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