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 static int pwm_backlight_parse_dt(struct device *dev,
 147                                   struct platform_pwm_backlight_data *data)
 148 {
 149         struct device_node *node = dev->of_node;
 150         struct property *prop;
 151         int length;
 152         u32 value;
 153         int ret;
 154
 155         if (!node)
 156                 return -ENODEV;
 157
 158         memset(data, 0, sizeof(*data));
 159
 160         /* determine the number of brightness levels */
 161         prop = of_find_property(node, "brightness-levels", &length);
 162         if (!prop)
 163                 return -EINVAL;
 164
 165         data->max_brightness = length / sizeof(u32);
 166
 167         /* read brightness levels from DT property */
 168         if (data->max_brightness > 0) {
 169                 size_t size = sizeof(*data->levels) * data->max_brightness;
 170
 171                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 172                 if (!data->levels)
 173                         return -ENOMEM;
 174
 175                 ret = of_property_read_u32_array(node, "brightness-levels",
 176                                                  data->levels,
 177                                                  data->max_brightness);
 178                 if (ret < 0)
 179                         return ret;
 180
 181                 ret = of_property_read_u32(node, "default-brightness-level",
 182                                            &value);
 183                 if (ret < 0)
 184                         return ret;
 185
 186                 data->dft_brightness = value;
 187                 data->max_brightness--;
 188         }
 189
 190         /*
 191          * These values are optional and set as 0 by default, the out values
 192          * are modified only if a valid u32 value can be decoded.
 193          */
 194         of_property_read_u32(node, "post-pwm-on-delay-ms",
 195                              &data->post_pwm_on_delay);
 196         of_property_read_u32(node, "pwm-off-delay-ms", &data->pwm_off_delay);
 197
 198         data->enable_gpio = -EINVAL;
 199         return 0;
 200 }
 201
 202 static const struct of_device_id pwm_backlight_of_match[] = {
 203         { .compatible = "pwm-backlight" },
 204         { }
 205 };
 206
 207 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 208 #else
 209 static int pwm_backlight_parse_dt(struct device *dev,
 210                                   struct platform_pwm_backlight_data *data)
 211 {
 212         return -ENODEV;
 213 }
 214 #endif
 215
 216 static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
 217 {
 218         struct device_node *node = pb->dev->of_node;
 219
 220         /* Not booted with device tree or no phandle link to the node */
 221         if (!node || !node->phandle)
 222                 return FB_BLANK_UNBLANK;
 223
 224         /*
 225          * If the driver is probed from the device tree and there is a
 226          * phandle link pointing to the backlight node, it is safe to
 227          * assume that another driver will enable the backlight at the
 228          * appropriate time. Therefore, if it is disabled, keep it so.
 229          */
 230
 231         /* if the enable GPIO is disabled, do not enable the backlight */
 232         if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
 233                 return FB_BLANK_POWERDOWN;
 234
 235         /* The regulator is disabled, do not enable the backlight */
 236         if (!regulator_is_enabled(pb->power_supply))
 237                 return FB_BLANK_POWERDOWN;
 238
 239         /* The PWM is disabled, keep it like this */
 240         if (!pwm_is_enabled(pb->pwm))
 241                 return FB_BLANK_POWERDOWN;
 242
 243         return FB_BLANK_UNBLANK;
 244 }
 245
 246 static int pwm_backlight_probe(struct platform_device *pdev)
 247 {
 248         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 249         struct platform_pwm_backlight_data defdata;
 250         struct backlight_properties props;
 251         struct backlight_device *bl;
 252         struct device_node *node = pdev->dev.of_node;
 253         struct pwm_bl_data *pb;
 254         struct pwm_args pargs;
 255         int ret;
 256
 257         if (!data) {
 258                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 259                 if (ret < 0) {
 260                         dev_err(&pdev->dev, "failed to find platform data\n");
 261                         return ret;
 262                 }
 263
 264                 data = &defdata;
 265         }
 266
 267         if (data->init) {
 268                 ret = data->init(&pdev->dev);
 269                 if (ret < 0)
 270                         return ret;
 271         }
 272
 273         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 274         if (!pb) {
 275                 ret = -ENOMEM;
 276                 goto err_alloc;
 277         }
 278
 279         if (data->levels) {
 280                 unsigned int i;
 281
 282                 for (i = 0; i <= data->max_brightness; i++)
 283                         if (data->levels[i] > pb->scale)
 284                                 pb->scale = data->levels[i];
 285
 286                 pb->levels = data->levels;
 287         } else
 288                 pb->scale = data->max_brightness;
 289
 290         pb->notify = data->notify;
 291         pb->notify_after = data->notify_after;
 292         pb->check_fb = data->check_fb;
 293         pb->exit = data->exit;
 294         pb->dev = &pdev->dev;
 295         pb->enabled = false;
 296         pb->post_pwm_on_delay = data->post_pwm_on_delay;
 297         pb->pwm_off_delay = data->pwm_off_delay;
 298
 299         pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 300                                                   GPIOD_ASIS);
 301         if (IS_ERR(pb->enable_gpio)) {
 302                 ret = PTR_ERR(pb->enable_gpio);
 303                 goto err_alloc;
 304         }
 305
 306         /*
 307          * Compatibility fallback for drivers still using the integer GPIO
 308          * platform data. Must go away soon.
 309          */
 310         if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
 311                 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 312                                             GPIOF_OUT_INIT_HIGH, "enable");
 313                 if (ret < 0) {
 314                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 315                                 data->enable_gpio, ret);
 316                         goto err_alloc;
 317                 }
 318
 319                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 320         }
 321
 322         /*
 323          * If the GPIO is not known to be already configured as output, that
 324          * is, if gpiod_get_direction returns either 1 or -EINVAL, change the
 325          * direction to output and set the GPIO as active.
 326          * Do not force the GPIO to active when it was already output as it
 327          * could cause backlight flickering or we would enable the backlight too
 328          * early. Leave the decision of the initial backlight state for later.
 329          */
 330         if (pb->enable_gpio &&
 331             gpiod_get_direction(pb->enable_gpio) != 0)
 332                 gpiod_direction_output(pb->enable_gpio, 1);
 333
 334         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 335         if (IS_ERR(pb->power_supply)) {
 336                 ret = PTR_ERR(pb->power_supply);
 337                 goto err_alloc;
 338         }
 339
 340         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 341         if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
 342                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 343                 pb->legacy = true;
 344                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 345         }
 346
 347         if (IS_ERR(pb->pwm)) {
 348                 ret = PTR_ERR(pb->pwm);
 349                 if (ret != -EPROBE_DEFER)
 350                         dev_err(&pdev->dev, "unable to request PWM\n");
 351                 goto err_alloc;
 352         }
 353
 354         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 355
 356         /*
 357          * FIXME: pwm_apply_args() should be removed when switching to
 358          * the atomic PWM API.
 359          */
 360         pwm_apply_args(pb->pwm);
 361
 362         /*
 363          * The DT case will set the pwm_period_ns field to 0 and store the
 364          * period, parsed from the DT, in the PWM device. For the non-DT case,
 365          * set the period from platform data if it has not already been set
 366          * via the PWM lookup table.
 367          */
 368         pwm_get_args(pb->pwm, &pargs);
 369         pb->period = pargs.period;
 370         if (!pb->period && (data->pwm_period_ns > 0))
 371                 pb->period = data->pwm_period_ns;
 372
 373         pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
 374
 375         memset(&props, 0, sizeof(struct backlight_properties));
 376         props.type = BACKLIGHT_RAW;
 377         props.max_brightness = data->max_brightness;
 378         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 379                                        &pwm_backlight_ops, &props);
 380         if (IS_ERR(bl)) {
 381                 dev_err(&pdev->dev, "failed to register backlight\n");
 382                 ret = PTR_ERR(bl);
 383                 if (pb->legacy)
 384                         pwm_free(pb->pwm);
 385                 goto err_alloc;
 386         }
 387
 388         if (data->dft_brightness > data->max_brightness) {
 389                 dev_warn(&pdev->dev,
 390                          "invalid default brightness level: %u, using %u\n",
 391                          data->dft_brightness, data->max_brightness);
 392                 data->dft_brightness = data->max_brightness;
 393         }
 394
 395         bl->props.brightness = data->dft_brightness;
 396         bl->props.power = pwm_backlight_initial_power_state(pb);
 397         backlight_update_status(bl);
 398
 399         platform_set_drvdata(pdev, bl);
 400         return 0;
 401
 402 err_alloc:
 403         if (data->exit)
 404                 data->exit(&pdev->dev);
 405         return ret;
 406 }
 407
 408 static int pwm_backlight_remove(struct platform_device *pdev)
 409 {
 410         struct backlight_device *bl = platform_get_drvdata(pdev);
 411         struct pwm_bl_data *pb = bl_get_data(bl);
 412
 413         backlight_device_unregister(bl);
 414         pwm_backlight_power_off(pb);
 415
 416         if (pb->exit)
 417                 pb->exit(&pdev->dev);
 418         if (pb->legacy)
 419                 pwm_free(pb->pwm);
 420
 421         return 0;
 422 }
 423
 424 static void pwm_backlight_shutdown(struct platform_device *pdev)
 425 {
 426         struct backlight_device *bl = platform_get_drvdata(pdev);
 427         struct pwm_bl_data *pb = bl_get_data(bl);
 428
 429         pwm_backlight_power_off(pb);
 430 }
 431
 432 #ifdef CONFIG_PM_SLEEP
 433 static int pwm_backlight_suspend(struct device *dev)
 434 {
 435         struct backlight_device *bl = dev_get_drvdata(dev);
 436         struct pwm_bl_data *pb = bl_get_data(bl);
 437
 438         if (pb->notify)
 439                 pb->notify(pb->dev, 0);
 440
 441         pwm_backlight_power_off(pb);
 442
 443         if (pb->notify_after)
 444                 pb->notify_after(pb->dev, 0);
 445
 446         return 0;
 447 }
 448
 449 static int pwm_backlight_resume(struct device *dev)
 450 {
 451         struct backlight_device *bl = dev_get_drvdata(dev);
 452
 453         backlight_update_status(bl);
 454
 455         return 0;
 456 }
 457 #endif
 458
 459 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 460 #ifdef CONFIG_PM_SLEEP
 461         .suspend = pwm_backlight_suspend,
 462         .resume = pwm_backlight_resume,
 463         .poweroff = pwm_backlight_suspend,
 464         .restore = pwm_backlight_resume,
 465 #endif
 466 };
 467
 468 static struct platform_driver pwm_backlight_driver = {
 469         .driver         = {
 470                 .name           = "pwm-backlight",
 471                 .pm             = &pwm_backlight_pm_ops,
 472                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 473         },
 474         .probe          = pwm_backlight_probe,
 475         .remove         = pwm_backlight_remove,
 476         .shutdown       = pwm_backlight_shutdown,
 477 };
 478
 479 module_platform_driver(pwm_backlight_driver);
 480
 481 MODULE_DESCRIPTION("PWM based Backlight Driver");
 482 MODULE_LICENSE("GPL");
 483 MODULE_ALIAS("platform:pwm-backlight");