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         struct device           *dev;
  26         unsigned int            period;
  27         int                     (*notify)(struct device *,
  28                                           int brightness);
  29 };
  30
  31 static int pwm_backlight_update_status(struct backlight_device *bl)
  32 {
  33         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
  34         int brightness = bl->props.brightness;
  35         int max = bl->props.max_brightness;
  36
  37         if (bl->props.power != FB_BLANK_UNBLANK)
  38                 brightness = 0;
  39
  40         if (bl->props.fb_blank != FB_BLANK_UNBLANK)
  41                 brightness = 0;
  42
  43         if (pb->notify)
  44                 brightness = pb->notify(pb->dev, brightness);
  45
  46         if (brightness == 0) {
  47                 pwm_config(pb->pwm, 0, pb->period);
  48                 pwm_disable(pb->pwm);
  49         } else {
  50                 pwm_config(pb->pwm, brightness * pb->period / max, pb->period);
  51                 pwm_enable(pb->pwm);
  52         }
  53         return 0;
  54 }
  55
  56 static int pwm_backlight_get_brightness(struct backlight_device *bl)
  57 {
  58         return bl->props.brightness;
  59 }
  60
  61 static const struct backlight_ops pwm_backlight_ops = {
  62         .update_status  = pwm_backlight_update_status,
  63         .get_brightness = pwm_backlight_get_brightness,
  64 };
  65
  66 static int pwm_backlight_probe(struct platform_device *pdev)
  67 {
  68         struct backlight_properties props;
  69         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
  70         struct backlight_device *bl;
  71         struct pwm_bl_data *pb;
  72         int ret;
  73
  74         if (!data) {
  75                 dev_err(&pdev->dev, "failed to find platform data\n");
  76                 return -EINVAL;
  77         }
  78
  79         if (data->init) {
  80                 ret = data->init(&pdev->dev);
  81                 if (ret < 0)
  82                         return ret;
  83         }
  84
  85         pb = kzalloc(sizeof(*pb), GFP_KERNEL);
  86         if (!pb) {
  87                 dev_err(&pdev->dev, "no memory for state\n");
  88                 ret = -ENOMEM;
  89                 goto err_alloc;
  90         }
  91
  92         pb->period = data->pwm_period_ns;
  93         pb->notify = data->notify;
  94         pb->dev = &pdev->dev;
  95
  96         pb->pwm = pwm_request(data->pwm_id, "backlight");
  97         if (IS_ERR(pb->pwm)) {
  98                 dev_err(&pdev->dev, "unable to request PWM for backlight\n");
  99                 ret = PTR_ERR(pb->pwm);
 100                 goto err_pwm;
 101         } else
 102                 dev_dbg(&pdev->dev, "got pwm for backlight\n");
 103
 104         memset(&props, 0, sizeof(struct backlight_properties));
 105         props.max_brightness = data->max_brightness;
 106         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 107                                        &pwm_backlight_ops, &props);
 108         if (IS_ERR(bl)) {
 109                 dev_err(&pdev->dev, "failed to register backlight\n");
 110                 ret = PTR_ERR(bl);
 111                 goto err_bl;
 112         }
 113
 114         bl->props.brightness = data->dft_brightness;
 115         backlight_update_status(bl);
 116
 117         platform_set_drvdata(pdev, bl);
 118         return 0;
 119
 120 err_bl:
 121         pwm_free(pb->pwm);
 122 err_pwm:
 123         kfree(pb);
 124 err_alloc:
 125         if (data->exit)
 126                 data->exit(&pdev->dev);
 127         return ret;
 128 }
 129
 130 static int pwm_backlight_remove(struct platform_device *pdev)
 131 {
 132         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
 133         struct backlight_device *bl = platform_get_drvdata(pdev);
 134         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 135
 136         backlight_device_unregister(bl);
 137         pwm_config(pb->pwm, 0, pb->period);
 138         pwm_disable(pb->pwm);
 139         pwm_free(pb->pwm);
 140         kfree(pb);
 141         if (data->exit)
 142                 data->exit(&pdev->dev);
 143         return 0;
 144 }
 145
 146 #ifdef CONFIG_PM
 147 static int pwm_backlight_suspend(struct platform_device *pdev,
 148                                  pm_message_t state)
 149 {
 150         struct backlight_device *bl = platform_get_drvdata(pdev);
 151         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 152
 153         if (pb->notify)
 154                 pb->notify(pb->dev, 0);
 155         pwm_config(pb->pwm, 0, pb->period);
 156         pwm_disable(pb->pwm);
 157         return 0;
 158 }
 159
 160 static int pwm_backlight_resume(struct platform_device *pdev)
 161 {
 162         struct backlight_device *bl = platform_get_drvdata(pdev);
 163
 164         backlight_update_status(bl);
 165         return 0;
 166 }
 167 #else
 168 #define pwm_backlight_suspend   NULL
 169 #define pwm_backlight_resume    NULL
 170 #endif
 171
 172 static struct platform_driver pwm_backlight_driver = {
 173         .driver         = {
 174                 .name   = "pwm-backlight",
 175                 .owner  = THIS_MODULE,
 176         },
 177         .probe          = pwm_backlight_probe,
 178         .remove         = pwm_backlight_remove,
 179         .suspend        = pwm_backlight_suspend,
 180         .resume         = pwm_backlight_resume,
 181 };
 182
 183 static int __init pwm_backlight_init(void)
 184 {
 185         return platform_driver_register(&pwm_backlight_driver);
 186 }
 187 module_init(pwm_backlight_init);
 188
 189 static void __exit pwm_backlight_exit(void)
 190 {
 191         platform_driver_unregister(&pwm_backlight_driver);
 192 }
 193 module_exit(pwm_backlight_exit);
 194
 195 MODULE_DESCRIPTION("PWM based Backlight Driver");
 196 MODULE_LICENSE("GPL");
 197 MODULE_ALIAS("platform:pwm-backlight");
 198