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 duty_cycle *= pb->period - lth;
90 do_div(duty_cycle, pb->scale);
92 return duty_cycle + lth;
95 static int pwm_backlight_update_status(struct backlight_device *bl)
97 struct pwm_bl_data *pb = bl_get_data(bl);
98 int brightness = bl->props.brightness;
101 if (bl->props.power != FB_BLANK_UNBLANK ||
102 bl->props.fb_blank != FB_BLANK_UNBLANK ||
103 bl->props.state & BL_CORE_FBBLANK)
107 brightness = pb->notify(pb->dev, brightness);
109 if (brightness > 0) {
110 duty_cycle = compute_duty_cycle(pb, brightness);
111 pwm_config(pb->pwm, duty_cycle, pb->period);
112 pwm_backlight_power_on(pb, brightness);
114 pwm_backlight_power_off(pb);
116 if (pb->notify_after)
117 pb->notify_after(pb->dev, brightness);
122 static int pwm_backlight_check_fb(struct backlight_device *bl,
123 struct fb_info *info)
125 struct pwm_bl_data *pb = bl_get_data(bl);
127 return !pb->check_fb || pb->check_fb(pb->dev, info);
130 static const struct backlight_ops pwm_backlight_ops = {
131 .update_status = pwm_backlight_update_status,
132 .check_fb = pwm_backlight_check_fb,
136 static int pwm_backlight_parse_dt(struct device *dev,
137 struct platform_pwm_backlight_data *data)
139 struct device_node *node = dev->of_node;
140 struct property *prop;
148 memset(data, 0, sizeof(*data));
150 /* determine the number of brightness levels */
151 prop = of_find_property(node, "brightness-levels", &length);
155 data->max_brightness = length / sizeof(u32);
157 /* read brightness levels from DT property */
158 if (data->max_brightness > 0) {
159 size_t size = sizeof(*data->levels) * data->max_brightness;
161 data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
165 ret = of_property_read_u32_array(node, "brightness-levels",
167 data->max_brightness);
171 ret = of_property_read_u32(node, "default-brightness-level",
176 data->dft_brightness = value;
177 data->max_brightness--;
180 data->enable_gpio = -EINVAL;
184 static struct of_device_id pwm_backlight_of_match[] = {
185 { .compatible = "pwm-backlight" },
189 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
191 static int pwm_backlight_parse_dt(struct device *dev,
192 struct platform_pwm_backlight_data *data)
198 static int pwm_backlight_probe(struct platform_device *pdev)
200 struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
201 struct platform_pwm_backlight_data defdata;
202 struct backlight_properties props;
203 struct backlight_device *bl;
204 struct pwm_bl_data *pb;
208 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
210 dev_err(&pdev->dev, "failed to find platform data\n");
218 ret = data->init(&pdev->dev);
223 pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
232 for (i = 0; i <= data->max_brightness; i++)
233 if (data->levels[i] > pb->scale)
234 pb->scale = data->levels[i];
236 pb->levels = data->levels;
238 pb->scale = data->max_brightness;
240 pb->notify = data->notify;
241 pb->notify_after = data->notify_after;
242 pb->check_fb = data->check_fb;
243 pb->exit = data->exit;
244 pb->dev = &pdev->dev;
247 pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
249 if (IS_ERR(pb->enable_gpio)) {
250 ret = PTR_ERR(pb->enable_gpio);
255 * Compatibility fallback for drivers still using the integer GPIO
256 * platform data. Must go away soon.
258 if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
259 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
260 GPIOF_OUT_INIT_HIGH, "enable");
262 dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
263 data->enable_gpio, ret);
267 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
270 pb->power_supply = devm_regulator_get(&pdev->dev, "power");
271 if (IS_ERR(pb->power_supply)) {
272 ret = PTR_ERR(pb->power_supply);
276 pb->pwm = devm_pwm_get(&pdev->dev, NULL);
277 if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
278 && !pdev->dev.of_node) {
279 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
281 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
284 if (IS_ERR(pb->pwm)) {
285 ret = PTR_ERR(pb->pwm);
286 if (ret != -EPROBE_DEFER)
287 dev_err(&pdev->dev, "unable to request PWM\n");
291 dev_dbg(&pdev->dev, "got pwm for backlight\n");
294 * The DT case will set the pwm_period_ns field to 0 and store the
295 * period, parsed from the DT, in the PWM device. For the non-DT case,
296 * set the period from platform data if it has not already been set
297 * via the PWM lookup table.
299 pb->period = pwm_get_period(pb->pwm);
300 if (!pb->period && (data->pwm_period_ns > 0)) {
301 pb->period = data->pwm_period_ns;
302 pwm_set_period(pb->pwm, data->pwm_period_ns);
305 pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
307 memset(&props, 0, sizeof(struct backlight_properties));
308 props.type = BACKLIGHT_RAW;
309 props.max_brightness = data->max_brightness;
310 bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
311 &pwm_backlight_ops, &props);
313 dev_err(&pdev->dev, "failed to register backlight\n");
318 if (data->dft_brightness > data->max_brightness) {
320 "invalid default brightness level: %u, using %u\n",
321 data->dft_brightness, data->max_brightness);
322 data->dft_brightness = data->max_brightness;
325 bl->props.brightness = data->dft_brightness;
326 backlight_update_status(bl);
328 platform_set_drvdata(pdev, bl);
333 data->exit(&pdev->dev);
337 static int pwm_backlight_remove(struct platform_device *pdev)
339 struct backlight_device *bl = platform_get_drvdata(pdev);
340 struct pwm_bl_data *pb = bl_get_data(bl);
342 backlight_device_unregister(bl);
343 pwm_backlight_power_off(pb);
346 pb->exit(&pdev->dev);
353 static void pwm_backlight_shutdown(struct platform_device *pdev)
355 struct backlight_device *bl = platform_get_drvdata(pdev);
356 struct pwm_bl_data *pb = bl_get_data(bl);
358 pwm_backlight_power_off(pb);
361 #ifdef CONFIG_PM_SLEEP
362 static int pwm_backlight_suspend(struct device *dev)
364 struct backlight_device *bl = dev_get_drvdata(dev);
365 struct pwm_bl_data *pb = bl_get_data(bl);
368 pb->notify(pb->dev, 0);
370 pwm_backlight_power_off(pb);
372 if (pb->notify_after)
373 pb->notify_after(pb->dev, 0);
378 static int pwm_backlight_resume(struct device *dev)
380 struct backlight_device *bl = dev_get_drvdata(dev);
382 backlight_update_status(bl);
388 static const struct dev_pm_ops pwm_backlight_pm_ops = {
389 #ifdef CONFIG_PM_SLEEP
390 .suspend = pwm_backlight_suspend,
391 .resume = pwm_backlight_resume,
392 .poweroff = pwm_backlight_suspend,
393 .restore = pwm_backlight_resume,
397 static struct platform_driver pwm_backlight_driver = {
399 .name = "pwm-backlight",
400 .pm = &pwm_backlight_pm_ops,
401 .of_match_table = of_match_ptr(pwm_backlight_of_match),
403 .probe = pwm_backlight_probe,
404 .remove = pwm_backlight_remove,
405 .shutdown = pwm_backlight_shutdown,
408 module_platform_driver(pwm_backlight_driver);
410 MODULE_DESCRIPTION("PWM based Backlight Driver");
411 MODULE_LICENSE("GPL");
412 MODULE_ALIAS("platform:pwm-backlight");