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         u32 *levels;
  43         int num_levels;
  44         uint default_level;
  45         int cur_level;
  46         uint min_level;
  47         uint max_level;
  48         bool enabled;
  49 };
  50
  51 static int set_pwm(struct pwm_backlight_priv *priv)
  52 {
  53         uint duty_cycle;
  54         int ret;
  55
  56         duty_cycle = priv->period_ns * (priv->cur_level - priv->min_level) /
  57                 (priv->max_level - priv->min_level + 1);
  58         ret = pwm_set_config(priv->pwm, priv->channel, priv->period_ns,
  59                              duty_cycle);
  60
  61         return log_ret(ret);
  62 }
  63
  64 static int enable_sequence(struct udevice *dev, int seq)
  65 {
  66         struct pwm_backlight_priv *priv = dev_get_priv(dev);
  67         int ret;
  68
  69         switch (seq) {
  70         case 0:
  71                 if (priv->reg) {
  72                         __maybe_unused struct dm_regulator_uclass_platdata
  73                                 *plat;
  74
  75                         plat = dev_get_uclass_platdata(priv->reg);
  76                         log_debug("Enable '%s', regulator '%s'/'%s'\n",
  77                                   dev->name, priv->reg->name, plat->name);
  78                         ret = regulator_set_enable(priv->reg, true);
  79                         if (ret) {
  80                                 log_debug("Cannot enable regulator for PWM '%s'\n",
  81                                           dev->name);
  82                                 return log_ret(ret);
  83                         }
  84                         mdelay(120);
  85                 }
  86                 break;
  87         case 1:
  88                 mdelay(10);
  89                 dm_gpio_set_value(&priv->enable, 1);
  90                 break;
  91         }
  92
  93         return 0;
  94 }
  95
  96 static int pwm_backlight_enable(struct udevice *dev)
  97 {
  98         struct pwm_backlight_priv *priv = dev_get_priv(dev);
  99         int ret;
 100
 101         ret = enable_sequence(dev, 0);
 102         if (ret)
 103                 return log_ret(ret);
 104         ret = set_pwm(priv);
 105         if (ret)
 106                 return log_ret(ret);
 107         ret = pwm_set_enable(priv->pwm, priv->channel, true);
 108         if (ret)
 109                 return log_ret(ret);
 110         ret = enable_sequence(dev, 1);
 111         if (ret)
 112                 return log_ret(ret);
 113         priv->enabled = true;
 114
 115         return 0;
 116 }
 117
 118 static int pwm_backlight_set_brightness(struct udevice *dev, int percent)
 119 {
 120         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 121         bool disable = false;
 122         int level;
 123         int ret;
 124
 125         if (!priv->enabled) {
 126                 ret = enable_sequence(dev, 0);
 127                 if (ret)
 128                         return log_ret(ret);
 129         }
 130         if (percent == BACKLIGHT_OFF) {
 131                 disable = true;
 132                 percent = 0;
 133         }
 134         if (percent == BACKLIGHT_DEFAULT) {
 135                 level = priv->default_level;
 136         } else {
 137                 if (priv->levels) {
 138                         level = priv->levels[percent * (priv->num_levels - 1)
 139                                 / 100];
 140                 } else {
 141                         level = priv->min_level +
 142                                 (priv->max_level - priv->min_level) *
 143                                 percent / 100;
 144                 }
 145         }
 146         priv->cur_level = level;
 147
 148         ret = set_pwm(priv);
 149         if (ret)
 150                 return log_ret(ret);
 151         if (!priv->enabled) {
 152                 ret = enable_sequence(dev, 1);
 153                 if (ret)
 154                         return log_ret(ret);
 155                 priv->enabled = true;
 156         }
 157         if (disable) {
 158                 dm_gpio_set_value(&priv->enable, 0);
 159                 if (priv->reg) {
 160                         ret = regulator_set_enable(priv->reg, false);
 161                         if (ret)
 162                                 return log_ret(ret);
 163                 }
 164                 priv->enabled = false;
 165         }
 166
 167         return 0;
 168 }
 169
 170 static int pwm_backlight_ofdata_to_platdata(struct udevice *dev)
 171 {
 172         struct pwm_backlight_priv *priv = dev_get_priv(dev);
 173         struct ofnode_phandle_args args;
 174         int index, ret, count, len;
 175         const u32 *cell;
 176
 177         log_debug("start\n");
 178         ret = uclass_get_device_by_phandle(UCLASS_REGULATOR, dev,
 179                                            "power-supply", &priv->reg);
 180         if (ret)
 181                 log_debug("Cannot get power supply: ret=%d\n", ret);
 182         ret = gpio_request_by_name(dev, "enable-gpios", 0, &priv->enable,
 183                                    GPIOD_IS_OUT);
 184         if (ret) {
 185                 log_debug("Warning: cannot get enable GPIO: ret=%d\n", ret);
 186                 if (ret != -ENOENT)
 187                         return log_ret(ret);
 188         }
 189         ret = dev_read_phandle_with_args(dev, "pwms", "#pwm-cells", 0, 0,
 190                                          &args);
 191         if (ret) {
 192                 log_debug("Cannot get PWM phandle: ret=%d\n", ret);
 193                 return log_ret(ret);
 194         }
 195
 196         ret = uclass_get_device_by_ofnode(UCLASS_PWM, args.node, &priv->pwm);
 197         if (ret) {
 198                 log_debug("Cannot get PWM: ret=%d\n", ret);
 199                 return log_ret(ret);
 200         }
 201         if (args.args_count < 2)
 202                 return log_msg_ret("Not enough arguments to pwm\n", -EINVAL);
 203         priv->channel = args.args[0];
 204         priv->period_ns = args.args[1];
 205
 206         index = dev_read_u32_default(dev, "default-brightness-level", 255);
 207         cell = dev_read_prop(dev, "brightness-levels", &len);
 208         count = len / sizeof(u32);
 209         if (cell && count > index) {
 210                 priv->levels = malloc(len);
 211                 if (!priv->levels)
 212                         return log_ret(-ENOMEM);
 213                 dev_read_u32_array(dev, "brightness-levels", priv->levels,
 214                                    count);
 215                 priv->num_levels = count;
 216                 priv->default_level = priv->levels[index];
 217                 priv->max_level = priv->levels[count - 1];
 218         } else {
 219                 priv->default_level = index;
 220                 priv->max_level = 255;
 221         }
 222         priv->cur_level = priv->default_level;
 223         log_debug("done\n");
 224
 225
 226         return 0;
 227 }
 228
 229 static int pwm_backlight_probe(struct udevice *dev)
 230 {
 231         return 0;
 232 }
 233
 234 static const struct backlight_ops pwm_backlight_ops = {
 235         .enable         = pwm_backlight_enable,
 236         .set_brightness = pwm_backlight_set_brightness,
 237 };
 238
 239 static const struct udevice_id pwm_backlight_ids[] = {
 240         { .compatible = "pwm-backlight" },
 241         { }
 242 };
 243
 244 U_BOOT_DRIVER(pwm_backlight) = {
 245         .name   = "pwm_backlight",
 246         .id     = UCLASS_PANEL_BACKLIGHT,
 247         .of_match = pwm_backlight_ids,
 248         .ops    = &pwm_backlight_ops,
 249         .ofdata_to_platdata     = pwm_backlight_ofdata_to_platdata,
 250         .probe          = pwm_backlight_probe,
 251         .priv_auto_alloc_size   = sizeof(struct pwm_backlight_priv),
 252 };