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 being correctly configured
   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                 dev_err(&pdev->dev, "failed to find platform data\n");
  73                 return -EINVAL;
  74         }
  75
  76         if (data->init) {
  77                 ret = data->init(&pdev->dev);
  78                 if (ret < 0)
  79                         return ret;
  80         }
  81
  82         pb = kzalloc(sizeof(*pb), GFP_KERNEL);
  83         if (!pb) {
  84                 dev_err(&pdev->dev, "no memory for state\n");
  85                 ret = -ENOMEM;
  86                 goto err_alloc;
  87         }
  88
  89         pb->period = data->pwm_period_ns;
  90         pb->notify = data->notify;
  91
  92         pb->pwm = pwm_request(data->pwm_id, "backlight");
  93         if (IS_ERR(pb->pwm)) {
  94                 dev_err(&pdev->dev, "unable to request PWM for backlight\n");
  95                 ret = PTR_ERR(pb->pwm);
  96                 goto err_pwm;
  97         } else
  98                 dev_dbg(&pdev->dev, "got pwm for backlight\n");
  99
 100         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev,
 101                         pb, &pwm_backlight_ops);
 102         if (IS_ERR(bl)) {
 103                 dev_err(&pdev->dev, "failed to register backlight\n");
 104                 ret = PTR_ERR(bl);
 105                 goto err_bl;
 106         }
 107
 108         bl->props.max_brightness = data->max_brightness;
 109         bl->props.brightness = data->dft_brightness;
 110         backlight_update_status(bl);
 111
 112         platform_set_drvdata(pdev, bl);
 113         return 0;
 114
 115 err_bl:
 116         pwm_free(pb->pwm);
 117 err_pwm:
 118         kfree(pb);
 119 err_alloc:
 120         if (data->exit)
 121                 data->exit(&pdev->dev);
 122         return ret;
 123 }
 124
 125 static int pwm_backlight_remove(struct platform_device *pdev)
 126 {
 127         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
 128         struct backlight_device *bl = platform_get_drvdata(pdev);
 129         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 130
 131         backlight_device_unregister(bl);
 132         pwm_config(pb->pwm, 0, pb->period);
 133         pwm_disable(pb->pwm);
 134         pwm_free(pb->pwm);
 135         kfree(pb);
 136         if (data->exit)
 137                 data->exit(&pdev->dev);
 138         return 0;
 139 }
 140
 141 #ifdef CONFIG_PM
 142 static int pwm_backlight_suspend(struct platform_device *pdev,
 143                                  pm_message_t state)
 144 {
 145         struct backlight_device *bl = platform_get_drvdata(pdev);
 146         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 147
 148         pwm_config(pb->pwm, 0, pb->period);
 149         pwm_disable(pb->pwm);
 150         return 0;
 151 }
 152
 153 static int pwm_backlight_resume(struct platform_device *pdev)
 154 {
 155         struct backlight_device *bl = platform_get_drvdata(pdev);
 156
 157         backlight_update_status(bl);
 158         return 0;
 159 }
 160 #else
 161 #define pwm_backlight_suspend   NULL
 162 #define pwm_backlight_resume    NULL
 163 #endif
 164
 165 static struct platform_driver pwm_backlight_driver = {
 166         .driver         = {
 167                 .name   = "pwm-backlight",
 168                 .owner  = THIS_MODULE,
 169         },
 170         .probe          = pwm_backlight_probe,
 171         .remove         = pwm_backlight_remove,
 172         .suspend        = pwm_backlight_suspend,
 173         .resume         = pwm_backlight_resume,
 174 };
 175
 176 static int __init pwm_backlight_init(void)
 177 {
 178         return platform_driver_register(&pwm_backlight_driver);
 179 }
 180 module_init(pwm_backlight_init);
 181
 182 static void __exit pwm_backlight_exit(void)
 183 {
 184         platform_driver_unregister(&pwm_backlight_driver);
 185 }
 186 module_exit(pwm_backlight_exit);
 187
 188 MODULE_DESCRIPTION("PWM based Backlight Driver");
 189 MODULE_LICENSE("GPL");
 190 MODULE_ALIAS("platform:pwm-backlight");
 191