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