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/slab.h>
  25
  26 struct pwm_bl_data {
  27         struct pwm_device       *pwm;
  28         struct device           *dev;
  29         unsigned int            period;
  30         unsigned int            lth_brightness;
  31         unsigned int            *levels;
  32         bool                    enabled;
  33         int                     enable_gpio;
  34         unsigned long           enable_gpio_flags;
  35         int                     (*notify)(struct device *,
  36                                           int brightness);
  37         void                    (*notify_after)(struct device *,
  38                                         int brightness);
  39         int                     (*check_fb)(struct device *, struct fb_info *);
  40         void                    (*exit)(struct device *);
  41 };
  42
  43 static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness,
  44                                    int max)
  45 {
  46         int duty_cycle, err;
  47
  48         if (pb->enabled)
  49                 return;
  50
  51         if (pb->levels) {
  52                 duty_cycle = pb->levels[brightness];
  53                 max = pb->levels[max];
  54         } else {
  55                 duty_cycle = brightness;
  56         }
  57
  58         duty_cycle = (duty_cycle * (pb->period - pb->lth_brightness) / max) +
  59                      pb->lth_brightness;
  60
  61         pwm_config(pb->pwm, duty_cycle, pb->period);
  62
  63         if (gpio_is_valid(pb->enable_gpio)) {
  64                 if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
  65                         gpio_set_value(pb->enable_gpio, 0);
  66                 else
  67                         gpio_set_value(pb->enable_gpio, 1);
  68         }
  69
  70         pwm_enable(pb->pwm);
  71         pb->enabled = true;
  72 }
  73
  74 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
  75 {
  76         if (!pb->enabled)
  77                 return;
  78
  79         pwm_config(pb->pwm, 0, pb->period);
  80         pwm_disable(pb->pwm);
  81
  82         if (gpio_is_valid(pb->enable_gpio)) {
  83                 if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
  84                         gpio_set_value(pb->enable_gpio, 1);
  85                 else
  86                         gpio_set_value(pb->enable_gpio, 0);
  87         }
  88
  89         pb->enabled = false;
  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 max = bl->props.max_brightness;
  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                 pwm_backlight_power_on(pb, brightness, max);
 108         else
 109                 pwm_backlight_power_off(pb);
 110
 111         if (pb->notify_after)
 112                 pb->notify_after(pb->dev, brightness);
 113
 114         return 0;
 115 }
 116
 117 static int pwm_backlight_get_brightness(struct backlight_device *bl)
 118 {
 119         return bl->props.brightness;
 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         .get_brightness = pwm_backlight_get_brightness,
 133         .check_fb       = pwm_backlight_check_fb,
 134 };
 135
 136 #ifdef CONFIG_OF
 137 static int pwm_backlight_parse_dt(struct device *dev,
 138                                   struct platform_pwm_backlight_data *data)
 139 {
 140         struct device_node *node = dev->of_node;
 141         enum of_gpio_flags flags;
 142         struct property *prop;
 143         int length;
 144         u32 value;
 145         int ret;
 146
 147         if (!node)
 148                 return -ENODEV;
 149
 150         memset(data, 0, sizeof(*data));
 151
 152         /* determine the number of brightness levels */
 153         prop = of_find_property(node, "brightness-levels", &length);
 154         if (!prop)
 155                 return -EINVAL;
 156
 157         data->max_brightness = length / sizeof(u32);
 158
 159         /* read brightness levels from DT property */
 160         if (data->max_brightness > 0) {
 161                 size_t size = sizeof(*data->levels) * data->max_brightness;
 162
 163                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 164                 if (!data->levels)
 165                         return -ENOMEM;
 166
 167                 ret = of_property_read_u32_array(node, "brightness-levels",
 168                                                  data->levels,
 169                                                  data->max_brightness);
 170                 if (ret < 0)
 171                         return ret;
 172
 173                 ret = of_property_read_u32(node, "default-brightness-level",
 174                                            &value);
 175                 if (ret < 0)
 176                         return ret;
 177
 178                 data->dft_brightness = value;
 179                 data->max_brightness--;
 180         }
 181
 182         data->enable_gpio = of_get_named_gpio_flags(node, "enable-gpios", 0,
 183                                                     &flags);
 184         if (data->enable_gpio == -EPROBE_DEFER)
 185                 return -EPROBE_DEFER;
 186
 187         if (gpio_is_valid(data->enable_gpio) && (flags & OF_GPIO_ACTIVE_LOW))
 188                 data->enable_gpio_flags |= PWM_BACKLIGHT_GPIO_ACTIVE_LOW;
 189
 190         return 0;
 191 }
 192
 193 static struct of_device_id pwm_backlight_of_match[] = {
 194         { .compatible = "pwm-backlight" },
 195         { }
 196 };
 197
 198 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 199 #else
 200 static int pwm_backlight_parse_dt(struct device *dev,
 201                                   struct platform_pwm_backlight_data *data)
 202 {
 203         return -ENODEV;
 204 }
 205 #endif
 206
 207 static int pwm_backlight_probe(struct platform_device *pdev)
 208 {
 209         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
 210         struct platform_pwm_backlight_data defdata;
 211         struct backlight_properties props;
 212         struct backlight_device *bl;
 213         struct pwm_bl_data *pb;
 214         unsigned int max;
 215         int ret;
 216
 217         if (!data) {
 218                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 219                 if (ret < 0) {
 220                         dev_err(&pdev->dev, "failed to find platform data\n");
 221                         return ret;
 222                 }
 223
 224                 data = &defdata;
 225         }
 226
 227         if (data->init) {
 228                 ret = data->init(&pdev->dev);
 229                 if (ret < 0)
 230                         return ret;
 231         }
 232
 233         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 234         if (!pb) {
 235                 dev_err(&pdev->dev, "no memory for state\n");
 236                 ret = -ENOMEM;
 237                 goto err_alloc;
 238         }
 239
 240         if (data->levels) {
 241                 max = data->levels[data->max_brightness];
 242                 pb->levels = data->levels;
 243         } else
 244                 max = data->max_brightness;
 245
 246         pb->enable_gpio = data->enable_gpio;
 247         pb->enable_gpio_flags = data->enable_gpio_flags;
 248         pb->notify = data->notify;
 249         pb->notify_after = data->notify_after;
 250         pb->check_fb = data->check_fb;
 251         pb->exit = data->exit;
 252         pb->dev = &pdev->dev;
 253         pb->enabled = false;
 254
 255         if (gpio_is_valid(pb->enable_gpio)) {
 256                 unsigned long flags;
 257
 258                 if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
 259                         flags = GPIOF_OUT_INIT_HIGH;
 260                 else
 261                         flags = GPIOF_OUT_INIT_LOW;
 262
 263                 ret = gpio_request_one(pb->enable_gpio, flags, "enable");
 264                 if (ret < 0) {
 265                         dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
 266                                 pb->enable_gpio, ret);
 267                         goto err_alloc;
 268                 }
 269         }
 270
 271         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 272         if (IS_ERR(pb->pwm)) {
 273                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 274
 275                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 276                 if (IS_ERR(pb->pwm)) {
 277                         dev_err(&pdev->dev, "unable to request legacy PWM\n");
 278                         ret = PTR_ERR(pb->pwm);
 279                         goto err_gpio;
 280                 }
 281         }
 282
 283         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 284
 285         /*
 286          * The DT case will set the pwm_period_ns field to 0 and store the
 287          * period, parsed from the DT, in the PWM device. For the non-DT case,
 288          * set the period from platform data.
 289          */
 290         if (data->pwm_period_ns > 0)
 291                 pwm_set_period(pb->pwm, data->pwm_period_ns);
 292
 293         pb->period = pwm_get_period(pb->pwm);
 294         pb->lth_brightness = data->lth_brightness * (pb->period / max);
 295
 296         memset(&props, 0, sizeof(struct backlight_properties));
 297         props.type = BACKLIGHT_RAW;
 298         props.max_brightness = data->max_brightness;
 299         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 300                                        &pwm_backlight_ops, &props);
 301         if (IS_ERR(bl)) {
 302                 dev_err(&pdev->dev, "failed to register backlight\n");
 303                 ret = PTR_ERR(bl);
 304                 goto err_gpio;
 305         }
 306
 307         if (data->dft_brightness > data->max_brightness) {
 308                 dev_warn(&pdev->dev,
 309                          "invalid default brightness level: %u, using %u\n",
 310                          data->dft_brightness, data->max_brightness);
 311                 data->dft_brightness = data->max_brightness;
 312         }
 313
 314         bl->props.brightness = data->dft_brightness;
 315         backlight_update_status(bl);
 316
 317         platform_set_drvdata(pdev, bl);
 318         return 0;
 319
 320 err_gpio:
 321         if (gpio_is_valid(pb->enable_gpio))
 322                 gpio_free(pb->enable_gpio);
 323 err_alloc:
 324         if (data->exit)
 325                 data->exit(&pdev->dev);
 326         return ret;
 327 }
 328
 329 static int pwm_backlight_remove(struct platform_device *pdev)
 330 {
 331         struct backlight_device *bl = platform_get_drvdata(pdev);
 332         struct pwm_bl_data *pb = bl_get_data(bl);
 333
 334         backlight_device_unregister(bl);
 335         pwm_backlight_power_off(pb);
 336
 337         if (pb->exit)
 338                 pb->exit(&pdev->dev);
 339
 340         return 0;
 341 }
 342
 343 #ifdef CONFIG_PM_SLEEP
 344 static int pwm_backlight_suspend(struct device *dev)
 345 {
 346         struct backlight_device *bl = dev_get_drvdata(dev);
 347         struct pwm_bl_data *pb = bl_get_data(bl);
 348
 349         if (pb->notify)
 350                 pb->notify(pb->dev, 0);
 351
 352         pwm_backlight_power_off(pb);
 353
 354         if (pb->notify_after)
 355                 pb->notify_after(pb->dev, 0);
 356
 357         return 0;
 358 }
 359
 360 static int pwm_backlight_resume(struct device *dev)
 361 {
 362         struct backlight_device *bl = dev_get_drvdata(dev);
 363
 364         backlight_update_status(bl);
 365
 366         return 0;
 367 }
 368 #endif
 369
 370 static SIMPLE_DEV_PM_OPS(pwm_backlight_pm_ops, pwm_backlight_suspend,
 371                          pwm_backlight_resume);
 372
 373 static struct platform_driver pwm_backlight_driver = {
 374         .driver         = {
 375                 .name           = "pwm-backlight",
 376                 .owner          = THIS_MODULE,
 377                 .pm             = &pwm_backlight_pm_ops,
 378                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 379         },
 380         .probe          = pwm_backlight_probe,
 381         .remove         = pwm_backlight_remove,
 382 };
 383
 384 module_platform_driver(pwm_backlight_driver);
 385
 386 MODULE_DESCRIPTION("PWM based Backlight Driver");
 387 MODULE_LICENSE("GPL");
 388 MODULE_ALIAS("platform:pwm-backlight");