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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1. #ifdef CONFIG_BACKLIGHT_RK29_BL
   
2. #define PWM_ID 3
   
3. #define PWM_MODE     PWM3
   
4. #define PWM_EFFECT_VALUE 1
   
5. 
   
6. static struct platform_device rk29_device_backlight = {
   
7.     .name    = "rk29_backlight",
   
8.     .id     = -1,
   
9.     .dev    = {
   
10.         .platform_data = &rk29_bl_info,
    
11.     }
    
12. };
    
13. 
    
14. 
    
15. static struct rk29_bl_info rk29_bl_info = {
    
16.         .min_brightness = 120,//65, //value must between 0~255
    
17.         .max_brightness = 255,//150, //value must between 0~255
    
18.         .brightness_mode =BRIGHTNESS_MODE_CONIC,
    
19.     .pre_div = 30 * 1000, // pwm output clk: 30k;
    
20.     .pwm_id = PWM_ID, //3
    
21.     .bl_ref = PWM_EFFECT_VALUE, //1
    
22.     .io_init = rk29_backlight_io_init,
    
23.     .io_deinit = rk29_backlight_io_deinit,
    
24.     .pwm_suspend = rk29_backlight_pwm_suspend,
    
25.     .pwm_resume = rk29_backlight_pwm_resume,
    
26. };
    
27. 
    
28. 
    
29. static int rk29_backlight_io_init(void)
    
30. {
    
31.     int ret = 0;
    
32.     iomux_set(PWM_MODE);
    
33.     return ret;
    
34. }
    
35. 
    
36. static int rk29_backlight_io_deinit(void)
    
37. {
    
38.     int ret = 0, pwm_gpio;
    
39.     pwm_gpio = iomux_mode_to_gpio(PWM_MODE);
    
40.     gpio_request(pwm_gpio, NULL);
    
41.     gpio_direction_output(pwm_gpio, GPIO_LOW);
    
42.     return ret;
    
43. }
    
44. 
    
45. 
    
46. static int rk29_backlight_pwm_suspend(void)
    
47. {
    
48.     int ret = 0, pwm_gpio;
    
49.     pwm_gpio = iomux_mode_to_gpio(PWM_MODE);
    
50.     if (gpio_request(pwm_gpio, NULL)) {
    
51.         printk("func %s, line %d: request gpio fail\n", __FUNCTION__, __LINE__);
    
52.         return -1;
    
53.     }
    
54.     gpio_direction_output(pwm_gpio, GPIO_LOW);
    
55.     return ret;
    
56. }
    
57. 
    
58. static int rk29_backlight_pwm_resume(void)
    
59. {
    
60.     int pwm_gpio = iomux_mode_to_gpio(PWM_MODE);
    
61.     gpio_free(pwm_gpio);
    
62.     iomux_set(PWM_MODE);
    
63.     return 0;
    
64. }
    
65. 
    
66. int iomux_mode_to_gpio(unsigned int mode)
    
67. {
    
68.         struct union_mode m;
    
69. 
    
70.     if(!mode_is_valid(mode)){
    
71.         INFO("<%s> mode(0x%x) is invalid\n", __func__, mode);
    
72.         return INVALID_GPIO;
    
73.     }
    
74. 
    
75.         m.mode = mode;
    
76.         return PIN_BASE + m.mux.bank * 32 + (m.mux.goff - 0x0A) * 8 + m.mux.off;
    
77. }