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/gpio/consumer.h>
  14 #include <linux/gpio.h>
  15 #include <linux/module.h>
  16 #include <linux/kernel.h>
  17 #include <linux/init.h>
  18 #include <linux/platform_device.h>
  19 #include <linux/fb.h>
  20 #include <linux/backlight.h>
  21 #include <linux/err.h>
  22 #include <linux/pwm.h>
  23 #include <linux/pwm_backlight.h>
  24 #include <linux/regulator/consumer.h>
  25 #include <linux/slab.h>
  26
  27 struct pwm_bl_data {
  28         struct pwm_device       *pwm;
  29         struct device           *dev;
  30         unsigned int            period;
  31         unsigned int            lth_brightness;
  32         unsigned int            *levels;
  33         bool                    enabled;
  34         struct regulator        *power_supply;
  35         struct gpio_desc        *enable_gpio;
  36         unsigned int            scale;
  37         int                     (*notify)(struct device *,
  38                                           int brightness);
  39         void                    (*notify_after)(struct device *,
  40                                         int brightness);
  41         int                     (*check_fb)(struct device *, struct fb_info *);
  42         void                    (*exit)(struct device *);
  43 };
  44
  45 static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
  46 {
  47         int err;
  48
  49         if (pb->enabled)
  50                 return;
  51
  52         err = regulator_enable(pb->power_supply);
  53         if (err < 0)
  54                 dev_err(pb->dev, "failed to enable power supply\n");
  55
  56         if (pb->enable_gpio)
  57                 gpiod_set_value(pb->enable_gpio, 1);
  58
  59         pwm_enable(pb->pwm);
  60         pb->enabled = true;
  61 }
  62
  63 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
  64 {
  65         if (!pb->enabled)
  66                 return;
  67
  68         pwm_config(pb->pwm, 0, pb->period);
  69         pwm_disable(pb->pwm);
  70
  71         if (pb->enable_gpio)
  72                 gpiod_set_value(pb->enable_gpio, 0);
  73
  74         regulator_disable(pb->power_supply);
  75         pb->enabled = false;
  76 }
  77
  78 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
  79 {
  80         unsigned int lth = pb->lth_brightness;
  81         int duty_cycle;
  82
  83         if (pb->levels)
  84                 duty_cycle = pb->levels[brightness];
  85         else
  86                 duty_cycle = brightness;
  87
  88         return (duty_cycle * (pb->period - lth) / pb->scale) + lth;
  89 }
  90
  91 static int pwm_backlight_update_status(struct backlight_device *bl)
  92 {
  93         struct pwm_bl_data *pb = bl_get_data(bl);
  94         int brightness = bl->props.brightness;
  95         int duty_cycle;
  96
  97         if (bl->props.power != FB_BLANK_UNBLANK ||
  98             bl->props.fb_blank != FB_BLANK_UNBLANK ||
  99             bl->props.state & BL_CORE_FBBLANK)
 100                 brightness = 0;
 101
 102         if (pb->notify)
 103                 brightness = pb->notify(pb->dev, brightness);
 104
 105         if (brightness > 0) {
 106                 duty_cycle = compute_duty_cycle(pb, brightness);
 107                 pwm_config(pb->pwm, duty_cycle, pb->period);
 108                 pwm_backlight_power_on(pb, brightness);
 109         } else
 110                 pwm_backlight_power_off(pb);
 111
 112         if (pb->notify_after)
 113                 pb->notify_after(pb->dev, brightness);
 114
 115         return 0;
 116 }
 117
 118 static int pwm_backlight_get_brightness(struct backlight_device *bl)
 119 {
 120         return bl->props.brightness;
 121 }
 122
 123 static int pwm_backlight_check_fb(struct backlight_device *bl,
 124                                   struct fb_info *info)
 125 {
 126         struct pwm_bl_data *pb = bl_get_data(bl);
 127
 128         return !pb->check_fb || pb->check_fb(pb->dev, info);
 129 }
 130
 131 static const struct backlight_ops pwm_backlight_ops = {
 132         .update_status  = pwm_backlight_update_status,
 133         .get_brightness = pwm_backlight_get_brightness,
 134         .check_fb       = pwm_backlight_check_fb,
 135 };
 136
 137 #ifdef CONFIG_OF
 138 static int pwm_backlight_parse_dt(struct device *dev,
 139                                   struct platform_pwm_backlight_data *data)
 140 {
 141         struct device_node *node = dev->of_node;
 142         struct property *prop;
 143         int length;
 144         u32 value;
 145         int ret;
 146
 147         if (!node)
 148                 return -ENODEV;
 149
 150         memset(data, 0, sizeof(*data));
 151
 152         /* determine the number of brightness levels */
 153         prop = of_find_property(node, "brightness-levels", &length);
 154         if (!prop)
 155                 return -EINVAL;
 156
 157         data->max_brightness = length / sizeof(u32);
 158
 159         /* read brightness levels from DT property */
 160         if (data->max_brightness > 0) {
 161                 size_t size = sizeof(*data->levels) * data->max_brightness;
 162
 163                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 164                 if (!data->levels)
 165                         return -ENOMEM;
 166
 167                 ret = of_property_read_u32_array(node, "brightness-levels",
 168                                                  data->levels,
 169                                                  data->max_brightness);
 170                 if (ret < 0)
 171                         return ret;
 172
 173                 ret = of_property_read_u32(node, "default-brightness-level",
 174                                            &value);
 175                 if (ret < 0)
 176                         return ret;
 177
 178                 data->dft_brightness = value;
 179                 data->max_brightness--;
 180         }
 181
 182         return 0;
 183 }
 184
 185 static struct of_device_id pwm_backlight_of_match[] = {
 186         { .compatible = "pwm-backlight" },
 187         { }
 188 };
 189
 190 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 191 #else
 192 static int pwm_backlight_parse_dt(struct device *dev,
 193                                   struct platform_pwm_backlight_data *data)
 194 {
 195         return -ENODEV;
 196 }
 197 #endif
 198
 199 static int pwm_backlight_probe(struct platform_device *pdev)
 200 {
 201         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 202         struct platform_pwm_backlight_data defdata;
 203         struct backlight_properties props;
 204         struct backlight_device *bl;
 205         struct pwm_bl_data *pb;
 206         int ret;
 207
 208         if (!data) {
 209                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 210                 if (ret < 0) {
 211                         dev_err(&pdev->dev, "failed to find platform data\n");
 212                         return ret;
 213                 }
 214
 215                 data = &defdata;
 216         }
 217
 218         if (data->init) {
 219                 ret = data->init(&pdev->dev);
 220                 if (ret < 0)
 221                         return ret;
 222         }
 223
 224         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 225         if (!pb) {
 226                 ret = -ENOMEM;
 227                 goto err_alloc;
 228         }
 229
 230         if (data->levels) {
 231                 unsigned int i;
 232
 233                 for (i = 0; i <= data->max_brightness; i++)
 234                         if (data->levels[i] > pb->scale)
 235                                 pb->scale = data->levels[i];
 236
 237                 pb->levels = data->levels;
 238         } else
 239                 pb->scale = data->max_brightness;
 240
 241         pb->notify = data->notify;
 242         pb->notify_after = data->notify_after;
 243         pb->check_fb = data->check_fb;
 244         pb->exit = data->exit;
 245         pb->dev = &pdev->dev;
 246         pb->enabled = false;
 247
 248         pb->enable_gpio = devm_gpiod_get(&pdev->dev, "enable");
 249         if (IS_ERR(pb->enable_gpio)) {
 250                 ret = PTR_ERR(pb->enable_gpio);
 251                 if (ret == -ENOENT)
 252                         pb->enable_gpio = NULL;
 253                 else
 254                         goto err_alloc;
 255         }
 256
 257         /*
 258          * Compatibility fallback for drivers still using the integer GPIO
 259          * platform data. Must go away soon.
 260          */
 261         if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
 262                 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 263                                             GPIOF_OUT_INIT_HIGH, "enable");
 264                 if (ret < 0) {
 265                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 266                                 data->enable_gpio, ret);
 267                         goto err_alloc;
 268                 }
 269
 270                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 271         }
 272
 273         if (pb->enable_gpio)
 274                 gpiod_direction_output(pb->enable_gpio, 1);
 275
 276         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 277         if (IS_ERR(pb->power_supply)) {
 278                 ret = PTR_ERR(pb->power_supply);
 279                 goto err_alloc;
 280         }
 281
 282         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 283         if (IS_ERR(pb->pwm)) {
 284                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 285
 286                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 287                 if (IS_ERR(pb->pwm)) {
 288                         dev_err(&pdev->dev, "unable to request legacy PWM\n");
 289                         ret = PTR_ERR(pb->pwm);
 290                         goto err_alloc;
 291                 }
 292         }
 293
 294         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 295
 296         /*
 297          * The DT case will set the pwm_period_ns field to 0 and store the
 298          * period, parsed from the DT, in the PWM device. For the non-DT case,
 299          * set the period from platform data if it has not already been set
 300          * via the PWM lookup table.
 301          */
 302         pb->period = pwm_get_period(pb->pwm);
 303         if (!pb->period && (data->pwm_period_ns > 0)) {
 304                 pb->period = data->pwm_period_ns;
 305                 pwm_set_period(pb->pwm, data->pwm_period_ns);
 306         }
 307
 308         pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
 309
 310         memset(&props, 0, sizeof(struct backlight_properties));
 311         props.type = BACKLIGHT_RAW;
 312         props.max_brightness = data->max_brightness;
 313         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 314                                        &pwm_backlight_ops, &props);
 315         if (IS_ERR(bl)) {
 316                 dev_err(&pdev->dev, "failed to register backlight\n");
 317                 ret = PTR_ERR(bl);
 318                 goto err_alloc;
 319         }
 320
 321         if (data->dft_brightness > data->max_brightness) {
 322                 dev_warn(&pdev->dev,
 323                          "invalid default brightness level: %u, using %u\n",
 324                          data->dft_brightness, data->max_brightness);
 325                 data->dft_brightness = data->max_brightness;
 326         }
 327
 328         bl->props.brightness = data->dft_brightness;
 329         backlight_update_status(bl);
 330
 331         platform_set_drvdata(pdev, bl);
 332         return 0;
 333
 334 err_alloc:
 335         if (data->exit)
 336                 data->exit(&pdev->dev);
 337         return ret;
 338 }
 339
 340 static int pwm_backlight_remove(struct platform_device *pdev)
 341 {
 342         struct backlight_device *bl = platform_get_drvdata(pdev);
 343         struct pwm_bl_data *pb = bl_get_data(bl);
 344
 345         backlight_device_unregister(bl);
 346         pwm_backlight_power_off(pb);
 347
 348         if (pb->exit)
 349                 pb->exit(&pdev->dev);
 350
 351         return 0;
 352 }
 353
 354 static void pwm_backlight_shutdown(struct platform_device *pdev)
 355 {
 356         struct backlight_device *bl = platform_get_drvdata(pdev);
 357         struct pwm_bl_data *pb = bl_get_data(bl);
 358
 359         pwm_backlight_power_off(pb);
 360 }
 361
 362 #ifdef CONFIG_PM_SLEEP
 363 static int pwm_backlight_suspend(struct device *dev)
 364 {
 365         struct backlight_device *bl = dev_get_drvdata(dev);
 366         struct pwm_bl_data *pb = bl_get_data(bl);
 367
 368         if (pb->notify)
 369                 pb->notify(pb->dev, 0);
 370
 371         pwm_backlight_power_off(pb);
 372
 373         if (pb->notify_after)
 374                 pb->notify_after(pb->dev, 0);
 375
 376         return 0;
 377 }
 378
 379 static int pwm_backlight_resume(struct device *dev)
 380 {
 381         struct backlight_device *bl = dev_get_drvdata(dev);
 382
 383         backlight_update_status(bl);
 384
 385         return 0;
 386 }
 387 #endif
 388
 389 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 390 #ifdef CONFIG_PM_SLEEP
 391         .suspend = pwm_backlight_suspend,
 392         .resume = pwm_backlight_resume,
 393         .poweroff = pwm_backlight_suspend,
 394         .restore = pwm_backlight_resume,
 395 #endif
 396 };
 397
 398 static struct platform_driver pwm_backlight_driver = {
 399         .driver         = {
 400                 .name           = "pwm-backlight",
 401                 .owner          = THIS_MODULE,
 402                 .pm             = &pwm_backlight_pm_ops,
 403                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 404         },
 405         .probe          = pwm_backlight_probe,
 406         .remove         = pwm_backlight_remove,
 407         .shutdown       = pwm_backlight_shutdown,
 408 };
 409
 410 module_platform_driver(pwm_backlight_driver);
 411
 412 MODULE_DESCRIPTION("PWM based Backlight Driver");
 413 MODULE_LICENSE("GPL");
 414 MODULE_ALIAS("platform:pwm-backlight");