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_cansleep(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_cansleep(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_initial_power_state(const struct pwm_bl_data *pb)
197 struct device_node *node = pb->dev->of_node;
199 /* Not booted with device tree or no phandle link to the node */
200 if (!node || !node->phandle)
201 return FB_BLANK_UNBLANK;
204 * If the driver is probed from the device tree and there is a
205 * phandle link pointing to the backlight node, it is safe to
206 * assume that another driver will enable the backlight at the
207 * appropriate time. Therefore, if it is disabled, keep it so.
210 /* if the enable GPIO is disabled, do not enable the backlight */
211 if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
212 return FB_BLANK_POWERDOWN;
214 /* The regulator is disabled, do not enable the backlight */
215 if (!regulator_is_enabled(pb->power_supply))
216 return FB_BLANK_POWERDOWN;
218 /* The PWM is disabled, keep it like this */
219 if (!pwm_is_enabled(pb->pwm))
220 return FB_BLANK_POWERDOWN;
222 return FB_BLANK_UNBLANK;
225 static int pwm_backlight_probe(struct platform_device *pdev)
227 struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
228 struct platform_pwm_backlight_data defdata;
229 struct backlight_properties props;
230 struct backlight_device *bl;
231 struct device_node *node = pdev->dev.of_node;
232 struct pwm_bl_data *pb;
233 struct pwm_args pargs;
237 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
239 dev_err(&pdev->dev, "failed to find platform data\n");
247 ret = data->init(&pdev->dev);
252 pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
261 for (i = 0; i <= data->max_brightness; i++)
262 if (data->levels[i] > pb->scale)
263 pb->scale = data->levels[i];
265 pb->levels = data->levels;
267 pb->scale = data->max_brightness;
269 pb->notify = data->notify;
270 pb->notify_after = data->notify_after;
271 pb->check_fb = data->check_fb;
272 pb->exit = data->exit;
273 pb->dev = &pdev->dev;
276 pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
278 if (IS_ERR(pb->enable_gpio)) {
279 ret = PTR_ERR(pb->enable_gpio);
284 * Compatibility fallback for drivers still using the integer GPIO
285 * platform data. Must go away soon.
287 if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
288 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
289 GPIOF_OUT_INIT_HIGH, "enable");
291 dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
292 data->enable_gpio, ret);
296 pb->enable_gpio = gpio_to_desc(data->enable_gpio);
300 * If the GPIO is not known to be already configured as output, that
301 * is, if gpiod_get_direction returns either GPIOF_DIR_IN or -EINVAL,
302 * change the direction to output and set the GPIO as active.
303 * Do not force the GPIO to active when it was already output as it
304 * could cause backlight flickering or we would enable the backlight too
305 * early. Leave the decision of the initial backlight state for later.
307 if (pb->enable_gpio &&
308 gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
309 gpiod_direction_output(pb->enable_gpio, 1);
311 pb->power_supply = devm_regulator_get(&pdev->dev, "power");
312 if (IS_ERR(pb->power_supply)) {
313 ret = PTR_ERR(pb->power_supply);
317 pb->pwm = devm_pwm_get(&pdev->dev, NULL);
318 if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
319 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
321 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
324 if (IS_ERR(pb->pwm)) {
325 ret = PTR_ERR(pb->pwm);
326 if (ret != -EPROBE_DEFER)
327 dev_err(&pdev->dev, "unable to request PWM\n");
331 dev_dbg(&pdev->dev, "got pwm for backlight\n");
334 * FIXME: pwm_apply_args() should be removed when switching to
335 * the atomic PWM API.
337 pwm_apply_args(pb->pwm);
340 * The DT case will set the pwm_period_ns field to 0 and store the
341 * period, parsed from the DT, in the PWM device. For the non-DT case,
342 * set the period from platform data if it has not already been set
343 * via the PWM lookup table.
345 pwm_get_args(pb->pwm, &pargs);
346 pb->period = pargs.period;
347 if (!pb->period && (data->pwm_period_ns > 0))
348 pb->period = data->pwm_period_ns;
350 pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
352 memset(&props, 0, sizeof(struct backlight_properties));
353 props.type = BACKLIGHT_RAW;
354 props.max_brightness = data->max_brightness;
355 bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
356 &pwm_backlight_ops, &props);
358 dev_err(&pdev->dev, "failed to register backlight\n");
365 if (data->dft_brightness > data->max_brightness) {
367 "invalid default brightness level: %u, using %u\n",
368 data->dft_brightness, data->max_brightness);
369 data->dft_brightness = data->max_brightness;
372 bl->props.brightness = data->dft_brightness;
373 bl->props.power = pwm_backlight_initial_power_state(pb);
374 backlight_update_status(bl);
376 platform_set_drvdata(pdev, bl);
381 data->exit(&pdev->dev);
385 static int pwm_backlight_remove(struct platform_device *pdev)
387 struct backlight_device *bl = platform_get_drvdata(pdev);
388 struct pwm_bl_data *pb = bl_get_data(bl);
390 backlight_device_unregister(bl);
391 pwm_backlight_power_off(pb);
394 pb->exit(&pdev->dev);
401 static void pwm_backlight_shutdown(struct platform_device *pdev)
403 struct backlight_device *bl = platform_get_drvdata(pdev);
404 struct pwm_bl_data *pb = bl_get_data(bl);
406 pwm_backlight_power_off(pb);
409 #ifdef CONFIG_PM_SLEEP
410 static int pwm_backlight_suspend(struct device *dev)
412 struct backlight_device *bl = dev_get_drvdata(dev);
413 struct pwm_bl_data *pb = bl_get_data(bl);
416 pb->notify(pb->dev, 0);
418 pwm_backlight_power_off(pb);
420 if (pb->notify_after)
421 pb->notify_after(pb->dev, 0);
426 static int pwm_backlight_resume(struct device *dev)
428 struct backlight_device *bl = dev_get_drvdata(dev);
430 backlight_update_status(bl);
436 static const struct dev_pm_ops pwm_backlight_pm_ops = {
437 #ifdef CONFIG_PM_SLEEP
438 .suspend = pwm_backlight_suspend,
439 .resume = pwm_backlight_resume,
440 .poweroff = pwm_backlight_suspend,
441 .restore = pwm_backlight_resume,
445 static struct platform_driver pwm_backlight_driver = {
447 .name = "pwm-backlight",
448 .pm = &pwm_backlight_pm_ops,
449 .of_match_table = of_match_ptr(pwm_backlight_of_match),
451 .probe = pwm_backlight_probe,
452 .remove = pwm_backlight_remove,
453 .shutdown = pwm_backlight_shutdown,
456 module_platform_driver(pwm_backlight_driver);
458 MODULE_DESCRIPTION("PWM based Backlight Driver");
459 MODULE_LICENSE("GPL");
460 MODULE_ALIAS("platform:pwm-backlight");