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