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
  27 struct pwm_bl_data {
  28         struct pwm_device       *pwm;
  29         struct device           *dev;
  30         unsigned int            period;
  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         int                     (*notify)(struct device *,
  39                                           int brightness);
  40         void                    (*notify_after)(struct device *,
  41                                         int brightness);
  42         int                     (*check_fb)(struct device *, struct fb_info *);
  43         void                    (*exit)(struct device *);
  44 };
  45
  46 static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
  47 {
  48         int err;
  49
  50         if (pb->enabled)
  51                 return;
  52
  53         err = regulator_enable(pb->power_supply);
  54         if (err < 0)
  55                 dev_err(pb->dev, "failed to enable power supply\n");
  56
  57         if (pb->enable_gpio)
  58                 gpiod_set_value_cansleep(pb->enable_gpio, 1);
  59
  60         pwm_enable(pb->pwm);
  61         pb->enabled = true;
  62 }
  63
  64 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
  65 {
  66         if (!pb->enabled)
  67                 return;
  68
  69         pwm_config(pb->pwm, 0, pb->period);
  70         pwm_disable(pb->pwm);
  71
  72         if (pb->enable_gpio)
  73                 gpiod_set_value_cansleep(pb->enable_gpio, 0);
  74
  75         regulator_disable(pb->power_supply);
  76         pb->enabled = false;
  77 }
  78
  79 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
  80 {
  81         unsigned int lth = pb->lth_brightness;
  82         u64 duty_cycle;
  83
  84         if (pb->levels)
  85                 duty_cycle = pb->levels[brightness];
  86         else
  87                 duty_cycle = brightness;
  88
  89         duty_cycle *= pb->period - lth;
  90         do_div(duty_cycle, pb->scale);
  91
  92         return duty_cycle + lth;
  93 }
  94
  95 static int pwm_backlight_update_status(struct backlight_device *bl)
  96 {
  97         struct pwm_bl_data *pb = bl_get_data(bl);
  98         int brightness = bl->props.brightness;
  99         int duty_cycle;
 100
 101         if (bl->props.power != FB_BLANK_UNBLANK ||
 102             bl->props.fb_blank != FB_BLANK_UNBLANK ||
 103             bl->props.state & BL_CORE_FBBLANK)
 104                 brightness = 0;
 105
 106         if (pb->notify)
 107                 brightness = pb->notify(pb->dev, brightness);
 108
 109         if (brightness > 0) {
 110                 duty_cycle = compute_duty_cycle(pb, brightness);
 111                 pwm_config(pb->pwm, duty_cycle, pb->period);
 112                 pwm_backlight_power_on(pb, brightness);
 113         } else
 114                 pwm_backlight_power_off(pb);
 115
 116         if (pb->notify_after)
 117                 pb->notify_after(pb->dev, brightness);
 118
 119         return 0;
 120 }
 121
 122 static int pwm_backlight_check_fb(struct backlight_device *bl,
 123                                   struct fb_info *info)
 124 {
 125         struct pwm_bl_data *pb = bl_get_data(bl);
 126
 127         return !pb->check_fb || pb->check_fb(pb->dev, info);
 128 }
 129
 130 static const struct backlight_ops pwm_backlight_ops = {
 131         .update_status  = pwm_backlight_update_status,
 132         .check_fb       = pwm_backlight_check_fb,
 133 };
 134
 135 #ifdef CONFIG_OF
 136 static int pwm_backlight_parse_dt(struct device *dev,
 137                                   struct platform_pwm_backlight_data *data)
 138 {
 139         struct device_node *node = dev->of_node;
 140         struct property *prop;
 141         int length;
 142         u32 value;
 143         int ret;
 144
 145         if (!node)
 146                 return -ENODEV;
 147
 148         memset(data, 0, sizeof(*data));
 149
 150         /* determine the number of brightness levels */
 151         prop = of_find_property(node, "brightness-levels", &length);
 152         if (!prop)
 153                 return -EINVAL;
 154
 155         data->max_brightness = length / sizeof(u32);
 156
 157         /* read brightness levels from DT property */
 158         if (data->max_brightness > 0) {
 159                 size_t size = sizeof(*data->levels) * data->max_brightness;
 160
 161                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 162                 if (!data->levels)
 163                         return -ENOMEM;
 164
 165                 ret = of_property_read_u32_array(node, "brightness-levels",
 166                                                  data->levels,
 167                                                  data->max_brightness);
 168                 if (ret < 0)
 169                         return ret;
 170
 171                 ret = of_property_read_u32(node, "default-brightness-level",
 172                                            &value);
 173                 if (ret < 0)
 174                         return ret;
 175
 176                 data->dft_brightness = value;
 177                 data->max_brightness--;
 178         }
 179
 180         data->enable_gpio = -EINVAL;
 181         return 0;
 182 }
 183
 184 static const struct of_device_id pwm_backlight_of_match[] = {
 185         { .compatible = "pwm-backlight" },
 186         { }
 187 };
 188
 189 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 190 #else
 191 static int pwm_backlight_parse_dt(struct device *dev,
 192                                   struct platform_pwm_backlight_data *data)
 193 {
 194         return -ENODEV;
 195 }
 196 #endif
 197
 198 static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
 199 {
 200         struct device_node *node = pb->dev->of_node;
 201
 202         /* Not booted with device tree or no phandle link to the node */
 203         if (!node || !node->phandle)
 204                 return FB_BLANK_UNBLANK;
 205
 206         /*
 207          * If the driver is probed from the device tree and there is a
 208          * phandle link pointing to the backlight node, it is safe to
 209          * assume that another driver will enable the backlight at the
 210          * appropriate time. Therefore, if it is disabled, keep it so.
 211          */
 212
 213         /* if the enable GPIO is disabled, do not enable the backlight */
 214         if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
 215                 return FB_BLANK_POWERDOWN;
 216
 217         /* The regulator is disabled, do not enable the backlight */
 218         if (!regulator_is_enabled(pb->power_supply))
 219                 return FB_BLANK_POWERDOWN;
 220
 221         /* The PWM is disabled, keep it like this */
 222         if (!pwm_is_enabled(pb->pwm))
 223                 return FB_BLANK_POWERDOWN;
 224
 225         return FB_BLANK_UNBLANK;
 226 }
 227
 228 static int pwm_backlight_probe(struct platform_device *pdev)
 229 {
 230         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 231         struct platform_pwm_backlight_data defdata;
 232         struct backlight_properties props;
 233         struct backlight_device *bl;
 234         struct device_node *node = pdev->dev.of_node;
 235         struct pwm_bl_data *pb;
 236         struct pwm_args pargs;
 237         int ret;
 238
 239         if (!data) {
 240                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 241                 if (ret < 0) {
 242                         dev_err(&pdev->dev, "failed to find platform data\n");
 243                         return ret;
 244                 }
 245
 246                 data = &defdata;
 247         }
 248
 249         if (data->init) {
 250                 ret = data->init(&pdev->dev);
 251                 if (ret < 0)
 252                         return ret;
 253         }
 254
 255         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 256         if (!pb) {
 257                 ret = -ENOMEM;
 258                 goto err_alloc;
 259         }
 260
 261         if (data->levels) {
 262                 unsigned int i;
 263
 264                 for (i = 0; i <= data->max_brightness; i++)
 265                         if (data->levels[i] > pb->scale)
 266                                 pb->scale = data->levels[i];
 267
 268                 pb->levels = data->levels;
 269         } else
 270                 pb->scale = data->max_brightness;
 271
 272         pb->notify = data->notify;
 273         pb->notify_after = data->notify_after;
 274         pb->check_fb = data->check_fb;
 275         pb->exit = data->exit;
 276         pb->dev = &pdev->dev;
 277         pb->enabled = false;
 278
 279         pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 280                                                   GPIOD_ASIS);
 281         if (IS_ERR(pb->enable_gpio)) {
 282                 ret = PTR_ERR(pb->enable_gpio);
 283                 goto err_alloc;
 284         }
 285
 286         /*
 287          * Compatibility fallback for drivers still using the integer GPIO
 288          * platform data. Must go away soon.
 289          */
 290         if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
 291                 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 292                                             GPIOF_OUT_INIT_HIGH, "enable");
 293                 if (ret < 0) {
 294                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 295                                 data->enable_gpio, ret);
 296                         goto err_alloc;
 297                 }
 298
 299                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 300         }
 301
 302         /*
 303          * If the GPIO is not known to be already configured as output, that
 304          * is, if gpiod_get_direction returns either GPIOF_DIR_IN or -EINVAL,
 305          * change the direction to output and set the GPIO as active.
 306          * Do not force the GPIO to active when it was already output as it
 307          * could cause backlight flickering or we would enable the backlight too
 308          * early. Leave the decision of the initial backlight state for later.
 309          */
 310         if (pb->enable_gpio &&
 311             gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
 312                 gpiod_direction_output(pb->enable_gpio, 1);
 313
 314         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 315         if (IS_ERR(pb->power_supply)) {
 316                 ret = PTR_ERR(pb->power_supply);
 317                 goto err_alloc;
 318         }
 319
 320         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 321         if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
 322                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 323                 pb->legacy = true;
 324                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 325         }
 326
 327         if (IS_ERR(pb->pwm)) {
 328                 ret = PTR_ERR(pb->pwm);
 329                 if (ret != -EPROBE_DEFER)
 330                         dev_err(&pdev->dev, "unable to request PWM\n");
 331                 goto err_alloc;
 332         }
 333
 334         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 335
 336         /*
 337          * FIXME: pwm_apply_args() should be removed when switching to
 338          * the atomic PWM API.
 339          */
 340         pwm_apply_args(pb->pwm);
 341
 342         /*
 343          * The DT case will set the pwm_period_ns field to 0 and store the
 344          * period, parsed from the DT, in the PWM device. For the non-DT case,
 345          * set the period from platform data if it has not already been set
 346          * via the PWM lookup table.
 347          */
 348         pwm_get_args(pb->pwm, &pargs);
 349         pb->period = pargs.period;
 350         if (!pb->period && (data->pwm_period_ns > 0))
 351                 pb->period = data->pwm_period_ns;
 352
 353         pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
 354
 355         memset(&props, 0, sizeof(struct backlight_properties));
 356         props.type = BACKLIGHT_RAW;
 357         props.max_brightness = data->max_brightness;
 358         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 359                                        &pwm_backlight_ops, &props);
 360         if (IS_ERR(bl)) {
 361                 dev_err(&pdev->dev, "failed to register backlight\n");
 362                 ret = PTR_ERR(bl);
 363                 if (pb->legacy)
 364                         pwm_free(pb->pwm);
 365                 goto err_alloc;
 366         }
 367
 368         if (data->dft_brightness > data->max_brightness) {
 369                 dev_warn(&pdev->dev,
 370                          "invalid default brightness level: %u, using %u\n",
 371                          data->dft_brightness, data->max_brightness);
 372                 data->dft_brightness = data->max_brightness;
 373         }
 374
 375         bl->props.brightness = data->dft_brightness;
 376         bl->props.power = pwm_backlight_initial_power_state(pb);
 377         backlight_update_status(bl);
 378
 379         platform_set_drvdata(pdev, bl);
 380         return 0;
 381
 382 err_alloc:
 383         if (data->exit)
 384                 data->exit(&pdev->dev);
 385         return ret;
 386 }
 387
 388 static int pwm_backlight_remove(struct platform_device *pdev)
 389 {
 390         struct backlight_device *bl = platform_get_drvdata(pdev);
 391         struct pwm_bl_data *pb = bl_get_data(bl);
 392
 393         backlight_device_unregister(bl);
 394         pwm_backlight_power_off(pb);
 395
 396         if (pb->exit)
 397                 pb->exit(&pdev->dev);
 398         if (pb->legacy)
 399                 pwm_free(pb->pwm);
 400
 401         return 0;
 402 }
 403
 404 static void pwm_backlight_shutdown(struct platform_device *pdev)
 405 {
 406         struct backlight_device *bl = platform_get_drvdata(pdev);
 407         struct pwm_bl_data *pb = bl_get_data(bl);
 408
 409         pwm_backlight_power_off(pb);
 410 }
 411
 412 #ifdef CONFIG_PM_SLEEP
 413 static int pwm_backlight_suspend(struct device *dev)
 414 {
 415         struct backlight_device *bl = dev_get_drvdata(dev);
 416         struct pwm_bl_data *pb = bl_get_data(bl);
 417
 418         if (pb->notify)
 419                 pb->notify(pb->dev, 0);
 420
 421         pwm_backlight_power_off(pb);
 422
 423         if (pb->notify_after)
 424                 pb->notify_after(pb->dev, 0);
 425
 426         return 0;
 427 }
 428
 429 static int pwm_backlight_resume(struct device *dev)
 430 {
 431         struct backlight_device *bl = dev_get_drvdata(dev);
 432
 433         backlight_update_status(bl);
 434
 435         return 0;
 436 }
 437 #endif
 438
 439 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 440 #ifdef CONFIG_PM_SLEEP
 441         .suspend = pwm_backlight_suspend,
 442         .resume = pwm_backlight_resume,
 443         .poweroff = pwm_backlight_suspend,
 444         .restore = pwm_backlight_resume,
 445 #endif
 446 };
 447
 448 static struct platform_driver pwm_backlight_driver = {
 449         .driver         = {
 450                 .name           = "pwm-backlight",
 451                 .pm             = &pwm_backlight_pm_ops,
 452                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 453         },
 454         .probe          = pwm_backlight_probe,
 455         .remove         = pwm_backlight_remove,
 456         .shutdown       = pwm_backlight_shutdown,
 457 };
 458
 459 module_platform_driver(pwm_backlight_driver);
 460
 461 MODULE_DESCRIPTION("PWM based Backlight Driver");
 462 MODULE_LICENSE("GPL");
 463 MODULE_ALIAS("platform:pwm-backlight");