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         int duty_cycle;
  83
  84         if (pb->levels)
  85                 duty_cycle = pb->levels[brightness];
  86         else
  87                 duty_cycle = brightness;
  88
  89         return (duty_cycle * (pb->period - lth) / pb->scale) + lth;
  90 }
  91
  92 static int pwm_backlight_update_status(struct backlight_device *bl)
  93 {
  94         struct pwm_bl_data *pb = bl_get_data(bl);
  95         int brightness = bl->props.brightness;
  96         int duty_cycle;
  97
  98         if (bl->props.power != FB_BLANK_UNBLANK ||
  99             bl->props.fb_blank != FB_BLANK_UNBLANK ||
 100             bl->props.state & BL_CORE_FBBLANK)
 101                 brightness = 0;
 102
 103         if (pb->notify)
 104                 brightness = pb->notify(pb->dev, brightness);
 105
 106         if (brightness > 0) {
 107                 duty_cycle = compute_duty_cycle(pb, brightness);
 108                 pwm_config(pb->pwm, duty_cycle, pb->period);
 109                 pwm_backlight_power_on(pb, brightness);
 110         } else
 111                 pwm_backlight_power_off(pb);
 112
 113         if (pb->notify_after)
 114                 pb->notify_after(pb->dev, brightness);
 115
 116         return 0;
 117 }
 118
 119 static int pwm_backlight_check_fb(struct backlight_device *bl,
 120                                   struct fb_info *info)
 121 {
 122         struct pwm_bl_data *pb = bl_get_data(bl);
 123
 124         return !pb->check_fb || pb->check_fb(pb->dev, info);
 125 }
 126
 127 static const struct backlight_ops pwm_backlight_ops = {
 128         .update_status  = pwm_backlight_update_status,
 129         .check_fb       = pwm_backlight_check_fb,
 130 };
 131
 132 #ifdef CONFIG_OF
 133 static int pwm_backlight_parse_dt(struct device *dev,
 134                                   struct platform_pwm_backlight_data *data)
 135 {
 136         struct device_node *node = dev->of_node;
 137         struct property *prop;
 138         int length;
 139         u32 value;
 140         int ret;
 141
 142         if (!node)
 143                 return -ENODEV;
 144
 145         memset(data, 0, sizeof(*data));
 146
 147         /* determine the number of brightness levels */
 148         prop = of_find_property(node, "brightness-levels", &length);
 149         if (!prop)
 150                 return -EINVAL;
 151
 152         data->max_brightness = length / sizeof(u32);
 153
 154         /* read brightness levels from DT property */
 155         if (data->max_brightness > 0) {
 156                 size_t size = sizeof(*data->levels) * data->max_brightness;
 157
 158                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 159                 if (!data->levels)
 160                         return -ENOMEM;
 161
 162                 ret = of_property_read_u32_array(node, "brightness-levels",
 163                                                  data->levels,
 164                                                  data->max_brightness);
 165                 if (ret < 0)
 166                         return ret;
 167
 168                 ret = of_property_read_u32(node, "default-brightness-level",
 169                                            &value);
 170                 if (ret < 0)
 171                         return ret;
 172
 173                 data->dft_brightness = value;
 174                 data->max_brightness--;
 175         }
 176
 177         data->enable_gpio = -EINVAL;
 178         return 0;
 179 }
 180
 181 static struct of_device_id pwm_backlight_of_match[] = {
 182         { .compatible = "pwm-backlight" },
 183         { }
 184 };
 185
 186 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 187 #else
 188 static int pwm_backlight_parse_dt(struct device *dev,
 189                                   struct platform_pwm_backlight_data *data)
 190 {
 191         return -ENODEV;
 192 }
 193 #endif
 194
 195 static int pwm_backlight_probe(struct platform_device *pdev)
 196 {
 197         struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
 198         struct platform_pwm_backlight_data defdata;
 199         struct backlight_properties props;
 200         struct backlight_device *bl;
 201         struct pwm_bl_data *pb;
 202         int ret;
 203
 204         if (!data) {
 205                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 206                 if (ret < 0) {
 207                         dev_err(&pdev->dev, "failed to find platform data\n");
 208                         return ret;
 209                 }
 210
 211                 data = &defdata;
 212         }
 213
 214         if (data->init) {
 215                 ret = data->init(&pdev->dev);
 216                 if (ret < 0)
 217                         return ret;
 218         }
 219
 220         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 221         if (!pb) {
 222                 ret = -ENOMEM;
 223                 goto err_alloc;
 224         }
 225
 226         if (data->levels) {
 227                 unsigned int i;
 228
 229                 for (i = 0; i <= data->max_brightness; i++)
 230                         if (data->levels[i] > pb->scale)
 231                                 pb->scale = data->levels[i];
 232
 233                 pb->levels = data->levels;
 234         } else
 235                 pb->scale = data->max_brightness;
 236
 237         pb->notify = data->notify;
 238         pb->notify_after = data->notify_after;
 239         pb->check_fb = data->check_fb;
 240         pb->exit = data->exit;
 241         pb->dev = &pdev->dev;
 242         pb->enabled = false;
 243
 244         pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
 245                                                   GPIOD_OUT_HIGH);
 246         if (IS_ERR(pb->enable_gpio)) {
 247                 ret = PTR_ERR(pb->enable_gpio);
 248                 goto err_alloc;
 249         }
 250
 251         /*
 252          * Compatibility fallback for drivers still using the integer GPIO
 253          * platform data. Must go away soon.
 254          */
 255         if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
 256                 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
 257                                             GPIOF_OUT_INIT_HIGH, "enable");
 258                 if (ret < 0) {
 259                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 260                                 data->enable_gpio, ret);
 261                         goto err_alloc;
 262                 }
 263
 264                 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
 265         }
 266
 267         pb->power_supply = devm_regulator_get(&pdev->dev, "power");
 268         if (IS_ERR(pb->power_supply)) {
 269                 ret = PTR_ERR(pb->power_supply);
 270                 goto err_alloc;
 271         }
 272
 273         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 274         if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
 275             && !pdev->dev.of_node) {
 276                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 277                 pb->legacy = true;
 278                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 279         }
 280
 281         if (IS_ERR(pb->pwm)) {
 282                 ret = PTR_ERR(pb->pwm);
 283                 if (ret != -EPROBE_DEFER)
 284                         dev_err(&pdev->dev, "unable to request PWM\n");
 285                 goto err_alloc;
 286         }
 287
 288         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 289
 290         /*
 291          * The DT case will set the pwm_period_ns field to 0 and store the
 292          * period, parsed from the DT, in the PWM device. For the non-DT case,
 293          * set the period from platform data if it has not already been set
 294          * via the PWM lookup table.
 295          */
 296         pb->period = pwm_get_period(pb->pwm);
 297         if (!pb->period && (data->pwm_period_ns > 0)) {
 298                 pb->period = data->pwm_period_ns;
 299                 pwm_set_period(pb->pwm, data->pwm_period_ns);
 300         }
 301
 302         pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
 303
 304         memset(&props, 0, sizeof(struct backlight_properties));
 305         props.type = BACKLIGHT_RAW;
 306         props.max_brightness = data->max_brightness;
 307         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 308                                        &pwm_backlight_ops, &props);
 309         if (IS_ERR(bl)) {
 310                 dev_err(&pdev->dev, "failed to register backlight\n");
 311                 ret = PTR_ERR(bl);
 312                 goto err_alloc;
 313         }
 314
 315         if (data->dft_brightness > data->max_brightness) {
 316                 dev_warn(&pdev->dev,
 317                          "invalid default brightness level: %u, using %u\n",
 318                          data->dft_brightness, data->max_brightness);
 319                 data->dft_brightness = data->max_brightness;
 320         }
 321
 322         bl->props.brightness = data->dft_brightness;
 323         backlight_update_status(bl);
 324
 325         platform_set_drvdata(pdev, bl);
 326         return 0;
 327
 328 err_alloc:
 329         if (data->exit)
 330                 data->exit(&pdev->dev);
 331         return ret;
 332 }
 333
 334 static int pwm_backlight_remove(struct platform_device *pdev)
 335 {
 336         struct backlight_device *bl = platform_get_drvdata(pdev);
 337         struct pwm_bl_data *pb = bl_get_data(bl);
 338
 339         backlight_device_unregister(bl);
 340         pwm_backlight_power_off(pb);
 341
 342         if (pb->exit)
 343                 pb->exit(&pdev->dev);
 344         if (pb->legacy)
 345                 pwm_free(pb->pwm);
 346
 347         return 0;
 348 }
 349
 350 static void pwm_backlight_shutdown(struct platform_device *pdev)
 351 {
 352         struct backlight_device *bl = platform_get_drvdata(pdev);
 353         struct pwm_bl_data *pb = bl_get_data(bl);
 354
 355         pwm_backlight_power_off(pb);
 356 }
 357
 358 #ifdef CONFIG_PM_SLEEP
 359 static int pwm_backlight_suspend(struct device *dev)
 360 {
 361         struct backlight_device *bl = dev_get_drvdata(dev);
 362         struct pwm_bl_data *pb = bl_get_data(bl);
 363
 364         if (pb->notify)
 365                 pb->notify(pb->dev, 0);
 366
 367         pwm_backlight_power_off(pb);
 368
 369         if (pb->notify_after)
 370                 pb->notify_after(pb->dev, 0);
 371
 372         return 0;
 373 }
 374
 375 static int pwm_backlight_resume(struct device *dev)
 376 {
 377         struct backlight_device *bl = dev_get_drvdata(dev);
 378
 379         backlight_update_status(bl);
 380
 381         return 0;
 382 }
 383 #endif
 384
 385 static const struct dev_pm_ops pwm_backlight_pm_ops = {
 386 #ifdef CONFIG_PM_SLEEP
 387         .suspend = pwm_backlight_suspend,
 388         .resume = pwm_backlight_resume,
 389         .poweroff = pwm_backlight_suspend,
 390         .restore = pwm_backlight_resume,
 391 #endif
 392 };
 393
 394 static struct platform_driver pwm_backlight_driver = {
 395         .driver         = {
 396                 .name           = "pwm-backlight",
 397                 .pm             = &pwm_backlight_pm_ops,
 398                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 399         },
 400         .probe          = pwm_backlight_probe,
 401         .remove         = pwm_backlight_remove,
 402         .shutdown       = pwm_backlight_shutdown,
 403 };
 404
 405 module_platform_driver(pwm_backlight_driver);
 406
 407 MODULE_DESCRIPTION("PWM based Backlight Driver");
 408 MODULE_LICENSE("GPL");
 409 MODULE_ALIAS("platform:pwm-backlight");