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            period;
  32         unsigned int            lth_brightness;
  33         unsigned int            *levels;
  34         bool                    enabled;
  35         struct regulator        *power_supply;
  36         struct gpio_desc        *enable_gpio;
  37         unsigned int            scale;
  38         bool                    legacy;
  39         unsigned int            post_pwm_on_delay;
  40         unsigned int            pwm_off_delay;
  41         int                     (*notify)(struct device *,
  42                                           int brightness);
  43         void                    (*notify_after)(struct device *,
  44                                         int brightness);
  45         int                     (*check_fb)(struct device *, struct fb_info *);
  46         void                    (*exit)(struct device *);
  47 };
  48
  49 static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
  50 {
  51         int err;
  52
  53         if (pb->enabled)
  54                 return;
  55
  56         err = regulator_enable(pb->power_supply);
  57         if (err < 0)
  58                 dev_err(pb->dev, "failed to enable power supply\n");
  59
  60         pwm_enable(pb->pwm);
  61
  62         if (pb->post_pwm_on_delay)
  63                 msleep(pb->post_pwm_on_delay);
  64
  65         if (pb->enable_gpio)
  66                 gpiod_set_value_cansleep(pb->enable_gpio, 1);
  67
  68         pb->enabled = true;
  69 }
  70
  71 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
  72 {
  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         pwm_config(pb->pwm, 0, pb->period);
  83         pwm_disable(pb->pwm);
  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         u64 duty_cycle;
  93
  94         if (pb->levels)
  95                 duty_cycle = pb->levels[brightness];
  96         else
  97                 duty_cycle = brightness;
  98
  99         duty_cycle *= pb->period - lth;
 100         do_div(duty_cycle, pb->scale);
 101
 102         return duty_cycle + lth;
 103 }
 104
 105 static int pwm_backlight_update_status(struct backlight_device *bl)
 106 {
 107         struct pwm_bl_data *pb = bl_get_data(bl);
 108         int brightness = bl->props.brightness;
 109         int duty_cycle;
 110
 111         if (bl->props.power != FB_BLANK_UNBLANK ||
 112             bl->props.fb_blank != FB_BLANK_UNBLANK ||
 113             bl->props.state & BL_CORE_FBBLANK)
 114                 brightness = 0;
 115
 116         if (pb->notify)
 117                 brightness = pb->notify(pb->dev, brightness);
 118
 119         if (brightness > 0) {
 120                 duty_cycle = compute_duty_cycle(pb, brightness);
 121                 pwm_config(pb->pwm, duty_cycle, pb->period);
 122                 pwm_backlight_power_on(pb, brightness);
 123         } else
 124                 pwm_backlight_power_off(pb);
 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_SCALE     10000 /* luminance scale */
 147
 148 /* An integer based power function */
 149 static u64 int_pow(u64 base, int exp)
 150 {
 151         u64 result = 1;
 152
 153         while (exp) {
 154                 if (exp & 1)
 155                         result *= base;
 156                 exp >>= 1;
 157                 base *= base;
 158         }
 159
 160         return result;
 161 }
 162
 163 /*
 164  * CIE lightness to PWM conversion.
 165  *
 166  * The CIE 1931 lightness formula is what actually describes how we perceive
 167  * light:
 168  *          Y = (L* / 902.3)           if L* ≤ 0.08856
 169  *          Y = ((L* + 16) / 116)^3    if L* > 0.08856
 170  *
 171  * Where Y is the luminance, the amount of light coming out of the screen, and
 172  * is a number between 0.0 and 1.0; and L* is the lightness, how bright a human
 173  * perceives the screen to be, and is a number between 0 and 100.
 174  *
 175  * The following function does the fixed point maths needed to implement the
 176  * above formula.
 177  */
 178 static u64 cie1931(unsigned int lightness, unsigned int scale)
 179 {
 180         u64 retval;
 181
 182         lightness *= 100;
 183         if (lightness <= (8 * scale)) {
 184                 retval = DIV_ROUND_CLOSEST_ULL(lightness * 10, 9023);
 185         } else {
 186                 retval = int_pow((lightness + (16 * scale)) / 116, 3);
 187                 retval = DIV_ROUND_CLOSEST_ULL(retval, (scale * scale));
 188         }
 189
 190         return retval;
 191 }
 192
 193 /*
 194  * Create a default correction table for PWM values to create linear brightness
 195  * for LED based backlights using the CIE1931 algorithm.
 196  */
 197 static
 198 int pwm_backlight_brightness_default(struct device *dev,
 199                                      struct platform_pwm_backlight_data *data,
 200                                      unsigned int period)
 201 {
 202         unsigned int counter = 0;
 203         unsigned int i, n;
 204         u64 retval;
 205
 206         /*
 207          * Count the number of bits needed to represent the period number. The
 208          * number of bits is used to calculate the number of levels used for the
 209          * brightness-levels table, the purpose of this calculation is have a
 210          * pre-computed table with enough levels to get linear brightness
 211          * perception. The period is divided by the number of bits so for a
 212          * 8-bit PWM we have 255 / 8 = 32 brightness levels or for a 16-bit PWM
 213          * we have 65535 / 16 = 4096 brightness levels.
 214          *
 215          * Note that this method is based on empirical testing on different
 216          * devices with PWM of 8 and 16 bits of resolution.
 217          */
 218         n = period;
 219         while (n) {
 220                 counter += n % 2;
 221                 n >>= 1;
 222         }
 223
 224         data->max_brightness = DIV_ROUND_UP(period, counter);
 225         data->levels = devm_kcalloc(dev, data->max_brightness,
 226                                     sizeof(*data->levels), GFP_KERNEL);
 227         if (!data->levels)
 228                 return -ENOMEM;
 229
 230         /* Fill the table using the cie1931 algorithm */
 231         for (i = 0; i < data->max_brightness; i++) {
 232                 retval = cie1931((i * PWM_LUMINANCE_SCALE) /
 233                                  data->max_brightness, PWM_LUMINANCE_SCALE) *
 234                                  period;
 235                 retval = DIV_ROUND_CLOSEST_ULL(retval, PWM_LUMINANCE_SCALE);
 236                 if (retval > UINT_MAX)
 237                         return -EINVAL;
 238                 data->levels[i] = (unsigned int)retval;
 239         }
 240
 241         data->dft_brightness = data->max_brightness / 2;
 242         data->max_brightness--;
 243
 244         return 0;
 245 }
 246
 247 static int pwm_backlight_parse_dt(struct device *dev,
 248                                   struct platform_pwm_backlight_data *data)
 249 {
 250         struct device_node *node = dev->of_node;
 251         unsigned int num_levels = 0;
 252         unsigned int levels_count;
 253         unsigned int num_steps = 0;
 254         struct property *prop;
 255         unsigned int *table;
 256         int length;
 257         u32 value;
 258         int ret;
 259
 260         if (!node)
 261                 return -ENODEV;
 262
 263         memset(data, 0, sizeof(*data));
 264
 265         /*
 266          * Determine the number of brightness levels, if this property is not
 267          * set a default table of brightness levels will be used.
 268          */
 269         prop = of_find_property(node, "brightness-levels", &length);
 270         if (!prop)
 271                 return 0;
 272
 273         data->max_brightness = length / sizeof(u32);
 274
 275         /* read brightness levels from DT property */
 276         if (data->max_brightness > 0) {
 277                 size_t size = sizeof(*data->levels) * data->max_brightness;
 278                 unsigned int i, j, n = 0;
 279
 280                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 281                 if (!data->levels)
 282                         return -ENOMEM;
 283
 284                 ret = of_property_read_u32_array(node, "brightness-levels",
 285                                                  data->levels,
 286                                                  data->max_brightness);
 287                 if (ret < 0)
 288                         return ret;
 289
 290                 ret = of_property_read_u32(node, "default-brightness-level",
 291                                            &value);
 292                 if (ret < 0)
 293                         return ret;
 294
 295                 data->dft_brightness = value;
 296
 297                 /*
 298                  * This property is optional, if is set enables linear
 299                  * interpolation between each of the values of brightness levels
 300                  * and creates a new pre-computed table.
 301                  */
 302                 of_property_read_u32(node, "num-interpolated-steps",
 303                                      &num_steps);
 304
 305                 /*
 306                  * Make sure that there is at least two entries in the
 307                  * brightness-levels table, otherwise we can't interpolate
 308                  * between two points.
 309                  */
 310                 if (num_steps) {
 311                         if (data->max_brightness < 2) {
 312                                 dev_err(dev, "can't interpolate\n");
 313                                 return -EINVAL;
 314                         }
 315
 316                         /*
 317                          * Recalculate the number of brightness levels, now
 318                          * taking in consideration the number of interpolated
 319                          * steps between two levels.
 320                          */
 321                         for (i = 0; i < data->max_brightness - 1; i++) {
 322                                 if ((data->levels[i + 1] - data->levels[i]) /
 323                                    num_steps)
 324                                         num_levels += num_steps;
 325                                 else
 326                                         num_levels++;
 327                         }
 328                         num_levels++;
 329                         dev_dbg(dev, "new number of brightness levels: %d\n",
 330                                 num_levels);
 331
 332                         /*
 333                          * Create a new table of brightness levels with all the
 334                          * interpolated steps.
 335                          */
 336                         size = sizeof(*table) * num_levels;
 337                         table = devm_kzalloc(dev, size, GFP_KERNEL);
 338                         if (!table)
 339                                 return -ENOMEM;
 340
 341                         /* Fill the interpolated table. */
 342                         levels_count = 0;
 343                         for (i = 0; i < data->max_brightness - 1; i++) {
 344                                 value = data->levels[i];
 345                                 n = (data->levels[i + 1] - value) / num_steps;
 346                                 if (n > 0) {
 347                                         for (j = 0; j < num_steps; j++) {
 348                                                 table[levels_count] = value;
 349                                                 value += n;
 350                                                 levels_count++;
 351                                         }
 352                                 } else {
 353                                         table[levels_count] = data->levels[i];
 354                                         levels_count++;
 355                                 }
 356                         }
 357                         table[levels_count] = data->levels[i];
 358
 359                         /*
 360                          * As we use interpolation lets remove current
 361                          * brightness levels table and replace for the
 362                          * new interpolated table.
 363                          */
 364                         devm_kfree(dev, data->levels);
 365                         data->levels = table;
 366
 367                         /*
 368                          * Reassign max_brightness value to the new total number
 369                          * of brightness levels.
 370                          */
 371                         data->max_brightness = num_levels;
 372                 }
 373
 374                 data->max_brightness--;
 375         }
 376
 377         /*
 378          * These values are optional and set as 0 by default, the out values
 379          * are modified only if a valid u32 value can be decoded.
 380          */
 381         of_property_read_u32(node, "post-pwm-on-delay-ms",
 382                              &data->post_pwm_on_delay);
 383         of_property_read_u32(node, "pwm-off-delay-ms", &data->pwm_off_delay);
 384
 385         data->enable_gpio = -EINVAL;
 386         return 0;
 387 }
 388
 389 static const struct of_device_id pwm_backlight_of_match[] = {
 390         { .compatible = "pwm-backlight" },
 391         { }
 392 };
 393
 394 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 395 #else
 396 static int pwm_backlight_parse_dt(struct device *dev,
 397                                   struct platform_pwm_backlight_data *data)
 398 {
 399         return -ENODEV;
 400 }
 401
 402 static
 403 int pwm_backlight_brightness_default(struct device *dev,
 404                                      struct platform_pwm_backlight_data *data,
 405                                      unsigned int period)
 406 {
 407         return -ENODEV;
 408 }
 409 #endif
 410
 411 static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
 412 {
 413         struct device_node *node = pb->dev->of_node;
 414
 415         /* Not booted with device tree or no phandle link to the node */
 416         if (!node || !node->phandle)
 417                 return FB_BLANK_UNBLANK;
 418
 419         /*
 420          * If the driver is probed from the device tree and there is a
 421          * phandle link pointing to the backlight node, it is safe to
 422          * assume that another driver will enable the backlight at the
 423          * appropriate time. Therefore, if it is disabled, keep it so.
 424          */
 425
 426         /* if the enable GPIO is disabled, do not enable the backlight */
 427         if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
 428                 return FB_BLANK_POWERDOWN;
 429
 430         /* The regulator is disabled, do not enable the backlight */
 431         if (!regulator_is_enabled(pb->power_supply))
 432                 return FB_BLANK_POWERDOWN;
 433
 434         /* The PWM is disabled, keep it like this */
 435         if (!pwm_is_enabled(pb->pwm))
 436                 return FB_BLANK_POWERDOWN;
 437
 438         return FB_BLANK_UNBLANK;
 439 }
 440
 441 static int pwm_backlight_probe(struct platform_device *pdev)
 442 {
 443         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 444         struct platform_pwm_backlight_data defdata;
 445         struct backlight_properties props;
 446         struct backlight_device *bl;
 447         struct device_node *node = pdev->dev.of_node;
 448         struct pwm_bl_data *pb;
 449         struct pwm_state state;
 450         struct pwm_args pargs;
 451         unsigned int i;
 452         int ret;
 453
 454         if (!data) {
 455                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 456                 if (ret < 0) {
 457                         dev_err(&pdev->dev, "failed to find platform data\n");
 458                         return ret;
 459                 }
 460
 461                 data = &defdata;
 462         }
 463
 464         if (data->init) {
 465                 ret = data->init(&pdev->dev);
 466                 if (ret < 0)
 467                         return ret;
 468         }
 469
 470         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 471         if (!pb) {
 472                 ret = -ENOMEM;
 473                 goto err_alloc;
 474         }
 475
 476         pb->notify = data->notify;
 477         pb->notify_after = data->notify_after;
 478         pb->check_fb = data->check_fb;
 479         pb->exit = data->exit;
 480         pb->dev = &pdev->dev;
 481         pb->enabled = false;
 482         pb->post_pwm_on_delay = data->post_pwm_on_delay;
 483         pb->pwm_off_delay = data->pwm_off_delay;
 484
 485         pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 486                                                   GPIOD_ASIS);
 487         if (IS_ERR(pb->enable_gpio)) {
 488                 ret = PTR_ERR(pb->enable_gpio);
 489                 goto err_alloc;
 490         }
 491
 492         /*
 493          * Compatibility fallback for drivers still using the integer GPIO
 494          * platform data. Must go away soon.
 495          */
 496         if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
 497                 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 498                                             GPIOF_OUT_INIT_HIGH, "enable");
 499                 if (ret < 0) {
 500                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 501                                 data->enable_gpio, ret);
 502                         goto err_alloc;
 503                 }
 504
 505                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 506         }
 507
 508         /*
 509          * If the GPIO is not known to be already configured as output, that
 510          * is, if gpiod_get_direction returns either 1 or -EINVAL, change the
 511          * direction to output and set the GPIO as active.
 512          * Do not force the GPIO to active when it was already output as it
 513          * could cause backlight flickering or we would enable the backlight too
 514          * early. Leave the decision of the initial backlight state for later.
 515          */
 516         if (pb->enable_gpio &&
 517             gpiod_get_direction(pb->enable_gpio) != 0)
 518                 gpiod_direction_output(pb->enable_gpio, 1);
 519
 520         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 521         if (IS_ERR(pb->power_supply)) {
 522                 ret = PTR_ERR(pb->power_supply);
 523                 goto err_alloc;
 524         }
 525
 526         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 527         if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
 528                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 529                 pb->legacy = true;
 530                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 531         }
 532
 533         if (IS_ERR(pb->pwm)) {
 534                 ret = PTR_ERR(pb->pwm);
 535                 if (ret != -EPROBE_DEFER)
 536                         dev_err(&pdev->dev, "unable to request PWM\n");
 537                 goto err_alloc;
 538         }
 539
 540         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 541
 542         if (!data->levels) {
 543                 /* Get the PWM period (in nanoseconds) */
 544                 pwm_get_state(pb->pwm, &state);
 545
 546                 ret = pwm_backlight_brightness_default(&pdev->dev, data,
 547                                                        state.period);
 548                 if (ret < 0) {
 549                         dev_err(&pdev->dev,
 550                                 "failed to setup default brightness table\n");
 551                         goto err_alloc;
 552                 }
 553         }
 554
 555         for (i = 0; i <= data->max_brightness; i++) {
 556                 if (data->levels[i] > pb->scale)
 557                         pb->scale = data->levels[i];
 558
 559                 pb->levels = data->levels;
 560         }
 561
 562         /*
 563          * FIXME: pwm_apply_args() should be removed when switching to
 564          * the atomic PWM API.
 565          */
 566         pwm_apply_args(pb->pwm);
 567
 568         /*
 569          * The DT case will set the pwm_period_ns field to 0 and store the
 570          * period, parsed from the DT, in the PWM device. For the non-DT case,
 571          * set the period from platform data if it has not already been set
 572          * via the PWM lookup table.
 573          */
 574         pwm_get_args(pb->pwm, &pargs);
 575         pb->period = pargs.period;
 576         if (!pb->period && (data->pwm_period_ns > 0))
 577                 pb->period = data->pwm_period_ns;
 578
 579         pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
 580
 581         memset(&props, 0, sizeof(struct backlight_properties));
 582         props.type = BACKLIGHT_RAW;
 583         props.max_brightness = data->max_brightness;
 584         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 585                                        &pwm_backlight_ops, &props);
 586         if (IS_ERR(bl)) {
 587                 dev_err(&pdev->dev, "failed to register backlight\n");
 588                 ret = PTR_ERR(bl);
 589                 if (pb->legacy)
 590                         pwm_free(pb->pwm);
 591                 goto err_alloc;
 592         }
 593
 594         if (data->dft_brightness > data->max_brightness) {
 595                 dev_warn(&pdev->dev,
 596                          "invalid default brightness level: %u, using %u\n",
 597                          data->dft_brightness, data->max_brightness);
 598                 data->dft_brightness = data->max_brightness;
 599         }
 600
 601         bl->props.brightness = data->dft_brightness;
 602         bl->props.power = pwm_backlight_initial_power_state(pb);
 603         backlight_update_status(bl);
 604
 605         platform_set_drvdata(pdev, bl);
 606         return 0;
 607
 608 err_alloc:
 609         if (data->exit)
 610                 data->exit(&pdev->dev);
 611         return ret;
 612 }
 613
 614 static int pwm_backlight_remove(struct platform_device *pdev)
 615 {
 616         struct backlight_device *bl = platform_get_drvdata(pdev);
 617         struct pwm_bl_data *pb = bl_get_data(bl);
 618
 619         backlight_device_unregister(bl);
 620         pwm_backlight_power_off(pb);
 621
 622         if (pb->exit)
 623                 pb->exit(&pdev->dev);
 624         if (pb->legacy)
 625                 pwm_free(pb->pwm);
 626
 627         return 0;
 628 }
 629
 630 static void pwm_backlight_shutdown(struct platform_device *pdev)
 631 {
 632         struct backlight_device *bl = platform_get_drvdata(pdev);
 633         struct pwm_bl_data *pb = bl_get_data(bl);
 634
 635         pwm_backlight_power_off(pb);
 636 }
 637
 638 #ifdef CONFIG_PM_SLEEP
 639 static int pwm_backlight_suspend(struct device *dev)
 640 {
 641         struct backlight_device *bl = dev_get_drvdata(dev);
 642         struct pwm_bl_data *pb = bl_get_data(bl);
 643
 644         if (pb->notify)
 645                 pb->notify(pb->dev, 0);
 646
 647         pwm_backlight_power_off(pb);
 648
 649         if (pb->notify_after)
 650                 pb->notify_after(pb->dev, 0);
 651
 652         return 0;
 653 }
 654
 655 static int pwm_backlight_resume(struct device *dev)
 656 {
 657         struct backlight_device *bl = dev_get_drvdata(dev);
 658
 659         backlight_update_status(bl);
 660
 661         return 0;
 662 }
 663 #endif
 664
 665 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 666 #ifdef CONFIG_PM_SLEEP
 667         .suspend = pwm_backlight_suspend,
 668         .resume = pwm_backlight_resume,
 669         .poweroff = pwm_backlight_suspend,
 670         .restore = pwm_backlight_resume,
 671 #endif
 672 };
 673
 674 static struct platform_driver pwm_backlight_driver = {
 675         .driver         = {
 676                 .name           = "pwm-backlight",
 677                 .pm             = &pwm_backlight_pm_ops,
 678                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 679         },
 680         .probe          = pwm_backlight_probe,
 681         .remove         = pwm_backlight_remove,
 682         .shutdown       = pwm_backlight_shutdown,
 683 };
 684
 685 module_platform_driver(pwm_backlight_driver);
 686
 687 MODULE_DESCRIPTION("PWM based Backlight Driver");
 688 MODULE_LICENSE("GPL");
 689 MODULE_ALIAS("platform:pwm-backlight");