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/gpio/consumer.h>
  14 #include <linux/gpio.h>
  15 #include <linux/module.h>
  16 #include <linux/kernel.h>
  17 #include <linux/init.h>
  18 #include <linux/platform_device.h>
  19 #include <linux/fb.h>
  20 #include <linux/backlight.h>
  21 #include <linux/err.h>
  22 #include <linux/pwm.h>
  23 #include <linux/pwm_backlight.h>
  24 #include <linux/regulator/consumer.h>
  25 #include <linux/slab.h>
  26 #include <linux/delay.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         int                     turn_on_delay_ms;
  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, int brightness)
  49 {
  50         int err;
  51
  52         if (pb->enabled)
  53                 return;
  54
  55         pwm_enable(pb->pwm);
  56
  57         if (pb->turn_on_delay_ms > 0) {
  58                 dev_dbg(pb->dev, "Sleeping %u..%uµs\n",
  59                         pb->turn_on_delay_ms * 1000,
  60                         pb->turn_on_delay_ms * 1100);
  61                 if (pb->turn_on_delay_ms > 20)
  62                         msleep(pb->turn_on_delay_ms);
  63                 else
  64                         usleep_range(pb->turn_on_delay_ms * 1000,
  65                              pb->turn_on_delay_ms * 1100);
  66         }
  67
  68         err = regulator_enable(pb->power_supply);
  69         if (err < 0)
  70                 dev_err(pb->dev, "failed to enable power supply\n");
  71
  72         if (pb->enable_gpio)
  73                 gpiod_set_value_cansleep(pb->enable_gpio, 1);
  74
  75         pb->enabled = true;
  76 }
  77
  78 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
  79 {
  80         if (!pb->enabled)
  81                 return;
  82
  83         pwm_config(pb->pwm, 0, pb->period);
  84         pwm_disable(pb->pwm);
  85
  86         if (pb->enable_gpio)
  87                 gpiod_set_value_cansleep(pb->enable_gpio, 0);
  88
  89         regulator_disable(pb->power_supply);
  90         pb->enabled = false;
  91 }
  92
  93 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
  94 {
  95         unsigned int lth = pb->lth_brightness;
  96         int duty_cycle;
  97
  98         if (pb->levels)
  99                 duty_cycle = pb->levels[brightness];
 100         else
 101                 duty_cycle = brightness;
 102
 103         return (duty_cycle * (pb->period - lth) / pb->scale) + lth;
 104 }
 105
 106 static int pwm_backlight_update_status(struct backlight_device *bl)
 107 {
 108         struct pwm_bl_data *pb = bl_get_data(bl);
 109         int brightness = bl->props.brightness;
 110         int duty_cycle;
 111
 112         if (bl->props.power != FB_BLANK_UNBLANK ||
 113             bl->props.fb_blank != FB_BLANK_UNBLANK ||
 114             bl->props.state & BL_CORE_FBBLANK)
 115                 brightness = 0;
 116
 117         if (pb->notify)
 118                 brightness = pb->notify(pb->dev, brightness);
 119
 120         if (brightness > 0) {
 121                 duty_cycle = compute_duty_cycle(pb, brightness);
 122                 pwm_config(pb->pwm, duty_cycle, pb->period);
 123                 pwm_backlight_power_on(pb, brightness);
 124         } else {
 125                 pwm_backlight_power_off(pb);
 126         }
 127
 128         if (pb->notify_after)
 129                 pb->notify_after(pb->dev, brightness);
 130
 131         return 0;
 132 }
 133
 134 static int pwm_backlight_check_fb(struct backlight_device *bl,
 135                                   struct fb_info *info)
 136 {
 137         struct pwm_bl_data *pb = bl_get_data(bl);
 138
 139         return !pb->check_fb || pb->check_fb(pb->dev, info);
 140 }
 141
 142 static const struct backlight_ops pwm_backlight_ops = {
 143         .update_status  = pwm_backlight_update_status,
 144         .check_fb       = pwm_backlight_check_fb,
 145 };
 146
 147 #ifdef CONFIG_OF
 148 static int pwm_backlight_parse_dt(struct device *dev,
 149                                   struct platform_pwm_backlight_data *data)
 150 {
 151         struct device_node *node = dev->of_node;
 152         struct property *prop;
 153         int length;
 154         u32 value;
 155         int ret;
 156
 157         if (!node)
 158                 return -ENODEV;
 159
 160         memset(data, 0, sizeof(*data));
 161
 162         /* determine the number of brightness levels */
 163         prop = of_find_property(node, "brightness-levels", &length);
 164         if (!prop)
 165                 return -EINVAL;
 166
 167         data->max_brightness = length / sizeof(u32);
 168
 169         /* read brightness levels from DT property */
 170         if (data->max_brightness > 0) {
 171                 size_t size = sizeof(*data->levels) * data->max_brightness;
 172
 173                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 174                 if (!data->levels)
 175                         return -ENOMEM;
 176
 177                 ret = of_property_read_u32_array(node, "brightness-levels",
 178                                                  data->levels,
 179                                                  data->max_brightness);
 180                 if (ret < 0)
 181                         return ret;
 182
 183                 ret = of_property_read_u32(node, "default-brightness-level",
 184                                            &value);
 185                 if (ret < 0)
 186                         return ret;
 187
 188                 data->dft_brightness = value;
 189                 data->max_brightness--;
 190         }
 191
 192         data->enable_gpio = -EINVAL;
 193         return 0;
 194 }
 195
 196 static struct of_device_id pwm_backlight_of_match[] = {
 197         { .compatible = "pwm-backlight" },
 198         { }
 199 };
 200
 201 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 202 #else
 203 static int pwm_backlight_parse_dt(struct device *dev,
 204                                   struct platform_pwm_backlight_data *data)
 205 {
 206         return -ENODEV;
 207 }
 208 #endif
 209
 210 static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
 211 {
 212         struct device_node *node = pb->dev->of_node;
 213
 214         /* Not booted with device tree or no phandle link to the node */
 215         if (!node || !node->phandle)
 216                 return FB_BLANK_UNBLANK;
 217
 218         /*
 219          * If the driver is probed from the device tree and there is a
 220          * phandle link pointing to the backlight node, it is safe to
 221          * assume that another driver will enable the backlight at the
 222          * appropriate time. Therefore, if it is disabled, keep it so.
 223          */
 224
 225         /* if the enable GPIO is disabled, do not enable the backlight */
 226         if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
 227                 return FB_BLANK_POWERDOWN;
 228
 229         /* The regulator is disabled, do not enable the backlight */
 230         if (!regulator_is_enabled(pb->power_supply))
 231                 return FB_BLANK_POWERDOWN;
 232
 233         /* The PWM is disabled, keep it like this */
 234         if (!pwm_is_enabled(pb->pwm))
 235                 return FB_BLANK_POWERDOWN;
 236
 237         return FB_BLANK_UNBLANK;
 238 }
 239
 240 static int pwm_backlight_probe(struct platform_device *pdev)
 241 {
 242         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 243         struct platform_pwm_backlight_data defdata;
 244         struct backlight_properties props;
 245         struct backlight_device *bl;
 246         struct device_node *node = pdev->dev.of_node;
 247         struct pwm_bl_data *pb;
 248         struct pwm_args pargs;
 249         int ret;
 250
 251         if (!data) {
 252                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 253                 if (ret < 0) {
 254                         dev_err(&pdev->dev, "failed to find platform data\n");
 255                         return ret;
 256                 }
 257
 258                 data = &defdata;
 259         }
 260
 261         if (data->init) {
 262                 ret = data->init(&pdev->dev);
 263                 if (ret < 0)
 264                         return ret;
 265         }
 266
 267         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 268         if (!pb) {
 269                 ret = -ENOMEM;
 270                 goto err_alloc;
 271         }
 272
 273         if (data->levels) {
 274                 unsigned int i;
 275
 276                 for (i = 0; i <= data->max_brightness; i++)
 277                         if (data->levels[i] > pb->scale)
 278                                 pb->scale = data->levels[i];
 279
 280                 pb->levels = data->levels;
 281         } else {
 282                 pb->scale = data->max_brightness;
 283         }
 284         pb->notify = data->notify;
 285         pb->notify_after = data->notify_after;
 286         pb->check_fb = data->check_fb;
 287         pb->exit = data->exit;
 288         pb->dev = &pdev->dev;
 289         pb->enabled = false;
 290
 291         pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 292                                                   GPIOD_ASIS);
 293         if (IS_ERR(pb->enable_gpio)) {
 294                 ret = PTR_ERR(pb->enable_gpio);
 295                 goto err_alloc;
 296         }
 297
 298         /*
 299          * Compatibility fallback for drivers still using the integer GPIO
 300          * platform data. Must go away soon.
 301          */
 302         if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
 303                 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 304                                             GPIOF_OUT_INIT_HIGH, "enable");
 305                 if (ret < 0) {
 306                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 307                                 data->enable_gpio, ret);
 308                         goto err_alloc;
 309                 }
 310
 311                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 312         }
 313
 314         /*
 315          * If the GPIO is not known to be already configured as output, that
 316          * is, if gpiod_get_direction returns either GPIOF_DIR_IN or -EINVAL,
 317          * change the direction to output and set the GPIO as active.
 318          * Do not force the GPIO to active when it was already output as it
 319          * could cause backlight flickering or we would enable the backlight too
 320          * early. Leave the decision of the initial backlight state for later.
 321          */
 322         if (pb->enable_gpio &&
 323             gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
 324                 gpiod_direction_output(pb->enable_gpio, 1);
 325
 326         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 327         if (IS_ERR(pb->power_supply)) {
 328                 ret = PTR_ERR(pb->power_supply);
 329                 goto err_alloc;
 330         }
 331
 332         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 333         if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
 334                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 335                 pb->legacy = true;
 336                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 337         }
 338
 339         if (IS_ERR(pb->pwm)) {
 340                 ret = PTR_ERR(pb->pwm);
 341                 if (ret != -EPROBE_DEFER)
 342                         dev_err(&pdev->dev, "unable to request PWM\n");
 343                 goto err_alloc;
 344         }
 345
 346         of_property_read_u32(node, "turn-on-delay-ms", &pb->turn_on_delay_ms);
 347
 348         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 349
 350         /*
 351          * FIXME: pwm_apply_args() should be removed when switching to
 352          * the atomic PWM API.
 353          */
 354         pwm_apply_args(pb->pwm);
 355
 356         /*
 357          * The DT case will set the pwm_period_ns field to 0 and store the
 358          * period, parsed from the DT, in the PWM device. For the non-DT case,
 359          * set the period from platform data if it has not already been set
 360          * via the PWM lookup table.
 361          */
 362         pwm_get_args(pb->pwm, &pargs);
 363         pb->period = pargs.period;
 364         if (!pb->period && (data->pwm_period_ns > 0))
 365                 pb->period = data->pwm_period_ns;
 366
 367         pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
 368
 369         memset(&props, 0, sizeof(struct backlight_properties));
 370         props.type = BACKLIGHT_RAW;
 371         props.max_brightness = data->max_brightness;
 372         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 373                                        &pwm_backlight_ops, &props);
 374         if (IS_ERR(bl)) {
 375                 dev_err(&pdev->dev, "failed to register backlight\n");
 376                 ret = PTR_ERR(bl);
 377                 if (pb->legacy)
 378                         pwm_free(pb->pwm);
 379                 goto err_alloc;
 380         }
 381
 382         if (data->dft_brightness > data->max_brightness) {
 383                 dev_warn(&pdev->dev,
 384                          "invalid default brightness level: %u, using %u\n",
 385                          data->dft_brightness, data->max_brightness);
 386                 data->dft_brightness = data->max_brightness;
 387         }
 388
 389         bl->props.brightness = data->dft_brightness;
 390         bl->props.power = pwm_backlight_initial_power_state(pb);
 391         backlight_update_status(bl);
 392
 393         platform_set_drvdata(pdev, bl);
 394         return 0;
 395
 396 err_alloc:
 397         if (data->exit)
 398                 data->exit(&pdev->dev);
 399         return ret;
 400 }
 401
 402 static int pwm_backlight_remove(struct platform_device *pdev)
 403 {
 404         struct backlight_device *bl = platform_get_drvdata(pdev);
 405         struct pwm_bl_data *pb = bl_get_data(bl);
 406
 407         backlight_device_unregister(bl);
 408         pwm_backlight_power_off(pb);
 409
 410         if (pb->exit)
 411                 pb->exit(&pdev->dev);
 412         if (pb->legacy)
 413                 pwm_free(pb->pwm);
 414
 415         return 0;
 416 }
 417
 418 static void pwm_backlight_shutdown(struct platform_device *pdev)
 419 {
 420         struct backlight_device *bl = platform_get_drvdata(pdev);
 421         struct pwm_bl_data *pb = bl_get_data(bl);
 422
 423         pwm_backlight_power_off(pb);
 424 }
 425
 426 #ifdef CONFIG_PM_SLEEP
 427 static int pwm_backlight_suspend(struct device *dev)
 428 {
 429         struct backlight_device *bl = dev_get_drvdata(dev);
 430         struct pwm_bl_data *pb = bl_get_data(bl);
 431
 432         if (pb->notify)
 433                 pb->notify(pb->dev, 0);
 434
 435         pwm_backlight_power_off(pb);
 436
 437         if (pb->notify_after)
 438                 pb->notify_after(pb->dev, 0);
 439
 440         return 0;
 441 }
 442
 443 static int pwm_backlight_resume(struct device *dev)
 444 {
 445         struct backlight_device *bl = dev_get_drvdata(dev);
 446
 447         backlight_update_status(bl);
 448
 449         return 0;
 450 }
 451 #endif
 452
 453 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 454 #ifdef CONFIG_PM_SLEEP
 455         .suspend = pwm_backlight_suspend,
 456         .resume = pwm_backlight_resume,
 457         .poweroff = pwm_backlight_suspend,
 458         .restore = pwm_backlight_resume,
 459 #endif
 460 };
 461
 462 static struct platform_driver pwm_backlight_driver = {
 463         .driver         = {
 464                 .name           = "pwm-backlight",
 465                 .pm             = &pwm_backlight_pm_ops,
 466                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 467         },
 468         .probe          = pwm_backlight_probe,
 469         .remove         = pwm_backlight_remove,
 470         .shutdown       = pwm_backlight_shutdown,
 471 };
 472
 473 module_platform_driver(pwm_backlight_driver);
 474
 475 MODULE_DESCRIPTION("PWM based Backlight Driver");
 476 MODULE_LICENSE("GPL");
 477 MODULE_ALIAS("platform:pwm-backlight");