linux pwm 应用

原创：kylin_zeng  http://blog.chinaunix.net/uid/23795897.html

lcd 背光灯 pwm  board配置。

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 #ifdef CONFIG_BACKLIGHT_RK29_BL
 #define PWM_ID 3
 #define PWM_MODE     PWM3
 #define PWM_EFFECT_VALUE 1

 static struct platform_device rk29_device_backlight = {
     .name    = "rk29_backlight",
     .id     = -1,
     .dev    = {
         .platform_data = &rk29_bl_info,
     }
 };


 static struct rk29_bl_info rk29_bl_info = {
         .min_brightness = 120,//65, //value must between 0~255
         .max_brightness = 255,//150, //value must between 0~255
         .brightness_mode =BRIGHTNESS_MODE_CONIC,
     .pre_div = 30 * 1000, // pwm output clk: 30k;
     .pwm_id = PWM_ID, //3
     .bl_ref = PWM_EFFECT_VALUE, //1
     .io_init = rk29_backlight_io_init,
     .io_deinit = rk29_backlight_io_deinit,
     .pwm_suspend = rk29_backlight_pwm_suspend,
     .pwm_resume = rk29_backlight_pwm_resume,
 };


 static int rk29_backlight_io_init(void)
 {
     int ret = 0;
     iomux_set(PWM_MODE);
     return ret;
 }

 static int rk29_backlight_io_deinit(void)
 {
     int ret = 0, pwm_gpio;
     pwm_gpio = iomux_mode_to_gpio(PWM_MODE);
     gpio_request(pwm_gpio, NULL);
     gpio_direction_output(pwm_gpio, GPIO_LOW);
     return ret;
 }


 static int rk29_backlight_pwm_suspend(void)
 {
     int ret = 0, pwm_gpio;
     pwm_gpio = iomux_mode_to_gpio(PWM_MODE);
     if (gpio_request(pwm_gpio, NULL)) {
         printk("func %s, line %d: request gpio fail\n", __FUNCTION__, __LINE__);
         return -1;
     }
     gpio_direction_output(pwm_gpio, GPIO_LOW);
     return ret;
 }

 static int rk29_backlight_pwm_resume(void)
 {
     int pwm_gpio = iomux_mode_to_gpio(PWM_MODE);
     gpio_free(pwm_gpio);
     iomux_set(PWM_MODE);
     return 0;
 }

 int iomux_mode_to_gpio(unsigned int mode)
 {
         struct union_mode m;

     if(!mode_is_valid(mode)){
         INFO("<%s> mode(0x%x) is invalid\n", __func__, mode);
         return INVALID_GPIO;
     }

         m.mode = mode;
         return PIN_BASE + m.mux.bank * 32 + (m.mux.goff - 0x0A) * 8 + m.mux.off;
 }

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