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/delay.h>
  14 #include <linux/gpio/consumer.h>
  15 #include <linux/gpio.h>
  16 #include <linux/module.h>
  17 #include <linux/kernel.h>
  18 #include <linux/init.h>
  19 #include <linux/platform_device.h>
  20 #include <linux/fb.h>
  21 #include <linux/backlight.h>
  22 #include <linux/err.h>
  23 #include <linux/pwm.h>
  24 #include <linux/pwm_backlight.h>
  25 #include <linux/regulator/consumer.h>
  26 #include <linux/slab.h>
  27
  28 struct pwm_bl_data {
  29         struct pwm_device       *pwm;
  30         struct device           *dev;
  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         bool                    legacy;
  38         unsigned int            post_pwm_on_delay;
  39         unsigned int            pwm_off_delay;
  40         int                     (*notify)(struct device *,
  41                                           int brightness);
  42         void                    (*notify_after)(struct device *,
  43                                         int brightness);
  44         int                     (*check_fb)(struct device *, struct fb_info *);
  45         void                    (*exit)(struct device *);
  46 };
  47
  48 static void pwm_backlight_power_on(struct pwm_bl_data *pb)
  49 {
  50         struct pwm_state state;
  51         int err;
  52
  53         pwm_get_state(pb->pwm, &state);
  54         if (pb->enabled)
  55                 return;
  56
  57         err = regulator_enable(pb->power_supply);
  58         if (err < 0)
  59                 dev_err(pb->dev, "failed to enable power supply\n");
  60
  61         state.enabled = true;
  62         pwm_apply_state(pb->pwm, &state);
  63
  64         if (pb->post_pwm_on_delay)
  65                 msleep(pb->post_pwm_on_delay);
  66
  67         if (pb->enable_gpio)
  68                 gpiod_set_value_cansleep(pb->enable_gpio, 1);
  69
  70         pb->enabled = true;
  71 }
  72
  73 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
  74 {
  75         struct pwm_state state;
  76
  77         pwm_get_state(pb->pwm, &state);
  78         if (!pb->enabled)
  79                 return;
  80
  81         if (pb->enable_gpio)
  82                 gpiod_set_value_cansleep(pb->enable_gpio, 0);
  83
  84         if (pb->pwm_off_delay)
  85                 msleep(pb->pwm_off_delay);
  86
  87         state.enabled = false;
  88         state.duty_cycle = 0;
  89         pwm_apply_state(pb->pwm, &state);
  90
  91         regulator_disable(pb->power_supply);
  92         pb->enabled = false;
  93 }
  94
  95 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
  96 {
  97         unsigned int lth = pb->lth_brightness;
  98         struct pwm_state state;
  99         u64 duty_cycle;
 100
 101         pwm_get_state(pb->pwm, &state);
 102
 103         if (pb->levels)
 104                 duty_cycle = pb->levels[brightness];
 105         else
 106                 duty_cycle = brightness;
 107
 108         duty_cycle *= state.period - lth;
 109         do_div(duty_cycle, pb->scale);
 110
 111         return duty_cycle + lth;
 112 }
 113
 114 static int pwm_backlight_update_status(struct backlight_device *bl)
 115 {
 116         struct pwm_bl_data *pb = bl_get_data(bl);
 117         int brightness = bl->props.brightness;
 118         struct pwm_state state;
 119
 120         if (bl->props.power != FB_BLANK_UNBLANK ||
 121             bl->props.fb_blank != FB_BLANK_UNBLANK ||
 122             bl->props.state & BL_CORE_FBBLANK)
 123                 brightness = 0;
 124
 125         if (pb->notify)
 126                 brightness = pb->notify(pb->dev, brightness);
 127
 128         if (brightness > 0) {
 129                 pwm_get_state(pb->pwm, &state);
 130                 state.duty_cycle = compute_duty_cycle(pb, brightness);
 131                 pwm_apply_state(pb->pwm, &state);
 132                 pwm_backlight_power_on(pb);
 133         } else
 134                 pwm_backlight_power_off(pb);
 135
 136         if (pb->notify_after)
 137                 pb->notify_after(pb->dev, brightness);
 138
 139         return 0;
 140 }
 141
 142 static int pwm_backlight_check_fb(struct backlight_device *bl,
 143                                   struct fb_info *info)
 144 {
 145         struct pwm_bl_data *pb = bl_get_data(bl);
 146
 147         return !pb->check_fb || pb->check_fb(pb->dev, info);
 148 }
 149
 150 static const struct backlight_ops pwm_backlight_ops = {
 151         .update_status  = pwm_backlight_update_status,
 152         .check_fb       = pwm_backlight_check_fb,
 153 };
 154
 155 #ifdef CONFIG_OF
 156 #define PWM_LUMINANCE_SCALE     10000 /* luminance scale */
 157
 158 /*
 159  * CIE lightness to PWM conversion.
 160  *
 161  * The CIE 1931 lightness formula is what actually describes how we perceive
 162  * light:
 163  *          Y = (L* / 902.3)           if L* ≤ 0.08856
 164  *          Y = ((L* + 16) / 116)^3    if L* > 0.08856
 165  *
 166  * Where Y is the luminance, the amount of light coming out of the screen, and
 167  * is a number between 0.0 and 1.0; and L* is the lightness, how bright a human
 168  * perceives the screen to be, and is a number between 0 and 100.
 169  *
 170  * The following function does the fixed point maths needed to implement the
 171  * above formula.
 172  */
 173 static u64 cie1931(unsigned int lightness, unsigned int scale)
 174 {
 175         u64 retval;
 176
 177         lightness *= 100;
 178         if (lightness <= (8 * scale)) {
 179                 retval = DIV_ROUND_CLOSEST_ULL(lightness * 10, 9023);
 180         } else {
 181                 retval = int_pow((lightness + (16 * scale)) / 116, 3);
 182                 retval = DIV_ROUND_CLOSEST_ULL(retval, (scale * scale));
 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 counter = 0;
 198         unsigned int i, n;
 199         u64 retval;
 200
 201         /*
 202          * Count the number of bits needed to represent the period number. The
 203          * number of bits is used to calculate the number of levels used for the
 204          * brightness-levels table, the purpose of this calculation is have a
 205          * pre-computed table with enough levels to get linear brightness
 206          * perception. The period is divided by the number of bits so for a
 207          * 8-bit PWM we have 255 / 8 = 32 brightness levels or for a 16-bit PWM
 208          * we have 65535 / 16 = 4096 brightness levels.
 209          *
 210          * Note that this method is based on empirical testing on different
 211          * devices with PWM of 8 and 16 bits of resolution.
 212          */
 213         n = period;
 214         while (n) {
 215                 counter += n % 2;
 216                 n >>= 1;
 217         }
 218
 219         data->max_brightness = DIV_ROUND_UP(period, counter);
 220         data->levels = devm_kcalloc(dev, data->max_brightness,
 221                                     sizeof(*data->levels), GFP_KERNEL);
 222         if (!data->levels)
 223                 return -ENOMEM;
 224
 225         /* Fill the table using the cie1931 algorithm */
 226         for (i = 0; i < data->max_brightness; i++) {
 227                 retval = cie1931((i * PWM_LUMINANCE_SCALE) /
 228                                  data->max_brightness, PWM_LUMINANCE_SCALE) *
 229                                  period;
 230                 retval = DIV_ROUND_CLOSEST_ULL(retval, PWM_LUMINANCE_SCALE);
 231                 if (retval > UINT_MAX)
 232                         return -EINVAL;
 233                 data->levels[i] = (unsigned int)retval;
 234         }
 235
 236         data->dft_brightness = data->max_brightness / 2;
 237         data->max_brightness--;
 238
 239         return 0;
 240 }
 241
 242 static int pwm_backlight_parse_dt(struct device *dev,
 243                                   struct platform_pwm_backlight_data *data)
 244 {
 245         struct device_node *node = dev->of_node;
 246         unsigned int num_levels = 0;
 247         unsigned int levels_count;
 248         unsigned int num_steps = 0;
 249         struct property *prop;
 250         unsigned int *table;
 251         int length;
 252         u32 value;
 253         int ret;
 254
 255         if (!node)
 256                 return -ENODEV;
 257
 258         memset(data, 0, sizeof(*data));
 259
 260         /*
 261          * These values are optional and set as 0 by default, the out values
 262          * are modified only if a valid u32 value can be decoded.
 263          */
 264         of_property_read_u32(node, "post-pwm-on-delay-ms",
 265                              &data->post_pwm_on_delay);
 266         of_property_read_u32(node, "pwm-off-delay-ms", &data->pwm_off_delay);
 267
 268         data->enable_gpio = -EINVAL;
 269
 270         /*
 271          * Determine the number of brightness levels, if this property is not
 272          * set a default table of brightness levels will be used.
 273          */
 274         prop = of_find_property(node, "brightness-levels", &length);
 275         if (!prop)
 276                 return 0;
 277
 278         data->max_brightness = length / sizeof(u32);
 279
 280         /* read brightness levels from DT property */
 281         if (data->max_brightness > 0) {
 282                 size_t size = sizeof(*data->levels) * data->max_brightness;
 283                 unsigned int i, j, n = 0;
 284
 285                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 286                 if (!data->levels)
 287                         return -ENOMEM;
 288
 289                 ret = of_property_read_u32_array(node, "brightness-levels",
 290                                                  data->levels,
 291                                                  data->max_brightness);
 292                 if (ret < 0)
 293                         return ret;
 294
 295                 ret = of_property_read_u32(node, "default-brightness-level",
 296                                            &value);
 297                 if (ret < 0)
 298                         return ret;
 299
 300                 data->dft_brightness = value;
 301
 302                 /*
 303                  * This property is optional, if is set enables linear
 304                  * interpolation between each of the values of brightness levels
 305                  * and creates a new pre-computed table.
 306                  */
 307                 of_property_read_u32(node, "num-interpolated-steps",
 308                                      &num_steps);
 309
 310                 /*
 311                  * Make sure that there is at least two entries in the
 312                  * brightness-levels table, otherwise we can't interpolate
 313                  * between two points.
 314                  */
 315                 if (num_steps) {
 316                         if (data->max_brightness < 2) {
 317                                 dev_err(dev, "can't interpolate\n");
 318                                 return -EINVAL;
 319                         }
 320
 321                         /*
 322                          * Recalculate the number of brightness levels, now
 323                          * taking in consideration the number of interpolated
 324                          * steps between two levels.
 325                          */
 326                         for (i = 0; i < data->max_brightness - 1; i++) {
 327                                 if ((data->levels[i + 1] - data->levels[i]) /
 328                                    num_steps)
 329                                         num_levels += num_steps;
 330                                 else
 331                                         num_levels++;
 332                         }
 333                         num_levels++;
 334                         dev_dbg(dev, "new number of brightness levels: %d\n",
 335                                 num_levels);
 336
 337                         /*
 338                          * Create a new table of brightness levels with all the
 339                          * interpolated steps.
 340                          */
 341                         size = sizeof(*table) * num_levels;
 342                         table = devm_kzalloc(dev, size, GFP_KERNEL);
 343                         if (!table)
 344                                 return -ENOMEM;
 345
 346                         /* Fill the interpolated table. */
 347                         levels_count = 0;
 348                         for (i = 0; i < data->max_brightness - 1; i++) {
 349                                 value = data->levels[i];
 350                                 n = (data->levels[i + 1] - value) / num_steps;
 351                                 if (n > 0) {
 352                                         for (j = 0; j < num_steps; j++) {
 353                                                 table[levels_count] = value;
 354                                                 value += n;
 355                                                 levels_count++;
 356                                         }
 357                                 } else {
 358                                         table[levels_count] = data->levels[i];
 359                                         levels_count++;
 360                                 }
 361                         }
 362                         table[levels_count] = data->levels[i];
 363
 364                         /*
 365                          * As we use interpolation lets remove current
 366                          * brightness levels table and replace for the
 367                          * new interpolated table.
 368                          */
 369                         devm_kfree(dev, data->levels);
 370                         data->levels = table;
 371
 372                         /*
 373                          * Reassign max_brightness value to the new total number
 374                          * of brightness levels.
 375                          */
 376                         data->max_brightness = num_levels;
 377                 }
 378
 379                 data->max_brightness--;
 380         }
 381
 382         return 0;
 383 }
 384
 385 static const struct of_device_id pwm_backlight_of_match[] = {
 386         { .compatible = "pwm-backlight" },
 387         { }
 388 };
 389
 390 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 391 #else
 392 static int pwm_backlight_parse_dt(struct device *dev,
 393                                   struct platform_pwm_backlight_data *data)
 394 {
 395         return -ENODEV;
 396 }
 397
 398 static
 399 int pwm_backlight_brightness_default(struct device *dev,
 400                                      struct platform_pwm_backlight_data *data,
 401                                      unsigned int period)
 402 {
 403         return -ENODEV;
 404 }
 405 #endif
 406
 407 static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
 408 {
 409         struct device_node *node = pb->dev->of_node;
 410
 411         /* Not booted with device tree or no phandle link to the node */
 412         if (!node || !node->phandle)
 413                 return FB_BLANK_UNBLANK;
 414
 415         /*
 416          * If the driver is probed from the device tree and there is a
 417          * phandle link pointing to the backlight node, it is safe to
 418          * assume that another driver will enable the backlight at the
 419          * appropriate time. Therefore, if it is disabled, keep it so.
 420          */
 421
 422         /* if the enable GPIO is disabled, do not enable the backlight */
 423         if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0)
 424                 return FB_BLANK_POWERDOWN;
 425
 426         /* The regulator is disabled, do not enable the backlight */
 427         if (!regulator_is_enabled(pb->power_supply))
 428                 return FB_BLANK_POWERDOWN;
 429
 430         /* The PWM is disabled, keep it like this */
 431         if (!pwm_is_enabled(pb->pwm))
 432                 return FB_BLANK_POWERDOWN;
 433
 434         return FB_BLANK_UNBLANK;
 435 }
 436
 437 static int pwm_backlight_probe(struct platform_device *pdev)
 438 {
 439         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 440         struct platform_pwm_backlight_data defdata;
 441         struct backlight_properties props;
 442         struct backlight_device *bl;
 443         struct device_node *node = pdev->dev.of_node;
 444         struct pwm_bl_data *pb;
 445         struct pwm_state state;
 446         unsigned int i;
 447         int ret;
 448
 449         if (!data) {
 450                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 451                 if (ret < 0) {
 452                         dev_err(&pdev->dev, "failed to find platform data\n");
 453                         return ret;
 454                 }
 455
 456                 data = &defdata;
 457         }
 458
 459         if (data->init) {
 460                 ret = data->init(&pdev->dev);
 461                 if (ret < 0)
 462                         return ret;
 463         }
 464
 465         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 466         if (!pb) {
 467                 ret = -ENOMEM;
 468                 goto err_alloc;
 469         }
 470
 471         pb->notify = data->notify;
 472         pb->notify_after = data->notify_after;
 473         pb->check_fb = data->check_fb;
 474         pb->exit = data->exit;
 475         pb->dev = &pdev->dev;
 476         pb->enabled = false;
 477         pb->post_pwm_on_delay = data->post_pwm_on_delay;
 478         pb->pwm_off_delay = data->pwm_off_delay;
 479
 480         pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 481                                                   GPIOD_ASIS);
 482         if (IS_ERR(pb->enable_gpio)) {
 483                 ret = PTR_ERR(pb->enable_gpio);
 484                 goto err_alloc;
 485         }
 486
 487         /*
 488          * Compatibility fallback for drivers still using the integer GPIO
 489          * platform data. Must go away soon.
 490          */
 491         if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
 492                 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 493                                             GPIOF_OUT_INIT_HIGH, "enable");
 494                 if (ret < 0) {
 495                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 496                                 data->enable_gpio, ret);
 497                         goto err_alloc;
 498                 }
 499
 500                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 501         }
 502
 503         /*
 504          * If the GPIO is not known to be already configured as output, that
 505          * is, if gpiod_get_direction returns either 1 or -EINVAL, change the
 506          * direction to output and set the GPIO as active.
 507          * Do not force the GPIO to active when it was already output as it
 508          * could cause backlight flickering or we would enable the backlight too
 509          * early. Leave the decision of the initial backlight state for later.
 510          */
 511         if (pb->enable_gpio &&
 512             gpiod_get_direction(pb->enable_gpio) != 0)
 513                 gpiod_direction_output(pb->enable_gpio, 1);
 514
 515         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 516         if (IS_ERR(pb->power_supply)) {
 517                 ret = PTR_ERR(pb->power_supply);
 518                 goto err_alloc;
 519         }
 520
 521         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 522         if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
 523                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 524                 pb->legacy = true;
 525                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 526         }
 527
 528         if (IS_ERR(pb->pwm)) {
 529                 ret = PTR_ERR(pb->pwm);
 530                 if (ret != -EPROBE_DEFER)
 531                         dev_err(&pdev->dev, "unable to request PWM\n");
 532                 goto err_alloc;
 533         }
 534
 535         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 536
 537         /* Sync up PWM state. */
 538         pwm_init_state(pb->pwm, &state);
 539
 540         /*
 541          * The DT case will set the pwm_period_ns field to 0 and store the
 542          * period, parsed from the DT, in the PWM device. For the non-DT case,
 543          * set the period from platform data if it has not already been set
 544          * via the PWM lookup table.
 545          */
 546         if (!state.period && (data->pwm_period_ns > 0))
 547                 state.period = data->pwm_period_ns;
 548
 549         ret = pwm_apply_state(pb->pwm, &state);
 550         if (ret) {
 551                 dev_err(&pdev->dev, "failed to apply initial PWM state: %d\n",
 552                         ret);
 553                 goto err_alloc;
 554         }
 555
 556         if (data->levels) {
 557                 /*
 558                  * For the DT case, only when brightness levels is defined
 559                  * data->levels is filled. For the non-DT case, data->levels
 560                  * can come from platform data, however is not usual.
 561                  */
 562                 for (i = 0; i <= data->max_brightness; i++) {
 563                         if (data->levels[i] > pb->scale)
 564                                 pb->scale = data->levels[i];
 565
 566                         pb->levels = data->levels;
 567                 }
 568         } else if (!data->max_brightness) {
 569                 /*
 570                  * If no brightness levels are provided and max_brightness is
 571                  * not set, use the default brightness table. For the DT case,
 572                  * max_brightness is set to 0 when brightness levels is not
 573                  * specified. For the non-DT case, max_brightness is usually
 574                  * set to some value.
 575                  */
 576
 577                 /* Get the PWM period (in nanoseconds) */
 578                 pwm_get_state(pb->pwm, &state);
 579
 580                 ret = pwm_backlight_brightness_default(&pdev->dev, data,
 581                                                        state.period);
 582                 if (ret < 0) {
 583                         dev_err(&pdev->dev,
 584                                 "failed to setup default brightness table\n");
 585                         goto err_alloc;
 586                 }
 587
 588                 for (i = 0; i <= data->max_brightness; i++) {
 589                         if (data->levels[i] > pb->scale)
 590                                 pb->scale = data->levels[i];
 591
 592                         pb->levels = data->levels;
 593                 }
 594         } else {
 595                 /*
 596                  * That only happens for the non-DT case, where platform data
 597                  * sets the max_brightness value.
 598                  */
 599                 pb->scale = data->max_brightness;
 600         }
 601
 602         pb->lth_brightness = data->lth_brightness * (state.period / pb->scale);
 603
 604         memset(&props, 0, sizeof(struct backlight_properties));
 605         props.type = BACKLIGHT_RAW;
 606         props.max_brightness = data->max_brightness;
 607         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 608                                        &pwm_backlight_ops, &props);
 609         if (IS_ERR(bl)) {
 610                 dev_err(&pdev->dev, "failed to register backlight\n");
 611                 ret = PTR_ERR(bl);
 612                 if (pb->legacy)
 613                         pwm_free(pb->pwm);
 614                 goto err_alloc;
 615         }
 616
 617         if (data->dft_brightness > data->max_brightness) {
 618                 dev_warn(&pdev->dev,
 619                          "invalid default brightness level: %u, using %u\n",
 620                          data->dft_brightness, data->max_brightness);
 621                 data->dft_brightness = data->max_brightness;
 622         }
 623
 624         bl->props.brightness = data->dft_brightness;
 625         bl->props.power = pwm_backlight_initial_power_state(pb);
 626         backlight_update_status(bl);
 627
 628         platform_set_drvdata(pdev, bl);
 629         return 0;
 630
 631 err_alloc:
 632         if (data->exit)
 633                 data->exit(&pdev->dev);
 634         return ret;
 635 }
 636
 637 static int pwm_backlight_remove(struct platform_device *pdev)
 638 {
 639         struct backlight_device *bl = platform_get_drvdata(pdev);
 640         struct pwm_bl_data *pb = bl_get_data(bl);
 641
 642         backlight_device_unregister(bl);
 643         pwm_backlight_power_off(pb);
 644
 645         if (pb->exit)
 646                 pb->exit(&pdev->dev);
 647         if (pb->legacy)
 648                 pwm_free(pb->pwm);
 649
 650         return 0;
 651 }
 652
 653 static void pwm_backlight_shutdown(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         pwm_backlight_power_off(pb);
 659 }
 660
 661 #ifdef CONFIG_PM_SLEEP
 662 static int pwm_backlight_suspend(struct device *dev)
 663 {
 664         struct backlight_device *bl = dev_get_drvdata(dev);
 665         struct pwm_bl_data *pb = bl_get_data(bl);
 666
 667         if (pb->notify)
 668                 pb->notify(pb->dev, 0);
 669
 670         pwm_backlight_power_off(pb);
 671
 672         if (pb->notify_after)
 673                 pb->notify_after(pb->dev, 0);
 674
 675         return 0;
 676 }
 677
 678 static int pwm_backlight_resume(struct device *dev)
 679 {
 680         struct backlight_device *bl = dev_get_drvdata(dev);
 681
 682         backlight_update_status(bl);
 683
 684         return 0;
 685 }
 686 #endif
 687
 688 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 689 #ifdef CONFIG_PM_SLEEP
 690         .suspend = pwm_backlight_suspend,
 691         .resume = pwm_backlight_resume,
 692         .poweroff = pwm_backlight_suspend,
 693         .restore = pwm_backlight_resume,
 694 #endif
 695 };
 696
 697 static struct platform_driver pwm_backlight_driver = {
 698         .driver         = {
 699                 .name           = "pwm-backlight",
 700                 .pm             = &pwm_backlight_pm_ops,
 701                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 702         },
 703         .probe          = pwm_backlight_probe,
 704         .remove         = pwm_backlight_remove,
 705         .shutdown       = pwm_backlight_shutdown,
 706 };
 707
 708 module_platform_driver(pwm_backlight_driver);
 709
 710 MODULE_DESCRIPTION("PWM based Backlight Driver");
 711 MODULE_LICENSE("GPL");
 712 MODULE_ALIAS("platform:pwm-backlight");