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 /* An integer based power function */
 159 static u64 int_pow(u64 base, int exp)
 160 {
 161         u64 result = 1;
 162
 163         while (exp) {
 164                 if (exp & 1)
 165                         result *= base;
 166                 exp >>= 1;
 167                 base *= base;
 168         }
 169
 170         return result;
 171 }
 172
 173 /*
 174  * CIE lightness to PWM conversion.
 175  *
 176  * The CIE 1931 lightness formula is what actually describes how we perceive
 177  * light:
 178  *          Y = (L* / 902.3)           if L* ≤ 0.08856
 179  *          Y = ((L* + 16) / 116)^3    if L* > 0.08856
 180  *
 181  * Where Y is the luminance, the amount of light coming out of the screen, and
 182  * is a number between 0.0 and 1.0; and L* is the lightness, how bright a human
 183  * perceives the screen to be, and is a number between 0 and 100.
 184  *
 185  * The following function does the fixed point maths needed to implement the
 186  * above formula.
 187  */
 188 static u64 cie1931(unsigned int lightness, unsigned int scale)
 189 {
 190         u64 retval;
 191
 192         lightness *= 100;
 193         if (lightness <= (8 * scale)) {
 194                 retval = DIV_ROUND_CLOSEST_ULL(lightness * 10, 9023);
 195         } else {
 196                 retval = int_pow((lightness + (16 * scale)) / 116, 3);
 197                 retval = DIV_ROUND_CLOSEST_ULL(retval, (scale * scale));
 198         }
 199
 200         return retval;
 201 }
 202
 203 /*
 204  * Create a default correction table for PWM values to create linear brightness
 205  * for LED based backlights using the CIE1931 algorithm.
 206  */
 207 static
 208 int pwm_backlight_brightness_default(struct device *dev,
 209                                      struct platform_pwm_backlight_data *data,
 210                                      unsigned int period)
 211 {
 212         unsigned int counter = 0;
 213         unsigned int i, n;
 214         u64 retval;
 215
 216         /*
 217          * Count the number of bits needed to represent the period number. The
 218          * number of bits is used to calculate the number of levels used for the
 219          * brightness-levels table, the purpose of this calculation is have a
 220          * pre-computed table with enough levels to get linear brightness
 221          * perception. The period is divided by the number of bits so for a
 222          * 8-bit PWM we have 255 / 8 = 32 brightness levels or for a 16-bit PWM
 223          * we have 65535 / 16 = 4096 brightness levels.
 224          *
 225          * Note that this method is based on empirical testing on different
 226          * devices with PWM of 8 and 16 bits of resolution.
 227          */
 228         n = period;
 229         while (n) {
 230                 counter += n % 2;
 231                 n >>= 1;
 232         }
 233
 234         data->max_brightness = DIV_ROUND_UP(period, counter);
 235         data->levels = devm_kcalloc(dev, data->max_brightness,
 236                                     sizeof(*data->levels), GFP_KERNEL);
 237         if (!data->levels)
 238                 return -ENOMEM;
 239
 240         /* Fill the table using the cie1931 algorithm */
 241         for (i = 0; i < data->max_brightness; i++) {
 242                 retval = cie1931((i * PWM_LUMINANCE_SCALE) /
 243                                  data->max_brightness, PWM_LUMINANCE_SCALE) *
 244                                  period;
 245                 retval = DIV_ROUND_CLOSEST_ULL(retval, PWM_LUMINANCE_SCALE);
 246                 if (retval > UINT_MAX)
 247                         return -EINVAL;
 248                 data->levels[i] = (unsigned int)retval;
 249         }
 250
 251         data->dft_brightness = data->max_brightness / 2;
 252         data->max_brightness--;
 253
 254         return 0;
 255 }
 256
 257 static int pwm_backlight_parse_dt(struct device *dev,
 258                                   struct platform_pwm_backlight_data *data)
 259 {
 260         struct device_node *node = dev->of_node;
 261         unsigned int num_levels = 0;
 262         unsigned int levels_count;
 263         unsigned int num_steps = 0;
 264         struct property *prop;
 265         unsigned int *table;
 266         int length;
 267         u32 value;
 268         int ret;
 269
 270         if (!node)
 271                 return -ENODEV;
 272
 273         memset(data, 0, sizeof(*data));
 274
 275         /*
 276          * These values are optional and set as 0 by default, the out values
 277          * are modified only if a valid u32 value can be decoded.
 278          */
 279         of_property_read_u32(node, "post-pwm-on-delay-ms",
 280                              &data->post_pwm_on_delay);
 281         of_property_read_u32(node, "pwm-off-delay-ms", &data->pwm_off_delay);
 282
 283         data->enable_gpio = -EINVAL;
 284
 285         /*
 286          * Determine the number of brightness levels, if this property is not
 287          * set a default table of brightness levels will be used.
 288          */
 289         prop = of_find_property(node, "brightness-levels", &length);
 290         if (!prop)
 291                 return 0;
 292
 293         data->max_brightness = length / sizeof(u32);
 294
 295         /* read brightness levels from DT property */
 296         if (data->max_brightness > 0) {
 297                 size_t size = sizeof(*data->levels) * data->max_brightness;
 298                 unsigned int i, j, n = 0;
 299
 300                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 301                 if (!data->levels)
 302                         return -ENOMEM;
 303
 304                 ret = of_property_read_u32_array(node, "brightness-levels",
 305                                                  data->levels,
 306                                                  data->max_brightness);
 307                 if (ret < 0)
 308                         return ret;
 309
 310                 ret = of_property_read_u32(node, "default-brightness-level",
 311                                            &value);
 312                 if (ret < 0)
 313                         return ret;
 314
 315                 data->dft_brightness = value;
 316
 317                 /*
 318                  * This property is optional, if is set enables linear
 319                  * interpolation between each of the values of brightness levels
 320                  * and creates a new pre-computed table.
 321                  */
 322                 of_property_read_u32(node, "num-interpolated-steps",
 323                                      &num_steps);
 324
 325                 /*
 326                  * Make sure that there is at least two entries in the
 327                  * brightness-levels table, otherwise we can't interpolate
 328                  * between two points.
 329                  */
 330                 if (num_steps) {
 331                         if (data->max_brightness < 2) {
 332                                 dev_err(dev, "can't interpolate\n");
 333                                 return -EINVAL;
 334                         }
 335
 336                         /*
 337                          * Recalculate the number of brightness levels, now
 338                          * taking in consideration the number of interpolated
 339                          * steps between two levels.
 340                          */
 341                         for (i = 0; i < data->max_brightness - 1; i++) {
 342                                 if ((data->levels[i + 1] - data->levels[i]) /
 343                                    num_steps)
 344                                         num_levels += num_steps;
 345                                 else
 346                                         num_levels++;
 347                         }
 348                         num_levels++;
 349                         dev_dbg(dev, "new number of brightness levels: %d\n",
 350                                 num_levels);
 351
 352                         /*
 353                          * Create a new table of brightness levels with all the
 354                          * interpolated steps.
 355                          */
 356                         size = sizeof(*table) * num_levels;
 357                         table = devm_kzalloc(dev, size, GFP_KERNEL);
 358                         if (!table)
 359                                 return -ENOMEM;
 360
 361                         /* Fill the interpolated table. */
 362                         levels_count = 0;
 363                         for (i = 0; i < data->max_brightness - 1; i++) {
 364                                 value = data->levels[i];
 365                                 n = (data->levels[i + 1] - value) / num_steps;
 366                                 if (n > 0) {
 367                                         for (j = 0; j < num_steps; j++) {
 368                                                 table[levels_count] = value;
 369                                                 value += n;
 370                                                 levels_count++;
 371                                         }
 372                                 } else {
 373                                         table[levels_count] = data->levels[i];
 374                                         levels_count++;
 375                                 }
 376                         }
 377                         table[levels_count] = data->levels[i];
 378
 379                         /*
 380                          * As we use interpolation lets remove current
 381                          * brightness levels table and replace for the
 382                          * new interpolated table.
 383                          */
 384                         devm_kfree(dev, data->levels);
 385                         data->levels = table;
 386
 387                         /*
 388                          * Reassign max_brightness value to the new total number
 389                          * of brightness levels.
 390                          */
 391                         data->max_brightness = num_levels;
 392                 }
 393
 394                 data->max_brightness--;
 395         }
 396
 397         return 0;
 398 }
 399
 400 static const struct of_device_id pwm_backlight_of_match[] = {
 401         { .compatible = "pwm-backlight" },
 402         { }
 403 };
 404
 405 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 406 #else
 407 static int pwm_backlight_parse_dt(struct device *dev,
 408                                   struct platform_pwm_backlight_data *data)
 409 {
 410         return -ENODEV;
 411 }
 412
 413 static
 414 int pwm_backlight_brightness_default(struct device *dev,
 415                                      struct platform_pwm_backlight_data *data,
 416                                      unsigned int period)
 417 {
 418         return -ENODEV;
 419 }
 420 #endif
 421
 422 static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
 423 {
 424         struct device_node *node = pb->dev->of_node;
 425
 426         /* Not booted with device tree or no phandle link to the node */
 427         if (!node || !node->phandle)
 428                 return FB_BLANK_UNBLANK;
 429
 430         /*
 431          * If the driver is probed from the device tree and there is a
 432          * phandle link pointing to the backlight node, it is safe to
 433          * assume that another driver will enable the backlight at the
 434          * appropriate time. Therefore, if it is disabled, keep it so.
 435          */
 436
 437         /* if the enable GPIO is disabled, do not enable the backlight */
 438         if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
 439                 return FB_BLANK_POWERDOWN;
 440
 441         /* The regulator is disabled, do not enable the backlight */
 442         if (!regulator_is_enabled(pb->power_supply))
 443                 return FB_BLANK_POWERDOWN;
 444
 445         /* The PWM is disabled, keep it like this */
 446         if (!pwm_is_enabled(pb->pwm))
 447                 return FB_BLANK_POWERDOWN;
 448
 449         return FB_BLANK_UNBLANK;
 450 }
 451
 452 static int pwm_backlight_probe(struct platform_device *pdev)
 453 {
 454         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 455         struct platform_pwm_backlight_data defdata;
 456         struct backlight_properties props;
 457         struct backlight_device *bl;
 458         struct device_node *node = pdev->dev.of_node;
 459         struct pwm_bl_data *pb;
 460         struct pwm_state state;
 461         unsigned int i;
 462         int ret;
 463
 464         if (!data) {
 465                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 466                 if (ret < 0) {
 467                         dev_err(&pdev->dev, "failed to find platform data\n");
 468                         return ret;
 469                 }
 470
 471                 data = &defdata;
 472         }
 473
 474         if (data->init) {
 475                 ret = data->init(&pdev->dev);
 476                 if (ret < 0)
 477                         return ret;
 478         }
 479
 480         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 481         if (!pb) {
 482                 ret = -ENOMEM;
 483                 goto err_alloc;
 484         }
 485
 486         pb->notify = data->notify;
 487         pb->notify_after = data->notify_after;
 488         pb->check_fb = data->check_fb;
 489         pb->exit = data->exit;
 490         pb->dev = &pdev->dev;
 491         pb->enabled = false;
 492         pb->post_pwm_on_delay = data->post_pwm_on_delay;
 493         pb->pwm_off_delay = data->pwm_off_delay;
 494
 495         pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 496                                                   GPIOD_ASIS);
 497         if (IS_ERR(pb->enable_gpio)) {
 498                 ret = PTR_ERR(pb->enable_gpio);
 499                 goto err_alloc;
 500         }
 501
 502         /*
 503          * Compatibility fallback for drivers still using the integer GPIO
 504          * platform data. Must go away soon.
 505          */
 506         if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
 507                 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 508                                             GPIOF_OUT_INIT_HIGH, "enable");
 509                 if (ret < 0) {
 510                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 511                                 data->enable_gpio, ret);
 512                         goto err_alloc;
 513                 }
 514
 515                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 516         }
 517
 518         /*
 519          * If the GPIO is not known to be already configured as output, that
 520          * is, if gpiod_get_direction returns either 1 or -EINVAL, change the
 521          * direction to output and set the GPIO as active.
 522          * Do not force the GPIO to active when it was already output as it
 523          * could cause backlight flickering or we would enable the backlight too
 524          * early. Leave the decision of the initial backlight state for later.
 525          */
 526         if (pb->enable_gpio &&
 527             gpiod_get_direction(pb->enable_gpio) != 0)
 528                 gpiod_direction_output(pb->enable_gpio, 1);
 529
 530         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 531         if (IS_ERR(pb->power_supply)) {
 532                 ret = PTR_ERR(pb->power_supply);
 533                 goto err_alloc;
 534         }
 535
 536         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 537         if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
 538                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 539                 pb->legacy = true;
 540                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 541         }
 542
 543         if (IS_ERR(pb->pwm)) {
 544                 ret = PTR_ERR(pb->pwm);
 545                 if (ret != -EPROBE_DEFER)
 546                         dev_err(&pdev->dev, "unable to request PWM\n");
 547                 goto err_alloc;
 548         }
 549
 550         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 551
 552         /* Sync up PWM state. */
 553         pwm_init_state(pb->pwm, &state);
 554
 555         /*
 556          * The DT case will set the pwm_period_ns field to 0 and store the
 557          * period, parsed from the DT, in the PWM device. For the non-DT case,
 558          * set the period from platform data if it has not already been set
 559          * via the PWM lookup table.
 560          */
 561         if (!state.period && (data->pwm_period_ns > 0))
 562                 state.period = data->pwm_period_ns;
 563
 564         ret = pwm_apply_state(pb->pwm, &state);
 565         if (ret) {
 566                 dev_err(&pdev->dev, "failed to apply initial PWM state: %d\n",
 567                         ret);
 568                 goto err_alloc;
 569         }
 570
 571         if (data->levels) {
 572                 /*
 573                  * For the DT case, only when brightness levels is defined
 574                  * data->levels is filled. For the non-DT case, data->levels
 575                  * can come from platform data, however is not usual.
 576                  */
 577                 for (i = 0; i <= data->max_brightness; i++) {
 578                         if (data->levels[i] > pb->scale)
 579                                 pb->scale = data->levels[i];
 580
 581                         pb->levels = data->levels;
 582                 }
 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         } else {
 610                 /*
 611                  * That only happens for the non-DT case, where platform data
 612                  * sets the max_brightness value.
 613                  */
 614                 pb->scale = data->max_brightness;
 615         }
 616
 617         pb->lth_brightness = data->lth_brightness * (state.period / pb->scale);
 618
 619         memset(&props, 0, sizeof(struct backlight_properties));
 620         props.type = BACKLIGHT_RAW;
 621         props.max_brightness = data->max_brightness;
 622         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 623                                        &pwm_backlight_ops, &props);
 624         if (IS_ERR(bl)) {
 625                 dev_err(&pdev->dev, "failed to register backlight\n");
 626                 ret = PTR_ERR(bl);
 627                 if (pb->legacy)
 628                         pwm_free(pb->pwm);
 629                 goto err_alloc;
 630         }
 631
 632         if (data->dft_brightness > data->max_brightness) {
 633                 dev_warn(&pdev->dev,
 634                          "invalid default brightness level: %u, using %u\n",
 635                          data->dft_brightness, data->max_brightness);
 636                 data->dft_brightness = data->max_brightness;
 637         }
 638
 639         bl->props.brightness = data->dft_brightness;
 640         bl->props.power = pwm_backlight_initial_power_state(pb);
 641         backlight_update_status(bl);
 642
 643         platform_set_drvdata(pdev, bl);
 644         return 0;
 645
 646 err_alloc:
 647         if (data->exit)
 648                 data->exit(&pdev->dev);
 649         return ret;
 650 }
 651
 652 static int pwm_backlight_remove(struct platform_device *pdev)
 653 {
 654         struct backlight_device *bl = platform_get_drvdata(pdev);
 655         struct pwm_bl_data *pb = bl_get_data(bl);
 656
 657         backlight_device_unregister(bl);
 658         pwm_backlight_power_off(pb);
 659
 660         if (pb->exit)
 661                 pb->exit(&pdev->dev);
 662         if (pb->legacy)
 663                 pwm_free(pb->pwm);
 664
 665         return 0;
 666 }
 667
 668 static void pwm_backlight_shutdown(struct platform_device *pdev)
 669 {
 670         struct backlight_device *bl = platform_get_drvdata(pdev);
 671         struct pwm_bl_data *pb = bl_get_data(bl);
 672
 673         pwm_backlight_power_off(pb);
 674 }
 675
 676 #ifdef CONFIG_PM_SLEEP
 677 static int pwm_backlight_suspend(struct device *dev)
 678 {
 679         struct backlight_device *bl = dev_get_drvdata(dev);
 680         struct pwm_bl_data *pb = bl_get_data(bl);
 681
 682         if (pb->notify)
 683                 pb->notify(pb->dev, 0);
 684
 685         pwm_backlight_power_off(pb);
 686
 687         if (pb->notify_after)
 688                 pb->notify_after(pb->dev, 0);
 689
 690         return 0;
 691 }
 692
 693 static int pwm_backlight_resume(struct device *dev)
 694 {
 695         struct backlight_device *bl = dev_get_drvdata(dev);
 696
 697         backlight_update_status(bl);
 698
 699         return 0;
 700 }
 701 #endif
 702
 703 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 704 #ifdef CONFIG_PM_SLEEP
 705         .suspend = pwm_backlight_suspend,
 706         .resume = pwm_backlight_resume,
 707         .poweroff = pwm_backlight_suspend,
 708         .restore = pwm_backlight_resume,
 709 #endif
 710 };
 711
 712 static struct platform_driver pwm_backlight_driver = {
 713         .driver         = {
 714                 .name           = "pwm-backlight",
 715                 .pm             = &pwm_backlight_pm_ops,
 716                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 717         },
 718         .probe          = pwm_backlight_probe,
 719         .remove         = pwm_backlight_remove,
 720         .shutdown       = pwm_backlight_shutdown,
 721 };
 722
 723 module_platform_driver(pwm_backlight_driver);
 724
 725 MODULE_DESCRIPTION("PWM based Backlight Driver");
 726 MODULE_LICENSE("GPL");
 727 MODULE_ALIAS("platform:pwm-backlight");