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         data->enable_gpio = -EINVAL;
 177         return 0;
 178 }
 179
 180 static struct of_device_id pwm_backlight_of_match[] = {
 181         { .compatible = "pwm-backlight" },
 182         { }
 183 };
 184
 185 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 186 #else
 187 static int pwm_backlight_parse_dt(struct device *dev,
 188                                   struct platform_pwm_backlight_data *data)
 189 {
 190         return -ENODEV;
 191 }
 192 #endif
 193
 194 static int pwm_backlight_probe(struct platform_device *pdev)
 195 {
 196         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 197         struct platform_pwm_backlight_data defdata;
 198         struct backlight_properties props;
 199         struct backlight_device *bl;
 200         struct pwm_bl_data *pb;
 201         int ret;
 202
 203         if (!data) {
 204                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 205                 if (ret < 0) {
 206                         dev_err(&pdev->dev, "failed to find platform data\n");
 207                         return ret;
 208                 }
 209
 210                 data = &defdata;
 211         }
 212
 213         if (data->init) {
 214                 ret = data->init(&pdev->dev);
 215                 if (ret < 0)
 216                         return ret;
 217         }
 218
 219         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 220         if (!pb) {
 221                 ret = -ENOMEM;
 222                 goto err_alloc;
 223         }
 224
 225         if (data->levels) {
 226                 unsigned int i;
 227
 228                 for (i = 0; i <= data->max_brightness; i++)
 229                         if (data->levels[i] > pb->scale)
 230                                 pb->scale = data->levels[i];
 231
 232                 pb->levels = data->levels;
 233         } else
 234                 pb->scale = data->max_brightness;
 235
 236         pb->notify = data->notify;
 237         pb->notify_after = data->notify_after;
 238         pb->check_fb = data->check_fb;
 239         pb->exit = data->exit;
 240         pb->dev = &pdev->dev;
 241         pb->enabled = false;
 242
 243         pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable");
 244         if (IS_ERR(pb->enable_gpio)) {
 245                 ret = PTR_ERR(pb->enable_gpio);
 246                 goto err_alloc;
 247         }
 248
 249         /*
 250          * Compatibility fallback for drivers still using the integer GPIO
 251          * platform data. Must go away soon.
 252          */
 253         if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
 254                 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 255                                             GPIOF_OUT_INIT_HIGH, "enable");
 256                 if (ret < 0) {
 257                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 258                                 data->enable_gpio, ret);
 259                         goto err_alloc;
 260                 }
 261
 262                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 263         }
 264
 265         if (pb->enable_gpio)
 266                 gpiod_direction_output(pb->enable_gpio, 1);
 267
 268         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 269         if (IS_ERR(pb->power_supply)) {
 270                 ret = PTR_ERR(pb->power_supply);
 271                 goto err_alloc;
 272         }
 273
 274         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 275         if (IS_ERR(pb->pwm)) {
 276                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 277
 278                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 279                 if (IS_ERR(pb->pwm)) {
 280                         dev_err(&pdev->dev, "unable to request legacy PWM\n");
 281                         ret = PTR_ERR(pb->pwm);
 282                         goto err_alloc;
 283                 }
 284         }
 285
 286         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 287
 288         /*
 289          * The DT case will set the pwm_period_ns field to 0 and store the
 290          * period, parsed from the DT, in the PWM device. For the non-DT case,
 291          * set the period from platform data if it has not already been set
 292          * via the PWM lookup table.
 293          */
 294         pb->period = pwm_get_period(pb->pwm);
 295         if (!pb->period && (data->pwm_period_ns > 0)) {
 296                 pb->period = data->pwm_period_ns;
 297                 pwm_set_period(pb->pwm, data->pwm_period_ns);
 298         }
 299
 300         pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
 301
 302         memset(&props, 0, sizeof(struct backlight_properties));
 303         props.type = BACKLIGHT_RAW;
 304         props.max_brightness = data->max_brightness;
 305         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 306                                        &pwm_backlight_ops, &props);
 307         if (IS_ERR(bl)) {
 308                 dev_err(&pdev->dev, "failed to register backlight\n");
 309                 ret = PTR_ERR(bl);
 310                 goto err_alloc;
 311         }
 312
 313         if (data->dft_brightness > data->max_brightness) {
 314                 dev_warn(&pdev->dev,
 315                          "invalid default brightness level: %u, using %u\n",
 316                          data->dft_brightness, data->max_brightness);
 317                 data->dft_brightness = data->max_brightness;
 318         }
 319
 320         bl->props.brightness = data->dft_brightness;
 321         backlight_update_status(bl);
 322
 323         platform_set_drvdata(pdev, bl);
 324         return 0;
 325
 326 err_alloc:
 327         if (data->exit)
 328                 data->exit(&pdev->dev);
 329         return ret;
 330 }
 331
 332 static int pwm_backlight_remove(struct platform_device *pdev)
 333 {
 334         struct backlight_device *bl = platform_get_drvdata(pdev);
 335         struct pwm_bl_data *pb = bl_get_data(bl);
 336
 337         backlight_device_unregister(bl);
 338         pwm_backlight_power_off(pb);
 339
 340         if (pb->exit)
 341                 pb->exit(&pdev->dev);
 342
 343         return 0;
 344 }
 345
 346 static void pwm_backlight_shutdown(struct platform_device *pdev)
 347 {
 348         struct backlight_device *bl = platform_get_drvdata(pdev);
 349         struct pwm_bl_data *pb = bl_get_data(bl);
 350
 351         pwm_backlight_power_off(pb);
 352 }
 353
 354 #ifdef CONFIG_PM_SLEEP
 355 static int pwm_backlight_suspend(struct device *dev)
 356 {
 357         struct backlight_device *bl = dev_get_drvdata(dev);
 358         struct pwm_bl_data *pb = bl_get_data(bl);
 359
 360         if (pb->notify)
 361                 pb->notify(pb->dev, 0);
 362
 363         pwm_backlight_power_off(pb);
 364
 365         if (pb->notify_after)
 366                 pb->notify_after(pb->dev, 0);
 367
 368         return 0;
 369 }
 370
 371 static int pwm_backlight_resume(struct device *dev)
 372 {
 373         struct backlight_device *bl = dev_get_drvdata(dev);
 374
 375         backlight_update_status(bl);
 376
 377         return 0;
 378 }
 379 #endif
 380
 381 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 382 #ifdef CONFIG_PM_SLEEP
 383         .suspend = pwm_backlight_suspend,
 384         .resume = pwm_backlight_resume,
 385         .poweroff = pwm_backlight_suspend,
 386         .restore = pwm_backlight_resume,
 387 #endif
 388 };
 389
 390 static struct platform_driver pwm_backlight_driver = {
 391         .driver         = {
 392                 .name           = "pwm-backlight",
 393                 .owner          = THIS_MODULE,
 394                 .pm             = &pwm_backlight_pm_ops,
 395                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 396         },
 397         .probe          = pwm_backlight_probe,
 398         .remove         = pwm_backlight_remove,
 399         .shutdown       = pwm_backlight_shutdown,
 400 };
 401
 402 module_platform_driver(pwm_backlight_driver);
 403
 404 MODULE_DESCRIPTION("PWM based Backlight Driver");
 405 MODULE_LICENSE("GPL");
 406 MODULE_ALIAS("platform:pwm-backlight");