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