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 <log.h>
  13 #include <malloc.h>
  14 #include <pwm.h>
  15 #include <asm/gpio.h>
  16 #include <linux/delay.h>
  17 #include <power/regulator.h>
  18
  19 /**
  20  * Private information for the PWM backlight
  21  *
  22  * If @num_levels is 0 then the levels are simple values with the backlight
  23  * value going between the minimum (default 0) and the maximum (default 255).
  24  * Otherwise the levels are an index into @levels (0..n-1).
  25  *
  26  * @reg: Regulator to enable to turn the backlight on (NULL if none)
  27  * @enable, GPIO to set to enable the backlight (can be missing)
  28  * @pwm: PWM to use to change the backlight brightness
  29  * @channel: PWM channel to use
  30  * @period_ns: Period of the backlight in nanoseconds
  31  * @levels: Levels for the backlight, or NULL if not using indexed levels
  32  * @num_levels: Number of levels
  33  * @cur_level: Current level for the backlight (index or value)
  34  * @default_level: Default level for the backlight (index or value)
  35  * @min_level: Minimum level of the backlight (full off)
  36  * @max_level: Maximum level of the backlight (full on)
  37  * @enabled: true if backlight is enabled
  38  */
  39 struct pwm_backlight_priv {
  40         struct udevice *reg;
  41         struct gpio_desc enable;
  42         struct udevice *pwm;
  43         uint channel;
  44         uint period_ns;
  45         /*
  46          * the polarity of one PWM
  47          * 0: normal polarity
  48          * 1: inverted polarity
  49          */
  50         bool polarity;
  51         u32 *levels;
  52         int num_levels;
  53         uint default_level;
  54         int cur_level;
  55         uint min_level;
  56         uint max_level;
  57         bool enabled;
  58 };
  59
  60 static int set_pwm(struct pwm_backlight_priv *priv)
  61 {
  62         uint duty_cycle;
  63         int ret;
  64
  65         if (priv->period_ns) {
  66                 duty_cycle = priv->period_ns * (priv->cur_level - priv->min_level) /
  67                         (priv->max_level - priv->min_level);
  68                 ret = pwm_set_config(priv->pwm, priv->channel, priv->period_ns,
  69                                      duty_cycle);
  70         } else {
  71                 /* PWM driver will internally scale these like the above. */
  72                 ret = pwm_set_config(priv->pwm, priv->channel,
  73                                      priv->max_level - priv->min_level,
  74                                      priv->cur_level - priv->min_level);
  75         }
  76         if (ret)
  77                 return log_ret(ret);
  78
  79         ret = pwm_set_invert(priv->pwm, priv->channel, priv->polarity);
  80         if (ret == -ENOSYS && !priv->polarity)
  81                 ret = 0;
  82
  83         return log_ret(ret);
  84 }
  85
  86 static int enable_sequence(struct udevice *dev, int seq)
  87 {
  88         struct pwm_backlight_priv *priv = dev_get_priv(dev);
  89         int ret;
  90
  91         switch (seq) {
  92         case 0:
  93                 if (priv->reg) {
  94                         __maybe_unused struct dm_regulator_uclass_plat
  95                                 *plat;
  96
  97                         plat = dev_get_uclass_plat(priv->reg);
  98                         log_debug("Enable '%s', regulator '%s'/'%s'\n",
  99                                   dev->name, priv->reg->name, plat->name);
 100                         ret = regulator_set_enable(priv->reg, true);
 101                         if (ret) {
 102                                 log_debug("Cannot enable regulator for PWM '%s'\n",
 103                                           dev->name);
 104                                 return log_ret(ret);
 105                         }
 106                         mdelay(120);
 107                 }
 108                 break;
 109         case 1:
 110                 mdelay(10);
 111                 dm_gpio_set_value(&priv->enable, 1);
 112                 break;
 113         }
 114
 115         return 0;
 116 }
 117
 118 static int pwm_backlight_enable(struct udevice *dev)
 119 {
 120         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 121         int ret;
 122
 123         ret = enable_sequence(dev, 0);
 124         if (ret)
 125                 return log_ret(ret);
 126         ret = set_pwm(priv);
 127         if (ret)
 128                 return log_ret(ret);
 129         ret = pwm_set_enable(priv->pwm, priv->channel, true);
 130         if (ret)
 131                 return log_ret(ret);
 132         ret = enable_sequence(dev, 1);
 133         if (ret)
 134                 return log_ret(ret);
 135         priv->enabled = true;
 136
 137         return 0;
 138 }
 139
 140 static int pwm_backlight_set_brightness(struct udevice *dev, int percent)
 141 {
 142         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 143         bool disable = false;
 144         int level;
 145         int ret;
 146
 147         if (!priv->enabled) {
 148                 ret = enable_sequence(dev, 0);
 149                 if (ret)
 150                         return log_ret(ret);
 151         }
 152         if (percent == BACKLIGHT_OFF) {
 153                 disable = true;
 154                 percent = 0;
 155         }
 156         if (percent == BACKLIGHT_DEFAULT) {
 157                 level = priv->default_level;
 158         } else {
 159                 if (priv->levels) {
 160                         level = priv->levels[percent * (priv->num_levels - 1)
 161                                 / 100];
 162                 } else {
 163                         level = priv->min_level +
 164                                 (priv->max_level - priv->min_level) *
 165                                 percent / 100;
 166                 }
 167         }
 168         priv->cur_level = level;
 169
 170         ret = set_pwm(priv);
 171         if (ret)
 172                 return log_ret(ret);
 173         if (!priv->enabled) {
 174                 ret = enable_sequence(dev, 1);
 175                 if (ret)
 176                         return log_ret(ret);
 177                 priv->enabled = true;
 178         }
 179         if (disable) {
 180                 dm_gpio_set_value(&priv->enable, 0);
 181                 if (priv->reg) {
 182                         ret = regulator_set_enable(priv->reg, false);
 183                         if (ret)
 184                                 return log_ret(ret);
 185                 }
 186                 priv->enabled = false;
 187         }
 188
 189         return 0;
 190 }
 191
 192 static int pwm_backlight_of_to_plat(struct udevice *dev)
 193 {
 194         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 195         struct ofnode_phandle_args args;
 196         int index, ret, count, len;
 197         const u32 *cell;
 198
 199         log_debug("start\n");
 200         ret = uclass_get_device_by_phandle(UCLASS_REGULATOR, dev,
 201                                            "power-supply", &priv->reg);
 202         if (ret)
 203                 log_debug("Cannot get power supply: ret=%d\n", ret);
 204         ret = gpio_request_by_name(dev, "enable-gpios", 0, &priv->enable,
 205                                    GPIOD_IS_OUT);
 206         if (ret) {
 207                 log_debug("Warning: cannot get enable GPIO: ret=%d\n", ret);
 208                 if (ret != -ENOENT)
 209                         return log_ret(ret);
 210         }
 211         ret = dev_read_phandle_with_args(dev, "pwms", "#pwm-cells", 0, 0,
 212                                          &args);
 213         if (ret) {
 214                 log_debug("Cannot get PWM phandle: ret=%d\n", ret);
 215                 return log_ret(ret);
 216         }
 217
 218         ret = uclass_get_device_by_ofnode(UCLASS_PWM, args.node, &priv->pwm);
 219         if (ret) {
 220                 log_debug("Cannot get PWM: ret=%d\n", ret);
 221                 return log_ret(ret);
 222         }
 223         if (args.args_count < 1)
 224                 return log_msg_ret("Not enough arguments to pwm\n", -EINVAL);
 225         priv->channel = args.args[0];
 226         if (args.args_count > 1)
 227                 priv->period_ns = args.args[1];
 228         if (args.args_count > 2)
 229                 priv->polarity = args.args[2];
 230
 231         index = dev_read_u32_default(dev, "default-brightness-level", 255);
 232         cell = dev_read_prop(dev, "brightness-levels", &len);
 233         count = len / sizeof(u32);
 234         if (cell && count > index) {
 235                 priv->levels = malloc(len);
 236                 if (!priv->levels)
 237                         return log_ret(-ENOMEM);
 238                 ret = dev_read_u32_array(dev, "brightness-levels", priv->levels,
 239                                          count);
 240                 if (ret)
 241                         return log_msg_ret("levels", ret);
 242                 priv->num_levels = count;
 243                 priv->default_level = priv->levels[index];
 244                 priv->max_level = priv->levels[count - 1];
 245         } else {
 246                 priv->default_level = index;
 247                 priv->max_level = 255;
 248         }
 249         priv->cur_level = priv->default_level;
 250         log_debug("done\n");
 251
 252
 253         return 0;
 254 }
 255
 256 static int pwm_backlight_probe(struct udevice *dev)
 257 {
 258         return 0;
 259 }
 260
 261 static const struct backlight_ops pwm_backlight_ops = {
 262         .enable         = pwm_backlight_enable,
 263         .set_brightness = pwm_backlight_set_brightness,
 264 };
 265
 266 static const struct udevice_id pwm_backlight_ids[] = {
 267         { .compatible = "pwm-backlight" },
 268         { }
 269 };
 270
 271 U_BOOT_DRIVER(pwm_backlight) = {
 272         .name   = "pwm_backlight",
 273         .id     = UCLASS_PANEL_BACKLIGHT,
 274         .of_match = pwm_backlight_ids,
 275         .ops    = &pwm_backlight_ops,
 276         .of_to_plat     = pwm_backlight_of_to_plat,
 277         .probe          = pwm_backlight_probe,
 278         .priv_auto      = sizeof(struct pwm_backlight_priv),
 279 };