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/module.h>
  14 #include <linux/kernel.h>
  15 #include <linux/init.h>
  16 #include <linux/platform_device.h>
  17 #include <linux/fb.h>
  18 #include <linux/backlight.h>
  19 #include <linux/err.h>
  20 #include <linux/pwm.h>
  21 #include <linux/pwm_backlight.h>
  22 #include <linux/slab.h>
  23
  24 struct pwm_bl_data {
  25         struct pwm_device       *pwm;
  26         struct device           *dev;
  27         unsigned int            period;
  28         unsigned int            lth_brightness;
  29         unsigned int            *levels;
  30         bool                    enabled;
  31         int                     (*notify)(struct device *,
  32                                           int brightness);
  33         void                    (*notify_after)(struct device *,
  34                                         int brightness);
  35         int                     (*check_fb)(struct device *, struct fb_info *);
  36         void                    (*exit)(struct device *);
  37 };
  38
  39 static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness,
  40                                    int max)
  41 {
  42         int duty_cycle, err;
  43
  44         if (pb->enabled)
  45                 return;
  46
  47         if (pb->levels) {
  48                 duty_cycle = pb->levels[brightness];
  49                 max = pb->levels[max];
  50         } else {
  51                 duty_cycle = brightness;
  52         }
  53
  54         duty_cycle = (duty_cycle * (pb->period - pb->lth_brightness) / max) +
  55                      pb->lth_brightness;
  56
  57         pwm_config(pb->pwm, duty_cycle, pb->period);
  58         pwm_enable(pb->pwm);
  59         pb->enabled = true;
  60 }
  61
  62 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
  63 {
  64         if (!pb->enabled)
  65                 return;
  66
  67         pwm_config(pb->pwm, 0, pb->period);
  68         pwm_disable(pb->pwm);
  69
  70         pb->enabled = false;
  71 }
  72
  73 static int pwm_backlight_update_status(struct backlight_device *bl)
  74 {
  75         struct pwm_bl_data *pb = bl_get_data(bl);
  76         int brightness = bl->props.brightness;
  77         int max = bl->props.max_brightness;
  78
  79         if (bl->props.power != FB_BLANK_UNBLANK ||
  80             bl->props.fb_blank != FB_BLANK_UNBLANK ||
  81             bl->props.state & BL_CORE_FBBLANK)
  82                 brightness = 0;
  83
  84         if (pb->notify)
  85                 brightness = pb->notify(pb->dev, brightness);
  86
  87         if (brightness > 0)
  88                 pwm_backlight_power_on(pb, brightness, max);
  89         else
  90                 pwm_backlight_power_off(pb);
  91
  92         if (pb->notify_after)
  93                 pb->notify_after(pb->dev, brightness);
  94
  95         return 0;
  96 }
  97
  98 static int pwm_backlight_get_brightness(struct backlight_device *bl)
  99 {
 100         return bl->props.brightness;
 101 }
 102
 103 static int pwm_backlight_check_fb(struct backlight_device *bl,
 104                                   struct fb_info *info)
 105 {
 106         struct pwm_bl_data *pb = bl_get_data(bl);
 107
 108         return !pb->check_fb || pb->check_fb(pb->dev, info);
 109 }
 110
 111 static const struct backlight_ops pwm_backlight_ops = {
 112         .update_status  = pwm_backlight_update_status,
 113         .get_brightness = pwm_backlight_get_brightness,
 114         .check_fb       = pwm_backlight_check_fb,
 115 };
 116
 117 #ifdef CONFIG_OF
 118 static int pwm_backlight_parse_dt(struct device *dev,
 119                                   struct platform_pwm_backlight_data *data)
 120 {
 121         struct device_node *node = dev->of_node;
 122         struct property *prop;
 123         int length;
 124         u32 value;
 125         int ret;
 126
 127         if (!node)
 128                 return -ENODEV;
 129
 130         memset(data, 0, sizeof(*data));
 131
 132         /* determine the number of brightness levels */
 133         prop = of_find_property(node, "brightness-levels", &length);
 134         if (!prop)
 135                 return -EINVAL;
 136
 137         data->max_brightness = length / sizeof(u32);
 138
 139         /* read brightness levels from DT property */
 140         if (data->max_brightness > 0) {
 141                 size_t size = sizeof(*data->levels) * data->max_brightness;
 142
 143                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 144                 if (!data->levels)
 145                         return -ENOMEM;
 146
 147                 ret = of_property_read_u32_array(node, "brightness-levels",
 148                                                  data->levels,
 149                                                  data->max_brightness);
 150                 if (ret < 0)
 151                         return ret;
 152
 153                 ret = of_property_read_u32(node, "default-brightness-level",
 154                                            &value);
 155                 if (ret < 0)
 156                         return ret;
 157
 158                 data->dft_brightness = value;
 159                 data->max_brightness--;
 160         }
 161
 162         /*
 163          * TODO: Most users of this driver use a number of GPIOs to control
 164          *       backlight power. Support for specifying these needs to be
 165          *       added.
 166          */
 167
 168         return 0;
 169 }
 170
 171 static struct of_device_id pwm_backlight_of_match[] = {
 172         { .compatible = "pwm-backlight" },
 173         { }
 174 };
 175
 176 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 177 #else
 178 static int pwm_backlight_parse_dt(struct device *dev,
 179                                   struct platform_pwm_backlight_data *data)
 180 {
 181         return -ENODEV;
 182 }
 183 #endif
 184
 185 static int pwm_backlight_probe(struct platform_device *pdev)
 186 {
 187         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
 188         struct platform_pwm_backlight_data defdata;
 189         struct backlight_properties props;
 190         struct backlight_device *bl;
 191         struct pwm_bl_data *pb;
 192         unsigned int max;
 193         int ret;
 194
 195         if (!data) {
 196                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 197                 if (ret < 0) {
 198                         dev_err(&pdev->dev, "failed to find platform data\n");
 199                         return ret;
 200                 }
 201
 202                 data = &defdata;
 203         }
 204
 205         if (data->init) {
 206                 ret = data->init(&pdev->dev);
 207                 if (ret < 0)
 208                         return ret;
 209         }
 210
 211         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 212         if (!pb) {
 213                 dev_err(&pdev->dev, "no memory for state\n");
 214                 ret = -ENOMEM;
 215                 goto err_alloc;
 216         }
 217
 218         if (data->levels) {
 219                 max = data->levels[data->max_brightness];
 220                 pb->levels = data->levels;
 221         } else
 222                 max = data->max_brightness;
 223
 224         pb->notify = data->notify;
 225         pb->notify_after = data->notify_after;
 226         pb->check_fb = data->check_fb;
 227         pb->exit = data->exit;
 228         pb->dev = &pdev->dev;
 229         pb->enabled = false;
 230
 231         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 232         if (IS_ERR(pb->pwm)) {
 233                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 234
 235                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 236                 if (IS_ERR(pb->pwm)) {
 237                         dev_err(&pdev->dev, "unable to request legacy PWM\n");
 238                         ret = PTR_ERR(pb->pwm);
 239                         goto err_alloc;
 240                 }
 241         }
 242
 243         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 244
 245         /*
 246          * The DT case will set the pwm_period_ns field to 0 and store the
 247          * period, parsed from the DT, in the PWM device. For the non-DT case,
 248          * set the period from platform data.
 249          */
 250         if (data->pwm_period_ns > 0)
 251                 pwm_set_period(pb->pwm, data->pwm_period_ns);
 252
 253         pb->period = pwm_get_period(pb->pwm);
 254         pb->lth_brightness = data->lth_brightness * (pb->period / max);
 255
 256         memset(&props, 0, sizeof(struct backlight_properties));
 257         props.type = BACKLIGHT_RAW;
 258         props.max_brightness = data->max_brightness;
 259         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 260                                        &pwm_backlight_ops, &props);
 261         if (IS_ERR(bl)) {
 262                 dev_err(&pdev->dev, "failed to register backlight\n");
 263                 ret = PTR_ERR(bl);
 264                 goto err_alloc;
 265         }
 266
 267         if (data->dft_brightness > data->max_brightness) {
 268                 dev_warn(&pdev->dev,
 269                          "invalid default brightness level: %u, using %u\n",
 270                          data->dft_brightness, data->max_brightness);
 271                 data->dft_brightness = data->max_brightness;
 272         }
 273
 274         bl->props.brightness = data->dft_brightness;
 275         backlight_update_status(bl);
 276
 277         platform_set_drvdata(pdev, bl);
 278         return 0;
 279
 280 err_alloc:
 281         if (data->exit)
 282                 data->exit(&pdev->dev);
 283         return ret;
 284 }
 285
 286 static int pwm_backlight_remove(struct platform_device *pdev)
 287 {
 288         struct backlight_device *bl = platform_get_drvdata(pdev);
 289         struct pwm_bl_data *pb = bl_get_data(bl);
 290
 291         backlight_device_unregister(bl);
 292         pwm_backlight_power_off(pb);
 293
 294         if (pb->exit)
 295                 pb->exit(&pdev->dev);
 296
 297         return 0;
 298 }
 299
 300 #ifdef CONFIG_PM_SLEEP
 301 static int pwm_backlight_suspend(struct device *dev)
 302 {
 303         struct backlight_device *bl = dev_get_drvdata(dev);
 304         struct pwm_bl_data *pb = bl_get_data(bl);
 305
 306         if (pb->notify)
 307                 pb->notify(pb->dev, 0);
 308
 309         pwm_backlight_power_off(pb);
 310
 311         if (pb->notify_after)
 312                 pb->notify_after(pb->dev, 0);
 313
 314         return 0;
 315 }
 316
 317 static int pwm_backlight_resume(struct device *dev)
 318 {
 319         struct backlight_device *bl = dev_get_drvdata(dev);
 320
 321         backlight_update_status(bl);
 322
 323         return 0;
 324 }
 325 #endif
 326
 327 static SIMPLE_DEV_PM_OPS(pwm_backlight_pm_ops, pwm_backlight_suspend,
 328                          pwm_backlight_resume);
 329
 330 static struct platform_driver pwm_backlight_driver = {
 331         .driver         = {
 332                 .name           = "pwm-backlight",
 333                 .owner          = THIS_MODULE,
 334                 .pm             = &pwm_backlight_pm_ops,
 335                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 336         },
 337         .probe          = pwm_backlight_probe,
 338         .remove         = pwm_backlight_remove,
 339 };
 340
 341 module_platform_driver(pwm_backlight_driver);
 342
 343 MODULE_DESCRIPTION("PWM based Backlight Driver");
 344 MODULE_LICENSE("GPL");
 345 MODULE_ALIAS("platform:pwm-backlight");