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