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
 148         /*
 149          * TODO: Most users of this driver use a number of GPIOs to control
 150          *       backlight power. Support for specifying these needs to be
 151          *       added.
 152          */
 153
 154         return 0;
 155 }
 156
 157 static struct of_device_id pwm_backlight_of_match[] = {
 158         { .compatible = "pwm-backlight" },
 159         { }
 160 };
 161
 162 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
 163 #else
 164 static int pwm_backlight_parse_dt(struct device *dev,
 165                                   struct platform_pwm_backlight_data *data)
 166 {
 167         return -ENODEV;
 168 }
 169 #endif
 170
 171 static int pwm_backlight_probe(struct platform_device *pdev)
 172 {
 173         struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
 174         struct platform_pwm_backlight_data defdata;
 175         struct backlight_properties props;
 176         struct backlight_device *bl;
 177         struct pwm_bl_data *pb;
 178         unsigned int max;
 179         int ret;
 180
 181         if (!data) {
 182                 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
 183                 if (ret < 0) {
 184                         dev_err(&pdev->dev, "failed to find platform data\n");
 185                         return ret;
 186                 }
 187
 188                 data = &defdata;
 189         }
 190
 191         if (data->init) {
 192                 ret = data->init(&pdev->dev);
 193                 if (ret < 0)
 194                         return ret;
 195         }
 196
 197         pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
 198         if (!pb) {
 199                 dev_err(&pdev->dev, "no memory for state\n");
 200                 ret = -ENOMEM;
 201                 goto err_alloc;
 202         }
 203
 204         if (data->levels) {
 205                 max = data->levels[data->max_brightness];
 206                 pb->levels = data->levels;
 207         } else
 208                 max = data->max_brightness;
 209
 210         pb->notify = data->notify;
 211         pb->notify_after = data->notify_after;
 212         pb->check_fb = data->check_fb;
 213         pb->exit = data->exit;
 214         pb->dev = &pdev->dev;
 215
 216         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
 217         if (IS_ERR(pb->pwm)) {
 218                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 219
 220                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
 221                 if (IS_ERR(pb->pwm)) {
 222                         dev_err(&pdev->dev, "unable to request legacy PWM\n");
 223                         ret = PTR_ERR(pb->pwm);
 224                         goto err_alloc;
 225                 }
 226         }
 227
 228         dev_dbg(&pdev->dev, "got pwm for backlight\n");
 229
 230         /*
 231          * The DT case will set the pwm_period_ns field to 0 and store the
 232          * period, parsed from the DT, in the PWM device. For the non-DT case,
 233          * set the period from platform data.
 234          */
 235         if (data->pwm_period_ns > 0)
 236                 pwm_set_period(pb->pwm, data->pwm_period_ns);
 237
 238         pb->period = pwm_get_period(pb->pwm);
 239         pb->lth_brightness = data->lth_brightness * (pb->period / max);
 240
 241         memset(&props, 0, sizeof(struct backlight_properties));
 242         props.type = BACKLIGHT_RAW;
 243         props.max_brightness = data->max_brightness;
 244         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
 245                                        &pwm_backlight_ops, &props);
 246         if (IS_ERR(bl)) {
 247                 dev_err(&pdev->dev, "failed to register backlight\n");
 248                 ret = PTR_ERR(bl);
 249                 goto err_alloc;
 250         }
 251
 252         bl->props.brightness = data->dft_brightness;
 253         backlight_update_status(bl);
 254
 255         platform_set_drvdata(pdev, bl);
 256         return 0;
 257
 258 err_alloc:
 259         if (data->exit)
 260                 data->exit(&pdev->dev);
 261         return ret;
 262 }
 263
 264 static int pwm_backlight_remove(struct platform_device *pdev)
 265 {
 266         struct backlight_device *bl = platform_get_drvdata(pdev);
 267         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 268
 269         backlight_device_unregister(bl);
 270         pwm_config(pb->pwm, 0, pb->period);
 271         pwm_disable(pb->pwm);
 272         if (pb->exit)
 273                 pb->exit(&pdev->dev);
 274         return 0;
 275 }
 276
 277 #ifdef CONFIG_PM
 278 static int pwm_backlight_suspend(struct device *dev)
 279 {
 280         struct backlight_device *bl = dev_get_drvdata(dev);
 281         struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 282
 283         if (pb->notify)
 284                 pb->notify(pb->dev, 0);
 285         pwm_config(pb->pwm, 0, pb->period);
 286         pwm_disable(pb->pwm);
 287         if (pb->notify_after)
 288                 pb->notify_after(pb->dev, 0);
 289         return 0;
 290 }
 291
 292 static int pwm_backlight_resume(struct device *dev)
 293 {
 294         struct backlight_device *bl = dev_get_drvdata(dev);
 295
 296         backlight_update_status(bl);
 297         return 0;
 298 }
 299
 300 static SIMPLE_DEV_PM_OPS(pwm_backlight_pm_ops, pwm_backlight_suspend,
 301                          pwm_backlight_resume);
 302
 303 #endif
 304
 305 static struct platform_driver pwm_backlight_driver = {
 306         .driver         = {
 307                 .name           = "pwm-backlight",
 308                 .owner          = THIS_MODULE,
 309 #ifdef CONFIG_PM
 310                 .pm             = &pwm_backlight_pm_ops,
 311 #endif
 312                 .of_match_table = of_match_ptr(pwm_backlight_of_match),
 313         },
 314         .probe          = pwm_backlight_probe,
 315         .remove         = pwm_backlight_remove,
 316 };
 317
 318 module_platform_driver(pwm_backlight_driver);
 319
 320 MODULE_DESCRIPTION("PWM based Backlight Driver");
 321 MODULE_LICENSE("GPL");
 322 MODULE_ALIAS("platform:pwm-backlight");
 323