drivers/video/backlight/pwm_bl.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Simple PWM based backlight control, board code has to setup
   4  * 1) pin configuration so PWM waveforms can output
   5  * 2) platform_data being correctly configured
   6  */
   7
   8 #include <linux/delay.h>
   9 #include <linux/gpio/consumer.h>
  10 #include <linux/gpio.h>
  11 #include <linux/module.h>
  12 #include <linux/kernel.h>
  13 #include <linux/init.h>
  14 #include <linux/platform_device.h>
  15 #include <linux/fb.h>
  16 #include <linux/backlight.h>
  17 #include <linux/err.h>
  18 #include <linux/pwm.h>
  19 #include <linux/pwm_backlight.h>
  20 #include <linux/regulator/consumer.h>
  21 #include <linux/slab.h>
  22
  23 struct pwm_bl_data {
  24         struct pwm_device       *pwm;
  25         struct device           *dev;
  26         unsigned int            lth_brightness;
  27         unsigned int            *levels;
  28         bool                    enabled;
  29         struct regulator        *power_supply;
  30         struct gpio_desc        *enable_gpio;
  31         unsigned int            scale;
  32         bool                    legacy;
  33         unsigned int            post_pwm_on_delay;
  34         unsigned int            pwm_off_delay;
  35         int                     (*notify)(struct device *,
  36                                           int brightness);
  37         void                    (*notify_after)(struct device *,
  38                                         int brightness);
  39         int                     (*check_fb)(struct device *, struct fb_info *);
  40         void                    (*exit)(struct device *);
  41 };
  42
  43 static void pwm_backlight_power_on(struct pwm_bl_data *pb)
  44 {
  45         struct pwm_state state;
  46         int err;
  47
  48         pwm_get_state(pb->pwm, &state);
  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         state.enabled = true;
  57         pwm_apply_state(pb->pwm, &state);
  58
  59         if (pb->post_pwm_on_delay)
  60                 msleep(pb->post_pwm_on_delay);
  61
  62         if (pb->enable_gpio)
  63                 gpiod_set_value_cansleep(pb->enable_gpio, 1);
  64
  65         pb->enabled = true;
  66 }
  67
  68 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
  69 {
  70         struct pwm_state state;
  71
  72         pwm_get_state(pb->pwm, &state);
  73         if (!pb->enabled)
  74                 return;
  75
  76         if (pb->enable_gpio)
  77                 gpiod_set_value_cansleep(pb->enable_gpio, 0);
  78
  79         if (pb->pwm_off_delay)
  80                 msleep(pb->pwm_off_delay);
  81
  82         state.enabled = false;
  83         state.duty_cycle = 0;
  84         pwm_apply_state(pb->pwm, &state);
  85
  86         regulator_disable(pb->power_supply);
  87         pb->enabled = false;
  88 }
  89
  90 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
  91 {
  92         unsigned int lth = pb->lth_brightness;
  93         struct pwm_state state;
  94         u64 duty_cycle;
  95
  96         pwm_get_state(pb->pwm, &state);
  97
  98         if (pb->levels)
  99                 duty_cycle = pb->levels[brightness];
 100         else
 101                 duty_cycle = brightness;
 102
 103         duty_cycle *= state.period - lth;
 104         do_div(duty_cycle, pb->scale);
 105
 106         return duty_cycle + lth;
 107 }
 108
 109 static int pwm_backlight_update_status(struct backlight_device *bl)
 110 {
 111         struct pwm_bl_data *pb = bl_get_data(bl);
 112         int brightness = bl->props.brightness;
 113         struct pwm_state state;
 114
 115         if (bl->props.power != FB_BLANK_UNBLANK ||
 116             bl->props.fb_blank != FB_BLANK_UNBLANK ||
 117             bl->props.state & BL_CORE_FBBLANK)
 118                 brightness = 0;
 119
 120         if (pb->notify)
 121                 brightness = pb->notify(pb->dev, brightness);
 122
 123         if (brightness > 0) {
 124                 pwm_get_state(pb->pwm, &state);
 125                 state.duty_cycle = compute_duty_cycle(pb, brightness);
 126                 pwm_apply_state(pb->pwm, &state);
 127                 pwm_backlight_power_on(pb);
 128         } else {
 129                 pwm_backlight_power_off(pb);
 130         }
 131
 132         if (pb->notify_after)
 133                 pb->notify_after(pb->dev, brightness);
 134
 135         return 0;
 136 }
 137
 138 static int pwm_backlight_check_fb(struct backlight_device *bl,
 139                                   struct fb_info *info)
 140 {
 141         struct pwm_bl_data *pb = bl_get_data(bl);
 142
 143         return !pb->check_fb || pb->check_fb(pb->dev, info);
 144 }
 145
 146 static const struct backlight_ops pwm_backlight_ops = {
 147         .update_status  = pwm_backlight_update_status,
 148         .check_fb       = pwm_backlight_check_fb,
 149 };
 150
 151 #ifdef CONFIG_OF
 152 #define PWM_LUMINANCE_SCALE     10000 /* luminance scale */
 153
 154 /*
 155  * CIE lightness to PWM conversion.
 156  *
 157  * The CIE 1931 lightness formula is what actually describes how we perceive
 158  * light:
 159  *          Y = (L* / 902.3)           if L* ≤ 0.08856
 160  *          Y = ((L* + 16) / 116)^3    if L* > 0.08856
 161  *
 162  * Where Y is the luminance, the amount of light coming out of the screen, and
 163  * is a number between 0.0 and 1.0; and L* is the lightness, how bright a human
 164  * perceives the screen to be, and is a number between 0 and 100.
 165  *
 166  * The following function does the fixed point maths needed to implement the
 167  * above formula.
 168  */
 169 static u64 cie1931(unsigned int lightness, unsigned int scale)
 170 {
 171         u64 retval;
 172
 173         lightness *= 100;
 174         if (lightness <= (8 * scale)) {
 175                 retval = DIV_ROUND_CLOSEST_ULL(lightness * 10, 9023);
 176         } else {
 177                 retval = int_pow((lightness + (16 * scale)) / 116, 3);
 178                 retval = DIV_ROUND_CLOSEST_ULL(retval, (scale * scale));
 179         }
 180
 181         return retval;
 182 }
 183
 184 /*
 185  * Create a default correction table for PWM values to create linear brightness
 186  * for LED based backlights using the CIE1931 algorithm.
 187  */
 188 static
 189 int pwm_backlight_brightness_default(struct device *dev,
 190                                      struct platform_pwm_backlight_data *data,
 191                                      unsigned int period)
 192 {
 193         unsigned int i;
 194         u64 retval;
 195
 196         /*
 197          * Once we have 4096 levels there's little point going much higher...
 198          * neither interactive sliders nor animation benefits from having
 199          * more values in the table.
 200          */
 201         data->max_brightness =
 202                 min((int)DIV_ROUND_UP(period, fls(period)), 4096);
 203
 204         data->levels = devm_kcalloc(dev, data->max_brightness,
 205                                     sizeof(*data->levels), GFP_KERNEL);
 206         if (!data->levels)
 207                 return -ENOMEM;
 208
 209         /* Fill the table using the cie1931 algorithm */
 210         for (i = 0; i < data->max_brightness; i++) {
 211                 retval = cie1931((i * PWM_LUMINANCE_SCALE) /
 212                                  data->max_brightness, PWM_LUMINANCE_SCALE) *
 213                                  period;
 214                 retval = DIV_ROUND_CLOSEST_ULL(retval, PWM_LUMINANCE_SCALE);
 215                 if (retval > UINT_MAX)
 216                         return -EINVAL;
 217                 data->levels[i] = (unsigned int)retval;
 218         }
 219
 220         data->dft_brightness = data->max_brightness / 2;
 221         data->max_brightness--;
 222
 223         return 0;
 224 }
 225
 226 static int pwm_backlight_parse_dt(struct device *dev,
 227                                   struct platform_pwm_backlight_data *data)
 228 {
 229         struct device_node *node = dev->of_node;
 230         unsigned int num_levels = 0;
 231         unsigned int levels_count;
 232         unsigned int num_steps = 0;
 233         struct property *prop;
 234         unsigned int *table;
 235         int length;
 236         u32 value;
 237         int ret;
 238
 239         if (!node)
 240                 return -ENODEV;
 241
 242         memset(data, 0, sizeof(*data));
 243
 244         /*
 245          * These values are optional and set as 0 by default, the out values
 246          * are modified only if a valid u32 value can be decoded.
 247          */
 248         of_property_read_u32(node, "post-pwm-on-delay-ms",
 249                              &data->post_pwm_on_delay);
 250         of_property_read_u32(node, "pwm-off-delay-ms", &data->pwm_off_delay);
 251
 252         data->enable_gpio = -EINVAL;
 253
 254         /*
 255          * Determine the number of brightness levels, if this property is not
 256          * set a default table of brightness levels will be used.
 257          */
 258         prop = of_find_property(node, "brightness-levels", &length);
 259         if (!prop)
 260                 return 0;
 261
 262         data->max_brightness = length / sizeof(u32);
 263
 264         /* read brightness levels from DT property */
 265         if (data->max_brightness > 0) {
 266                 size_t size = sizeof(*data->levels) * data->max_brightness;
 267                 unsigned int i, j, n = 0;
 268
 269                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 270                 if (!data->levels)
 271                         return -ENOMEM;
 272
 273                 ret = of_property_read_u32_array(node, "brightness-levels",
 274                                                  data->levels,
 275                                                  data->max_brightness);
 276                 if (ret < 0)
 277                         return ret;
 278
 279                 ret = of_property_read_u32(node, "default-brightness-level",
 280                                            &value);
 281                 if (ret < 0)
 282                         return ret;
 283
 284                 data->dft_brightness = value;
 285
 286                 /*
 287                  * This property is optional, if is set enables linear
 288                  * interpolation between each of the values of brightness levels
 289                  * and creates a new pre-computed table.
 290                  */
 291                 of_property_read_u32(node, "num-interpolated-steps",
 292                                      &num_steps);
 293
 294                 /*
 295                  * Make sure that there is at least two entries in the
 296                  * brightness-levels table, otherwise we can't interpolate
 297                  * between two points.
 298                  */
 299                 if (num_steps) {
 300                         if (data->max_brightness < 2) {
 301                                 dev_err(dev, "can't interpolate\n");
 302                                 return -EINVAL;
 303                         }
 304
 305                         /*
 306                          * Recalculate the number of brightness levels, now
 307                          * taking in consideration the number of interpolated
 308                          * steps between two levels.
 309                          */
 310                         for (i = 0; i < data->max_brightness - 1; i++) {
 311                                 if ((data->levels[i + 1] - data->levels[i]) /
 312                                    num_steps)
 313                                         num_levels += num_steps;
 314                                 else
 315                                         num_levels++;
 316                         }
 317                         num_levels++;
 318                         dev_dbg(dev, "new number of brightness levels: %d\n",
 319                                 num_levels);
 320
 321                         /*
 322                          * Create a new table of brightness levels with all the
 323                          * interpolated steps.
 324                          */
 325                         size = sizeof(*table) * num_levels;
 326                         table = devm_kzalloc(dev, size, GFP_KERNEL);
 327                         if (!table)
 328                                 return -ENOMEM;
 329
 330                         /* Fill the interpolated table. */
 331                         levels_count = 0;
 332                         for (i = 0; i < data->max_brightness - 1; i++) {
 333                                 value = data->levels[i];
 334                                 n = (data->levels[i + 1] - value) / num_steps;
 335                                 if (n > 0) {
 336                                         for (j = 0; j < num_steps; j++) {
 337                                                 table[levels_count] = value;
 338                                                 value += n;
 339                                                 levels_count++;
 340                                         }
 341                                 } else {
 342                                         table[levels_count] = data->levels[i];
 343                                         levels_count++;
 344                                 }
 345                         }
 346                         table[levels_count] = data->levels[i];
 347
 348                         /*
 349                          * As we use interpolation lets remove current
 350                          * brightness levels table and replace for the
 351                          * new interpolated table.
 352                          */
 353                         devm_kfree(dev, data->levels);
 354                         data->levels = table;
 355
 356                         /*
 357                          * Reassign max_brightness value to the new total number
 358                          * of brightness levels.
 359                          */
 360                         data->max_brightness = num_levels;
 361                 }
 362
 363                 data->max_brightness--;
 364         }
 365
 366         return 0;
 367 }
 368
 369 static const struct of_device_id pwm_backlight_of_match[] = {
 370         { .compatible = "pwm-backlight" },
 371         { }
 372 };
 373
 374 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 375 #else
 376 static int pwm_backlight_parse_dt(struct device *dev,
 377                                   struct platform_pwm_backlight_data *data)
 378 {
 379         return -ENODEV;
 380 }
 381
 382 static
 383 int pwm_backlight_brightness_default(struct device *dev,
 384                                      struct platform_pwm_backlight_data *data,
 385                                      unsigned int period)
 386 {
 387         return -ENODEV;
 388 }
 389 #endif
 390
 391 static bool pwm_backlight_is_linear(struct platform_pwm_backlight_data *data)
 392 {
 393         unsigned int nlevels = data->max_brightness + 1;
 394         unsigned int min_val = data->levels[0];
 395         unsigned int max_val = data->levels[nlevels - 1];
 396         /*
 397          * Multiplying by 128 means that even in pathological cases such
 398          * as (max_val - min_val) == nlevels the error at max_val is less
 399          * than 1%.
 400          */
 401         unsigned int slope = (128 * (max_val - min_val)) / nlevels;
 402         unsigned int margin = (max_val - min_val) / 20; /* 5% */
 403         int i;
 404
 405         for (i = 1; i < nlevels; i++) {
 406                 unsigned int linear_value = min_val + ((i * slope) / 128);
 407                 unsigned int delta = abs(linear_value - data->levels[i]);
 408
 409                 if (delta > margin)
 410                         return false;
 411         }
 412
 413         return true;
 414 }
 415
 416 static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
 417 {
 418         struct device_node *node = pb->dev->of_node;
 419
 420         /* Not booted with device tree or no phandle link to the node */
 421         if (!node || !node->phandle)
 422                 return FB_BLANK_UNBLANK;
 423
 424         /*
 425          * If the driver is probed from the device tree and there is a
 426          * phandle link pointing to the backlight node, it is safe to
 427          * assume that another driver will enable the backlight at the
 428          * appropriate time. Therefore, if it is disabled, keep it so.
 429          */
 430
 431         /* if the enable GPIO is disabled, do not enable the backlight */
 432         if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0)
 433                 return FB_BLANK_POWERDOWN;
 434
 435         /* The regulator is disabled, do not enable the backlight */
 436         if (!regulator_is_enabled(pb->power_supply))
 437                 return FB_BLANK_POWERDOWN;
 438
 439         /* The PWM is disabled, keep it like this */
 440         if (!pwm_is_enabled(pb->pwm))
 441                 return FB_BLANK_POWERDOWN;
 442
 443         return FB_BLANK_UNBLANK;
 444 }
 445
 446 static int pwm_backlight_probe(struct platform_device *pdev)
 447 {
 448         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 449         struct platform_pwm_backlight_data defdata;
 450         struct backlight_properties props;
 451         struct backlight_device *bl;
 452         struct device_node *node = pdev->dev.of_node;
 453         struct pwm_bl_data *pb;
 454         struct pwm_state state;
 455         unsigned int i;
 456         int ret;
 457
 458         if (!data) {
 459                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 460                 if (ret < 0) {
 461                         dev_err(&pdev->dev, "failed to find platform data\n");
 462                         return ret;
 463                 }
 464
 465                 data = &defdata;
 466         }
 467
 468         if (data->init) {
 469                 ret = data->init(&pdev->dev);
 470                 if (ret < 0)
 471                         return ret;
 472         }
 473
 474         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 475         if (!pb) {
 476                 ret = -ENOMEM;
 477                 goto err_alloc;
 478         }
 479
 480         pb->notify = data->notify;
 481         pb->notify_after = data->notify_after;
 482         pb->check_fb = data->check_fb;
 483         pb->exit = data->exit;
 484         pb->dev = &pdev->dev;
 485         pb->enabled = false;
 486         pb->post_pwm_on_delay = data->post_pwm_on_delay;
 487         pb->pwm_off_delay = data->pwm_off_delay;
 488
 489         pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 490                                                   GPIOD_ASIS);
 491         if (IS_ERR(pb->enable_gpio)) {
 492                 ret = PTR_ERR(pb->enable_gpio);
 493                 goto err_alloc;
 494         }
 495
 496         /*
 497          * Compatibility fallback for drivers still using the integer GPIO
 498          * platform data. Must go away soon.
 499          */
 500         if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
 501                 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 502                                             GPIOF_OUT_INIT_HIGH, "enable");
 503                 if (ret < 0) {
 504                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 505                                 data->enable_gpio, ret);
 506                         goto err_alloc;
 507                 }
 508
 509                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 510         }
 511
 512         /*
 513          * If the GPIO is not known to be already configured as output, that
 514          * is, if gpiod_get_direction returns either 1 or -EINVAL, change the
 515          * direction to output and set the GPIO as active.
 516          * Do not force the GPIO to active when it was already output as it
 517          * could cause backlight flickering or we would enable the backlight too
 518          * early. Leave the decision of the initial backlight state for later.
 519          */
 520         if (pb->enable_gpio &&
 521             gpiod_get_direction(pb->enable_gpio) != 0)
 522                 gpiod_direction_output(pb->enable_gpio, 1);
 523
 524         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 525         if (IS_ERR(pb->power_supply)) {
 526                 ret = PTR_ERR(pb->power_supply);
 527                 goto err_alloc;
 528         }
 529
 530         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 531         if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
 532                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 533                 pb->legacy = true;
 534                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 535         }
 536
 537         if (IS_ERR(pb->pwm)) {
 538                 ret = PTR_ERR(pb->pwm);
 539                 if (ret != -EPROBE_DEFER)
 540                         dev_err(&pdev->dev, "unable to request PWM\n");
 541                 goto err_alloc;
 542         }
 543
 544         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 545
 546         /* Sync up PWM state. */
 547         pwm_init_state(pb->pwm, &state);
 548
 549         /*
 550          * The DT case will set the pwm_period_ns field to 0 and store the
 551          * period, parsed from the DT, in the PWM device. For the non-DT case,
 552          * set the period from platform data if it has not already been set
 553          * via the PWM lookup table.
 554          */
 555         if (!state.period && (data->pwm_period_ns > 0))
 556                 state.period = data->pwm_period_ns;
 557
 558         ret = pwm_apply_state(pb->pwm, &state);
 559         if (ret) {
 560                 dev_err(&pdev->dev, "failed to apply initial PWM state: %d\n",
 561                         ret);
 562                 goto err_alloc;
 563         }
 564
 565         memset(&props, 0, sizeof(struct backlight_properties));
 566
 567         if (data->levels) {
 568                 pb->levels = data->levels;
 569
 570                 /*
 571                  * For the DT case, only when brightness levels is defined
 572                  * data->levels is filled. For the non-DT case, data->levels
 573                  * can come from platform data, however is not usual.
 574                  */
 575                 for (i = 0; i <= data->max_brightness; i++)
 576                         if (data->levels[i] > pb->scale)
 577                                 pb->scale = data->levels[i];
 578
 579                 if (pwm_backlight_is_linear(data))
 580                         props.scale = BACKLIGHT_SCALE_LINEAR;
 581                 else
 582                         props.scale = BACKLIGHT_SCALE_NON_LINEAR;
 583         } else if (!data->max_brightness) {
 584                 /*
 585                  * If no brightness levels are provided and max_brightness is
 586                  * not set, use the default brightness table. For the DT case,
 587                  * max_brightness is set to 0 when brightness levels is not
 588                  * specified. For the non-DT case, max_brightness is usually
 589                  * set to some value.
 590                  */
 591
 592                 /* Get the PWM period (in nanoseconds) */
 593                 pwm_get_state(pb->pwm, &state);
 594
 595                 ret = pwm_backlight_brightness_default(&pdev->dev, data,
 596                                                        state.period);
 597                 if (ret < 0) {
 598                         dev_err(&pdev->dev,
 599                                 "failed to setup default brightness table\n");
 600                         goto err_alloc;
 601                 }
 602
 603                 for (i = 0; i <= data->max_brightness; i++) {
 604                         if (data->levels[i] > pb->scale)
 605                                 pb->scale = data->levels[i];
 606
 607                         pb->levels = data->levels;
 608                 }
 609
 610                 props.scale = BACKLIGHT_SCALE_NON_LINEAR;
 611         } else {
 612                 /*
 613                  * That only happens for the non-DT case, where platform data
 614                  * sets the max_brightness value.
 615                  */
 616                 pb->scale = data->max_brightness;
 617         }
 618
 619         pb->lth_brightness = data->lth_brightness * (state.period / pb->scale);
 620
 621         props.type = BACKLIGHT_RAW;
 622         props.max_brightness = data->max_brightness;
 623         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 624                                        &pwm_backlight_ops, &props);
 625         if (IS_ERR(bl)) {
 626                 dev_err(&pdev->dev, "failed to register backlight\n");
 627                 ret = PTR_ERR(bl);
 628                 if (pb->legacy)
 629                         pwm_free(pb->pwm);
 630                 goto err_alloc;
 631         }
 632
 633         if (data->dft_brightness > data->max_brightness) {
 634                 dev_warn(&pdev->dev,
 635                          "invalid default brightness level: %u, using %u\n",
 636                          data->dft_brightness, data->max_brightness);
 637                 data->dft_brightness = data->max_brightness;
 638         }
 639
 640         bl->props.brightness = data->dft_brightness;
 641         bl->props.power = pwm_backlight_initial_power_state(pb);
 642         backlight_update_status(bl);
 643
 644         platform_set_drvdata(pdev, bl);
 645         return 0;
 646
 647 err_alloc:
 648         if (data->exit)
 649                 data->exit(&pdev->dev);
 650         return ret;
 651 }
 652
 653 static int pwm_backlight_remove(struct platform_device *pdev)
 654 {
 655         struct backlight_device *bl = platform_get_drvdata(pdev);
 656         struct pwm_bl_data *pb = bl_get_data(bl);
 657
 658         backlight_device_unregister(bl);
 659         pwm_backlight_power_off(pb);
 660
 661         if (pb->exit)
 662                 pb->exit(&pdev->dev);
 663         if (pb->legacy)
 664                 pwm_free(pb->pwm);
 665
 666         return 0;
 667 }
 668
 669 static void pwm_backlight_shutdown(struct platform_device *pdev)
 670 {
 671         struct backlight_device *bl = platform_get_drvdata(pdev);
 672         struct pwm_bl_data *pb = bl_get_data(bl);
 673
 674         pwm_backlight_power_off(pb);
 675 }
 676
 677 #ifdef CONFIG_PM_SLEEP
 678 static int pwm_backlight_suspend(struct device *dev)
 679 {
 680         struct backlight_device *bl = dev_get_drvdata(dev);
 681         struct pwm_bl_data *pb = bl_get_data(bl);
 682
 683         if (pb->notify)
 684                 pb->notify(pb->dev, 0);
 685
 686         pwm_backlight_power_off(pb);
 687
 688         if (pb->notify_after)
 689                 pb->notify_after(pb->dev, 0);
 690
 691         return 0;
 692 }
 693
 694 static int pwm_backlight_resume(struct device *dev)
 695 {
 696         struct backlight_device *bl = dev_get_drvdata(dev);
 697
 698         backlight_update_status(bl);
 699
 700         return 0;
 701 }
 702 #endif
 703
 704 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 705 #ifdef CONFIG_PM_SLEEP
 706         .suspend = pwm_backlight_suspend,
 707         .resume = pwm_backlight_resume,
 708         .poweroff = pwm_backlight_suspend,
 709         .restore = pwm_backlight_resume,
 710 #endif
 711 };
 712
 713 static struct platform_driver pwm_backlight_driver = {
 714         .driver         = {
 715                 .name           = "pwm-backlight",
 716                 .pm             = &pwm_backlight_pm_ops,
 717                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 718         },
 719         .probe          = pwm_backlight_probe,
 720         .remove         = pwm_backlight_remove,
 721         .shutdown       = pwm_backlight_shutdown,
 722 };
 723
 724 module_platform_driver(pwm_backlight_driver);
 725
 726 MODULE_DESCRIPTION("PWM based Backlight Driver");
 727 MODULE_LICENSE("GPL v2");
 728 MODULE_ALIAS("platform:pwm-backlight");