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