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         unsigned int            *levels;
  30         int                     (*notify)(struct device *,
  31                                           int brightness);
  32         void                    (*notify_after)(struct device *,
  33                                         int brightness);
  34         int                     (*check_fb)(struct device *, struct fb_info *);
  35         void                    (*exit)(struct device *);
  36 };
  37
  38 static int pwm_backlight_update_status(struct backlight_device *bl)
  39 {
  40         struct pwm_bl_data *pb = bl_get_data(bl);
  41         int brightness = bl->props.brightness;
  42         int max = bl->props.max_brightness;
  43
  44         if (bl->props.power != FB_BLANK_UNBLANK ||
  45             bl->props.fb_blank != FB_BLANK_UNBLANK ||
  46             bl->props.state & BL_CORE_FBBLANK)
  47                 brightness = 0;
  48
  49         if (pb->notify)
  50                 brightness = pb->notify(pb->dev, brightness);
  51
  52         if (brightness == 0) {
  53                 pwm_config(pb->pwm, 0, pb->period);
  54                 pwm_disable(pb->pwm);
  55         } else {
  56                 int duty_cycle;
  57
  58                 if (pb->levels) {
  59                         duty_cycle = pb->levels[brightness];
  60                         max = pb->levels[max];
  61                 } else {
  62                         duty_cycle = brightness;
  63                 }
  64
  65                 duty_cycle = pb->lth_brightness +
  66                      (duty_cycle * (pb->period - pb->lth_brightness) / max);
  67                 pwm_config(pb->pwm, duty_cycle, pb->period);
  68                 pwm_enable(pb->pwm);
  69         }
  70
  71         if (pb->notify_after)
  72                 pb->notify_after(pb->dev, brightness);
  73
  74         return 0;
  75 }
  76
  77 static int pwm_backlight_get_brightness(struct backlight_device *bl)
  78 {
  79         return bl->props.brightness;
  80 }
  81
  82 static int pwm_backlight_check_fb(struct backlight_device *bl,
  83                                   struct fb_info *info)
  84 {
  85         struct pwm_bl_data *pb = bl_get_data(bl);
  86
  87         return !pb->check_fb || pb->check_fb(pb->dev, info);
  88 }
  89
  90 static const struct backlight_ops pwm_backlight_ops = {
  91         .update_status  = pwm_backlight_update_status,
  92         .get_brightness = pwm_backlight_get_brightness,
  93         .check_fb       = pwm_backlight_check_fb,
  94 };
  95
  96 #ifdef CONFIG_OF
  97 static int pwm_backlight_parse_dt(struct device *dev,
  98                                   struct platform_pwm_backlight_data *data)
  99 {
 100         struct device_node *node = dev->of_node;
 101         struct property *prop;
 102         int length;
 103         u32 value;
 104         int ret;
 105
 106         if (!node)
 107                 return -ENODEV;
 108
 109         memset(data, 0, sizeof(*data));
 110
 111         /* determine the number of brightness levels */
 112         prop = of_find_property(node, "brightness-levels", &length);
 113         if (!prop)
 114                 return -EINVAL;
 115
 116         data->max_brightness = length / sizeof(u32);
 117
 118         /* read brightness levels from DT property */
 119         if (data->max_brightness > 0) {
 120                 size_t size = sizeof(*data->levels) * data->max_brightness;
 121
 122                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 123                 if (!data->levels)
 124                         return -ENOMEM;
 125
 126                 ret = of_property_read_u32_array(node, "brightness-levels",
 127                                                  data->levels,
 128                                                  data->max_brightness);
 129                 if (ret < 0)
 130                         return ret;
 131
 132                 ret = of_property_read_u32(node, "default-brightness-level",
 133                                            &value);
 134                 if (ret < 0)
 135                         return ret;
 136
 137                 data->dft_brightness = value;
 138                 data->max_brightness--;
 139         }
 140
 141         /*
 142          * TODO: Most users of this driver use a number of GPIOs to control
 143          *       backlight power. Support for specifying these needs to be
 144          *       added.
 145          */
 146
 147         return 0;
 148 }
 149
 150 static struct of_device_id pwm_backlight_of_match[] = {
 151         { .compatible = "pwm-backlight" },
 152         { }
 153 };
 154
 155 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 156 #else
 157 static int pwm_backlight_parse_dt(struct device *dev,
 158                                   struct platform_pwm_backlight_data *data)
 159 {
 160         return -ENODEV;
 161 }
 162 #endif
 163
 164 static int pwm_backlight_probe(struct platform_device *pdev)
 165 {
 166         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
 167         struct platform_pwm_backlight_data defdata;
 168         struct backlight_properties props;
 169         struct backlight_device *bl;
 170         struct pwm_bl_data *pb;
 171         unsigned int max;
 172         int ret;
 173
 174         if (!data) {
 175                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 176                 if (ret < 0) {
 177                         dev_err(&pdev->dev, "failed to find platform data\n");
 178                         return ret;
 179                 }
 180
 181                 data = &defdata;
 182         }
 183
 184         if (data->init) {
 185                 ret = data->init(&pdev->dev);
 186                 if (ret < 0)
 187                         return ret;
 188         }
 189
 190         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 191         if (!pb) {
 192                 dev_err(&pdev->dev, "no memory for state\n");
 193                 ret = -ENOMEM;
 194                 goto err_alloc;
 195         }
 196
 197         if (data->levels) {
 198                 max = data->levels[data->max_brightness];
 199                 pb->levels = data->levels;
 200         } else
 201                 max = data->max_brightness;
 202
 203         pb->notify = data->notify;
 204         pb->notify_after = data->notify_after;
 205         pb->check_fb = data->check_fb;
 206         pb->exit = data->exit;
 207         pb->dev = &pdev->dev;
 208
 209         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 210         if (IS_ERR(pb->pwm)) {
 211                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 212
 213                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 214                 if (IS_ERR(pb->pwm)) {
 215                         dev_err(&pdev->dev, "unable to request legacy PWM\n");
 216                         ret = PTR_ERR(pb->pwm);
 217                         goto err_alloc;
 218                 }
 219         }
 220
 221         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 222
 223         /*
 224          * The DT case will set the pwm_period_ns field to 0 and store the
 225          * period, parsed from the DT, in the PWM device. For the non-DT case,
 226          * set the period from platform data.
 227          */
 228         if (data->pwm_period_ns > 0)
 229                 pwm_set_period(pb->pwm, data->pwm_period_ns);
 230
 231         pb->period = pwm_get_period(pb->pwm);
 232         pb->lth_brightness = data->lth_brightness * (pb->period / max);
 233
 234         memset(&props, 0, sizeof(struct backlight_properties));
 235         props.type = BACKLIGHT_RAW;
 236         props.max_brightness = data->max_brightness;
 237         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 238                                        &pwm_backlight_ops, &props);
 239         if (IS_ERR(bl)) {
 240                 dev_err(&pdev->dev, "failed to register backlight\n");
 241                 ret = PTR_ERR(bl);
 242                 goto err_alloc;
 243         }
 244
 245         if (data->dft_brightness > data->max_brightness) {
 246                 dev_warn(&pdev->dev,
 247                          "invalid default brightness level: %u, using %u\n",
 248                          data->dft_brightness, data->max_brightness);
 249                 data->dft_brightness = data->max_brightness;
 250         }
 251
 252         bl->props.brightness = data->dft_brightness;
 253         backlight_update_status(bl);
 254
 255         platform_set_drvdata(pdev, bl);
 256         return 0;
 257
 258 err_alloc:
 259         if (data->exit)
 260                 data->exit(&pdev->dev);
 261         return ret;
 262 }
 263
 264 static int pwm_backlight_remove(struct platform_device *pdev)
 265 {
 266         struct backlight_device *bl = platform_get_drvdata(pdev);
 267         struct pwm_bl_data *pb = bl_get_data(bl);
 268
 269         backlight_device_unregister(bl);
 270         pwm_config(pb->pwm, 0, pb->period);
 271         pwm_disable(pb->pwm);
 272         if (pb->exit)
 273                 pb->exit(&pdev->dev);
 274         return 0;
 275 }
 276
 277 #ifdef CONFIG_PM_SLEEP
 278 static int pwm_backlight_suspend(struct device *dev)
 279 {
 280         struct backlight_device *bl = dev_get_drvdata(dev);
 281         struct pwm_bl_data *pb = bl_get_data(bl);
 282
 283         if (pb->notify)
 284                 pb->notify(pb->dev, 0);
 285         pwm_config(pb->pwm, 0, pb->period);
 286         pwm_disable(pb->pwm);
 287         if (pb->notify_after)
 288                 pb->notify_after(pb->dev, 0);
 289         return 0;
 290 }
 291
 292 static int pwm_backlight_resume(struct device *dev)
 293 {
 294         struct backlight_device *bl = dev_get_drvdata(dev);
 295
 296         backlight_update_status(bl);
 297         return 0;
 298 }
 299 #endif
 300
 301 static SIMPLE_DEV_PM_OPS(pwm_backlight_pm_ops, pwm_backlight_suspend,
 302                          pwm_backlight_resume);
 303
 304 static struct platform_driver pwm_backlight_driver = {
 305         .driver         = {
 306                 .name           = "pwm-backlight",
 307                 .owner          = THIS_MODULE,
 308                 .pm             = &pwm_backlight_pm_ops,
 309                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 310         },
 311         .probe          = pwm_backlight_probe,
 312         .remove         = pwm_backlight_remove,
 313 };
 314
 315 module_platform_driver(pwm_backlight_driver);
 316
 317 MODULE_DESCRIPTION("PWM based Backlight Driver");
 318 MODULE_LICENSE("GPL");
 319 MODULE_ALIAS("platform:pwm-backlight");
 320