* WIN0 cannot support alpha channel. */  窗口0不支持透明度模式
if( (fbi->win_id == 0) && (var->bits_per_pixel == 28) ){
var->transp.length = 0;
}

return 0;
}

当然，说是详细说这些函数，其实还不是特别详细，因为这涉及到太多的东西，但我们弄明白了这些函数的大致作用，至于具体参数的设置，就需要进一步分析了。