pwm_bl.c revision 6728f2b109392484d38ac9e365496ac5fa1071f1 
1/*
2 * linux/drivers/video/backlight/pwm_bl.c
3 *
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
7 *
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.
11 */
12
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>
19#include <linux/fb.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>
26
27struct pwm_bl_data {
28	struct pwm_device	*pwm;
29	struct device		*dev;
30	unsigned int		period;
31	unsigned int		lth_brightness;
32	unsigned int		*levels;
33	bool			enabled;
34	struct regulator	*power_supply;
35	struct gpio_desc	*enable_gpio;
36	unsigned int		scale;
37	int			(*notify)(struct device *,
38					  int brightness);
39	void			(*notify_after)(struct device *,
40					int brightness);
41	int			(*check_fb)(struct device *, struct fb_info *);
42	void			(*exit)(struct device *);
43};
44
45static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
46{
47	int err;
48
49	if (pb->enabled)
50		return;
51
52	err = regulator_enable(pb->power_supply);
53	if (err < 0)
54		dev_err(pb->dev, "failed to enable power supply\n");
55
56	if (pb->enable_gpio)
57		gpiod_set_value(pb->enable_gpio, 1);
58
59	pwm_enable(pb->pwm);
60	pb->enabled = true;
61}
62
63static void pwm_backlight_power_off(struct pwm_bl_data *pb)
64{
65	if (!pb->enabled)
66		return;
67
68	pwm_config(pb->pwm, 0, pb->period);
69	pwm_disable(pb->pwm);
70
71	if (pb->enable_gpio)
72		gpiod_set_value(pb->enable_gpio, 0);
73
74	regulator_disable(pb->power_supply);
75	pb->enabled = false;
76}
77
78static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
79{
80	unsigned int lth = pb->lth_brightness;
81	int duty_cycle;
82
83	if (pb->levels)
84		duty_cycle = pb->levels[brightness];
85	else
86		duty_cycle = brightness;
87
88	return (duty_cycle * (pb->period - lth) / pb->scale) + lth;
89}
90
91static int pwm_backlight_update_status(struct backlight_device *bl)
92{
93	struct pwm_bl_data *pb = bl_get_data(bl);
94	int brightness = bl->props.brightness;
95	int duty_cycle;
96
97	if (bl->props.power != FB_BLANK_UNBLANK ||
98	    bl->props.fb_blank != FB_BLANK_UNBLANK ||
99	    bl->props.state & BL_CORE_FBBLANK)
100		brightness = 0;
101
102	if (pb->notify)
103		brightness = pb->notify(pb->dev, brightness);
104
105	if (brightness > 0) {
106		duty_cycle = compute_duty_cycle(pb, brightness);
107		pwm_config(pb->pwm, duty_cycle, pb->period);
108		pwm_backlight_power_on(pb, brightness);
109	} else
110		pwm_backlight_power_off(pb);
111
112	if (pb->notify_after)
113		pb->notify_after(pb->dev, brightness);
114
115	return 0;
116}
117
118static int pwm_backlight_check_fb(struct backlight_device *bl,
119				  struct fb_info *info)
120{
121	struct pwm_bl_data *pb = bl_get_data(bl);
122
123	return !pb->check_fb || pb->check_fb(pb->dev, info);
124}
125
126static const struct backlight_ops pwm_backlight_ops = {
127	.update_status	= pwm_backlight_update_status,
128	.check_fb	= pwm_backlight_check_fb,
129};
130
131#ifdef CONFIG_OF
132static int pwm_backlight_parse_dt(struct device *dev,
133				  struct platform_pwm_backlight_data *data)
134{
135	struct device_node *node = dev->of_node;
136	struct property *prop;
137	int length;
138	u32 value;
139	int ret;
140
141	if (!node)
142		return -ENODEV;
143
144	memset(data, 0, sizeof(*data));
145
146	/* determine the number of brightness levels */
147	prop = of_find_property(node, "brightness-levels", &length);
148	if (!prop)
149		return -EINVAL;
150
151	data->max_brightness = length / sizeof(u32);
152
153	/* read brightness levels from DT property */
154	if (data->max_brightness > 0) {
155		size_t size = sizeof(*data->levels) * data->max_brightness;
156
157		data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
158		if (!data->levels)
159			return -ENOMEM;
160
161		ret = of_property_read_u32_array(node, "brightness-levels",
162						 data->levels,
163						 data->max_brightness);
164		if (ret < 0)
165			return ret;
166
167		ret = of_property_read_u32(node, "default-brightness-level",
168					   &value);
169		if (ret < 0)
170			return ret;
171
172		data->dft_brightness = value;
173		data->max_brightness--;
174	}
175
176	return 0;
177}
178
179static struct of_device_id pwm_backlight_of_match[] = {
180	{ .compatible = "pwm-backlight" },
181	{ }
182};
183
184MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
185#else
186static int pwm_backlight_parse_dt(struct device *dev,
187				  struct platform_pwm_backlight_data *data)
188{
189	return -ENODEV;
190}
191#endif
192
193static int pwm_backlight_probe(struct platform_device *pdev)
194{
195	struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
196	struct platform_pwm_backlight_data defdata;
197	struct backlight_properties props;
198	struct backlight_device *bl;
199	struct pwm_bl_data *pb;
200	int ret;
201
202	if (!data) {
203		ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
204		if (ret < 0) {
205			dev_err(&pdev->dev, "failed to find platform data\n");
206			return ret;
207		}
208
209		data = &defdata;
210	}
211
212	if (data->init) {
213		ret = data->init(&pdev->dev);
214		if (ret < 0)
215			return ret;
216	}
217
218	pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
219	if (!pb) {
220		ret = -ENOMEM;
221		goto err_alloc;
222	}
223
224	if (data->levels) {
225		unsigned int i;
226
227		for (i = 0; i <= data->max_brightness; i++)
228			if (data->levels[i] > pb->scale)
229				pb->scale = data->levels[i];
230
231		pb->levels = data->levels;
232	} else
233		pb->scale = data->max_brightness;
234
235	pb->notify = data->notify;
236	pb->notify_after = data->notify_after;
237	pb->check_fb = data->check_fb;
238	pb->exit = data->exit;
239	pb->dev = &pdev->dev;
240	pb->enabled = false;
241
242	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable");
243	if (IS_ERR(pb->enable_gpio)) {
244		ret = PTR_ERR(pb->enable_gpio);
245		goto err_alloc;
246	}
247
248	/*
249	 * Compatibility fallback for drivers still using the integer GPIO
250	 * platform data. Must go away soon.
251	 */
252	if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
253		ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
254					    GPIOF_OUT_INIT_HIGH, "enable");
255		if (ret < 0) {
256			dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
257				data->enable_gpio, ret);
258			goto err_alloc;
259		}
260
261		pb->enable_gpio = gpio_to_desc(data->enable_gpio);
262	}
263
264	if (pb->enable_gpio)
265		gpiod_direction_output(pb->enable_gpio, 1);
266
267	pb->power_supply = devm_regulator_get(&pdev->dev, "power");
268	if (IS_ERR(pb->power_supply)) {
269		ret = PTR_ERR(pb->power_supply);
270		goto err_alloc;
271	}
272
273	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
274	if (IS_ERR(pb->pwm)) {
275		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
276
277		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
278		if (IS_ERR(pb->pwm)) {
279			dev_err(&pdev->dev, "unable to request legacy PWM\n");
280			ret = PTR_ERR(pb->pwm);
281			goto err_alloc;
282		}
283	}
284
285	dev_dbg(&pdev->dev, "got pwm for backlight\n");
286
287	/*
288	 * The DT case will set the pwm_period_ns field to 0 and store the
289	 * period, parsed from the DT, in the PWM device. For the non-DT case,
290	 * set the period from platform data if it has not already been set
291	 * via the PWM lookup table.
292	 */
293	pb->period = pwm_get_period(pb->pwm);
294	if (!pb->period && (data->pwm_period_ns > 0)) {
295		pb->period = data->pwm_period_ns;
296		pwm_set_period(pb->pwm, data->pwm_period_ns);
297	}
298
299	pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
300
301	memset(&props, 0, sizeof(struct backlight_properties));
302	props.type = BACKLIGHT_RAW;
303	props.max_brightness = data->max_brightness;
304	bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
305				       &pwm_backlight_ops, &props);
306	if (IS_ERR(bl)) {
307		dev_err(&pdev->dev, "failed to register backlight\n");
308		ret = PTR_ERR(bl);
309		goto err_alloc;
310	}
311
312	if (data->dft_brightness > data->max_brightness) {
313		dev_warn(&pdev->dev,
314			 "invalid default brightness level: %u, using %u\n",
315			 data->dft_brightness, data->max_brightness);
316		data->dft_brightness = data->max_brightness;
317	}
318
319	bl->props.brightness = data->dft_brightness;
320	backlight_update_status(bl);
321
322	platform_set_drvdata(pdev, bl);
323	return 0;
324
325err_alloc:
326	if (data->exit)
327		data->exit(&pdev->dev);
328	return ret;
329}
330
331static int pwm_backlight_remove(struct platform_device *pdev)
332{
333	struct backlight_device *bl = platform_get_drvdata(pdev);
334	struct pwm_bl_data *pb = bl_get_data(bl);
335
336	backlight_device_unregister(bl);
337	pwm_backlight_power_off(pb);
338
339	if (pb->exit)
340		pb->exit(&pdev->dev);
341
342	return 0;
343}
344
345static void pwm_backlight_shutdown(struct platform_device *pdev)
346{
347	struct backlight_device *bl = platform_get_drvdata(pdev);
348	struct pwm_bl_data *pb = bl_get_data(bl);
349
350	pwm_backlight_power_off(pb);
351}
352
353#ifdef CONFIG_PM_SLEEP
354static int pwm_backlight_suspend(struct device *dev)
355{
356	struct backlight_device *bl = dev_get_drvdata(dev);
357	struct pwm_bl_data *pb = bl_get_data(bl);
358
359	if (pb->notify)
360		pb->notify(pb->dev, 0);
361
362	pwm_backlight_power_off(pb);
363
364	if (pb->notify_after)
365		pb->notify_after(pb->dev, 0);
366
367	return 0;
368}
369
370static int pwm_backlight_resume(struct device *dev)
371{
372	struct backlight_device *bl = dev_get_drvdata(dev);
373
374	backlight_update_status(bl);
375
376	return 0;
377}
378#endif
379
380static const struct dev_pm_ops pwm_backlight_pm_ops = {
381#ifdef CONFIG_PM_SLEEP
382	.suspend = pwm_backlight_suspend,
383	.resume = pwm_backlight_resume,
384	.poweroff = pwm_backlight_suspend,
385	.restore = pwm_backlight_resume,
386#endif
387};
388
389static struct platform_driver pwm_backlight_driver = {
390	.driver		= {
391		.name		= "pwm-backlight",
392		.pm		= &pwm_backlight_pm_ops,
393		.of_match_table	= of_match_ptr(pwm_backlight_of_match),
394	},
395	.probe		= pwm_backlight_probe,
396	.remove		= pwm_backlight_remove,
397	.shutdown	= pwm_backlight_shutdown,
398};
399
400module_platform_driver(pwm_backlight_driver);
401
402MODULE_DESCRIPTION("PWM based Backlight Driver");
403MODULE_LICENSE("GPL");
404MODULE_ALIAS("platform:pwm-backlight");
405