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.h>
  14 #include <linux/of_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         int                     enable_gpio;
  36         unsigned long           enable_gpio_flags;
  37         unsigned int            scale;
  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 (gpio_is_valid(pb->enable_gpio)) {
  58                 if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
  59                         gpio_set_value(pb->enable_gpio, 0);
  60                 else
  61                         gpio_set_value(pb->enable_gpio, 1);
  62         }
  63
  64         pwm_enable(pb->pwm);
  65         pb->enabled = true;
  66 }
  67
  68 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
  69 {
  70         if (!pb->enabled)
  71                 return;
  72
  73         pwm_config(pb->pwm, 0, pb->period);
  74         pwm_disable(pb->pwm);
  75
  76         if (gpio_is_valid(pb->enable_gpio)) {
  77                 if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
  78                         gpio_set_value(pb->enable_gpio, 1);
  79                 else
  80                         gpio_set_value(pb->enable_gpio, 0);
  81         }
  82
  83         regulator_disable(pb->power_supply);
  84         pb->enabled = false;
  85 }
  86
  87 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
  88 {
  89         unsigned int lth = pb->lth_brightness;
  90         int duty_cycle;
  91
  92         if (pb->levels)
  93                 duty_cycle = pb->levels[brightness];
  94         else
  95                 duty_cycle = brightness;
  96
  97         return (duty_cycle * (pb->period - lth) / pb->scale) + lth;
  98 }
  99
 100 static int pwm_backlight_update_status(struct backlight_device *bl)
 101 {
 102         struct pwm_bl_data *pb = bl_get_data(bl);
 103         int brightness = bl->props.brightness;
 104         int duty_cycle;
 105
 106         if (bl->props.power != FB_BLANK_UNBLANK ||
 107             bl->props.fb_blank != FB_BLANK_UNBLANK ||
 108             bl->props.state & BL_CORE_FBBLANK)
 109                 brightness = 0;
 110
 111         if (pb->notify)
 112                 brightness = pb->notify(pb->dev, brightness);
 113
 114         if (brightness > 0) {
 115                 duty_cycle = compute_duty_cycle(pb, brightness);
 116                 pwm_config(pb->pwm, duty_cycle, pb->period);
 117                 pwm_backlight_power_on(pb, brightness);
 118         } else
 119                 pwm_backlight_power_off(pb);
 120
 121         if (pb->notify_after)
 122                 pb->notify_after(pb->dev, brightness);
 123
 124         return 0;
 125 }
 126
 127 static int pwm_backlight_get_brightness(struct backlight_device *bl)
 128 {
 129         return bl->props.brightness;
 130 }
 131
 132 static int pwm_backlight_check_fb(struct backlight_device *bl,
 133                                   struct fb_info *info)
 134 {
 135         struct pwm_bl_data *pb = bl_get_data(bl);
 136
 137         return !pb->check_fb || pb->check_fb(pb->dev, info);
 138 }
 139
 140 static const struct backlight_ops pwm_backlight_ops = {
 141         .update_status  = pwm_backlight_update_status,
 142         .get_brightness = pwm_backlight_get_brightness,
 143         .check_fb       = pwm_backlight_check_fb,
 144 };
 145
 146 #ifdef CONFIG_OF
 147 static int pwm_backlight_parse_dt(struct device *dev,
 148                                   struct platform_pwm_backlight_data *data)
 149 {
 150         struct device_node *node = dev->of_node;
 151         enum of_gpio_flags flags;
 152         struct property *prop;
 153         int length;
 154         u32 value;
 155         int ret;
 156
 157         if (!node)
 158                 return -ENODEV;
 159
 160         memset(data, 0, sizeof(*data));
 161
 162         /* determine the number of brightness levels */
 163         prop = of_find_property(node, "brightness-levels", &length);
 164         if (!prop)
 165                 return -EINVAL;
 166
 167         data->max_brightness = length / sizeof(u32);
 168
 169         /* read brightness levels from DT property */
 170         if (data->max_brightness > 0) {
 171                 size_t size = sizeof(*data->levels) * data->max_brightness;
 172
 173                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 174                 if (!data->levels)
 175                         return -ENOMEM;
 176
 177                 ret = of_property_read_u32_array(node, "brightness-levels",
 178                                                  data->levels,
 179                                                  data->max_brightness);
 180                 if (ret < 0)
 181                         return ret;
 182
 183                 ret = of_property_read_u32(node, "default-brightness-level",
 184                                            &value);
 185                 if (ret < 0)
 186                         return ret;
 187
 188                 data->dft_brightness = value;
 189                 data->max_brightness--;
 190         }
 191
 192         data->enable_gpio = of_get_named_gpio_flags(node, "enable-gpios", 0,
 193                                                     &flags);
 194         if (data->enable_gpio == -EPROBE_DEFER)
 195                 return -EPROBE_DEFER;
 196
 197         if (gpio_is_valid(data->enable_gpio) && (flags & OF_GPIO_ACTIVE_LOW))
 198                 data->enable_gpio_flags |= PWM_BACKLIGHT_GPIO_ACTIVE_LOW;
 199
 200         return 0;
 201 }
 202
 203 static struct of_device_id pwm_backlight_of_match[] = {
 204         { .compatible = "pwm-backlight" },
 205         { }
 206 };
 207
 208 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 209 #else
 210 static int pwm_backlight_parse_dt(struct device *dev,
 211                                   struct platform_pwm_backlight_data *data)
 212 {
 213         return -ENODEV;
 214 }
 215 #endif
 216
 217 static int pwm_backlight_probe(struct platform_device *pdev)
 218 {
 219         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 220         struct platform_pwm_backlight_data defdata;
 221         struct backlight_properties props;
 222         struct backlight_device *bl;
 223         struct pwm_bl_data *pb;
 224         int ret;
 225
 226         if (!data) {
 227                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 228                 if (ret < 0) {
 229                         dev_err(&pdev->dev, "failed to find platform data\n");
 230                         return ret;
 231                 }
 232
 233                 data = &defdata;
 234         }
 235
 236         if (data->init) {
 237                 ret = data->init(&pdev->dev);
 238                 if (ret < 0)
 239                         return ret;
 240         }
 241
 242         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 243         if (!pb) {
 244                 ret = -ENOMEM;
 245                 goto err_alloc;
 246         }
 247
 248         if (data->levels) {
 249                 unsigned int i;
 250
 251                 for (i = 0; i <= data->max_brightness; i++)
 252                         if (data->levels[i] > pb->scale)
 253                                 pb->scale = data->levels[i];
 254
 255                 pb->levels = data->levels;
 256         } else
 257                 pb->scale = data->max_brightness;
 258
 259         pb->enable_gpio = data->enable_gpio;
 260         pb->enable_gpio_flags = data->enable_gpio_flags;
 261         pb->notify = data->notify;
 262         pb->notify_after = data->notify_after;
 263         pb->check_fb = data->check_fb;
 264         pb->exit = data->exit;
 265         pb->dev = &pdev->dev;
 266         pb->enabled = false;
 267
 268         if (gpio_is_valid(pb->enable_gpio)) {
 269                 unsigned long flags;
 270
 271                 if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
 272                         flags = GPIOF_OUT_INIT_HIGH;
 273                 else
 274                         flags = GPIOF_OUT_INIT_LOW;
 275
 276                 ret = gpio_request_one(pb->enable_gpio, flags, "enable");
 277                 if (ret < 0) {
 278                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 279                                 pb->enable_gpio, ret);
 280                         goto err_alloc;
 281                 }
 282         }
 283
 284         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 285         if (IS_ERR(pb->power_supply)) {
 286                 ret = PTR_ERR(pb->power_supply);
 287                 goto err_gpio;
 288         }
 289
 290         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 291         if (IS_ERR(pb->pwm)) {
 292                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 293
 294                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 295                 if (IS_ERR(pb->pwm)) {
 296                         dev_err(&pdev->dev, "unable to request legacy PWM\n");
 297                         ret = PTR_ERR(pb->pwm);
 298                         goto err_gpio;
 299                 }
 300         }
 301
 302         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 303
 304         /*
 305          * The DT case will set the pwm_period_ns field to 0 and store the
 306          * period, parsed from the DT, in the PWM device. For the non-DT case,
 307          * set the period from platform data.
 308          */
 309         if (data->pwm_period_ns > 0)
 310                 pwm_set_period(pb->pwm, data->pwm_period_ns);
 311
 312         pb->period = pwm_get_period(pb->pwm);
 313         pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
 314
 315         memset(&props, 0, sizeof(struct backlight_properties));
 316         props.type = BACKLIGHT_RAW;
 317         props.max_brightness = data->max_brightness;
 318         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 319                                        &pwm_backlight_ops, &props);
 320         if (IS_ERR(bl)) {
 321                 dev_err(&pdev->dev, "failed to register backlight\n");
 322                 ret = PTR_ERR(bl);
 323                 goto err_gpio;
 324         }
 325
 326         if (data->dft_brightness > data->max_brightness) {
 327                 dev_warn(&pdev->dev,
 328                          "invalid default brightness level: %u, using %u\n",
 329                          data->dft_brightness, data->max_brightness);
 330                 data->dft_brightness = data->max_brightness;
 331         }
 332
 333         bl->props.brightness = data->dft_brightness;
 334         backlight_update_status(bl);
 335
 336         platform_set_drvdata(pdev, bl);
 337         return 0;
 338
 339 err_gpio:
 340         if (gpio_is_valid(pb->enable_gpio))
 341                 gpio_free(pb->enable_gpio);
 342 err_alloc:
 343         if (data->exit)
 344                 data->exit(&pdev->dev);
 345         return ret;
 346 }
 347
 348 static int pwm_backlight_remove(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         backlight_device_unregister(bl);
 354         pwm_backlight_power_off(pb);
 355
 356         if (pb->exit)
 357                 pb->exit(&pdev->dev);
 358
 359         return 0;
 360 }
 361
 362 #ifdef CONFIG_PM_SLEEP
 363 static int pwm_backlight_suspend(struct device *dev)
 364 {
 365         struct backlight_device *bl = dev_get_drvdata(dev);
 366         struct pwm_bl_data *pb = bl_get_data(bl);
 367
 368         if (pb->notify)
 369                 pb->notify(pb->dev, 0);
 370
 371         pwm_backlight_power_off(pb);
 372
 373         if (pb->notify_after)
 374                 pb->notify_after(pb->dev, 0);
 375
 376         return 0;
 377 }
 378
 379 static int pwm_backlight_resume(struct device *dev)
 380 {
 381         struct backlight_device *bl = dev_get_drvdata(dev);
 382
 383         backlight_update_status(bl);
 384
 385         return 0;
 386 }
 387 #endif
 388
 389 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 390 #ifdef CONFIG_PM_SLEEP
 391         .suspend = pwm_backlight_suspend,
 392         .resume = pwm_backlight_resume,
 393         .poweroff = pwm_backlight_suspend,
 394         .restore = pwm_backlight_resume,
 395 #endif
 396 };
 397
 398 static struct platform_driver pwm_backlight_driver = {
 399         .driver         = {
 400                 .name           = "pwm-backlight",
 401                 .owner          = THIS_MODULE,
 402                 .pm             = &pwm_backlight_pm_ops,
 403                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 404         },
 405         .probe          = pwm_backlight_probe,
 406         .remove         = pwm_backlight_remove,
 407 };
 408
 409 module_platform_driver(pwm_backlight_driver);
 410
 411 MODULE_DESCRIPTION("PWM based Backlight Driver");
 412 MODULE_LICENSE("GPL");
 413 MODULE_ALIAS("platform:pwm-backlight");