关键词：androidLCD TFTSN75LVDS83B TTL-LVDSLCD电压背光电压

平台信息:
内核：linux2.6/linux3.0
系统：android/android4.0
平台：samsungexynos4210、exynos4412、exynos5250

作者：xubin341719(欢迎转载，请注明作者)

欢迎指正错误，共同学习、共同进步！！

下载链接：LCD规格书（404份），之前工作用用到的、LCD规格书00 、LCD规格书01 、 LCD测试图片，彩条灰阶等

Android LCD(一)：LCD基本原理篇

Android LCD(二)：LCD常用接口原理篇

Android LCD(三)：Samsung LCD接口篇

Android LCD(四)：LCD驱动调试篇


这篇我们以一个实例来说明,Samsung Exynos4412搭配TTL转LVDS芯片SN75LVDS83B、LVDS接口LCD为例说明。从硬件接口、驱动配置、背光PWM调节三部分说明。

下载：SN75LVDS83B规格书

一、LCD接口原理以及硬件电路

Samsung Exynos4412、SN75LVDS83B、LVDS接口LCD（24bit）为例说明，三者的关系如下：


如上图所示，我们在应用中我，主控（Exynos4412）输出RGB信号到TFT-LCD大体经过三部分：

（1）、标号1部分，主控（Exynos4412）输出TTL信号；

（2）、标号2部分，TTL（RGB）-LVDS转换芯片SN75LVDS83B,把ＴＴＬ信号转换成LVDS信号，传输到显示器的LVDS接收端；这部分有SN75LVDS83B编码芯片自动完成，所以我们不需要程序控制；

（3）、标号3部分，分两个小部分，LVDS转换成TTL，TFT-LCD显示部分；我们前面说过，TFT-LCD其实只识别TTL信号，所以要有一个转换的过程，先把LVDS信号转换、解码成TTL信号，在TFT-LCD上显示。

有上面的过程，其实我们关心调试的部分只有标号1部分到标号2部分，后面标号2到标号3的部分是自动完成的，不需要我们程序上控制，把标号2部分、标号3部分合并：


标号二部分可以理解为一个TTL（RGB）接口的LCD,如下图所示，标号一部分就是主控信号输出端，简化图如下所示:


其实最简单的做法就是找个TTL接口的TFT-LCD，这样直接接上就可以。下面我们看下硬件上的电路连接：这个和我们上篇用的相同。


有上面图可以看出：硬件连接

网络标号

说明

管脚

XvVD[0：23]

XvVDEN

XvVSYNC

XvHSYNC

XvVCLK

RGB数据、使能、行场同步、时钟信号

这是TTL信号输出

LCD_PWM

调节背光

XpwmTOUT1/LCD_PWM/GPD0_1

LCD_LED_EN

LCD电压（TFT电压）使能

GPC1_2

LED_BL_EN

LED背光使能

GPL2_4

上面可分为几部分，电路连接部分分析：

（1）、TTL数据部分

这张图有木有烂掉呀，哈哈，就是这些数据了。还有有木有想起来摄像头的数据（ITU接口）也是这样的？？其实视频这种信号的原理是通用的，所以LCD通了，摄像头也就知道怎么回事了。


（2）、PWM背光调节

PWM其实也是芯片的一个功能模块，看到他的管脚就是一个复用脚XpwmTOUT1/LCD_PWM/GPD0_1。上一篇我们粗略的了解了PWM，就是用到这里。但是有一个疑问，PWM是调节背光电压的，背光电压一般都是12V以上的，我们PWM只有0-3V的样子，Exynos4412的IO只有1.8V。怎么调节电压？？？


其实这个PWM只是给LCD上PWM控制部分，真正的电压还是通过LCD控制板上的电路实现。

（3）、LED背光、LCD电压控制

a、背光：LED+

我们可以看到这个升压电路，通过SY7208把VBATT升压到18V，供给LED背光。SY7208最大升压26V。这个电压是提供给我们前面讲的背光的，也就是CCFL灯管或者LED背光组的电压。


b、LCD电压

这个电压也就是给你我们TFT阵列组用的，控制LCD液晶元素。

这部分电路分析完成，我们就有比较清晰的思路出，要一个LCD工作，要完成两部分内容：LCD上电控制，背光、LCD电压；信号输出。

二、LCD 驱动部分调试

LCD这部分，像上篇我们说的frambuffer这些部分一般平台都是可以用的，除非你是芯片厂的要写这部分。一般公司拿到的demo板子这部分都是通的，只是针对自己的lCD换一些参数。

下面我们针对三星平台我们调试LCD的时时候程序方面的改动：

1、屏参数的配置

/kernel/drivers/video/Samsung/s3cfb_wa101s.c

[cpp] view plain copy print ?
  1. staticstructs3cfb_lcdwa101={
  3. .width=1280,//LCD分辨率宽1280
  4. .height=800,//LCD分辨率高800
  5. .bpp=24,//CLD数据位24bit
  6. .freq=60,//LCD像素时钟60MHz
  7. .timing={//LCDporch无效值
  8. .h_fp=70,
  9. .h_bp=70,
  10. .h_sw=20,
  12. .v_fp=10,
  13. .v_fpe=0,
  14. .v_bp=10,
  15. .v_bpe=0,
  16. .v_sw=3,
  17. },
  19. .polarity={//时钟、行场的极性；
  20. .rise_vclk=1,
  21. .inv_hsync=1,
  22. .inv_vsync=1,
  23. .inv_vden=0,
  24. },
  25. };
  26. /*nameshouldbefixedas's3cfb_set_lcd_info'*/
  27. voids3cfb_set_lcd_info(structs3cfb_global*ctrl)//初始化结构体
  28. {
  29. wa101.init_ldi=NULL;
  30. ctrl->lcd=&wa101;
  31. #endif
  32. }
static struct s3cfb_lcd wa101 = {.width= 1280,//LCD 分辨率宽1280.height = 800, //LCD 分辨率高 800.bpp= 24,//CLD 数据位 24bit.freq= 60,//LCD 像素时钟 60MHz.timing = {//LCD porch无效值.h_fp= 70,.h_bp= 70,.h_sw= 20,.v_fp= 10,.v_fpe= 0,.v_bp= 10,.v_bpe= 0,.v_sw= 3,},.polarity = {//时钟、行场的极性；.rise_vclk= 1,.inv_hsync= 1,.inv_vsync= 1,.inv_vden= 0,},};/* name should be fixed as 's3cfb_set_lcd_info' */void s3cfb_set_lcd_info(struct s3cfb_global *ctrl)//初始化结构体{wa101.init_ldi = NULL;ctrl->lcd = &wa101;#endif}
还能想起上一篇的如何阅读规格书中的那些参数不，把这些填入就可以。
2、数据管脚初始化


kernel/arch/arm/mach-exynos/setup-fb-s5p.c

[cpp] view plain copy print ?
  1. voids3cfb_cfg_gpio(structplatform_device*pdev)
  2. {
  3. s3cfb_gpio_setup_24bpp(EXYNOS4_GPF0(0),8,S3C_GPIO_SFN(2),S5P_GPIO_DRVSTR_LV4);
  4. s3cfb_gpio_setup_24bpp(EXYNOS4_GPF1(0),8,S3C_GPIO_SFN(2),S5P_GPIO_DRVSTR_LV4);
  5. s3cfb_gpio_setup_24bpp(EXYNOS4_GPF2(0),8,S3C_GPIO_SFN(2),S5P_GPIO_DRVSTR_LV4);
  6. s3cfb_gpio_setup_24bpp(EXYNOS4_GPF3(0),4,S3C_GPIO_SFN(2),S5P_GPIO_DRVSTR_LV4);
  7. }
void s3cfb_cfg_gpio(struct platform_device *pdev){s3cfb_gpio_setup_24bpp(EXYNOS4_GPF0(0), 8, S3C_GPIO_SFN(2), S5P_GPIO_DRVSTR_LV4);s3cfb_gpio_setup_24bpp(EXYNOS4_GPF1(0), 8, S3C_GPIO_SFN(2), S5P_GPIO_DRVSTR_LV4);s3cfb_gpio_setup_24bpp(EXYNOS4_GPF2(0), 8, S3C_GPIO_SFN(2), S5P_GPIO_DRVSTR_LV4);s3cfb_gpio_setup_24bpp(EXYNOS4_GPF3(0), 4, S3C_GPIO_SFN(2), S5P_GPIO_DRVSTR_LV4);}

LCD 数据脚初始化，驱动能力设为最高S5P_GPIO_DRVSTR_LV4；管脚驱动能力，S5P_GPIO_DRVSTR_LV1-4四个等级选择。

3、时钟控制部分

kernel/arch/arm/mach-exynos/setup-fb-s5p.c

[cpp] view plain copy print ?
  1. ints3cfb_clk_on(structplatform_device*pdev,structclk**s3cfb_clk)
  2. {
  3. structclk*sclk=NULL;
  4. structclk*mout_mpll=NULL;
  5. structclk*lcd_clk=NULL;
  7. u32rate=0;
  8. intret=0;
  10. lcd_clk=clk_get(&pdev->dev,"lcd");
  11. if(IS_ERR(lcd_clk)){
  12. dev_err(&pdev->dev,"failedtogetoperationclkforfimd\n");
  13. gotoerr_clk0;
  14. }
  16. ret=clk_enable(lcd_clk);
  17. if(ret<0){
  18. dev_err(&pdev->dev,"failedtoclk_enableoflcdclkforfimd\n");
  19. gotoerr_clk0;
  20. }
  21. clk_put(lcd_clk);
  23. sclk=clk_get(&pdev->dev,"sclk_fimd");
  24. if(IS_ERR(sclk)){
  25. dev_err(&pdev->dev,"failedtogetsclkforfimd\n");
  26. gotoerr_clk1;
  27. }
  29. if(soc_is_exynos4210())
  30. mout_mpll=clk_get(&pdev->dev,"mout_mpll");
  31. else
  32. mout_mpll=clk_get(&pdev->dev,"mout_mpll_user");
  34. if(IS_ERR(mout_mpll)){
  35. dev_err(&pdev->dev,"failedtogetmout_mpllforfimd\n");
  36. gotoerr_clk2;
  37. }
  39. ret=clk_set_parent(sclk,mout_mpll);
  40. if(ret<0){
  41. dev_err(&pdev->dev,"failedtoclk_set_parentforfimd\n");
  42. gotoerr_clk2;
  43. }
  45. if((soc_is_exynos4412())&&(samsung_rev()>=EXYNOS4412_REV_2_0))
  46. ret=clk_set_rate(sclk,880000000);
  47. else
  48. ret=clk_set_rate(sclk,800000000);
  49. if(ret<0){
  50. dev_err(&pdev->dev,"failedtoclk_set_rateofsclkforfimd\n");
  51. gotoerr_clk2;
  52. }
  53. dev_dbg(&pdev->dev,"setfimdsclkrateto%d\n",rate);
  55. clk_put(mout_mpll);
  57. ret=clk_enable(sclk);
  58. if(ret<0){
  59. dev_err(&pdev->dev,"failedtoclk_enableofsclkforfimd\n");
  60. gotoerr_clk2;
  61. }
  63. *s3cfb_clk=sclk;
  65. return0;
  67. err_clk2:
  68. clk_put(mout_mpll);
  69. err_clk1:
  70. clk_put(sclk);
  71. err_clk0:
  72. clk_put(lcd_clk);
  74. return-EINVAL;
  75. }
  76. ints3cfb_clk_off(structplatform_device*pdev,structclk**clk)
  77. {
  78. structclk*lcd_clk=NULL;
  80. lcd_clk=clk_get(&pdev->dev,"lcd");
  81. if(IS_ERR(lcd_clk)){
  82. printk(KERN_ERR"failedtogetipclkforfimd0\n");
  83. gotoerr_clk0;
  84. }
  86. clk_disable(lcd_clk);
  87. clk_put(lcd_clk);
  89. clk_disable(*clk);
  90. clk_put(*clk);
  92. *clk=NULL;
  94. return0;
  96. err_clk0:
  97. clk_put(lcd_clk);
  99. return-EINVAL;
  100. }
  102. voids3cfb_get_clk_name(char*clk_name)
  103. {
  104. strcpy(clk_name,"sclk_fimd");
  105. }
int s3cfb_clk_on(struct platform_device *pdev, struct clk **s3cfb_clk){struct clk *sclk = NULL;struct clk *mout_mpll = NULL;struct clk *lcd_clk = NULL;u32 rate = 0;int ret = 0;lcd_clk = clk_get(&pdev->dev, "lcd");if (IS_ERR(lcd_clk)) {dev_err(&pdev->dev, "failed to get operation clk for fimd\n");goto err_clk0;}ret = clk_enable(lcd_clk);if (ret < 0) {dev_err(&pdev->dev, "failed to clk_enable of lcd clk for fimd\n");goto err_clk0;}clk_put(lcd_clk);sclk = clk_get(&pdev->dev, "sclk_fimd");if (IS_ERR(sclk)) {dev_err(&pdev->dev, "failed to get sclk for fimd\n");goto err_clk1;}if (soc_is_exynos4210())mout_mpll = clk_get(&pdev->dev, "mout_mpll");elsemout_mpll = clk_get(&pdev->dev, "mout_mpll_user");if (IS_ERR(mout_mpll)) {dev_err(&pdev->dev, "failed to get mout_mpll for fimd\n");goto err_clk2;}ret = clk_set_parent(sclk, mout_mpll);if (ret < 0) {dev_err(&pdev->dev, "failed to clk_set_parent for fimd\n");goto err_clk2;}if ((soc_is_exynos4412()) && (samsung_rev() >= EXYNOS4412_REV_2_0))ret = clk_set_rate(sclk, 880000000);elseret = clk_set_rate(sclk, 800000000);if (ret < 0) {dev_err(&pdev->dev, "failed to clk_set_rate of sclk for fimd\n");goto err_clk2;}dev_dbg(&pdev->dev, "set fimd sclk rate to %d\n", rate);clk_put(mout_mpll);ret = clk_enable(sclk);if (ret < 0) {dev_err(&pdev->dev, "failed to clk_enable of sclk for fimd\n");goto err_clk2;}*s3cfb_clk = sclk;return 0;err_clk2:clk_put(mout_mpll);err_clk1:clk_put(sclk);err_clk0:clk_put(lcd_clk);return -EINVAL;}int s3cfb_clk_off(struct platform_device *pdev, struct clk **clk){struct clk *lcd_clk = NULL;lcd_clk = clk_get(&pdev->dev, "lcd");if (IS_ERR(lcd_clk)) {printk(KERN_ERR "failed to get ip clk for fimd0\n");goto err_clk0;}clk_disable(lcd_clk);clk_put(lcd_clk);clk_disable(*clk);clk_put(*clk);*clk = NULL;return 0;err_clk0:clk_put(lcd_clk);return -EINVAL;}void s3cfb_get_clk_name(char *clk_name){strcpy(clk_name, "sclk_fimd");}
4、背光、LCD电压的控制


LCD_LED_EN

LCD电压（TFT电压）使能

GPC1_2

LED_BL_EN

LED背光使能

GPL2_4

[cpp] view plain copy print ?
  1. ints3cfb_backlight_on(structplatform_device*pdev)
  2. {
  3. interr;
  4. pwm_set();
  5. err=gpio_request_one(EXYNOS4_GPL2(4),GPIOF_OUT_INIT_HIGH,"GPL2_4");
  6. if(err){
  7. printk(KERN_ERR"failedtorequestGPL2for"
  8. "lcdbacklightcontrol\n");
  9. returnerr;
  10. }
  11. s3c_gpio_setpull(EXYNOS4_GPL2(4),S3C_GPIO_PULL_NONE);
  12. gpio_direction_output(EXYNOS4_GPL2(4),1);
  13. gpio_free(EXYNOS4_GPL2(4));
  14. mdelay(20);
  15. err=gpio_request_one(EXYNOS4_GPC1(2),GPIOF_OUT_INIT_HIGH,"GPC1_2");
  16. if(err){
  17. printk(KERN_ERR"failedtorequestGPC1for"
  18. "lcdbacklightcontrol\n");
  19. returnerr;
  20. }
  21. s3c_gpio_setpull(EXYNOS4_GPC1(2),S3C_GPIO_PULL_NONE);
  22. gpio_direction_output(EXYNOS4_GPC1(2),0);
  23. gpio_free(EXYNOS4_GPC1(2));
  25. mdelay(20);
  26. err=gpio_request(EXYNOS4_GPD0(1),"GPD0_1");
  28. if(err){
  29. printk(KERN_ERR"failedtorequestGPD0_1for"
  30. "lcdpwmcontrol\n");
  31. returnerr;
  32. }
  33. s3c_gpio_setpull(EXYNOS4_GPD0(1),S3C_GPIO_PULL_NONE);
  34. s5p_gpio_set_drvstr(EXYNOS4_GPD0(1),S5P_GPIO_DRVSTR_LV4);
  35. gpio_direction_output(EXYNOS4_GPD0(1),1);
  36. s3c_gpio_cfgpin(EXYNOS4_GPD0(1),EXYNOS4_GPD_0_1_TOUT_1);
  38. gpio_free(EXYNOS4_GPD0(1));
  39. mdelay(20);
  40. return0;
  42. return0;
  43. }
  45. ints3cfb_backlight_off(structplatform_device*pdev)
  46. {
  47. interr;
  48. err=gpio_request_one(EXYNOS4_GPL2(4),GPIOF_OUT_INIT_LOW,"GPL2_4");
  49. if(err){
  50. printk(KERN_ERR"failedtorequestGPL2for"
  51. "lcdbacklightcontrol\n");
  52. returnerr;
  53. }
  54. s3c_gpio_setpull(EXYNOS4_GPL2(4),S3C_GPIO_PULL_NONE);
  55. gpio_direction_output(EXYNOS4_GPL2(4),0);
  56. gpio_free(EXYNOS4_GPL2(4));
  58. err=gpio_request_one(EXYNOS4_GPC1(2),GPIOF_OUT_INIT_HIGH,"GPC1_2");
  59. if(err){
  60. printk(KERN_ERR"failedtorequestGPC1for"
  61. "lcdbacklightcontrol\n");
  62. returnerr;
  63. }
  64. gpio_free(EXYNOS4_GPC1(2));
  66. return0;
  67. }
int s3cfb_backlight_on(struct platform_device *pdev){        int err;      pwm_set();err = gpio_request_one(EXYNOS4_GPL2(4), GPIOF_OUT_INIT_HIGH, "GPL2_4");if (err) {printk(KERN_ERR "failed to request GPL2 for ""lcd backlight control\n");return err;}s3c_gpio_setpull(EXYNOS4_GPL2(4),S3C_GPIO_PULL_NONE);gpio_direction_output(EXYNOS4_GPL2(4), 1);gpio_free(EXYNOS4_GPL2(4));mdelay(20);err = gpio_request_one(EXYNOS4_GPC1(2), GPIOF_OUT_INIT_HIGH, "GPC1_2");if (err) {printk(KERN_ERR "failed to request GPC1 for ""lcd backlight control\n");return err;}s3c_gpio_setpull(EXYNOS4_GPC1(2),S3C_GPIO_PULL_NONE);gpio_direction_output(EXYNOS4_GPC1(2), 0);gpio_free(EXYNOS4_GPC1(2));mdelay(20);err = gpio_request(EXYNOS4_GPD0(1), "GPD0_1");if (err) {printk(KERN_ERR "failed to request GPD0_1 for ""lcd pwm control\n");return err;}s3c_gpio_setpull(EXYNOS4_GPD0(1),S3C_GPIO_PULL_NONE);s5p_gpio_set_drvstr(EXYNOS4_GPD0(1), S5P_GPIO_DRVSTR_LV4);gpio_direction_output(EXYNOS4_GPD0(1), 1);s3c_gpio_cfgpin(EXYNOS4_GPD0(1), EXYNOS4_GPD_0_1_TOUT_1);gpio_free(EXYNOS4_GPD0(1));mdelay(20);return 0;return 0;}int s3cfb_backlight_off(struct platform_device *pdev){int err;err = gpio_request_one(EXYNOS4_GPL2(4), GPIOF_OUT_INIT_LOW, "GPL2_4");if (err) {printk(KERN_ERR "failed to request GPL2 for ""lcd backlight control\n");return err;}s3c_gpio_setpull(EXYNOS4_GPL2(4),S3C_GPIO_PULL_NONE);gpio_direction_output(EXYNOS4_GPL2(4), 0);gpio_free(EXYNOS4_GPL2(4));err = gpio_request_one(EXYNOS4_GPC1(2), GPIOF_OUT_INIT_HIGH, "GPC1_2");if (err) {printk(KERN_ERR "failed to request GPC1 for ""lcd backlight control\n");return err;}gpio_free(EXYNOS4_GPC1(2));return 0;}

5、PWM的设置

arch/arm/mach-exynos/mach-smdk4x12.c


[cpp] view plain copy print ?
  1. Arch/arm/mach-exynos/mach-smdk4x12.c
  2. /*LCDBacklightdata*/
  3. staticstructsamsung_bl_gpio_infosmdk4x12_bl_gpio_info={
  4. .no=EXYNOS4_GPD0(1),//PWM管脚XpwmTOUT1/LCD_PWM/GPD0_1
  5. .func=S3C_GPIO_SFN(2),
  6. };
  7. staticstructplatform_pwm_backlight_datasmdk4x12_bl_data={
  8. .pwm_id=1,//PWMIDPWM编号为1号；
  9. .pwm_period_ns=90000,//22k
  10. };
  11. staticvoid__initsmdk4x12_machine_init(void)
  12. {
  13. ………………
  14. samsung_bl_set(&smdk4x12_bl_gpio_info,&smdk4x12_bl_data);//在初始化的时候把对应的结构体初始化
  15. ………………
  16. }
Arch/arm/mach-exynos/mach-smdk4x12.c/* LCD Backlight data */static struct samsung_bl_gpio_info smdk4x12_bl_gpio_info = {.no = EXYNOS4_GPD0(1),//PWM管脚XpwmTOUT1/LCD_PWM/GPD0_1.func = S3C_GPIO_SFN(2),};static struct platform_pwm_backlight_data smdk4x12_bl_data = {.pwm_id = 1,//PWM ID PWM编号为1号；.pwm_period_ns  = 90000,  //22k};static void __init smdk4x12_machine_init(void){………………samsung_bl_set(&smdk4x12_bl_gpio_info, &smdk4x12_bl_data);//在初始化的时候把对应的结构体初始化………………}

samsung_bl_set看下这个函数的实现：

kernel/arch/arm/palt-samsung/dev-backlight.c

[cpp] view plain copy print ?
  1. voidsamsung_bl_set(structsamsung_bl_gpio_info*gpio_info,
  2. structplatform_pwm_backlight_data*bl_data)
  3. {
  4. intret=0;
  5. structplatform_device*samsung_bl_device;
  6. structplatform_pwm_backlight_data*samsung_bl_data;
  8. samsung_bl_device=kmemdup(&samsung_dfl_bl_device,
  9. sizeof(structplatform_device),GFP_KERNEL);//（1）、分配内存空间；
  10. if(!samsung_bl_device){
  11. printk(KERN_ERR"%s:nomemoryforplatformdev\n",__func__);
  12. return;
  13. }
  15. samsung_bl_data=s3c_set_platdata(&samsung_dfl_bl_data,
  16. sizeof(structplatform_pwm_backlight_data),samsung_bl_device);//（2）、
  17. if(!samsung_bl_data){
  18. printk(KERN_ERR"%s:nomemoryforplatformdev\n",__func__);
  19. gotoerr_data;
  20. }
  22. /*Copyboardspecificdataprovidedbyuser*/
  23. samsung_bl_data->pwm_id=bl_data->pwm_id;//(3）、把具体配置的数据给samsung_bl_data
  24. samsung_bl_device->dev.parent=
  25. &s3c_device_timer[samsung_bl_data->pwm_id].dev;
  27. if(bl_data->max_brightness)//(4)、对bl_data的结构体检查，如果没有复制则用default的值
  28. samsung_bl_data->max_brightness=bl_data->max_brightness;
  29. if(bl_data->dft_brightness)
  30. samsung_bl_data->dft_brightness=bl_data->dft_brightness;
  31. if(bl_data->lth_brightness)
  32. samsung_bl_data->lth_brightness=bl_data->lth_brightness;
  33. if(bl_data->pwm_period_ns)
  34. samsung_bl_data->pwm_period_ns=bl_data->pwm_period_ns;
  35. if(bl_data->init)
  36. samsung_bl_data->init=bl_data->init;
  37. if(bl_data->notify)
  38. samsung_bl_data->notify=bl_data->notify;
  39. if(bl_data->exit)
  40. samsung_bl_data->exit=bl_data->exit;
  41. if(bl_data->check_fb)
  42. samsung_bl_data->check_fb=bl_data->check_fb;
  44. /*KeeptheGPIOinfoforfutureuse*/
  45. s3c_device_timer[samsung_bl_data->pwm_id].dev.platform_data=gpio_info;
  47. /*RegisterthespecificPWMtimerdevforBacklightcontrol*/
  48. ret=platform_device_register(//(5)、注册PWM设备驱动；
  49. &s3c_device_timer[samsung_bl_data->pwm_id]);
  50. if(ret){
  51. printk(KERN_ERR"failedtoregisterpwmtimerforbacklight:%d\n",ret);
  52. gotoerr_plat_reg1;
  53. }
  55. /*RegistertheBacklightdev*/
  56. ret=platform_device_register(samsung_bl_device);//(6)、注册背光设备驱动；
  57. if(ret){
  58. printk(KERN_ERR"failedtoregisterbacklightdevice:%d\n",ret);
  59. gotoerr_plat_reg2;
  60. }
  62. return;
  64. err_plat_reg2://(7)、如果有异常的情况下退出；
  65. platform_device_unregister(&s3c_device_timer[samsung_bl_data->pwm_id]);
  66. err_plat_reg1:
  67. kfree(samsung_bl_data);
  68. err_data:
  69. kfree(samsung_bl_device);
  70. return;
  71. }
void samsung_bl_set(struct samsung_bl_gpio_info *gpio_info,struct platform_pwm_backlight_data *bl_data){int ret = 0;struct platform_device *samsung_bl_device;struct platform_pwm_backlight_data *samsung_bl_data;samsung_bl_device = kmemdup(&samsung_dfl_bl_device,sizeof(struct platform_device), GFP_KERNEL);//（1）、分配内存空间；if (!samsung_bl_device) {printk(KERN_ERR "%s: no memory for platform dev\n", __func__);return;}samsung_bl_data = s3c_set_platdata(&samsung_dfl_bl_data,sizeof(struct platform_pwm_backlight_data), samsung_bl_device);//（2）、if (!samsung_bl_data) {printk(KERN_ERR "%s: no memory for platform dev\n", __func__);goto err_data;}/* Copy board specific data provided by user */samsung_bl_data->pwm_id = bl_data->pwm_id;//(3）、把具体配置的数据给samsung_bl_datasamsung_bl_device->dev.parent =&s3c_device_timer[samsung_bl_data->pwm_id].dev;if (bl_data->max_brightness)//(4)、对bl_data的结构体检查，如果没有复制则用default的值samsung_bl_data->max_brightness = bl_data->max_brightness;if (bl_data->dft_brightness)samsung_bl_data->dft_brightness = bl_data->dft_brightness;if (bl_data->lth_brightness)samsung_bl_data->lth_brightness = bl_data->lth_brightness;if (bl_data->pwm_period_ns)samsung_bl_data->pwm_period_ns = bl_data->pwm_period_ns;if (bl_data->init)samsung_bl_data->init = bl_data->init;if (bl_data->notify)samsung_bl_data->notify = bl_data->notify;if (bl_data->exit)samsung_bl_data->exit = bl_data->exit;if (bl_data->check_fb)samsung_bl_data->check_fb = bl_data->check_fb;/* Keep the GPIO info for future use */s3c_device_timer[samsung_bl_data->pwm_id].dev.platform_data = gpio_info;/* Register the specific PWM timer dev for Backlight control */ret = platform_device_register(//(5)、注册PWM设备驱动；&s3c_device_timer[samsung_bl_data->pwm_id]);if (ret) {printk(KERN_ERR "failed to register pwm timer for backlight: %d\n", ret);goto err_plat_reg1;}/* Register the Backlight dev */ret = platform_device_register(samsung_bl_device);//(6)、注册背光设备驱动；if (ret) {printk(KERN_ERR "failed to register backlight device: %d\n", ret);goto err_plat_reg2;}return;err_plat_reg2://(7)、如果有异常的情况下退出；platform_device_unregister(&s3c_device_timer[samsung_bl_data->pwm_id]);err_plat_reg1:kfree(samsung_bl_data);err_data:kfree(samsung_bl_device);return;}

(1)、分配内存空间

[cpp] view plain copy print ?
  1. samsung_bl_device=kmemdup(&samsung_dfl_bl_device,
  2. sizeof(structplatform_device),GFP_KERNEL);
  3. 其中：
  4. staticstructplatform_pwm_backlight_datasamsung_dfl_bl_data={
  5. .max_brightness=255,
  6. .dft_brightness=140,
  7. .pwm_period_ns=78770,
  8. .init=samsung_bl_init,
  9. .exit=samsung_bl_exit,
  10. };
  12. staticstructplatform_devicesamsung_dfl_bl_device={
  13. .name="pwm-backlight",
  14. };
samsung_bl_device = kmemdup(&samsung_dfl_bl_device,sizeof(struct platform_device), GFP_KERNEL);其中：static struct platform_pwm_backlight_data samsung_dfl_bl_data = {.max_brightness = 255,.dft_brightness = 140, .pwm_period_ns  = 78770,.init           = samsung_bl_init,.exit           = samsung_bl_exit,};static struct platform_device samsung_dfl_bl_device = {.name= "pwm-backlight",};

(2)、

(3)、把具体配置的数据给samsung_bl_data

[cpp] view plain copy print ?
  1. arch/arm/mach-exynos/mach-smdk4x12.c
  2. staticstructsamsung_bl_gpio_infosmdk4x12_bl_gpio_info={
  3. .no=EXYNOS4_GPD0(1),//PWM管脚XpwmTOUT1/LCD_PWM/GPD0_1
  4. .func=S3C_GPIO_SFN(2),
  5. };
  6. staticstructplatform_pwm_backlight_datasmdk4x12_bl_data={
  7. .pwm_id=1,//PWMIDPWM编号为1号；
  8. .pwm_period_ns=90000,//22k
  9. };
arch/arm/mach-exynos/mach-smdk4x12.cstatic struct samsung_bl_gpio_info smdk4x12_bl_gpio_info = {.no = EXYNOS4_GPD0(1),//PWM管脚XpwmTOUT1/LCD_PWM/GPD0_1.func = S3C_GPIO_SFN(2),};static struct platform_pwm_backlight_data smdk4x12_bl_data = {.pwm_id = 1,//PWM ID PWM编号为1号；.pwm_period_ns  = 90000,  //22k};

(4)、对bl_data的结构体检查，如果没有复制则用default的值

参考（1）中的那些值。

(5)、注册PWM设备驱动；

[cpp] view plain copy print ?
  1. ret=platform_device_register(
  2. &s3c_device_timer[samsung_bl_data->pwm_id]);
    ret = platform_device_register(            &s3c_device_timer[samsung_bl_data->pwm_id]);
其中s3c_device_timer[]这个结构体如下：

[cpp] view plain copy print ?
  1. structplatform_devices3c_device_timer[]={
  2. [0]={DEFINE_S3C_TIMER(0,IRQ_TIMER0)},
  3. [1]={DEFINE_S3C_TIMER(1,IRQ_TIMER1)},
  4. [2]={DEFINE_S3C_TIMER(2,IRQ_TIMER2)},
  5. [3]={DEFINE_S3C_TIMER(3,IRQ_TIMER3)},
  6. [4]={DEFINE_S3C_TIMER(4,IRQ_TIMER4)},
struct platform_device s3c_device_timer[] = {[0] = { DEFINE_S3C_TIMER(0, IRQ_TIMER0) },[1] = { DEFINE_S3C_TIMER(1, IRQ_TIMER1) },[2] = { DEFINE_S3C_TIMER(2, IRQ_TIMER2) },[3] = { DEFINE_S3C_TIMER(3, IRQ_TIMER3) },[4] = { DEFINE_S3C_TIMER(4, IRQ_TIMER4) },
我们饿samsung_bl_data->pwm_id=1;所以选择[1] = { DEFINE_S3C_TIMER(1, IRQ_TIMER1) },

(6)、注册背光设备驱动；

[cpp] view plain copy print ?
  1. ret=platform_device_register(samsung_bl_device);
    ret =platform_device_register(samsung_bl_device);
其中：samsung_bl_device

[cpp] view plain copy print ?
  1. samsung_bl_data=s3c_set_platdata(&samsung_dfl_bl_data,
  2. sizeof(structplatform_pwm_backlight_data),samsung_bl_device);
samsung_bl_data = s3c_set_platdata(&samsung_dfl_bl_data,sizeof(struct platform_pwm_backlight_data), samsung_bl_device);


(7)、如果有异常的情况下退出；

6、PWM_BL背光驱动分析：

Kernel/drivers/video/backlight/pwm_bl.c

（1）、驱动注册：

[cpp] view plain copy print ?
  1. staticstructplatform_driverpwm_backlight_driver={
  2. .driver={
  3. .name="pwm-backlight",
  4. .owner=THIS_MODULE,
  5. },
  6. .probe=pwm_backlight_probe,
  7. .remove=pwm_backlight_remove,
  8. .suspend=pwm_backlight_suspend,
  9. .resume=pwm_backlight_resume,
  10. };
  12. staticint__initpwm_backlight_init(void)
  13. {
  14. returnplatform_driver_register(&pwm_backlight_driver);
  15. }
static struct platform_driver pwm_backlight_driver = {.driver= {.name= "pwm-backlight",.owner= THIS_MODULE,},.probe= pwm_backlight_probe,.remove= pwm_backlight_remove,.suspend= pwm_backlight_suspend,.resume= pwm_backlight_resume,};static int __init pwm_backlight_init(void){return platform_driver_register(&pwm_backlight_driver);}

（2）、probe函数分析

[cpp] view plain copy print ?
  1. staticintpwm_backlight_probe(structplatform_device*pdev)
  2. {
  3. structbacklight_propertiesprops;
  4. structplatform_pwm_backlight_data*data=pdev->dev.platform_data;
  5. structbacklight_device*bl;
  6. structpwm_bl_data*pb;
  7. intret;
  9. if(!data){
  10. dev_err(&pdev->dev,"failedtofindplatformdata\n");
  11. return-EINVAL;
  12. }
  14. if(data->init){
  15. ret=data->init(&pdev->dev);
  16. if(ret<0)
  17. returnret;
  18. }
  20. pb=kzalloc(sizeof(*pb),GFP_KERNEL);
  21. if(!pb){
  22. dev_err(&pdev->dev,"nomemoryforstate\n");
  23. ret=-ENOMEM;
  24. gotoerr_alloc;
  25. }
  27. global_pb=pb;
  28. INIT_DELAYED_WORK_DEFERRABLE(&key_event,key_event_work);//1）、任务队列初始化；
  30. pb->period=data->pwm_period_ns;//2）、pb结构体初始化；
  31. pb->notify=data->notify;
  32. pb->check_fb=data->check_fb;
  33. pb->lth_brightness=data->lth_brightness*
  34. (data->pwm_period_ns/data->max_brightness);
  35. pb->dev=&pdev->dev;
  37. pb->pwm=pwm_request(data->pwm_id,"backlight");
  38. if(IS_ERR(pb->pwm)){
  39. dev_err(&pdev->dev,"unabletorequestPWMforbacklight\n");
  40. ret=PTR_ERR(pb->pwm);
  41. gotoerr_pwm;
  42. }else
  43. dev_dbg(&pdev->dev,"gotpwmforbacklight\n");
  45. memset(&props,0,sizeof(structbacklight_properties));
  46. props.type=BACKLIGHT_RAW;
  47. props.max_brightness=data->max_brightness;
  48. bl=backlight_device_register(dev_name(&pdev->dev),&pdev->dev,pb,
  49. &pwm_backlight_ops,&props);
  50. if(IS_ERR(bl)){
  51. dev_err(&pdev->dev,"failedtoregisterbacklight\n");
  52. ret=PTR_ERR(bl);
  53. gotoerr_bl;
  54. }
  55. global_bl=bl;
  56. bl->props.brightness=data->dft_brightness;
  57. backlight_update_status(bl);//3）、更新背光状态；
  59. platform_set_drvdata(pdev,bl);
  60. return0;
  62. err_bl:
  63. pwm_free(pb->pwm);
  64. err_pwm:
  65. kfree(pb);
  66. err_alloc:
  67. if(data->exit)
  68. data->exit(&pdev->dev);
  69. returnret;
  70. }
static int pwm_backlight_probe(struct platform_device *pdev){struct backlight_properties props;struct platform_pwm_backlight_data *data = pdev->dev.platform_data;struct backlight_device *bl;struct pwm_bl_data *pb;int ret;if (!data) {dev_err(&pdev->dev, "failed to find platform data\n");return -EINVAL;}if (data->init) {ret = data->init(&pdev->dev);if (ret < 0)return ret;}pb = kzalloc(sizeof(*pb), GFP_KERNEL);if (!pb) {dev_err(&pdev->dev, "no memory for state\n");ret = -ENOMEM;goto err_alloc;}global_pb=pb;INIT_DELAYED_WORK_DEFERRABLE(&key_event, key_event_work);//1）、任务队列初始化；pb->period = data->pwm_period_ns;//2）、pb结构体初始化；pb->notify = data->notify;pb->check_fb = data->check_fb;pb->lth_brightness = data->lth_brightness *(data->pwm_period_ns / data->max_brightness);pb->dev = &pdev->dev;pb->pwm = pwm_request(data->pwm_id, "backlight");if (IS_ERR(pb->pwm)) {dev_err(&pdev->dev, "unable to request PWM for backlight\n");ret = PTR_ERR(pb->pwm);goto err_pwm;} elsedev_dbg(&pdev->dev, "got pwm for backlight\n");memset(&props, 0, sizeof(struct backlight_properties));props.type = BACKLIGHT_RAW;props.max_brightness = data->max_brightness;bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,       &pwm_backlight_ops, &props);if (IS_ERR(bl)) {dev_err(&pdev->dev, "failed to register backlight\n");ret = PTR_ERR(bl);goto err_bl;}global_bl=bl;bl->props.brightness = data->dft_brightness;backlight_update_status(bl);//3）、更新背光状态；platform_set_drvdata(pdev, bl);return 0;err_bl:pwm_free(pb->pwm);err_pwm:kfree(pb);err_alloc:if (data->exit)data->exit(&pdev->dev);return ret;}

1）、任务队列初始化；

把key_event_work加入key_event队列，

[cpp] view plain copy print ?
  1. INIT_DELAYED_WORK_DEFERRABLE(&key_event,key_event_work);
INIT_DELAYED_WORK_DEFERRABLE(&key_event, key_event_work);

队列调度函数：

[cpp] view plain copy print ?
  1. staticvoidkey_event_work(structwork_struct*work)
  2. {
  3. global_pb->period=90000;
  4. global_bl->props.brightness=global_brightness;
  5. backlight_update_status(global_bl);
  6. return;
  7. }
static void key_event_work(struct work_struct *work){global_pb->period=90000;global_bl->props.brightness=global_brightness;backlight_update_status(global_bl);return ;}
backlight_update_status

[cpp] view plain copy print ?
  1. staticinlinevoidbacklight_update_status(structbacklight_device*bd)
  2. {
  3. mutex_lock(&bd->update_lock);
  4. if(bd->ops&&bd->ops->update_status)
  5. bd->ops->update_status(bd);
  6. mutex_unlock(&bd->update_lock);
  7. }
static inline void backlight_update_status(struct backlight_device *bd){mutex_lock(&bd->update_lock);if (bd->ops && bd->ops->update_status)bd->ops->update_status(bd);mutex_unlock(&bd->update_lock);}

update_status在pwm_backlight_ops结构体重指定：

[cpp] view plain copy print ?
  1. staticconststructbacklight_opspwm_backlight_ops={
  2. .update_status=pwm_backlight_update_status,
  3. …………}
static const struct backlight_ops pwm_backlight_ops = {.update_status= pwm_backlight_update_status,…………}

pwm_backlight_update_status我们后面分析，这个其实就是我们PWM设定实现的具体实施过程。

2）、pb结构体初始化；

[cpp] view plain copy print ?
  1. pb->period=data->pwm_period_ns;pb->notify=data->notify;
  2. pb->check_fb=data->check_fb;
  3. pb->lth_brightness=data->lth_brightness*
  4. (data->pwm_period_ns/data->max_brightness);
  5. pb->dev=&pdev->dev;
  6. pb->pwm=pwm_request(data->pwm_id,"backlight");
pb->period = data->pwm_period_ns;pb->notify = data->notify;pb->check_fb = data->check_fb;pb->lth_brightness = data->lth_brightness *(data->pwm_period_ns / data->max_brightness);pb->dev = &pdev->dev;pb->pwm = pwm_request(data->pwm_id, "backlight");

3）、更新背光状态

[cpp] view plain copy print ?
  1. backlight_update_status(bl);
backlight_update_status(bl);

（4）、PWM_SET

当UI设置PWM时，会调用到驱动中的pwm_set(void)这个函数。这个函数主要在开机时使用。

[cpp] view plain copy print ?
  1. intpwm_set(void)
  2. {
  3. interror;
  4. structbacklight_device*bl=global_bl;
  5. structpwm_bl_data*pb=global_pb;
  6. printk("%s__%d\n",__func__,pb->period);
  7. pb->period=410000;
  8. backlight_update_status(bl);
  9. schedule_delayed_work(&key_event,600);//调用队列，跟新亮度信息；
  11. return0;
  12. }
int pwm_set(void){int error;struct backlight_device *bl = global_bl;struct pwm_bl_data *pb = global_pb;printk("%s__%d\n",__func__,pb->period);pb->period=410000;backlight_update_status(bl);schedule_delayed_work(&key_event, 600);//调用队列，跟新亮度信息；return 0;}

（5）、pwm_backlight_update_status这个就是PWM变化的具体实现，当应用层调节时，会调用到这个函数，把改变的值填入寄存器。

[cpp] view plain copy print ?
  1. staticintpwm_backlight_update_status(structbacklight_device*bl)
  2. {
  3. structpwm_bl_data*pb=dev_get_drvdata(&bl->dev);
  4. intbrightness=bl->props.brightness;
  5. intmax=bl->props.max_brightness;
  6. //if(brightness==0)
  7. //return0;
  8. //printk("#####%s#%d__%d\n",__func__,pb->period,brightness);
  9. global_brightness=brightness;
  10. if(bl->props.power!=FB_BLANK_UNBLANK)
  11. brightness=0;
  13. if(bl->props.fb_blank!=FB_BLANK_UNBLANK)
  14. brightness=0;
  16. if(pb->notify)
  17. brightness=pb->notify(pb->dev,brightness);
  19. if(brightness==0){
  20. pwm_config(pb->pwm,0,pb->period);
  21. pwm_disable(pb->pwm);
  22. }else{
  23. #if1
  24. brightness=pb->lth_brightness+
  25. (brightness*(pb->period-pb->lth_brightness)/max);
  26. #else
  27. brightness=pb->lth_brightness+
  28. (((pb->period-pb->lth_brightness)/max)*brightness);
  29. #endif
  31. pwm_config(pb->pwm,brightness,pb->period);//这里对PWM寄存器的具体操作；
  32. pwm_enable(pb->pwm);
  33. }
  34. return0;
  35. }
static int pwm_backlight_update_status(struct backlight_device *bl){struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);int brightness = bl->props.brightness;int max = bl->props.max_brightness;//if(brightness==0)//return 0;//printk("#####%s#%d__%d\n",__func__,pb->period,brightness);global_brightness=brightness;if (bl->props.power != FB_BLANK_UNBLANK)brightness = 0;if (bl->props.fb_blank != FB_BLANK_UNBLANK)brightness = 0;if (pb->notify)brightness = pb->notify(pb->dev, brightness);if (brightness == 0) {pwm_config(pb->pwm, 0, pb->period);pwm_disable(pb->pwm);} else {#if 1brightness = pb->lth_brightness +(brightness * (pb->period - pb->lth_brightness) / max);#else brightness = pb->lth_brightness +                        (((pb->period - pb->lth_brightness) / max) * brightness );#endifpwm_config(pb->pwm, brightness, pb->period);//这里对PWM寄存器的具体操作；pwm_enable(pb->pwm);}return 0;}


三、LCD UBOOT下的控制（待整理…………）
LCD 在UBOOT下的控制，这部分我们没做过，后面有机会做了再把这部分完善，或者找个机会把代码详细看看。


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