Android(安卓)LCD(四):LCD驱动调试篇
关键词:android LCD TFTSN75LVDS83B TTL-LVDS LCD电压背光电压
平台信息:
内核:linux2.6/linux3.0
系统:android/android4.0
平台:samsung exynos 4210、exynos 4412 、exynos 5250
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。
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
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
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
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 |
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
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
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
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
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;
ret = platform_device_register( &s3c_device_timer[samsung_bl_data->pwm_id]);
其中s3c_device_timer[]这个结构体如下:
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;
ret =platform_device_register(samsung_bl_device);
其中: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:
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
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,
INIT_DELAYED_WORK_DEFERRABLE(&key_event, key_event_work);
队列调度函数:
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
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:
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;
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
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。
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。
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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