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         bool                    legacy;
  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 (pb->enable_gpio)
  58                 gpiod_set_value(pb->enable_gpio, 1);
  59
  60         pwm_enable(pb->pwm);
  61         pb->enabled = true;
  62 }
  63
  64 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
  65 {
  66         if (!pb->enabled)
  67                 return;
  68
  69         pwm_config(pb->pwm, 0, pb->period);
  70         pwm_disable(pb->pwm);
  71
  72         if (pb->enable_gpio)
  73                 gpiod_set_value(pb->enable_gpio, 0);
  74
  75         regulator_disable(pb->power_supply);
  76         pb->enabled = false;
  77 }
  78
  79 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
  80 {
  81         unsigned int lth = pb->lth_brightness;
  82         u64 duty_cycle;
  83
  84         if (pb->levels)
  85                 duty_cycle = pb->levels[brightness];
  86         else
  87                 duty_cycle = brightness;
  88
  89         duty_cycle *= pb->period - lth;
  90         do_div(duty_cycle, pb->scale);
  91
  92         return duty_cycle + lth;
  93 }
  94
  95 static int pwm_backlight_update_status(struct backlight_device *bl)
  96 {
  97         struct pwm_bl_data *pb = bl_get_data(bl);
  98         int brightness = bl->props.brightness;
  99         int duty_cycle;
 100
 101         if (bl->props.power != FB_BLANK_UNBLANK ||
 102             bl->props.fb_blank != FB_BLANK_UNBLANK ||
 103             bl->props.state & BL_CORE_FBBLANK)
 104                 brightness = 0;
 105
 106         if (pb->notify)
 107                 brightness = pb->notify(pb->dev, brightness);
 108
 109         if (brightness > 0) {
 110                 duty_cycle = compute_duty_cycle(pb, brightness);
 111                 pwm_config(pb->pwm, duty_cycle, pb->period);
 112                 pwm_backlight_power_on(pb, brightness);
 113         } else
 114                 pwm_backlight_power_off(pb);
 115
 116         if (pb->notify_after)
 117                 pb->notify_after(pb->dev, brightness);
 118
 119         return 0;
 120 }
 121
 122 static int pwm_backlight_check_fb(struct backlight_device *bl,
 123                                   struct fb_info *info)
 124 {
 125         struct pwm_bl_data *pb = bl_get_data(bl);
 126
 127         return !pb->check_fb || pb->check_fb(pb->dev, info);
 128 }
 129
 130 static const struct backlight_ops pwm_backlight_ops = {
 131         .update_status  = pwm_backlight_update_status,
 132         .check_fb       = pwm_backlight_check_fb,
 133 };
 134
 135 #ifdef CONFIG_OF
 136 static int pwm_backlight_parse_dt(struct device *dev,
 137                                   struct platform_pwm_backlight_data *data)
 138 {
 139         struct device_node *node = dev->of_node;
 140         struct property *prop;
 141         int length;
 142         u32 value;
 143         int ret;
 144
 145         if (!node)
 146                 return -ENODEV;
 147
 148         memset(data, 0, sizeof(*data));
 149
 150         /* determine the number of brightness levels */
 151         prop = of_find_property(node, "brightness-levels", &length);
 152         if (!prop)
 153                 return -EINVAL;
 154
 155         data->max_brightness = length / sizeof(u32);
 156
 157         /* read brightness levels from DT property */
 158         if (data->max_brightness > 0) {
 159                 size_t size = sizeof(*data->levels) * data->max_brightness;
 160
 161                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 162                 if (!data->levels)
 163                         return -ENOMEM;
 164
 165                 ret = of_property_read_u32_array(node, "brightness-levels",
 166                                                  data->levels,
 167                                                  data->max_brightness);
 168                 if (ret < 0)
 169                         return ret;
 170
 171                 ret = of_property_read_u32(node, "default-brightness-level",
 172                                            &value);
 173                 if (ret < 0)
 174                         return ret;
 175
 176                 data->dft_brightness = value;
 177                 data->max_brightness--;
 178         }
 179
 180         data->enable_gpio = -EINVAL;
 181         return 0;
 182 }
 183
 184 static struct of_device_id pwm_backlight_of_match[] = {
 185         { .compatible = "pwm-backlight" },
 186         { }
 187 };
 188
 189 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 190 #else
 191 static int pwm_backlight_parse_dt(struct device *dev,
 192                                   struct platform_pwm_backlight_data *data)
 193 {
 194         return -ENODEV;
 195 }
 196 #endif
 197
 198 static int pwm_backlight_probe(struct platform_device *pdev)
 199 {
 200         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 201         struct platform_pwm_backlight_data defdata;
 202         struct backlight_properties props;
 203         struct backlight_device *bl;
 204         struct pwm_bl_data *pb;
 205         int ret;
 206
 207         if (!data) {
 208                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 209                 if (ret < 0) {
 210                         dev_err(&pdev->dev, "failed to find platform data\n");
 211                         return ret;
 212                 }
 213
 214                 data = &defdata;
 215         }
 216
 217         if (data->init) {
 218                 ret = data->init(&pdev->dev);
 219                 if (ret < 0)
 220                         return ret;
 221         }
 222
 223         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 224         if (!pb) {
 225                 ret = -ENOMEM;
 226                 goto err_alloc;
 227         }
 228
 229         if (data->levels) {
 230                 unsigned int i;
 231
 232                 for (i = 0; i <= data->max_brightness; i++)
 233                         if (data->levels[i] > pb->scale)
 234                                 pb->scale = data->levels[i];
 235
 236                 pb->levels = data->levels;
 237         } else
 238                 pb->scale = data->max_brightness;
 239
 240         pb->notify = data->notify;
 241         pb->notify_after = data->notify_after;
 242         pb->check_fb = data->check_fb;
 243         pb->exit = data->exit;
 244         pb->dev = &pdev->dev;
 245         pb->enabled = false;
 246
 247         pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 248                                                   GPIOD_OUT_HIGH);
 249         if (IS_ERR(pb->enable_gpio)) {
 250                 ret = PTR_ERR(pb->enable_gpio);
 251                 goto err_alloc;
 252         }
 253
 254         /*
 255          * Compatibility fallback for drivers still using the integer GPIO
 256          * platform data. Must go away soon.
 257          */
 258         if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
 259                 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 260                                             GPIOF_OUT_INIT_HIGH, "enable");
 261                 if (ret < 0) {
 262                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 263                                 data->enable_gpio, ret);
 264                         goto err_alloc;
 265                 }
 266
 267                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 268         }
 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) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
 278             && !pdev->dev.of_node) {
 279                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 280                 pb->legacy = true;
 281                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 282         }
 283
 284         if (IS_ERR(pb->pwm)) {
 285                 ret = PTR_ERR(pb->pwm);
 286                 if (ret != -EPROBE_DEFER)
 287                         dev_err(&pdev->dev, "unable to request PWM\n");
 288                 goto err_alloc;
 289         }
 290
 291         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 292
 293         /*
 294          * The DT case will set the pwm_period_ns field to 0 and store the
 295          * period, parsed from the DT, in the PWM device. For the non-DT case,
 296          * set the period from platform data if it has not already been set
 297          * via the PWM lookup table.
 298          */
 299         pb->period = pwm_get_period(pb->pwm);
 300         if (!pb->period && (data->pwm_period_ns > 0)) {
 301                 pb->period = data->pwm_period_ns;
 302                 pwm_set_period(pb->pwm, data->pwm_period_ns);
 303         }
 304
 305         pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
 306
 307         memset(&props, 0, sizeof(struct backlight_properties));
 308         props.type = BACKLIGHT_RAW;
 309         props.max_brightness = data->max_brightness;
 310         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 311                                        &pwm_backlight_ops, &props);
 312         if (IS_ERR(bl)) {
 313                 dev_err(&pdev->dev, "failed to register backlight\n");
 314                 ret = PTR_ERR(bl);
 315                 goto err_alloc;
 316         }
 317
 318         if (data->dft_brightness > data->max_brightness) {
 319                 dev_warn(&pdev->dev,
 320                          "invalid default brightness level: %u, using %u\n",
 321                          data->dft_brightness, data->max_brightness);
 322                 data->dft_brightness = data->max_brightness;
 323         }
 324
 325         bl->props.brightness = data->dft_brightness;
 326         backlight_update_status(bl);
 327
 328         platform_set_drvdata(pdev, bl);
 329         return 0;
 330
 331 err_alloc:
 332         if (data->exit)
 333                 data->exit(&pdev->dev);
 334         return ret;
 335 }
 336
 337 static int pwm_backlight_remove(struct platform_device *pdev)
 338 {
 339         struct backlight_device *bl = platform_get_drvdata(pdev);
 340         struct pwm_bl_data *pb = bl_get_data(bl);
 341
 342         backlight_device_unregister(bl);
 343         pwm_backlight_power_off(pb);
 344
 345         if (pb->exit)
 346                 pb->exit(&pdev->dev);
 347         if (pb->legacy)
 348                 pwm_free(pb->pwm);
 349
 350         return 0;
 351 }
 352
 353 static void pwm_backlight_shutdown(struct platform_device *pdev)
 354 {
 355         struct backlight_device *bl = platform_get_drvdata(pdev);
 356         struct pwm_bl_data *pb = bl_get_data(bl);
 357
 358         pwm_backlight_power_off(pb);
 359 }
 360
 361 #ifdef CONFIG_PM_SLEEP
 362 static int pwm_backlight_suspend(struct device *dev)
 363 {
 364         struct backlight_device *bl = dev_get_drvdata(dev);
 365         struct pwm_bl_data *pb = bl_get_data(bl);
 366
 367         if (pb->notify)
 368                 pb->notify(pb->dev, 0);
 369
 370         pwm_backlight_power_off(pb);
 371
 372         if (pb->notify_after)
 373                 pb->notify_after(pb->dev, 0);
 374
 375         return 0;
 376 }
 377
 378 static int pwm_backlight_resume(struct device *dev)
 379 {
 380         struct backlight_device *bl = dev_get_drvdata(dev);
 381
 382         backlight_update_status(bl);
 383
 384         return 0;
 385 }
 386 #endif
 387
 388 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 389 #ifdef CONFIG_PM_SLEEP
 390         .suspend = pwm_backlight_suspend,
 391         .resume = pwm_backlight_resume,
 392         .poweroff = pwm_backlight_suspend,
 393         .restore = pwm_backlight_resume,
 394 #endif
 395 };
 396
 397 static struct platform_driver pwm_backlight_driver = {
 398         .driver         = {
 399                 .name           = "pwm-backlight",
 400                 .pm             = &pwm_backlight_pm_ops,
 401                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 402         },
 403         .probe          = pwm_backlight_probe,
 404         .remove         = pwm_backlight_remove,
 405         .shutdown       = pwm_backlight_shutdown,
 406 };
 407
 408 module_platform_driver(pwm_backlight_driver);
 409
 410 MODULE_DESCRIPTION("PWM based Backlight Driver");
 411 MODULE_LICENSE("GPL");
 412 MODULE_ALIAS("platform:pwm-backlight");