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/module.h>
  11 #include <linux/kernel.h>
  12 #include <linux/init.h>
  13 #include <linux/platform_device.h>
  14 #include <linux/fb.h>
  15 #include <linux/backlight.h>
  16 #include <linux/err.h>
  17 #include <linux/pwm.h>
  18 #include <linux/pwm_backlight.h>
  19 #include <linux/regulator/consumer.h>
  20 #include <linux/slab.h>
  21
  22 struct pwm_bl_data {
  23         struct pwm_device       *pwm;
  24         struct device           *dev;
  25         unsigned int            lth_brightness;
  26         unsigned int            *levels;
  27         bool                    enabled;
  28         struct regulator        *power_supply;
  29         struct gpio_desc        *enable_gpio;
  30         unsigned int            scale;
  31         bool                    legacy;
  32         unsigned int            post_pwm_on_delay;
  33         unsigned int            pwm_off_delay;
  34         int                     (*notify)(struct device *,
  35                                           int brightness);
  36         void                    (*notify_after)(struct device *,
  37                                         int brightness);
  38         int                     (*check_fb)(struct device *, struct fb_info *);
  39         void                    (*exit)(struct device *);
  40 };
  41
  42 static void pwm_backlight_power_on(struct pwm_bl_data *pb)
  43 {
  44         struct pwm_state state;
  45         int err;
  46
  47         pwm_get_state(pb->pwm, &state);
  48         if (pb->enabled)
  49                 return;
  50
  51         err = regulator_enable(pb->power_supply);
  52         if (err < 0)
  53                 dev_err(pb->dev, "failed to enable power supply\n");
  54
  55         state.enabled = true;
  56         pwm_apply_state(pb->pwm, &state);
  57
  58         if (pb->post_pwm_on_delay)
  59                 msleep(pb->post_pwm_on_delay);
  60
  61         if (pb->enable_gpio)
  62                 gpiod_set_value_cansleep(pb->enable_gpio, 1);
  63
  64         pb->enabled = true;
  65 }
  66
  67 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
  68 {
  69         struct pwm_state state;
  70
  71         pwm_get_state(pb->pwm, &state);
  72         if (!pb->enabled)
  73                 return;
  74
  75         if (pb->enable_gpio)
  76                 gpiod_set_value_cansleep(pb->enable_gpio, 0);
  77
  78         if (pb->pwm_off_delay)
  79                 msleep(pb->pwm_off_delay);
  80
  81         state.enabled = false;
  82         state.duty_cycle = 0;
  83         pwm_apply_state(pb->pwm, &state);
  84
  85         regulator_disable(pb->power_supply);
  86         pb->enabled = false;
  87 }
  88
  89 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
  90 {
  91         unsigned int lth = pb->lth_brightness;
  92         struct pwm_state state;
  93         u64 duty_cycle;
  94
  95         pwm_get_state(pb->pwm, &state);
  96
  97         if (pb->levels)
  98                 duty_cycle = pb->levels[brightness];
  99         else
 100                 duty_cycle = brightness;
 101
 102         duty_cycle *= state.period - lth;
 103         do_div(duty_cycle, pb->scale);
 104
 105         return duty_cycle + lth;
 106 }
 107
 108 static int pwm_backlight_update_status(struct backlight_device *bl)
 109 {
 110         struct pwm_bl_data *pb = bl_get_data(bl);
 111         int brightness = backlight_get_brightness(bl);
 112         struct pwm_state state;
 113
 114         if (pb->notify)
 115                 brightness = pb->notify(pb->dev, brightness);
 116
 117         if (brightness > 0) {
 118                 pwm_get_state(pb->pwm, &state);
 119                 state.duty_cycle = compute_duty_cycle(pb, brightness);
 120                 pwm_apply_state(pb->pwm, &state);
 121                 pwm_backlight_power_on(pb);
 122         } else {
 123                 pwm_backlight_power_off(pb);
 124         }
 125
 126         if (pb->notify_after)
 127                 pb->notify_after(pb->dev, brightness);
 128
 129         return 0;
 130 }
 131
 132 static int pwm_backlight_check_fb(struct backlight_device *bl,
 133                                   struct fb_info *info)
 134 {
 135         struct pwm_bl_data *pb = bl_get_data(bl);
 136
 137         return !pb->check_fb || pb->check_fb(pb->dev, info);
 138 }
 139
 140 static const struct backlight_ops pwm_backlight_ops = {
 141         .update_status  = pwm_backlight_update_status,
 142         .check_fb       = pwm_backlight_check_fb,
 143 };
 144
 145 #ifdef CONFIG_OF
 146 #define PWM_LUMINANCE_SHIFT     16
 147 #define PWM_LUMINANCE_SCALE     (1 << PWM_LUMINANCE_SHIFT) /* luminance scale */
 148
 149 /*
 150  * CIE lightness to PWM conversion.
 151  *
 152  * The CIE 1931 lightness formula is what actually describes how we perceive
 153  * light:
 154  *          Y = (L* / 903.3)           if L* ≤ 8
 155  *          Y = ((L* + 16) / 116)^3    if L* > 8
 156  *
 157  * Where Y is the luminance, the amount of light coming out of the screen, and
 158  * is a number between 0.0 and 1.0; and L* is the lightness, how bright a human
 159  * perceives the screen to be, and is a number between 0 and 100.
 160  *
 161  * The following function does the fixed point maths needed to implement the
 162  * above formula.
 163  */
 164 static u64 cie1931(unsigned int lightness)
 165 {
 166         u64 retval;
 167
 168         /*
 169          * @lightness is given as a number between 0 and 1, expressed
 170          * as a fixed-point number in scale
 171          * PWM_LUMINANCE_SCALE. Convert to a percentage, still
 172          * expressed as a fixed-point number, so the above formulas
 173          * can be applied.
 174          */
 175         lightness *= 100;
 176         if (lightness <= (8 * PWM_LUMINANCE_SCALE)) {
 177                 retval = DIV_ROUND_CLOSEST(lightness * 10, 9033);
 178         } else {
 179                 retval = (lightness + (16 * PWM_LUMINANCE_SCALE)) / 116;
 180                 retval *= retval * retval;
 181                 retval += 1ULL << (2*PWM_LUMINANCE_SHIFT - 1);
 182                 retval >>= 2*PWM_LUMINANCE_SHIFT;
 183         }
 184
 185         return retval;
 186 }
 187
 188 /*
 189  * Create a default correction table for PWM values to create linear brightness
 190  * for LED based backlights using the CIE1931 algorithm.
 191  */
 192 static
 193 int pwm_backlight_brightness_default(struct device *dev,
 194                                      struct platform_pwm_backlight_data *data,
 195                                      unsigned int period)
 196 {
 197         unsigned int i;
 198         u64 retval;
 199
 200         /*
 201          * Once we have 4096 levels there's little point going much higher...
 202          * neither interactive sliders nor animation benefits from having
 203          * more values in the table.
 204          */
 205         data->max_brightness =
 206                 min((int)DIV_ROUND_UP(period, fls(period)), 4096);
 207
 208         data->levels = devm_kcalloc(dev, data->max_brightness,
 209                                     sizeof(*data->levels), GFP_KERNEL);
 210         if (!data->levels)
 211                 return -ENOMEM;
 212
 213         /* Fill the table using the cie1931 algorithm */
 214         for (i = 0; i < data->max_brightness; i++) {
 215                 retval = cie1931((i * PWM_LUMINANCE_SCALE) /
 216                                  data->max_brightness) * period;
 217                 retval = DIV_ROUND_CLOSEST_ULL(retval, PWM_LUMINANCE_SCALE);
 218                 if (retval > UINT_MAX)
 219                         return -EINVAL;
 220                 data->levels[i] = (unsigned int)retval;
 221         }
 222
 223         data->dft_brightness = data->max_brightness / 2;
 224         data->max_brightness--;
 225
 226         return 0;
 227 }
 228
 229 static int pwm_backlight_parse_dt(struct device *dev,
 230                                   struct platform_pwm_backlight_data *data)
 231 {
 232         struct device_node *node = dev->of_node;
 233         unsigned int num_levels;
 234         unsigned int num_steps = 0;
 235         struct property *prop;
 236         unsigned int *table;
 237         int length;
 238         u32 value;
 239         int ret;
 240
 241         if (!node)
 242                 return -ENODEV;
 243
 244         memset(data, 0, sizeof(*data));
 245
 246         /*
 247          * These values are optional and set as 0 by default, the out values
 248          * are modified only if a valid u32 value can be decoded.
 249          */
 250         of_property_read_u32(node, "post-pwm-on-delay-ms",
 251                              &data->post_pwm_on_delay);
 252         of_property_read_u32(node, "pwm-off-delay-ms", &data->pwm_off_delay);
 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         num_levels = length / sizeof(u32);
 263
 264         /* read brightness levels from DT property */
 265         if (num_levels > 0) {
 266                 size_t size = sizeof(*data->levels) * num_levels;
 267
 268                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 269                 if (!data->levels)
 270                         return -ENOMEM;
 271
 272                 ret = of_property_read_u32_array(node, "brightness-levels",
 273                                                  data->levels,
 274                                                  num_levels);
 275                 if (ret < 0)
 276                         return ret;
 277
 278                 ret = of_property_read_u32(node, "default-brightness-level",
 279                                            &value);
 280                 if (ret < 0)
 281                         return ret;
 282
 283                 data->dft_brightness = value;
 284
 285                 /*
 286                  * This property is optional, if is set enables linear
 287                  * interpolation between each of the values of brightness levels
 288                  * and creates a new pre-computed table.
 289                  */
 290                 of_property_read_u32(node, "num-interpolated-steps",
 291                                      &num_steps);
 292
 293                 /*
 294                  * Make sure that there is at least two entries in the
 295                  * brightness-levels table, otherwise we can't interpolate
 296                  * between two points.
 297                  */
 298                 if (num_steps) {
 299                         unsigned int num_input_levels = num_levels;
 300                         unsigned int i;
 301                         u32 x1, x2, x, dx;
 302                         u32 y1, y2;
 303                         s64 dy;
 304
 305                         if (num_input_levels < 2) {
 306                                 dev_err(dev, "can't interpolate\n");
 307                                 return -EINVAL;
 308                         }
 309
 310                         /*
 311                          * Recalculate the number of brightness levels, now
 312                          * taking in consideration the number of interpolated
 313                          * steps between two levels.
 314                          */
 315                         num_levels = (num_input_levels - 1) * num_steps + 1;
 316                         dev_dbg(dev, "new number of brightness levels: %d\n",
 317                                 num_levels);
 318
 319                         /*
 320                          * Create a new table of brightness levels with all the
 321                          * interpolated steps.
 322                          */
 323                         size = sizeof(*table) * num_levels;
 324                         table = devm_kzalloc(dev, size, GFP_KERNEL);
 325                         if (!table)
 326                                 return -ENOMEM;
 327                         /*
 328                          * Fill the interpolated table[x] = y
 329                          * by draw lines between each (x1, y1) to (x2, y2).
 330                          */
 331                         dx = num_steps;
 332                         for (i = 0; i < num_input_levels - 1; i++) {
 333                                 x1 = i * dx;
 334                                 x2 = x1 + dx;
 335                                 y1 = data->levels[i];
 336                                 y2 = data->levels[i + 1];
 337                                 dy = (s64)y2 - y1;
 338
 339                                 for (x = x1; x < x2; x++) {
 340                                         table[x] = y1 +
 341                                                 div_s64(dy * (x - x1), dx);
 342                                 }
 343                         }
 344                         /* Fill in the last point, since no line starts here. */
 345                         table[x2] = y2;
 346
 347                         /*
 348                          * As we use interpolation lets remove current
 349                          * brightness levels table and replace for the
 350                          * new interpolated table.
 351                          */
 352                         devm_kfree(dev, data->levels);
 353                         data->levels = table;
 354                 }
 355
 356                 data->max_brightness = num_levels - 1;
 357         }
 358
 359         return 0;
 360 }
 361
 362 static const struct of_device_id pwm_backlight_of_match[] = {
 363         { .compatible = "pwm-backlight" },
 364         { }
 365 };
 366
 367 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 368 #else
 369 static int pwm_backlight_parse_dt(struct device *dev,
 370                                   struct platform_pwm_backlight_data *data)
 371 {
 372         return -ENODEV;
 373 }
 374
 375 static
 376 int pwm_backlight_brightness_default(struct device *dev,
 377                                      struct platform_pwm_backlight_data *data,
 378                                      unsigned int period)
 379 {
 380         return -ENODEV;
 381 }
 382 #endif
 383
 384 static bool pwm_backlight_is_linear(struct platform_pwm_backlight_data *data)
 385 {
 386         unsigned int nlevels = data->max_brightness + 1;
 387         unsigned int min_val = data->levels[0];
 388         unsigned int max_val = data->levels[nlevels - 1];
 389         /*
 390          * Multiplying by 128 means that even in pathological cases such
 391          * as (max_val - min_val) == nlevels the error at max_val is less
 392          * than 1%.
 393          */
 394         unsigned int slope = (128 * (max_val - min_val)) / nlevels;
 395         unsigned int margin = (max_val - min_val) / 20; /* 5% */
 396         int i;
 397
 398         for (i = 1; i < nlevels; i++) {
 399                 unsigned int linear_value = min_val + ((i * slope) / 128);
 400                 unsigned int delta = abs(linear_value - data->levels[i]);
 401
 402                 if (delta > margin)
 403                         return false;
 404         }
 405
 406         return true;
 407 }
 408
 409 static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
 410 {
 411         struct device_node *node = pb->dev->of_node;
 412         bool active = true;
 413
 414         /*
 415          * If the enable GPIO is present, observable (either as input
 416          * or output) and off then the backlight is not currently active.
 417          * */
 418         if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0)
 419                 active = false;
 420
 421         if (!regulator_is_enabled(pb->power_supply))
 422                 active = false;
 423
 424         if (!pwm_is_enabled(pb->pwm))
 425                 active = false;
 426
 427         /*
 428          * Synchronize the enable_gpio with the observed state of the
 429          * hardware.
 430          */
 431         if (pb->enable_gpio)
 432                 gpiod_direction_output(pb->enable_gpio, active);
 433
 434         /*
 435          * Do not change pb->enabled here! pb->enabled essentially
 436          * tells us if we own one of the regulator's use counts and
 437          * right now we do not.
 438          */
 439
 440         /* Not booted with device tree or no phandle link to the node */
 441         if (!node || !node->phandle)
 442                 return FB_BLANK_UNBLANK;
 443
 444         /*
 445          * If the driver is probed from the device tree and there is a
 446          * phandle link pointing to the backlight node, it is safe to
 447          * assume that another driver will enable the backlight at the
 448          * appropriate time. Therefore, if it is disabled, keep it so.
 449          */
 450         return active ? FB_BLANK_UNBLANK: FB_BLANK_POWERDOWN;
 451 }
 452
 453 static int pwm_backlight_probe(struct platform_device *pdev)
 454 {
 455         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 456         struct platform_pwm_backlight_data defdata;
 457         struct backlight_properties props;
 458         struct backlight_device *bl;
 459         struct device_node *node = pdev->dev.of_node;
 460         struct pwm_bl_data *pb;
 461         struct pwm_state state;
 462         unsigned int i;
 463         int ret;
 464
 465         if (!data) {
 466                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 467                 if (ret < 0) {
 468                         dev_err(&pdev->dev, "failed to find platform data\n");
 469                         return ret;
 470                 }
 471
 472                 data = &defdata;
 473         }
 474
 475         if (data->init) {
 476                 ret = data->init(&pdev->dev);
 477                 if (ret < 0)
 478                         return ret;
 479         }
 480
 481         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 482         if (!pb) {
 483                 ret = -ENOMEM;
 484                 goto err_alloc;
 485         }
 486
 487         pb->notify = data->notify;
 488         pb->notify_after = data->notify_after;
 489         pb->check_fb = data->check_fb;
 490         pb->exit = data->exit;
 491         pb->dev = &pdev->dev;
 492         pb->enabled = false;
 493         pb->post_pwm_on_delay = data->post_pwm_on_delay;
 494         pb->pwm_off_delay = data->pwm_off_delay;
 495
 496         pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 497                                                   GPIOD_ASIS);
 498         if (IS_ERR(pb->enable_gpio)) {
 499                 ret = PTR_ERR(pb->enable_gpio);
 500                 goto err_alloc;
 501         }
 502
 503         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 504         if (IS_ERR(pb->power_supply)) {
 505                 ret = PTR_ERR(pb->power_supply);
 506                 goto err_alloc;
 507         }
 508
 509         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 510         if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
 511                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 512                 pb->legacy = true;
 513                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 514         }
 515
 516         if (IS_ERR(pb->pwm)) {
 517                 ret = PTR_ERR(pb->pwm);
 518                 if (ret != -EPROBE_DEFER)
 519                         dev_err(&pdev->dev, "unable to request PWM\n");
 520                 goto err_alloc;
 521         }
 522
 523         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 524
 525         /* Sync up PWM state. */
 526         pwm_init_state(pb->pwm, &state);
 527
 528         /*
 529          * The DT case will set the pwm_period_ns field to 0 and store the
 530          * period, parsed from the DT, in the PWM device. For the non-DT case,
 531          * set the period from platform data if it has not already been set
 532          * via the PWM lookup table.
 533          */
 534         if (!state.period && (data->pwm_period_ns > 0))
 535                 state.period = data->pwm_period_ns;
 536
 537         ret = pwm_apply_state(pb->pwm, &state);
 538         if (ret) {
 539                 dev_err(&pdev->dev, "failed to apply initial PWM state: %d\n",
 540                         ret);
 541                 goto err_alloc;
 542         }
 543
 544         memset(&props, 0, sizeof(struct backlight_properties));
 545
 546         if (data->levels) {
 547                 pb->levels = data->levels;
 548
 549                 /*
 550                  * For the DT case, only when brightness levels is defined
 551                  * data->levels is filled. For the non-DT case, data->levels
 552                  * can come from platform data, however is not usual.
 553                  */
 554                 for (i = 0; i <= data->max_brightness; i++)
 555                         if (data->levels[i] > pb->scale)
 556                                 pb->scale = data->levels[i];
 557
 558                 if (pwm_backlight_is_linear(data))
 559                         props.scale = BACKLIGHT_SCALE_LINEAR;
 560                 else
 561                         props.scale = BACKLIGHT_SCALE_NON_LINEAR;
 562         } else if (!data->max_brightness) {
 563                 /*
 564                  * If no brightness levels are provided and max_brightness is
 565                  * not set, use the default brightness table. For the DT case,
 566                  * max_brightness is set to 0 when brightness levels is not
 567                  * specified. For the non-DT case, max_brightness is usually
 568                  * set to some value.
 569                  */
 570
 571                 /* Get the PWM period (in nanoseconds) */
 572                 pwm_get_state(pb->pwm, &state);
 573
 574                 ret = pwm_backlight_brightness_default(&pdev->dev, data,
 575                                                        state.period);
 576                 if (ret < 0) {
 577                         dev_err(&pdev->dev,
 578                                 "failed to setup default brightness table\n");
 579                         goto err_alloc;
 580                 }
 581
 582                 for (i = 0; i <= data->max_brightness; i++) {
 583                         if (data->levels[i] > pb->scale)
 584                                 pb->scale = data->levels[i];
 585
 586                         pb->levels = data->levels;
 587                 }
 588
 589                 props.scale = BACKLIGHT_SCALE_NON_LINEAR;
 590         } else {
 591                 /*
 592                  * That only happens for the non-DT case, where platform data
 593                  * sets the max_brightness value.
 594                  */
 595                 pb->scale = data->max_brightness;
 596         }
 597
 598         pb->lth_brightness = data->lth_brightness * (div_u64(state.period,
 599                                 pb->scale));
 600
 601         props.type = BACKLIGHT_RAW;
 602         props.max_brightness = data->max_brightness;
 603         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 604                                        &pwm_backlight_ops, &props);
 605         if (IS_ERR(bl)) {
 606                 dev_err(&pdev->dev, "failed to register backlight\n");
 607                 ret = PTR_ERR(bl);
 608                 if (pb->legacy)
 609                         pwm_free(pb->pwm);
 610                 goto err_alloc;
 611         }
 612
 613         if (data->dft_brightness > data->max_brightness) {
 614                 dev_warn(&pdev->dev,
 615                          "invalid default brightness level: %u, using %u\n",
 616                          data->dft_brightness, data->max_brightness);
 617                 data->dft_brightness = data->max_brightness;
 618         }
 619
 620         bl->props.brightness = data->dft_brightness;
 621         bl->props.power = pwm_backlight_initial_power_state(pb);
 622         backlight_update_status(bl);
 623
 624         platform_set_drvdata(pdev, bl);
 625         return 0;
 626
 627 err_alloc:
 628         if (data->exit)
 629                 data->exit(&pdev->dev);
 630         return ret;
 631 }
 632
 633 static int pwm_backlight_remove(struct platform_device *pdev)
 634 {
 635         struct backlight_device *bl = platform_get_drvdata(pdev);
 636         struct pwm_bl_data *pb = bl_get_data(bl);
 637
 638         backlight_device_unregister(bl);
 639         pwm_backlight_power_off(pb);
 640
 641         if (pb->exit)
 642                 pb->exit(&pdev->dev);
 643         if (pb->legacy)
 644                 pwm_free(pb->pwm);
 645
 646         return 0;
 647 }
 648
 649 static void pwm_backlight_shutdown(struct platform_device *pdev)
 650 {
 651         struct backlight_device *bl = platform_get_drvdata(pdev);
 652         struct pwm_bl_data *pb = bl_get_data(bl);
 653
 654         pwm_backlight_power_off(pb);
 655 }
 656
 657 #ifdef CONFIG_PM_SLEEP
 658 static int pwm_backlight_suspend(struct device *dev)
 659 {
 660         struct backlight_device *bl = dev_get_drvdata(dev);
 661         struct pwm_bl_data *pb = bl_get_data(bl);
 662
 663         if (pb->notify)
 664                 pb->notify(pb->dev, 0);
 665
 666         pwm_backlight_power_off(pb);
 667
 668         if (pb->notify_after)
 669                 pb->notify_after(pb->dev, 0);
 670
 671         return 0;
 672 }
 673
 674 static int pwm_backlight_resume(struct device *dev)
 675 {
 676         struct backlight_device *bl = dev_get_drvdata(dev);
 677
 678         backlight_update_status(bl);
 679
 680         return 0;
 681 }
 682 #endif
 683
 684 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 685 #ifdef CONFIG_PM_SLEEP
 686         .suspend = pwm_backlight_suspend,
 687         .resume = pwm_backlight_resume,
 688         .poweroff = pwm_backlight_suspend,
 689         .restore = pwm_backlight_resume,
 690 #endif
 691 };
 692
 693 static struct platform_driver pwm_backlight_driver = {
 694         .driver         = {
 695                 .name           = "pwm-backlight",
 696                 .pm             = &pwm_backlight_pm_ops,
 697                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 698         },
 699         .probe          = pwm_backlight_probe,
 700         .remove         = pwm_backlight_remove,
 701         .shutdown       = pwm_backlight_shutdown,
 702 };
 703
 704 module_platform_driver(pwm_backlight_driver);
 705
 706 MODULE_DESCRIPTION("PWM based Backlight Driver");
 707 MODULE_LICENSE("GPL v2");
 708 MODULE_ALIAS("platform:pwm-backlight");