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 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_probe(struct platform_device *pdev)
 200 {
 201         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 202         struct platform_pwm_backlight_data defdata;
 203         struct backlight_properties props;
 204         struct backlight_device *bl;
 205         struct device_node *node = pdev->dev.of_node;
 206         struct pwm_bl_data *pb;
 207         int initial_blank = FB_BLANK_UNBLANK;
 208         struct pwm_args pargs;
 209         int ret;
 210
 211         if (!data) {
 212                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 213                 if (ret < 0) {
 214                         dev_err(&pdev->dev, "failed to find platform data\n");
 215                         return ret;
 216                 }
 217
 218                 data = &defdata;
 219         }
 220
 221         if (data->init) {
 222                 ret = data->init(&pdev->dev);
 223                 if (ret < 0)
 224                         return ret;
 225         }
 226
 227         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 228         if (!pb) {
 229                 ret = -ENOMEM;
 230                 goto err_alloc;
 231         }
 232
 233         if (data->levels) {
 234                 unsigned int i;
 235
 236                 for (i = 0; i <= data->max_brightness; i++)
 237                         if (data->levels[i] > pb->scale)
 238                                 pb->scale = data->levels[i];
 239
 240                 pb->levels = data->levels;
 241         } else
 242                 pb->scale = data->max_brightness;
 243
 244         pb->notify = data->notify;
 245         pb->notify_after = data->notify_after;
 246         pb->check_fb = data->check_fb;
 247         pb->exit = data->exit;
 248         pb->dev = &pdev->dev;
 249         pb->enabled = false;
 250
 251         pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 252                                                   GPIOD_ASIS);
 253         if (IS_ERR(pb->enable_gpio)) {
 254                 ret = PTR_ERR(pb->enable_gpio);
 255                 goto err_alloc;
 256         }
 257
 258         /*
 259          * Compatibility fallback for drivers still using the integer GPIO
 260          * platform data. Must go away soon.
 261          */
 262         if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
 263                 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 264                                             GPIOF_OUT_INIT_HIGH, "enable");
 265                 if (ret < 0) {
 266                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 267                                 data->enable_gpio, ret);
 268                         goto err_alloc;
 269                 }
 270
 271                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 272         }
 273
 274         if (pb->enable_gpio) {
 275                 /*
 276                  * If the driver is probed from the device tree and there is a
 277                  * phandle link pointing to the backlight node, it is safe to
 278                  * assume that another driver will enable the backlight at the
 279                  * appropriate time. Therefore, if it is disabled, keep it so.
 280                  */
 281                 if (node && node->phandle &&
 282                     gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT &&
 283                     gpiod_get_value(pb->enable_gpio) == 0)
 284                         initial_blank = FB_BLANK_POWERDOWN;
 285                 else
 286                         gpiod_direction_output(pb->enable_gpio, 1);
 287         }
 288
 289         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 290         if (IS_ERR(pb->power_supply)) {
 291                 ret = PTR_ERR(pb->power_supply);
 292                 goto err_alloc;
 293         }
 294
 295         if (node && node->phandle && !regulator_is_enabled(pb->power_supply))
 296                 initial_blank = FB_BLANK_POWERDOWN;
 297
 298         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 299         if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
 300                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 301                 pb->legacy = true;
 302                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 303         }
 304
 305         if (IS_ERR(pb->pwm)) {
 306                 ret = PTR_ERR(pb->pwm);
 307                 if (ret != -EPROBE_DEFER)
 308                         dev_err(&pdev->dev, "unable to request PWM\n");
 309                 goto err_alloc;
 310         }
 311
 312         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 313
 314         /*
 315          * FIXME: pwm_apply_args() should be removed when switching to
 316          * the atomic PWM API.
 317          */
 318         pwm_apply_args(pb->pwm);
 319
 320         /*
 321          * The DT case will set the pwm_period_ns field to 0 and store the
 322          * period, parsed from the DT, in the PWM device. For the non-DT case,
 323          * set the period from platform data if it has not already been set
 324          * via the PWM lookup table.
 325          */
 326         pwm_get_args(pb->pwm, &pargs);
 327         pb->period = pargs.period;
 328         if (!pb->period && (data->pwm_period_ns > 0))
 329                 pb->period = data->pwm_period_ns;
 330
 331         pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
 332
 333         memset(&props, 0, sizeof(struct backlight_properties));
 334         props.type = BACKLIGHT_RAW;
 335         props.max_brightness = data->max_brightness;
 336         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 337                                        &pwm_backlight_ops, &props);
 338         if (IS_ERR(bl)) {
 339                 dev_err(&pdev->dev, "failed to register backlight\n");
 340                 ret = PTR_ERR(bl);
 341                 if (pb->legacy)
 342                         pwm_free(pb->pwm);
 343                 goto err_alloc;
 344         }
 345
 346         if (data->dft_brightness > data->max_brightness) {
 347                 dev_warn(&pdev->dev,
 348                          "invalid default brightness level: %u, using %u\n",
 349                          data->dft_brightness, data->max_brightness);
 350                 data->dft_brightness = data->max_brightness;
 351         }
 352
 353         bl->props.brightness = data->dft_brightness;
 354         bl->props.power = initial_blank;
 355         backlight_update_status(bl);
 356
 357         platform_set_drvdata(pdev, bl);
 358         return 0;
 359
 360 err_alloc:
 361         if (data->exit)
 362                 data->exit(&pdev->dev);
 363         return ret;
 364 }
 365
 366 static int pwm_backlight_remove(struct platform_device *pdev)
 367 {
 368         struct backlight_device *bl = platform_get_drvdata(pdev);
 369         struct pwm_bl_data *pb = bl_get_data(bl);
 370
 371         backlight_device_unregister(bl);
 372         pwm_backlight_power_off(pb);
 373
 374         if (pb->exit)
 375                 pb->exit(&pdev->dev);
 376         if (pb->legacy)
 377                 pwm_free(pb->pwm);
 378
 379         return 0;
 380 }
 381
 382 static void pwm_backlight_shutdown(struct platform_device *pdev)
 383 {
 384         struct backlight_device *bl = platform_get_drvdata(pdev);
 385         struct pwm_bl_data *pb = bl_get_data(bl);
 386
 387         pwm_backlight_power_off(pb);
 388 }
 389
 390 #ifdef CONFIG_PM_SLEEP
 391 static int pwm_backlight_suspend(struct device *dev)
 392 {
 393         struct backlight_device *bl = dev_get_drvdata(dev);
 394         struct pwm_bl_data *pb = bl_get_data(bl);
 395
 396         if (pb->notify)
 397                 pb->notify(pb->dev, 0);
 398
 399         pwm_backlight_power_off(pb);
 400
 401         if (pb->notify_after)
 402                 pb->notify_after(pb->dev, 0);
 403
 404         return 0;
 405 }
 406
 407 static int pwm_backlight_resume(struct device *dev)
 408 {
 409         struct backlight_device *bl = dev_get_drvdata(dev);
 410
 411         backlight_update_status(bl);
 412
 413         return 0;
 414 }
 415 #endif
 416
 417 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 418 #ifdef CONFIG_PM_SLEEP
 419         .suspend = pwm_backlight_suspend,
 420         .resume = pwm_backlight_resume,
 421         .poweroff = pwm_backlight_suspend,
 422         .restore = pwm_backlight_resume,
 423 #endif
 424 };
 425
 426 static struct platform_driver pwm_backlight_driver = {
 427         .driver         = {
 428                 .name           = "pwm-backlight",
 429                 .pm             = &pwm_backlight_pm_ops,
 430                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 431         },
 432         .probe          = pwm_backlight_probe,
 433         .remove         = pwm_backlight_remove,
 434         .shutdown       = pwm_backlight_shutdown,
 435 };
 436
 437 module_platform_driver(pwm_backlight_driver);
 438
 439 MODULE_DESCRIPTION("PWM based Backlight Driver");
 440 MODULE_LICENSE("GPL");
 441 MODULE_ALIAS("platform:pwm-backlight");