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