drivers/video/backlight/pwm_bl.c

   1 /*
   2  * linux/drivers/video/backlight/pwm_bl.c
   3  *
   4  * simple PWM based backlight control, board code has to setup
   5  * 1) pin configuration so PWM waveforms can output
   6  * 2) platform_data casts to the PWM id (0/1/2/3 on PXA)
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/kernel.h>
  15 #include <linux/init.h>
  16 #include <linux/platform_device.h>
  17 #include <linux/fb.h>
  18 #include <linux/backlight.h>
  19 #include <linux/err.h>
  20 #include <linux/pwm.h>
  21 #include <linux/pwm_backlight.h>
  22
  23 struct pwm_bl_data {
  24         struct pwm_device       *pwm;
  25         unsigned int            period;
  26 };
  27
  28 static int pwm_backlight_update_status(struct backlight_device *bl)
  29 {
  30         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
  31         int brightness = bl->props.brightness;
  32         int max = bl->props.max_brightness;
  33
  34         if (bl->props.power != FB_BLANK_UNBLANK)
  35                 brightness = 0;
  36
  37         if (bl->props.fb_blank != FB_BLANK_UNBLANK)
  38                 brightness = 0;
  39
  40         if (brightness == 0) {
  41                 pwm_config(pb->pwm, 0, pb->period);
  42                 pwm_disable(pb->pwm);
  43         } else {
  44                 pwm_config(pb->pwm, brightness * pb->period / max, pb->period);
  45                 pwm_enable(pb->pwm);
  46         }
  47         return 0;
  48 }
  49
  50 static int pwm_backlight_get_brightness(struct backlight_device *bl)
  51 {
  52         return bl->props.brightness;
  53 }
  54
  55 static struct backlight_ops pwm_backlight_ops = {
  56         .update_status  = pwm_backlight_update_status,
  57         .get_brightness = pwm_backlight_get_brightness,
  58 };
  59
  60 static int pwm_backlight_probe(struct platform_device *pdev)
  61 {
  62         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
  63         struct backlight_device *bl;
  64         struct pwm_bl_data *pb;
  65
  66         if (!data)
  67                 return -EINVAL;
  68
  69         pb = kzalloc(sizeof(*pb), GFP_KERNEL);
  70         if (!pb)
  71                 return -ENOMEM;
  72
  73         pb->period = data->pwm_period_ns;
  74
  75         pb->pwm = pwm_request(data->pwm_id, "backlight");
  76         if (pb->pwm == NULL) {
  77                 dev_err(&pdev->dev, "unable to request PWM for backlight\n");
  78                 kfree(pb);
  79                 return -EBUSY;
  80         }
  81
  82         bl = backlight_device_register(pdev->name, &pdev->dev,
  83                         pb, &pwm_backlight_ops);
  84         if (IS_ERR(bl)) {
  85                 dev_err(&pdev->dev, "failed to register backlight\n");
  86                 pwm_free(pb->pwm);
  87                 kfree(pb);
  88                 return PTR_ERR(bl);
  89         }
  90
  91         bl->props.max_brightness = data->max_brightness;
  92         bl->props.brightness = data->dft_brightness;
  93         backlight_update_status(bl);
  94
  95         platform_set_drvdata(pdev, bl);
  96         return 0;
  97 }
  98
  99 static int pwm_backlight_remove(struct platform_device *pdev)
 100 {
 101         struct backlight_device *bl = platform_get_drvdata(pdev);
 102         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 103
 104         backlight_device_unregister(bl);
 105         pwm_config(pb->pwm, 0, pb->period);
 106         pwm_disable(pb->pwm);
 107         pwm_free(pb->pwm);
 108         kfree(pb);
 109         return 0;
 110 }
 111
 112 #ifdef CONFIG_PM
 113 static int pwm_backlight_suspend(struct platform_device *pdev,
 114                                  pm_message_t state)
 115 {
 116         struct backlight_device *bl = platform_get_drvdata(pdev);
 117         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 118
 119         pwm_config(pb->pwm, 0, pb->period);
 120         pwm_disable(pb->pwm);
 121         return 0;
 122 }
 123
 124 static int pwm_backlight_resume(struct platform_device *pdev)
 125 {
 126         struct backlight_device *bl = platform_get_drvdata(pdev);
 127
 128         backlight_update_status(bl);
 129         return 0;
 130 }
 131 #else
 132 #define pwm_backlight_suspend   NULL
 133 #define pwm_backlight_resume    NULL
 134 #endif
 135
 136 static struct platform_driver pwm_backlight_driver = {
 137         .driver         = {
 138                 .name   = "pwm-backlight",
 139                 .owner  = THIS_MODULE,
 140         },
 141         .probe          = pwm_backlight_probe,
 142         .remove         = pwm_backlight_remove,
 143         .suspend        = pwm_backlight_suspend,
 144         .resume         = pwm_backlight_resume,
 145 };
 146
 147 static int __init pwm_backlight_init(void)
 148 {
 149         return platform_driver_register(&pwm_backlight_driver);
 150 }
 151 module_init(pwm_backlight_init);
 152
 153 static void __exit pwm_backlight_exit(void)
 154 {
 155         platform_driver_unregister(&pwm_backlight_driver);
 156 }
 157 module_exit(pwm_backlight_exit);
 158
 159 MODULE_DESCRIPTION("PWM based Backlight Driver");
 160 MODULE_LICENSE("GPL");