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