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 #include <linux/slab.h>
  23
  24 struct pwm_bl_data {
  25         struct pwm_device       *pwm;
  26         struct device           *dev;
  27         unsigned int            period;
  28         unsigned int            lth_brightness;
  29         int                     (*notify)(struct device *,
  30                                           int brightness);
  31         void                    (*notify_after)(struct device *,
  32                                         int brightness);
  33         int                     (*check_fb)(struct device *, struct fb_info *);
  34 };
  35
  36 static int pwm_backlight_update_status(struct backlight_device *bl)
  37 {
  38         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
  39         int brightness = bl->props.brightness;
  40         int max = bl->props.max_brightness;
  41
  42         if (bl->props.power != FB_BLANK_UNBLANK)
  43                 brightness = 0;
  44
  45         if (bl->props.fb_blank != FB_BLANK_UNBLANK)
  46                 brightness = 0;
  47
  48         if (pb->notify)
  49                 brightness = pb->notify(pb->dev, brightness);
  50
  51         if (brightness == 0) {
  52                 pwm_config(pb->pwm, 0, pb->period);
  53                 pwm_disable(pb->pwm);
  54         } else {
  55                 brightness = pb->lth_brightness +
  56                         (brightness * (pb->period - pb->lth_brightness) / max);
  57                 pwm_config(pb->pwm, brightness, pb->period);
  58                 pwm_enable(pb->pwm);
  59         }
  60
  61         if (pb->notify_after)
  62                 pb->notify_after(pb->dev, brightness);
  63
  64         return 0;
  65 }
  66
  67 static int pwm_backlight_get_brightness(struct backlight_device *bl)
  68 {
  69         return bl->props.brightness;
  70 }
  71
  72 static int pwm_backlight_check_fb(struct backlight_device *bl,
  73                                   struct fb_info *info)
  74 {
  75         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
  76
  77         return !pb->check_fb || pb->check_fb(pb->dev, info);
  78 }
  79
  80 static const struct backlight_ops pwm_backlight_ops = {
  81         .update_status  = pwm_backlight_update_status,
  82         .get_brightness = pwm_backlight_get_brightness,
  83         .check_fb       = pwm_backlight_check_fb,
  84 };
  85
  86 static int pwm_backlight_probe(struct platform_device *pdev)
  87 {
  88         struct backlight_properties props;
  89         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
  90         struct backlight_device *bl;
  91         struct pwm_bl_data *pb;
  92         int ret;
  93
  94         if (!data) {
  95                 dev_err(&pdev->dev, "failed to find platform data\n");
  96                 return -EINVAL;
  97         }
  98
  99         if (data->init) {
 100                 ret = data->init(&pdev->dev);
 101                 if (ret < 0)
 102                         return ret;
 103         }
 104
 105         pb = kzalloc(sizeof(*pb), GFP_KERNEL);
 106         if (!pb) {
 107                 dev_err(&pdev->dev, "no memory for state\n");
 108                 ret = -ENOMEM;
 109                 goto err_alloc;
 110         }
 111
 112         pb->period = data->pwm_period_ns;
 113         pb->notify = data->notify;
 114         pb->notify_after = data->notify_after;
 115         pb->check_fb = data->check_fb;
 116         pb->lth_brightness = data->lth_brightness *
 117                 (data->pwm_period_ns / data->max_brightness);
 118         pb->dev = &pdev->dev;
 119
 120         pb->pwm = pwm_request(data->pwm_id, "backlight");
 121         if (IS_ERR(pb->pwm)) {
 122                 dev_err(&pdev->dev, "unable to request PWM for backlight\n");
 123                 ret = PTR_ERR(pb->pwm);
 124                 goto err_pwm;
 125         } else
 126                 dev_dbg(&pdev->dev, "got pwm for backlight\n");
 127
 128         memset(&props, 0, sizeof(struct backlight_properties));
 129         props.type = BACKLIGHT_RAW;
 130         props.max_brightness = data->max_brightness;
 131         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 132                                        &pwm_backlight_ops, &props);
 133         if (IS_ERR(bl)) {
 134                 dev_err(&pdev->dev, "failed to register backlight\n");
 135                 ret = PTR_ERR(bl);
 136                 goto err_bl;
 137         }
 138
 139         bl->props.brightness = data->dft_brightness;
 140         backlight_update_status(bl);
 141
 142         platform_set_drvdata(pdev, bl);
 143         return 0;
 144
 145 err_bl:
 146         pwm_free(pb->pwm);
 147 err_pwm:
 148         kfree(pb);
 149 err_alloc:
 150         if (data->exit)
 151                 data->exit(&pdev->dev);
 152         return ret;
 153 }
 154
 155 static int pwm_backlight_remove(struct platform_device *pdev)
 156 {
 157         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
 158         struct backlight_device *bl = platform_get_drvdata(pdev);
 159         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 160
 161         backlight_device_unregister(bl);
 162         pwm_config(pb->pwm, 0, pb->period);
 163         pwm_disable(pb->pwm);
 164         pwm_free(pb->pwm);
 165         kfree(pb);
 166         if (data->exit)
 167                 data->exit(&pdev->dev);
 168         return 0;
 169 }
 170
 171 #ifdef CONFIG_PM
 172 static int pwm_backlight_suspend(struct platform_device *pdev,
 173                                  pm_message_t state)
 174 {
 175         struct backlight_device *bl = platform_get_drvdata(pdev);
 176         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 177
 178         if (pb->notify)
 179                 pb->notify(pb->dev, 0);
 180         pwm_config(pb->pwm, 0, pb->period);
 181         pwm_disable(pb->pwm);
 182         if (pb->notify_after)
 183                 pb->notify_after(pb->dev, 0);
 184         return 0;
 185 }
 186
 187 static int pwm_backlight_resume(struct platform_device *pdev)
 188 {
 189         struct backlight_device *bl = platform_get_drvdata(pdev);
 190
 191         backlight_update_status(bl);
 192         return 0;
 193 }
 194 #else
 195 #define pwm_backlight_suspend   NULL
 196 #define pwm_backlight_resume    NULL
 197 #endif
 198
 199 static struct platform_driver pwm_backlight_driver = {
 200         .driver         = {
 201                 .name   = "pwm-backlight",
 202                 .owner  = THIS_MODULE,
 203         },
 204         .probe          = pwm_backlight_probe,
 205         .remove         = pwm_backlight_remove,
 206         .suspend        = pwm_backlight_suspend,
 207         .resume         = pwm_backlight_resume,
 208 };
 209
 210 static int __init pwm_backlight_init(void)
 211 {
 212         return platform_driver_register(&pwm_backlight_driver);
 213 }
 214 module_init(pwm_backlight_init);
 215
 216 static void __exit pwm_backlight_exit(void)
 217 {
 218         platform_driver_unregister(&pwm_backlight_driver);
 219 }
 220 module_exit(pwm_backlight_exit);
 221
 222 MODULE_DESCRIPTION("PWM based Backlight Driver");
 223 MODULE_LICENSE("GPL");
 224 MODULE_ALIAS("platform:pwm-backlight");
 225