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  * @min_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         duty_cycle = priv->period_ns * (priv->cur_level - priv->min_level) /
  66                 (priv->max_level - priv->min_level + 1);
  67         ret = pwm_set_config(priv->pwm, priv->channel, priv->period_ns,
  68                              duty_cycle);
  69         if (ret)
  70                 return log_ret(ret);
  71
  72         ret = pwm_set_invert(priv->pwm, priv->channel, priv->polarity);
  73         if (ret == -ENOSYS && !priv->polarity)
  74                 ret = 0;
  75
  76         return log_ret(ret);
  77 }
  78
  79 static int enable_sequence(struct udevice *dev, int seq)
  80 {
  81         struct pwm_backlight_priv *priv = dev_get_priv(dev);
  82         int ret;
  83
  84         switch (seq) {
  85         case 0:
  86                 if (priv->reg) {
  87                         __maybe_unused struct dm_regulator_uclass_platdata
  88                                 *plat;
  89
  90                         plat = dev_get_uclass_platdata(priv->reg);
  91                         log_debug("Enable '%s', regulator '%s'/'%s'\n",
  92                                   dev->name, priv->reg->name, plat->name);
  93                         ret = regulator_set_enable(priv->reg, true);
  94                         if (ret) {
  95                                 log_debug("Cannot enable regulator for PWM '%s'\n",
  96                                           dev->name);
  97                                 return log_ret(ret);
  98                         }
  99                         mdelay(120);
 100                 }
 101                 break;
 102         case 1:
 103                 mdelay(10);
 104                 dm_gpio_set_value(&priv->enable, 1);
 105                 break;
 106         }
 107
 108         return 0;
 109 }
 110
 111 static int pwm_backlight_enable(struct udevice *dev)
 112 {
 113         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 114         int ret;
 115
 116         ret = enable_sequence(dev, 0);
 117         if (ret)
 118                 return log_ret(ret);
 119         ret = set_pwm(priv);
 120         if (ret)
 121                 return log_ret(ret);
 122         ret = pwm_set_enable(priv->pwm, priv->channel, true);
 123         if (ret)
 124                 return log_ret(ret);
 125         ret = enable_sequence(dev, 1);
 126         if (ret)
 127                 return log_ret(ret);
 128         priv->enabled = true;
 129
 130         return 0;
 131 }
 132
 133 static int pwm_backlight_set_brightness(struct udevice *dev, int percent)
 134 {
 135         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 136         bool disable = false;
 137         int level;
 138         int ret;
 139
 140         if (!priv->enabled) {
 141                 ret = enable_sequence(dev, 0);
 142                 if (ret)
 143                         return log_ret(ret);
 144         }
 145         if (percent == BACKLIGHT_OFF) {
 146                 disable = true;
 147                 percent = 0;
 148         }
 149         if (percent == BACKLIGHT_DEFAULT) {
 150                 level = priv->default_level;
 151         } else {
 152                 if (priv->levels) {
 153                         level = priv->levels[percent * (priv->num_levels - 1)
 154                                 / 100];
 155                 } else {
 156                         level = priv->min_level +
 157                                 (priv->max_level - priv->min_level) *
 158                                 percent / 100;
 159                 }
 160         }
 161         priv->cur_level = level;
 162
 163         ret = set_pwm(priv);
 164         if (ret)
 165                 return log_ret(ret);
 166         if (!priv->enabled) {
 167                 ret = enable_sequence(dev, 1);
 168                 if (ret)
 169                         return log_ret(ret);
 170                 priv->enabled = true;
 171         }
 172         if (disable) {
 173                 dm_gpio_set_value(&priv->enable, 0);
 174                 if (priv->reg) {
 175                         ret = regulator_set_enable(priv->reg, false);
 176                         if (ret)
 177                                 return log_ret(ret);
 178                 }
 179                 priv->enabled = false;
 180         }
 181
 182         return 0;
 183 }
 184
 185 static int pwm_backlight_ofdata_to_platdata(struct udevice *dev)
 186 {
 187         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 188         struct ofnode_phandle_args args;
 189         int index, ret, count, len;
 190         const u32 *cell;
 191
 192         log_debug("start\n");
 193         ret = uclass_get_device_by_phandle(UCLASS_REGULATOR, dev,
 194                                            "power-supply", &priv->reg);
 195         if (ret)
 196                 log_debug("Cannot get power supply: ret=%d\n", ret);
 197         ret = gpio_request_by_name(dev, "enable-gpios", 0, &priv->enable,
 198                                    GPIOD_IS_OUT);
 199         if (ret) {
 200                 log_debug("Warning: cannot get enable GPIO: ret=%d\n", ret);
 201                 if (ret != -ENOENT)
 202                         return log_ret(ret);
 203         }
 204         ret = dev_read_phandle_with_args(dev, "pwms", "#pwm-cells", 0, 0,
 205                                          &args);
 206         if (ret) {
 207                 log_debug("Cannot get PWM phandle: ret=%d\n", ret);
 208                 return log_ret(ret);
 209         }
 210
 211         ret = uclass_get_device_by_ofnode(UCLASS_PWM, args.node, &priv->pwm);
 212         if (ret) {
 213                 log_debug("Cannot get PWM: ret=%d\n", ret);
 214                 return log_ret(ret);
 215         }
 216         if (args.args_count < 2)
 217                 return log_msg_ret("Not enough arguments to pwm\n", -EINVAL);
 218         priv->channel = args.args[0];
 219         priv->period_ns = args.args[1];
 220         if (args.args_count > 2)
 221                 priv->polarity = args.args[2];
 222
 223         index = dev_read_u32_default(dev, "default-brightness-level", 255);
 224         cell = dev_read_prop(dev, "brightness-levels", &len);
 225         count = len / sizeof(u32);
 226         if (cell && count > index) {
 227                 priv->levels = malloc(len);
 228                 if (!priv->levels)
 229                         return log_ret(-ENOMEM);
 230                 dev_read_u32_array(dev, "brightness-levels", priv->levels,
 231                                    count);
 232                 priv->num_levels = count;
 233                 priv->default_level = priv->levels[index];
 234                 priv->max_level = priv->levels[count - 1];
 235         } else {
 236                 priv->default_level = index;
 237                 priv->max_level = 255;
 238         }
 239         priv->cur_level = priv->default_level;
 240         log_debug("done\n");
 241
 242
 243         return 0;
 244 }
 245
 246 static int pwm_backlight_probe(struct udevice *dev)
 247 {
 248         return 0;
 249 }
 250
 251 static const struct backlight_ops pwm_backlight_ops = {
 252         .enable         = pwm_backlight_enable,
 253         .set_brightness = pwm_backlight_set_brightness,
 254 };
 255
 256 static const struct udevice_id pwm_backlight_ids[] = {
 257         { .compatible = "pwm-backlight" },
 258         { }
 259 };
 260
 261 U_BOOT_DRIVER(pwm_backlight) = {
 262         .name   = "pwm_backlight",
 263         .id     = UCLASS_PANEL_BACKLIGHT,
 264         .of_match = pwm_backlight_ids,
 265         .ops    = &pwm_backlight_ops,
 266         .ofdata_to_platdata     = pwm_backlight_ofdata_to_platdata,
 267         .probe          = pwm_backlight_probe,
 268         .priv_auto_alloc_size   = sizeof(struct pwm_backlight_priv),
 269 };