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 <linux/math64.h>
  18 #include <power/regulator.h>
  19
  20 /**
  21  * Private information for the PWM backlight
  22  *
  23  * If @num_levels is 0 then the levels are simple values with the backlight
  24  * value going between the minimum (default 0) and the maximum (default 255).
  25  * Otherwise the levels are an index into @levels (0..n-1).
  26  *
  27  * @reg: Regulator to enable to turn the backlight on (NULL if none)
  28  * @enable, GPIO to set to enable the backlight (can be missing)
  29  * @pwm: PWM to use to change the backlight brightness
  30  * @channel: PWM channel to use
  31  * @period_ns: Period of the backlight in nanoseconds
  32  * @levels: Levels for the backlight, or NULL if not using indexed levels
  33  * @num_levels: Number of levels
  34  * @cur_level: Current level for the backlight (index or value)
  35  * @default_level: Default level for the backlight (index or value)
  36  * @min_level: Minimum level of the backlight (full off)
  37  * @max_level: Maximum level of the backlight (full on)
  38  * @enabled: true if backlight is enabled
  39  */
  40 struct pwm_backlight_priv {
  41         struct udevice *reg;
  42         struct gpio_desc enable;
  43         struct udevice *pwm;
  44         uint channel;
  45         uint period_ns;
  46         /*
  47          * the polarity of one PWM
  48          * 0: normal polarity
  49          * 1: inverted polarity
  50          */
  51         bool polarity;
  52         u32 *levels;
  53         int num_levels;
  54         uint default_level;
  55         int cur_level;
  56         uint min_level;
  57         uint max_level;
  58         bool enabled;
  59 };
  60
  61 static int set_pwm(struct pwm_backlight_priv *priv)
  62 {
  63         u64 width;
  64         uint duty_cycle;
  65         int ret;
  66
  67         if (priv->period_ns) {
  68                 width = priv->period_ns * (priv->cur_level - priv->min_level);
  69                 duty_cycle = div_u64(width,
  70                                      (priv->max_level - priv->min_level));
  71                 ret = pwm_set_config(priv->pwm, priv->channel, priv->period_ns,
  72                                      duty_cycle);
  73         } else {
  74                 /* PWM driver will internally scale these like the above. */
  75                 ret = pwm_set_config(priv->pwm, priv->channel,
  76                                      priv->max_level - priv->min_level,
  77                                      priv->cur_level - priv->min_level);
  78         }
  79         if (ret)
  80                 return log_ret(ret);
  81
  82         ret = pwm_set_invert(priv->pwm, priv->channel, priv->polarity);
  83         if (ret == -ENOSYS && !priv->polarity)
  84                 ret = 0;
  85
  86         return log_ret(ret);
  87 }
  88
  89 static int enable_sequence(struct udevice *dev, int seq)
  90 {
  91         struct pwm_backlight_priv *priv = dev_get_priv(dev);
  92         int ret;
  93
  94         switch (seq) {
  95         case 0:
  96                 if (priv->reg) {
  97                         __maybe_unused struct dm_regulator_uclass_plat
  98                                 *plat;
  99
 100                         plat = dev_get_uclass_plat(priv->reg);
 101                         log_debug("Enable '%s', regulator '%s'/'%s'\n",
 102                                   dev->name, priv->reg->name, plat->name);
 103                         ret = regulator_set_enable(priv->reg, true);
 104                         if (ret) {
 105                                 log_debug("Cannot enable regulator for PWM '%s'\n",
 106                                           dev->name);
 107                                 return log_ret(ret);
 108                         }
 109                         mdelay(120);
 110                 }
 111                 break;
 112         case 1:
 113                 mdelay(10);
 114                 dm_gpio_set_value(&priv->enable, 1);
 115                 break;
 116         }
 117
 118         return 0;
 119 }
 120
 121 static int pwm_backlight_enable(struct udevice *dev)
 122 {
 123         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 124         int ret;
 125
 126         ret = enable_sequence(dev, 0);
 127         if (ret)
 128                 return log_ret(ret);
 129         ret = set_pwm(priv);
 130         if (ret)
 131                 return log_ret(ret);
 132         ret = pwm_set_enable(priv->pwm, priv->channel, true);
 133         if (ret)
 134                 return log_ret(ret);
 135         ret = enable_sequence(dev, 1);
 136         if (ret)
 137                 return log_ret(ret);
 138         priv->enabled = true;
 139
 140         return 0;
 141 }
 142
 143 static int pwm_backlight_set_brightness(struct udevice *dev, int percent)
 144 {
 145         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 146         bool disable = false;
 147         int level;
 148         int ret;
 149
 150         if (!priv->enabled) {
 151                 ret = enable_sequence(dev, 0);
 152                 if (ret)
 153                         return log_ret(ret);
 154         }
 155         if (percent == BACKLIGHT_OFF) {
 156                 disable = true;
 157                 percent = 0;
 158         }
 159         if (percent == BACKLIGHT_DEFAULT) {
 160                 level = priv->default_level;
 161         } else {
 162                 if (priv->levels) {
 163                         level = priv->levels[percent * (priv->num_levels - 1)
 164                                 / 100];
 165                 } else {
 166                         level = priv->min_level +
 167                                 (priv->max_level - priv->min_level) *
 168                                 percent / 100;
 169                 }
 170         }
 171         priv->cur_level = level;
 172
 173         ret = set_pwm(priv);
 174         if (ret)
 175                 return log_ret(ret);
 176         if (!priv->enabled) {
 177                 ret = enable_sequence(dev, 1);
 178                 if (ret)
 179                         return log_ret(ret);
 180                 priv->enabled = true;
 181         }
 182         if (disable) {
 183                 dm_gpio_set_value(&priv->enable, 0);
 184                 if (priv->reg) {
 185                         ret = regulator_set_enable(priv->reg, false);
 186                         if (ret)
 187                                 return log_ret(ret);
 188                 }
 189                 priv->enabled = false;
 190         }
 191
 192         return 0;
 193 }
 194
 195 static int pwm_backlight_of_to_plat(struct udevice *dev)
 196 {
 197         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 198         struct ofnode_phandle_args args;
 199         int index, ret, count, len;
 200         const u32 *cell;
 201
 202         log_debug("start\n");
 203         ret = uclass_get_device_by_phandle(UCLASS_REGULATOR, dev,
 204                                            "power-supply", &priv->reg);
 205         if (ret)
 206                 log_debug("Cannot get power supply: ret=%d\n", ret);
 207         ret = gpio_request_by_name(dev, "enable-gpios", 0, &priv->enable,
 208                                    GPIOD_IS_OUT);
 209         if (ret) {
 210                 log_debug("Warning: cannot get enable GPIO: ret=%d\n", ret);
 211                 if (ret != -ENOENT)
 212                         return log_ret(ret);
 213         }
 214         ret = dev_read_phandle_with_args(dev, "pwms", "#pwm-cells", 0, 0,
 215                                          &args);
 216         if (ret) {
 217                 log_debug("Cannot get PWM phandle: ret=%d\n", ret);
 218                 return log_ret(ret);
 219         }
 220
 221         ret = uclass_get_device_by_ofnode(UCLASS_PWM, args.node, &priv->pwm);
 222         if (ret) {
 223                 log_debug("Cannot get PWM: ret=%d\n", ret);
 224                 return log_ret(ret);
 225         }
 226         if (args.args_count < 1)
 227                 return log_msg_ret("Not enough arguments to pwm\n", -EINVAL);
 228         priv->channel = args.args[0];
 229         if (args.args_count > 1)
 230                 priv->period_ns = args.args[1];
 231         if (args.args_count > 2)
 232                 priv->polarity = args.args[2];
 233
 234         index = dev_read_u32_default(dev, "default-brightness-level", 255);
 235         cell = dev_read_prop(dev, "brightness-levels", &len);
 236         count = len / sizeof(u32);
 237         if (cell && count > index) {
 238                 priv->levels = malloc(len);
 239                 if (!priv->levels)
 240                         return log_ret(-ENOMEM);
 241                 ret = dev_read_u32_array(dev, "brightness-levels", priv->levels,
 242                                          count);
 243                 if (ret)
 244                         return log_msg_ret("levels", ret);
 245                 priv->num_levels = count;
 246                 priv->default_level = priv->levels[index];
 247                 priv->max_level = priv->levels[count - 1];
 248         } else {
 249                 priv->default_level = index;
 250                 priv->max_level = 255;
 251         }
 252         priv->cur_level = priv->default_level;
 253         log_debug("done\n");
 254
 255
 256         return 0;
 257 }
 258
 259 static int pwm_backlight_probe(struct udevice *dev)
 260 {
 261         return 0;
 262 }
 263
 264 static const struct backlight_ops pwm_backlight_ops = {
 265         .enable         = pwm_backlight_enable,
 266         .set_brightness = pwm_backlight_set_brightness,
 267 };
 268
 269 static const struct udevice_id pwm_backlight_ids[] = {
 270         { .compatible = "pwm-backlight" },
 271         { }
 272 };
 273
 274 U_BOOT_DRIVER(pwm_backlight) = {
 275         .name   = "pwm_backlight",
 276         .id     = UCLASS_PANEL_BACKLIGHT,
 277         .of_match = pwm_backlight_ids,
 278         .ops    = &pwm_backlight_ops,
 279         .of_to_plat     = pwm_backlight_of_to_plat,
 280         .probe          = pwm_backlight_probe,
 281         .priv_auto      = sizeof(struct pwm_backlight_priv),
 282 };