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