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