drivers/video/pwm_backlight.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Copyright (c) 2016 Google, Inc
   4  * Written by Simon Glass <sjg@chromium.org>
   5  */
   6
   7 #define LOG_CATEGORY UCLASS_PANEL_BACKLIGHT
   8
   9 #include <common.h>
  10 #include <dm.h>
  11 #include <backlight.h>
  12 #include <malloc.h>
  13 #include <pwm.h>
  14 #include <asm/gpio.h>
  15 #include <power/regulator.h>
  16
  17 /**
  18  * Private information for the PWM backlight
  19  *
  20  * If @num_levels is 0 then the levels are simple values with the backlight
  21  * value going between the minimum (default 0) and the maximum (default 255).
  22  * Otherwise the levels are an index into @levels (0..n-1).
  23  *
  24  * @reg: Regulator to enable to turn the backlight on (NULL if none)
  25  * @enable, GPIO to set to enable the backlight (can be missing)
  26  * @pwm: PWM to use to change the backlight brightness
  27  * @channel: PWM channel to use
  28  * @period_ns: Period of the backlight in nanoseconds
  29  * @levels: Levels for the backlight, or NULL if not using indexed levels
  30  * @num_levels: Number of levels
  31  * @cur_level: Current level for the backlight (index or value)
  32  * @default_level: Default level for the backlight (index or value)
  33  * @min_level: Minimum level of the backlight (full off)
  34  * @min_level: Maximum level of the backlight (full on)
  35  * @enabled: true if backlight is enabled
  36  */
  37 struct pwm_backlight_priv {
  38         struct udevice *reg;
  39         struct gpio_desc enable;
  40         struct udevice *pwm;
  41         uint channel;
  42         uint period_ns;
  43         /*
  44          * the polarity of one PWM
  45          * 0: normal polarity
  46          * 1: inverted polarity
  47          */
  48         bool polarity;
  49         u32 *levels;
  50         int num_levels;
  51         uint default_level;
  52         int cur_level;
  53         uint min_level;
  54         uint max_level;
  55         bool enabled;
  56 };
  57
  58 static int set_pwm(struct pwm_backlight_priv *priv)
  59 {
  60         uint duty_cycle;
  61         int ret;
  62
  63         duty_cycle = priv->period_ns * (priv->cur_level - priv->min_level) /
  64                 (priv->max_level - priv->min_level + 1);
  65         ret = pwm_set_config(priv->pwm, priv->channel, priv->period_ns,
  66                              duty_cycle);
  67         if (ret)
  68                 return log_ret(ret);
  69
  70         ret = pwm_set_invert(priv->pwm, priv->channel, priv->polarity);
  71         if (ret == -ENOSYS && !priv->polarity)
  72                 ret = 0;
  73
  74         return log_ret(ret);
  75 }
  76
  77 static int enable_sequence(struct udevice *dev, int seq)
  78 {
  79         struct pwm_backlight_priv *priv = dev_get_priv(dev);
  80         int ret;
  81
  82         switch (seq) {
  83         case 0:
  84                 if (priv->reg) {
  85                         __maybe_unused struct dm_regulator_uclass_platdata
  86                                 *plat;
  87
  88                         plat = dev_get_uclass_platdata(priv->reg);
  89                         log_debug("Enable '%s', regulator '%s'/'%s'\n",
  90                                   dev->name, priv->reg->name, plat->name);
  91                         ret = regulator_set_enable(priv->reg, true);
  92                         if (ret) {
  93                                 log_debug("Cannot enable regulator for PWM '%s'\n",
  94                                           dev->name);
  95                                 return log_ret(ret);
  96                         }
  97                         mdelay(120);
  98                 }
  99                 break;
 100         case 1:
 101                 mdelay(10);
 102                 dm_gpio_set_value(&priv->enable, 1);
 103                 break;
 104         }
 105
 106         return 0;
 107 }
 108
 109 static int pwm_backlight_enable(struct udevice *dev)
 110 {
 111         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 112         int ret;
 113
 114         ret = enable_sequence(dev, 0);
 115         if (ret)
 116                 return log_ret(ret);
 117         ret = set_pwm(priv);
 118         if (ret)
 119                 return log_ret(ret);
 120         ret = pwm_set_enable(priv->pwm, priv->channel, true);
 121         if (ret)
 122                 return log_ret(ret);
 123         ret = enable_sequence(dev, 1);
 124         if (ret)
 125                 return log_ret(ret);
 126         priv->enabled = true;
 127
 128         return 0;
 129 }
 130
 131 static int pwm_backlight_set_brightness(struct udevice *dev, int percent)
 132 {
 133         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 134         bool disable = false;
 135         int level;
 136         int ret;
 137
 138         if (!priv->enabled) {
 139                 ret = enable_sequence(dev, 0);
 140                 if (ret)
 141                         return log_ret(ret);
 142         }
 143         if (percent == BACKLIGHT_OFF) {
 144                 disable = true;
 145                 percent = 0;
 146         }
 147         if (percent == BACKLIGHT_DEFAULT) {
 148                 level = priv->default_level;
 149         } else {
 150                 if (priv->levels) {
 151                         level = priv->levels[percent * (priv->num_levels - 1)
 152                                 / 100];
 153                 } else {
 154                         level = priv->min_level +
 155                                 (priv->max_level - priv->min_level) *
 156                                 percent / 100;
 157                 }
 158         }
 159         priv->cur_level = level;
 160
 161         ret = set_pwm(priv);
 162         if (ret)
 163                 return log_ret(ret);
 164         if (!priv->enabled) {
 165                 ret = enable_sequence(dev, 1);
 166                 if (ret)
 167                         return log_ret(ret);
 168                 priv->enabled = true;
 169         }
 170         if (disable) {
 171                 dm_gpio_set_value(&priv->enable, 0);
 172                 if (priv->reg) {
 173                         ret = regulator_set_enable(priv->reg, false);
 174                         if (ret)
 175                                 return log_ret(ret);
 176                 }
 177                 priv->enabled = false;
 178         }
 179
 180         return 0;
 181 }
 182
 183 static int pwm_backlight_ofdata_to_platdata(struct udevice *dev)
 184 {
 185         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 186         struct ofnode_phandle_args args;
 187         int index, ret, count, len;
 188         const u32 *cell;
 189
 190         log_debug("start\n");
 191         ret = uclass_get_device_by_phandle(UCLASS_REGULATOR, dev,
 192                                            "power-supply", &priv->reg);
 193         if (ret)
 194                 log_debug("Cannot get power supply: ret=%d\n", ret);
 195         ret = gpio_request_by_name(dev, "enable-gpios", 0, &priv->enable,
 196                                    GPIOD_IS_OUT);
 197         if (ret) {
 198                 log_debug("Warning: cannot get enable GPIO: ret=%d\n", ret);
 199                 if (ret != -ENOENT)
 200                         return log_ret(ret);
 201         }
 202         ret = dev_read_phandle_with_args(dev, "pwms", "#pwm-cells", 0, 0,
 203                                          &args);
 204         if (ret) {
 205                 log_debug("Cannot get PWM phandle: ret=%d\n", ret);
 206                 return log_ret(ret);
 207         }
 208
 209         ret = uclass_get_device_by_ofnode(UCLASS_PWM, args.node, &priv->pwm);
 210         if (ret) {
 211                 log_debug("Cannot get PWM: ret=%d\n", ret);
 212                 return log_ret(ret);
 213         }
 214         if (args.args_count < 2)
 215                 return log_msg_ret("Not enough arguments to pwm\n", -EINVAL);
 216         priv->channel = args.args[0];
 217         priv->period_ns = args.args[1];
 218         if (args.args_count > 2)
 219                 priv->polarity = args.args[2];
 220
 221         index = dev_read_u32_default(dev, "default-brightness-level", 255);
 222         cell = dev_read_prop(dev, "brightness-levels", &len);
 223         count = len / sizeof(u32);
 224         if (cell && count > index) {
 225                 priv->levels = malloc(len);
 226                 if (!priv->levels)
 227                         return log_ret(-ENOMEM);
 228                 dev_read_u32_array(dev, "brightness-levels", priv->levels,
 229                                    count);
 230                 priv->num_levels = count;
 231                 priv->default_level = priv->levels[index];
 232                 priv->max_level = priv->levels[count - 1];
 233         } else {
 234                 priv->default_level = index;
 235                 priv->max_level = 255;
 236         }
 237         priv->cur_level = priv->default_level;
 238         log_debug("done\n");
 239
 240
 241         return 0;
 242 }
 243
 244 static int pwm_backlight_probe(struct udevice *dev)
 245 {
 246         return 0;
 247 }
 248
 249 static const struct backlight_ops pwm_backlight_ops = {
 250         .enable         = pwm_backlight_enable,
 251         .set_brightness = pwm_backlight_set_brightness,
 252 };
 253
 254 static const struct udevice_id pwm_backlight_ids[] = {
 255         { .compatible = "pwm-backlight" },
 256         { }
 257 };
 258
 259 U_BOOT_DRIVER(pwm_backlight) = {
 260         .name   = "pwm_backlight",
 261         .id     = UCLASS_PANEL_BACKLIGHT,
 262         .of_match = pwm_backlight_ids,
 263         .ops    = &pwm_backlight_ops,
 264         .ofdata_to_platdata     = pwm_backlight_ofdata_to_platdata,
 265         .probe          = pwm_backlight_probe,
 266         .priv_auto_alloc_size   = sizeof(struct pwm_backlight_priv),
 267 };