2 * linux/drivers/video/backlight/pwm_bl.c
4 * simple PWM based backlight control, board code has to setup
5 * 1) pin configuration so PWM waveforms can output
6 * 2) platform_data being correctly configured
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
13 #include <linux/gpio/consumer.h>
14 #include <linux/gpio.h>
15 #include <linux/module.h>
16 #include <linux/kernel.h>
17 #include <linux/init.h>
18 #include <linux/platform_device.h>
20 #include <linux/backlight.h>
21 #include <linux/err.h>
22 #include <linux/pwm.h>
23 #include <linux/pwm_backlight.h>
24 #include <linux/regulator/consumer.h>
25 #include <linux/slab.h>
28 struct pwm_device *pwm;
31 unsigned int lth_brightness;
34 struct regulator *power_supply;
35 struct gpio_desc *enable_gpio;
38 int (*notify)(struct device *,
40 void (*notify_after)(struct device *,
42 int (*check_fb)(struct device *, struct fb_info *);
43 void (*exit)(struct device *);
46 static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
53 err = regulator_enable(pb->power_supply);
55 dev_err(pb->dev, "failed to enable power supply\n");
58 gpiod_set_value(pb->enable_gpio, 1);
64 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
69 pwm_config(pb->pwm, 0, pb->period);
73 gpiod_set_value(pb->enable_gpio, 0);
75 regulator_disable(pb->power_supply);
79 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
81 unsigned int lth = pb->lth_brightness;
85 duty_cycle = pb->levels[brightness];
87 duty_cycle = brightness;
89 return (duty_cycle * (pb->period - lth) / pb->scale) + lth;
92 static int pwm_backlight_update_status(struct backlight_device *bl)
94 struct pwm_bl_data *pb = bl_get_data(bl);
95 int brightness = bl->props.brightness;
98 if (bl->props.power != FB_BLANK_UNBLANK ||
99 bl->props.fb_blank != FB_BLANK_UNBLANK ||
100 bl->props.state & BL_CORE_FBBLANK)
104 brightness = pb->notify(pb->dev, brightness);
106 if (brightness > 0) {
107 duty_cycle = compute_duty_cycle(pb, brightness);
108 pwm_config(pb->pwm, duty_cycle, pb->period);
109 pwm_backlight_power_on(pb, brightness);
111 pwm_backlight_power_off(pb);
113 if (pb->notify_after)
114 pb->notify_after(pb->dev, brightness);
119 static int pwm_backlight_check_fb(struct backlight_device *bl,
120 struct fb_info *info)
122 struct pwm_bl_data *pb = bl_get_data(bl);
124 return !pb->check_fb || pb->check_fb(pb->dev, info);
127 static const struct backlight_ops pwm_backlight_ops = {
128 .update_status = pwm_backlight_update_status,
129 .check_fb = pwm_backlight_check_fb,
133 static int pwm_backlight_parse_dt(struct device *dev,
134 struct platform_pwm_backlight_data *data)
136 struct device_node *node = dev->of_node;
137 struct property *prop;
145 memset(data, 0, sizeof(*data));
147 /* determine the number of brightness levels */
148 prop = of_find_property(node, "brightness-levels", &length);
152 data->max_brightness = length / sizeof(u32);
154 /* read brightness levels from DT property */
155 if (data->max_brightness > 0) {
156 size_t size = sizeof(*data->levels) * data->max_brightness;
158 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
162 ret = of_property_read_u32_array(node, "brightness-levels",
164 data->max_brightness);
168 ret = of_property_read_u32(node, "default-brightness-level",
173 data->dft_brightness = value;
174 data->max_brightness--;
177 data->enable_gpio = -EINVAL;
181 static struct of_device_id pwm_backlight_of_match[] = {
182 { .compatible = "pwm-backlight" },
186 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
188 static int pwm_backlight_parse_dt(struct device *dev,
189 struct platform_pwm_backlight_data *data)
195 static int pwm_backlight_probe(struct platform_device *pdev)
197 struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
198 struct platform_pwm_backlight_data defdata;
199 struct backlight_properties props;
200 struct backlight_device *bl;
201 struct pwm_bl_data *pb;
205 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
207 dev_err(&pdev->dev, "failed to find platform data\n");
215 ret = data->init(&pdev->dev);
220 pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
229 for (i = 0; i <= data->max_brightness; i++)
230 if (data->levels[i] > pb->scale)
231 pb->scale = data->levels[i];
233 pb->levels = data->levels;
235 pb->scale = data->max_brightness;
237 pb->notify = data->notify;
238 pb->notify_after = data->notify_after;
239 pb->check_fb = data->check_fb;
240 pb->exit = data->exit;
241 pb->dev = &pdev->dev;
244 pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
246 if (IS_ERR(pb->enable_gpio)) {
247 ret = PTR_ERR(pb->enable_gpio);
252 * Compatibility fallback for drivers still using the integer GPIO
253 * platform data. Must go away soon.
255 if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
256 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
257 GPIOF_OUT_INIT_HIGH, "enable");
259 dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
260 data->enable_gpio, ret);
264 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
267 pb->power_supply = devm_regulator_get(&pdev->dev, "power");
268 if (IS_ERR(pb->power_supply)) {
269 ret = PTR_ERR(pb->power_supply);
273 pb->pwm = devm_pwm_get(&pdev->dev, NULL);
274 if (IS_ERR(pb->pwm)) {
275 ret = PTR_ERR(pb->pwm);
276 if (ret == -EPROBE_DEFER)
279 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
281 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
282 if (IS_ERR(pb->pwm)) {
283 dev_err(&pdev->dev, "unable to request legacy PWM\n");
284 ret = PTR_ERR(pb->pwm);
289 dev_dbg(&pdev->dev, "got pwm for backlight\n");
292 * The DT case will set the pwm_period_ns field to 0 and store the
293 * period, parsed from the DT, in the PWM device. For the non-DT case,
294 * set the period from platform data if it has not already been set
295 * via the PWM lookup table.
297 pb->period = pwm_get_period(pb->pwm);
298 if (!pb->period && (data->pwm_period_ns > 0)) {
299 pb->period = data->pwm_period_ns;
300 pwm_set_period(pb->pwm, data->pwm_period_ns);
303 pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
305 memset(&props, 0, sizeof(struct backlight_properties));
306 props.type = BACKLIGHT_RAW;
307 props.max_brightness = data->max_brightness;
308 bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
309 &pwm_backlight_ops, &props);
311 dev_err(&pdev->dev, "failed to register backlight\n");
316 if (data->dft_brightness > data->max_brightness) {
318 "invalid default brightness level: %u, using %u\n",
319 data->dft_brightness, data->max_brightness);
320 data->dft_brightness = data->max_brightness;
323 bl->props.brightness = data->dft_brightness;
324 backlight_update_status(bl);
326 platform_set_drvdata(pdev, bl);
331 data->exit(&pdev->dev);
335 static int pwm_backlight_remove(struct platform_device *pdev)
337 struct backlight_device *bl = platform_get_drvdata(pdev);
338 struct pwm_bl_data *pb = bl_get_data(bl);
340 backlight_device_unregister(bl);
341 pwm_backlight_power_off(pb);
344 pb->exit(&pdev->dev);
351 static void pwm_backlight_shutdown(struct platform_device *pdev)
353 struct backlight_device *bl = platform_get_drvdata(pdev);
354 struct pwm_bl_data *pb = bl_get_data(bl);
356 pwm_backlight_power_off(pb);
359 #ifdef CONFIG_PM_SLEEP
360 static int pwm_backlight_suspend(struct device *dev)
362 struct backlight_device *bl = dev_get_drvdata(dev);
363 struct pwm_bl_data *pb = bl_get_data(bl);
366 pb->notify(pb->dev, 0);
368 pwm_backlight_power_off(pb);
370 if (pb->notify_after)
371 pb->notify_after(pb->dev, 0);
376 static int pwm_backlight_resume(struct device *dev)
378 struct backlight_device *bl = dev_get_drvdata(dev);
380 backlight_update_status(bl);
386 static const struct dev_pm_ops pwm_backlight_pm_ops = {
387 #ifdef CONFIG_PM_SLEEP
388 .suspend = pwm_backlight_suspend,
389 .resume = pwm_backlight_resume,
390 .poweroff = pwm_backlight_suspend,
391 .restore = pwm_backlight_resume,
395 static struct platform_driver pwm_backlight_driver = {
397 .name = "pwm-backlight",
398 .pm = &pwm_backlight_pm_ops,
399 .of_match_table = of_match_ptr(pwm_backlight_of_match),
401 .probe = pwm_backlight_probe,
402 .remove = pwm_backlight_remove,
403 .shutdown = pwm_backlight_shutdown,
406 module_platform_driver(pwm_backlight_driver);
408 MODULE_DESCRIPTION("PWM based Backlight Driver");
409 MODULE_LICENSE("GPL");
410 MODULE_ALIAS("platform:pwm-backlight");