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         int                     (*notify)(int brightness);
  27 };
  28
  29 static int pwm_backlight_update_status(struct backlight_device *bl)
  30 {
  31         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
  32         int brightness = bl->props.brightness;
  33         int max = bl->props.max_brightness;
  34
  35         if (bl->props.power != FB_BLANK_UNBLANK)
  36                 brightness = 0;
  37
  38         if (bl->props.fb_blank != FB_BLANK_UNBLANK)
  39                 brightness = 0;
  40
  41         if (pb->notify)
  42                 brightness = pb->notify(brightness);
  43
  44         if (brightness == 0) {
  45                 pwm_config(pb->pwm, 0, pb->period);
  46                 pwm_disable(pb->pwm);
  47         } else {
  48                 pwm_config(pb->pwm, brightness * pb->period / max, pb->period);
  49                 pwm_enable(pb->pwm);
  50         }
  51         return 0;
  52 }
  53
  54 static int pwm_backlight_get_brightness(struct backlight_device *bl)
  55 {
  56         return bl->props.brightness;
  57 }
  58
  59 static struct backlight_ops pwm_backlight_ops = {
  60         .update_status  = pwm_backlight_update_status,
  61         .get_brightness = pwm_backlight_get_brightness,
  62 };
  63
  64 static int pwm_backlight_probe(struct platform_device *pdev)
  65 {
  66         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
  67         struct backlight_device *bl;
  68         struct pwm_bl_data *pb;
  69         int ret;
  70
  71         if (!data)
  72                 return -EINVAL;
  73
  74         if (data->init) {
  75                 ret = data->init(&pdev->dev);
  76                 if (ret < 0)
  77                         return ret;
  78         }
  79
  80         pb = kzalloc(sizeof(*pb), GFP_KERNEL);
  81         if (!pb) {
  82                 ret = -ENOMEM;
  83                 goto err_alloc;
  84         }
  85
  86         pb->period = data->pwm_period_ns;
  87         pb->notify = data->notify;
  88
  89         pb->pwm = pwm_request(data->pwm_id, "backlight");
  90         if (IS_ERR(pb->pwm)) {
  91                 dev_err(&pdev->dev, "unable to request PWM for backlight\n");
  92                 ret = PTR_ERR(pb->pwm);
  93                 goto err_pwm;
  94         }
  95
  96         bl = backlight_device_register(pdev->name, &pdev->dev,
  97                         pb, &pwm_backlight_ops);
  98         if (IS_ERR(bl)) {
  99                 dev_err(&pdev->dev, "failed to register backlight\n");
 100                 ret = PTR_ERR(bl);
 101                 goto err_bl;
 102         }
 103
 104         bl->props.max_brightness = data->max_brightness;
 105         bl->props.brightness = data->dft_brightness;
 106         backlight_update_status(bl);
 107
 108         platform_set_drvdata(pdev, bl);
 109         return 0;
 110
 111 err_bl:
 112         pwm_free(pb->pwm);
 113 err_pwm:
 114         kfree(pb);
 115 err_alloc:
 116         if (data->exit)
 117                 data->exit(&pdev->dev);
 118         return ret;
 119 }
 120
 121 static int pwm_backlight_remove(struct platform_device *pdev)
 122 {
 123         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
 124         struct backlight_device *bl = platform_get_drvdata(pdev);
 125         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 126
 127         backlight_device_unregister(bl);
 128         pwm_config(pb->pwm, 0, pb->period);
 129         pwm_disable(pb->pwm);
 130         pwm_free(pb->pwm);
 131         kfree(pb);
 132         if (data->exit)
 133                 data->exit(&pdev->dev);
 134         return 0;
 135 }
 136
 137 #ifdef CONFIG_PM
 138 static int pwm_backlight_suspend(struct platform_device *pdev,
 139                                  pm_message_t state)
 140 {
 141         struct backlight_device *bl = platform_get_drvdata(pdev);
 142         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 143
 144         pwm_config(pb->pwm, 0, pb->period);
 145         pwm_disable(pb->pwm);
 146         return 0;
 147 }
 148
 149 static int pwm_backlight_resume(struct platform_device *pdev)
 150 {
 151         struct backlight_device *bl = platform_get_drvdata(pdev);
 152
 153         backlight_update_status(bl);
 154         return 0;
 155 }
 156 #else
 157 #define pwm_backlight_suspend   NULL
 158 #define pwm_backlight_resume    NULL
 159 #endif
 160
 161 static struct platform_driver pwm_backlight_driver = {
 162         .driver         = {
 163                 .name   = "pwm-backlight",
 164                 .owner  = THIS_MODULE,
 165         },
 166         .probe          = pwm_backlight_probe,
 167         .remove         = pwm_backlight_remove,
 168         .suspend        = pwm_backlight_suspend,
 169         .resume         = pwm_backlight_resume,
 170 };
 171
 172 static int __init pwm_backlight_init(void)
 173 {
 174         return platform_driver_register(&pwm_backlight_driver);
 175 }
 176 module_init(pwm_backlight_init);
 177
 178 static void __exit pwm_backlight_exit(void)
 179 {
 180         platform_driver_unregister(&pwm_backlight_driver);
 181 }
 182 module_exit(pwm_backlight_exit);
 183
 184 MODULE_DESCRIPTION("PWM based Backlight Driver");
 185 MODULE_LICENSE("GPL");