1 // SPDX-License-Identifier: GPL-2.0+
3 * Copyright (c) 2016 Google, Inc
4 * Written by Simon Glass <sjg@chromium.org>
7 #define LOG_CATEGORY UCLASS_PANEL_BACKLIGHT
11 #include <backlight.h>
16 #include <linux/delay.h>
17 #include <power/regulator.h>
20 * Private information for the PWM backlight
22 * If @num_levels is 0 then the levels are simple values with the backlight
23 * value going between the minimum (default 0) and the maximum (default 255).
24 * Otherwise the levels are an index into @levels (0..n-1).
26 * @reg: Regulator to enable to turn the backlight on (NULL if none)
27 * @enable, GPIO to set to enable the backlight (can be missing)
28 * @pwm: PWM to use to change the backlight brightness
29 * @channel: PWM channel to use
30 * @period_ns: Period of the backlight in nanoseconds
31 * @levels: Levels for the backlight, or NULL if not using indexed levels
32 * @num_levels: Number of levels
33 * @cur_level: Current level for the backlight (index or value)
34 * @default_level: Default level for the backlight (index or value)
35 * @min_level: Minimum level of the backlight (full off)
36 * @max_level: Maximum level of the backlight (full on)
37 * @enabled: true if backlight is enabled
39 struct pwm_backlight_priv {
41 struct gpio_desc enable;
46 * the polarity of one PWM
48 * 1: inverted polarity
60 static int set_pwm(struct pwm_backlight_priv *priv)
65 if (priv->period_ns) {
66 duty_cycle = priv->period_ns * (priv->cur_level - priv->min_level) /
67 (priv->max_level - priv->min_level);
68 ret = pwm_set_config(priv->pwm, priv->channel, priv->period_ns,
71 /* PWM driver will internally scale these like the above. */
72 ret = pwm_set_config(priv->pwm, priv->channel,
73 priv->max_level - priv->min_level,
74 priv->cur_level - priv->min_level);
79 ret = pwm_set_invert(priv->pwm, priv->channel, priv->polarity);
80 if (ret == -ENOSYS && !priv->polarity)
86 static int enable_sequence(struct udevice *dev, int seq)
88 struct pwm_backlight_priv *priv = dev_get_priv(dev);
94 __maybe_unused struct dm_regulator_uclass_plat
97 plat = dev_get_uclass_plat(priv->reg);
98 log_debug("Enable '%s', regulator '%s'/'%s'\n",
99 dev->name, priv->reg->name, plat->name);
100 ret = regulator_set_enable(priv->reg, true);
102 log_debug("Cannot enable regulator for PWM '%s'\n",
111 dm_gpio_set_value(&priv->enable, 1);
118 static int pwm_backlight_enable(struct udevice *dev)
120 struct pwm_backlight_priv *priv = dev_get_priv(dev);
123 ret = enable_sequence(dev, 0);
129 ret = pwm_set_enable(priv->pwm, priv->channel, true);
132 ret = enable_sequence(dev, 1);
135 priv->enabled = true;
140 static int pwm_backlight_set_brightness(struct udevice *dev, int percent)
142 struct pwm_backlight_priv *priv = dev_get_priv(dev);
143 bool disable = false;
147 if (!priv->enabled) {
148 ret = enable_sequence(dev, 0);
152 if (percent == BACKLIGHT_OFF) {
156 if (percent == BACKLIGHT_DEFAULT) {
157 level = priv->default_level;
160 level = priv->levels[percent * (priv->num_levels - 1)
163 level = priv->min_level +
164 (priv->max_level - priv->min_level) *
168 priv->cur_level = level;
173 if (!priv->enabled) {
174 ret = enable_sequence(dev, 1);
177 priv->enabled = true;
180 dm_gpio_set_value(&priv->enable, 0);
182 ret = regulator_set_enable(priv->reg, false);
186 priv->enabled = false;
192 static int pwm_backlight_of_to_plat(struct udevice *dev)
194 struct pwm_backlight_priv *priv = dev_get_priv(dev);
195 struct ofnode_phandle_args args;
196 int index, ret, count, len;
199 log_debug("start\n");
200 ret = uclass_get_device_by_phandle(UCLASS_REGULATOR, dev,
201 "power-supply", &priv->reg);
203 log_debug("Cannot get power supply: ret=%d\n", ret);
204 ret = gpio_request_by_name(dev, "enable-gpios", 0, &priv->enable,
207 log_debug("Warning: cannot get enable GPIO: ret=%d\n", ret);
211 ret = dev_read_phandle_with_args(dev, "pwms", "#pwm-cells", 0, 0,
214 log_debug("Cannot get PWM phandle: ret=%d\n", ret);
218 ret = uclass_get_device_by_ofnode(UCLASS_PWM, args.node, &priv->pwm);
220 log_debug("Cannot get PWM: ret=%d\n", ret);
223 if (args.args_count < 1)
224 return log_msg_ret("Not enough arguments to pwm\n", -EINVAL);
225 priv->channel = args.args[0];
226 if (args.args_count > 1)
227 priv->period_ns = args.args[1];
228 if (args.args_count > 2)
229 priv->polarity = args.args[2];
231 index = dev_read_u32_default(dev, "default-brightness-level", 255);
232 cell = dev_read_prop(dev, "brightness-levels", &len);
233 count = len / sizeof(u32);
234 if (cell && count > index) {
235 priv->levels = malloc(len);
237 return log_ret(-ENOMEM);
238 dev_read_u32_array(dev, "brightness-levels", priv->levels,
240 priv->num_levels = count;
241 priv->default_level = priv->levels[index];
242 priv->max_level = priv->levels[count - 1];
244 priv->default_level = index;
245 priv->max_level = 255;
247 priv->cur_level = priv->default_level;
254 static int pwm_backlight_probe(struct udevice *dev)
259 static const struct backlight_ops pwm_backlight_ops = {
260 .enable = pwm_backlight_enable,
261 .set_brightness = pwm_backlight_set_brightness,
264 static const struct udevice_id pwm_backlight_ids[] = {
265 { .compatible = "pwm-backlight" },
269 U_BOOT_DRIVER(pwm_backlight) = {
270 .name = "pwm_backlight",
271 .id = UCLASS_PANEL_BACKLIGHT,
272 .of_match = pwm_backlight_ids,
273 .ops = &pwm_backlight_ops,
274 .of_to_plat = pwm_backlight_of_to_plat,
275 .probe = pwm_backlight_probe,
276 .priv_auto = sizeof(struct pwm_backlight_priv),