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         int                     (*notify)(struct device *,
  31                                           int brightness);
  32         void                    (*notify_after)(struct device *,
  33                                         int brightness);
  34         int                     (*check_fb)(struct device *, struct fb_info *);
  35         void                    (*exit)(struct device *);
  36 };
  37
  38 static int pwm_backlight_update_status(struct backlight_device *bl)
  39 {
  40         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
  41         int brightness = bl->props.brightness;
  42         int max = bl->props.max_brightness;
  43
  44         if (bl->props.power != FB_BLANK_UNBLANK)
  45                 brightness = 0;
  46
  47         if (bl->props.fb_blank != FB_BLANK_UNBLANK)
  48                 brightness = 0;
  49
  50         if (pb->notify)
  51                 brightness = pb->notify(pb->dev, brightness);
  52
  53         if (brightness == 0) {
  54                 pwm_config(pb->pwm, 0, pb->period);
  55                 pwm_disable(pb->pwm);
  56         } else {
  57                 int duty_cycle;
  58
  59                 if (pb->levels) {
  60                         duty_cycle = pb->levels[brightness];
  61                         max = pb->levels[max];
  62                 } else {
  63                         duty_cycle = brightness;
  64                 }
  65
  66                 duty_cycle = pb->lth_brightness +
  67                      (duty_cycle * (pb->period - pb->lth_brightness) / max);
  68                 pwm_config(pb->pwm, duty_cycle, pb->period);
  69                 pwm_enable(pb->pwm);
  70         }
  71
  72         if (pb->notify_after)
  73                 pb->notify_after(pb->dev, brightness);
  74
  75         return 0;
  76 }
  77
  78 static int pwm_backlight_get_brightness(struct backlight_device *bl)
  79 {
  80         return bl->props.brightness;
  81 }
  82
  83 static int pwm_backlight_check_fb(struct backlight_device *bl,
  84                                   struct fb_info *info)
  85 {
  86         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
  87
  88         return !pb->check_fb || pb->check_fb(pb->dev, info);
  89 }
  90
  91 static const struct backlight_ops pwm_backlight_ops = {
  92         .update_status  = pwm_backlight_update_status,
  93         .get_brightness = pwm_backlight_get_brightness,
  94         .check_fb       = pwm_backlight_check_fb,
  95 };
  96
  97 #ifdef CONFIG_OF
  98 static int pwm_backlight_parse_dt(struct device *dev,
  99                                   struct platform_pwm_backlight_data *data)
 100 {
 101         struct device_node *node = dev->of_node;
 102         struct property *prop;
 103         int length;
 104         u32 value;
 105         int ret;
 106
 107         if (!node)
 108                 return -ENODEV;
 109
 110         memset(data, 0, sizeof(*data));
 111
 112         /* determine the number of brightness levels */
 113         prop = of_find_property(node, "brightness-levels", &length);
 114         if (!prop)
 115                 return -EINVAL;
 116
 117         data->max_brightness = length / sizeof(u32);
 118
 119         /* read brightness levels from DT property */
 120         if (data->max_brightness > 0) {
 121                 size_t size = sizeof(*data->levels) * data->max_brightness;
 122
 123                 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
 124                 if (!data->levels)
 125                         return -ENOMEM;
 126
 127                 ret = of_property_read_u32_array(node, "brightness-levels",
 128                                                  data->levels,
 129                                                  data->max_brightness);
 130                 if (ret < 0)
 131                         return ret;
 132
 133                 ret = of_property_read_u32(node, "default-brightness-level",
 134                                            &value);
 135                 if (ret < 0)
 136                         return ret;
 137
 138                 if (value >= data->max_brightness) {
 139                         dev_warn(dev, "invalid default brightness level: %u, using %u\n",
 140                                  value, data->max_brightness - 1);
 141                         value = data->max_brightness - 1;
 142                 }
 143
 144                 data->dft_brightness = value;
 145                 data->max_brightness--;
 146
 147                 ret = of_property_read_u32(node, "low-threshold-brightness",
 148                                            &value);
 149                 if (!ret)
 150                         data->lth_brightness = value;
 151         }
 152
 153         /*
 154          * TODO: Most users of this driver use a number of GPIOs to control
 155          *       backlight power. Support for specifying these needs to be
 156          *       added.
 157          */
 158
 159         return 0;
 160 }
 161
 162 static struct of_device_id pwm_backlight_of_match[] = {
 163         { .compatible = "pwm-backlight" },
 164         { }
 165 };
 166
 167 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 168 #else
 169 static int pwm_backlight_parse_dt(struct device *dev,
 170                                   struct platform_pwm_backlight_data *data)
 171 {
 172         return -ENODEV;
 173 }
 174 #endif
 175
 176 static int pwm_backlight_probe(struct platform_device *pdev)
 177 {
 178         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
 179         struct platform_pwm_backlight_data defdata;
 180         struct backlight_properties props;
 181         struct backlight_device *bl;
 182         struct pwm_bl_data *pb;
 183         unsigned int max;
 184         int ret;
 185
 186         if (!data) {
 187                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 188                 if (ret < 0) {
 189                         dev_err(&pdev->dev, "failed to find platform data\n");
 190                         return ret;
 191                 }
 192
 193                 data = &defdata;
 194         }
 195
 196         if (data->init) {
 197                 ret = data->init(&pdev->dev);
 198                 if (ret < 0)
 199                         return ret;
 200         }
 201
 202         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 203         if (!pb) {
 204                 dev_err(&pdev->dev, "no memory for state\n");
 205                 ret = -ENOMEM;
 206                 goto err_alloc;
 207         }
 208
 209         if (data->levels) {
 210                 max = data->levels[data->max_brightness];
 211                 pb->levels = data->levels;
 212         } else
 213                 max = data->max_brightness;
 214
 215         pb->notify = data->notify;
 216         pb->notify_after = data->notify_after;
 217         pb->check_fb = data->check_fb;
 218         pb->exit = data->exit;
 219         pb->dev = &pdev->dev;
 220
 221         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 222         if (IS_ERR(pb->pwm)) {
 223                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 224
 225                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 226                 if (IS_ERR(pb->pwm)) {
 227                         dev_err(&pdev->dev, "unable to request legacy PWM\n");
 228                         ret = PTR_ERR(pb->pwm);
 229                         goto err_alloc;
 230                 }
 231         }
 232
 233         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 234
 235         /*
 236          * The DT case will set the pwm_period_ns field to 0 and store the
 237          * period, parsed from the DT, in the PWM device. For the non-DT case,
 238          * set the period from platform data.
 239          */
 240         if (data->pwm_period_ns > 0)
 241                 pwm_set_period(pb->pwm, data->pwm_period_ns);
 242
 243         pb->period = pwm_get_period(pb->pwm);
 244         pb->lth_brightness = data->lth_brightness * (pb->period / max);
 245
 246         memset(&props, 0, sizeof(struct backlight_properties));
 247         props.type = BACKLIGHT_RAW;
 248         props.max_brightness = data->max_brightness;
 249         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 250                                        &pwm_backlight_ops, &props);
 251         if (IS_ERR(bl)) {
 252                 dev_err(&pdev->dev, "failed to register backlight\n");
 253                 ret = PTR_ERR(bl);
 254                 goto err_alloc;
 255         }
 256
 257         bl->props.brightness = data->dft_brightness;
 258         backlight_update_status(bl);
 259
 260         platform_set_drvdata(pdev, bl);
 261         return 0;
 262
 263 err_alloc:
 264         if (data->exit)
 265                 data->exit(&pdev->dev);
 266         return ret;
 267 }
 268
 269 static int pwm_backlight_remove(struct platform_device *pdev)
 270 {
 271         struct backlight_device *bl = platform_get_drvdata(pdev);
 272         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 273
 274         backlight_device_unregister(bl);
 275         pwm_config(pb->pwm, 0, pb->period);
 276         pwm_disable(pb->pwm);
 277         if (pb->exit)
 278                 pb->exit(&pdev->dev);
 279         return 0;
 280 }
 281
 282 #ifdef CONFIG_PM
 283 static int pwm_backlight_suspend(struct device *dev)
 284 {
 285         struct backlight_device *bl = dev_get_drvdata(dev);
 286         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 287
 288         if (pb->notify)
 289                 pb->notify(pb->dev, 0);
 290         pwm_config(pb->pwm, 0, pb->period);
 291         pwm_disable(pb->pwm);
 292         if (pb->notify_after)
 293                 pb->notify_after(pb->dev, 0);
 294         return 0;
 295 }
 296
 297 static int pwm_backlight_resume(struct device *dev)
 298 {
 299         struct backlight_device *bl = dev_get_drvdata(dev);
 300
 301         backlight_update_status(bl);
 302         return 0;
 303 }
 304
 305 static SIMPLE_DEV_PM_OPS(pwm_backlight_pm_ops, pwm_backlight_suspend,
 306                          pwm_backlight_resume);
 307
 308 #endif
 309
 310 static struct platform_driver pwm_backlight_driver = {
 311         .driver         = {
 312                 .name           = "pwm-backlight",
 313                 .owner          = THIS_MODULE,
 314 #ifdef CONFIG_PM
 315                 .pm             = &pwm_backlight_pm_ops,
 316 #endif
 317                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 318         },
 319         .probe          = pwm_backlight_probe,
 320         .remove         = pwm_backlight_remove,
 321 };
 322
 323 module_platform_driver(pwm_backlight_driver);
 324
 325 MODULE_DESCRIPTION("PWM based Backlight Driver");
 326 MODULE_LICENSE("GPL");
 327 MODULE_ALIAS("platform:pwm-backlight");
 328