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	bool			legacy;
38	int			(*notify)(struct device *,
39					  int brightness);
40	void			(*notify_after)(struct device *,
41					int brightness);
42	int			(*check_fb)(struct device *, struct fb_info *);
43	void			(*exit)(struct device *);
44};
45
46static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
47{
48	int err;
49
50	if (pb->enabled)
51		return;
52
53	err = regulator_enable(pb->power_supply);
54	if (err < 0)
55		dev_err(pb->dev, "failed to enable power supply\n");
56
57	if (pb->enable_gpio)
58		gpiod_set_value(pb->enable_gpio, 1);
59
60	pwm_enable(pb->pwm);
61	pb->enabled = true;
62}
63
64static void pwm_backlight_power_off(struct pwm_bl_data *pb)
65{
66	if (!pb->enabled)
67		return;
68
69	pwm_config(pb->pwm, 0, pb->period);
70	pwm_disable(pb->pwm);
71
72	if (pb->enable_gpio)
73		gpiod_set_value(pb->enable_gpio, 0);
74
75	regulator_disable(pb->power_supply);
76	pb->enabled = false;
77}
78
79static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
80{
81	unsigned int lth = pb->lth_brightness;
82	int duty_cycle;
83
84	if (pb->levels)
85		duty_cycle = pb->levels[brightness];
86	else
87		duty_cycle = brightness;
88
89	return (duty_cycle * (pb->period - lth) / pb->scale) + lth;
90}
91
92static int pwm_backlight_update_status(struct backlight_device *bl)
93{
94	struct pwm_bl_data *pb = bl_get_data(bl);
95	int brightness = bl->props.brightness;
96	int duty_cycle;
97
98	if (bl->props.power != FB_BLANK_UNBLANK ||
99	    bl->props.fb_blank != FB_BLANK_UNBLANK ||
100	    bl->props.state & BL_CORE_FBBLANK)
101		brightness = 0;
102
103	if (pb->notify)
104		brightness = pb->notify(pb->dev, brightness);
105
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);
110	} else
111		pwm_backlight_power_off(pb);
112
113	if (pb->notify_after)
114		pb->notify_after(pb->dev, brightness);
115
116	return 0;
117}
118
119static int pwm_backlight_check_fb(struct backlight_device *bl,
120				  struct fb_info *info)
121{
122	struct pwm_bl_data *pb = bl_get_data(bl);
123
124	return !pb->check_fb || pb->check_fb(pb->dev, info);
125}
126
127static const struct backlight_ops pwm_backlight_ops = {
128	.update_status	= pwm_backlight_update_status,
129	.check_fb	= pwm_backlight_check_fb,
130};
131
132#ifdef CONFIG_OF
133static int pwm_backlight_parse_dt(struct device *dev,
134				  struct platform_pwm_backlight_data *data)
135{
136	struct device_node *node = dev->of_node;
137	struct property *prop;
138	int length;
139	u32 value;
140	int ret;
141
142	if (!node)
143		return -ENODEV;
144
145	memset(data, 0, sizeof(*data));
146
147	/* determine the number of brightness levels */
148	prop = of_find_property(node, "brightness-levels", &length);
149	if (!prop)
150		return -EINVAL;
151
152	data->max_brightness = length / sizeof(u32);
153
154	/* read brightness levels from DT property */
155	if (data->max_brightness > 0) {
156		size_t size = sizeof(*data->levels) * data->max_brightness;
157
158		data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
159		if (!data->levels)
160			return -ENOMEM;
161
162		ret = of_property_read_u32_array(node, "brightness-levels",
163						 data->levels,
164						 data->max_brightness);
165		if (ret < 0)
166			return ret;
167
168		ret = of_property_read_u32(node, "default-brightness-level",
169					   &value);
170		if (ret < 0)
171			return ret;
172
173		data->dft_brightness = value;
174		data->max_brightness--;
175	}
176
177	data->enable_gpio = -EINVAL;
178	return 0;
179}
180
181static struct of_device_id pwm_backlight_of_match[] = {
182	{ .compatible = "pwm-backlight" },
183	{ }
184};
185
186MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
187#else
188static int pwm_backlight_parse_dt(struct device *dev,
189				  struct platform_pwm_backlight_data *data)
190{
191	return -ENODEV;
192}
193#endif
194
195static int pwm_backlight_probe(struct platform_device *pdev)
196{
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;
202	int ret;
203
204	if (!data) {
205		ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
206		if (ret < 0) {
207			dev_err(&pdev->dev, "failed to find platform data\n");
208			return ret;
209		}
210
211		data = &defdata;
212	}
213
214	if (data->init) {
215		ret = data->init(&pdev->dev);
216		if (ret < 0)
217			return ret;
218	}
219
220	pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
221	if (!pb) {
222		ret = -ENOMEM;
223		goto err_alloc;
224	}
225
226	if (data->levels) {
227		unsigned int i;
228
229		for (i = 0; i <= data->max_brightness; i++)
230			if (data->levels[i] > pb->scale)
231				pb->scale = data->levels[i];
232
233		pb->levels = data->levels;
234	} else
235		pb->scale = data->max_brightness;
236
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;
242	pb->enabled = false;
243
244	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable");
245	if (IS_ERR(pb->enable_gpio)) {
246		ret = PTR_ERR(pb->enable_gpio);
247		goto err_alloc;
248	}
249
250	/*
251	 * Compatibility fallback for drivers still using the integer GPIO
252	 * platform data. Must go away soon.
253	 */
254	if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
255		ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
256					    GPIOF_OUT_INIT_HIGH, "enable");
257		if (ret < 0) {
258			dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
259				data->enable_gpio, ret);
260			goto err_alloc;
261		}
262
263		pb->enable_gpio = gpio_to_desc(data->enable_gpio);
264	}
265
266	if (pb->enable_gpio)
267		gpiod_direction_output(pb->enable_gpio, 1);
268
269	pb->power_supply = devm_regulator_get(&pdev->dev, "power");
270	if (IS_ERR(pb->power_supply)) {
271		ret = PTR_ERR(pb->power_supply);
272		goto err_alloc;
273	}
274
275	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
276	if (IS_ERR(pb->pwm)) {
277		ret = PTR_ERR(pb->pwm);
278		if (ret == -EPROBE_DEFER)
279			goto err_alloc;
280
281		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
282		pb->legacy = true;
283		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
284		if (IS_ERR(pb->pwm)) {
285			dev_err(&pdev->dev, "unable to request legacy PWM\n");
286			ret = PTR_ERR(pb->pwm);
287			goto err_alloc;
288		}
289	}
290
291	dev_dbg(&pdev->dev, "got pwm for backlight\n");
292
293	/*
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.
298	 */
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);
303	}
304
305	pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
306
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);
312	if (IS_ERR(bl)) {
313		dev_err(&pdev->dev, "failed to register backlight\n");
314		ret = PTR_ERR(bl);
315		goto err_alloc;
316	}
317
318	if (data->dft_brightness > data->max_brightness) {
319		dev_warn(&pdev->dev,
320			 "invalid default brightness level: %u, using %u\n",
321			 data->dft_brightness, data->max_brightness);
322		data->dft_brightness = data->max_brightness;
323	}
324
325	bl->props.brightness = data->dft_brightness;
326	backlight_update_status(bl);
327
328	platform_set_drvdata(pdev, bl);
329	return 0;
330
331err_alloc:
332	if (data->exit)
333		data->exit(&pdev->dev);
334	return ret;
335}
336
337static int pwm_backlight_remove(struct platform_device *pdev)
338{
339	struct backlight_device *bl = platform_get_drvdata(pdev);
340	struct pwm_bl_data *pb = bl_get_data(bl);
341
342	backlight_device_unregister(bl);
343	pwm_backlight_power_off(pb);
344
345	if (pb->exit)
346		pb->exit(&pdev->dev);
347	if (pb->legacy)
348		pwm_free(pb->pwm);
349
350	return 0;
351}
352
353static void pwm_backlight_shutdown(struct platform_device *pdev)
354{
355	struct backlight_device *bl = platform_get_drvdata(pdev);
356	struct pwm_bl_data *pb = bl_get_data(bl);
357
358	pwm_backlight_power_off(pb);
359}
360
361#ifdef CONFIG_PM_SLEEP
362static int pwm_backlight_suspend(struct device *dev)
363{
364	struct backlight_device *bl = dev_get_drvdata(dev);
365	struct pwm_bl_data *pb = bl_get_data(bl);
366
367	if (pb->notify)
368		pb->notify(pb->dev, 0);
369
370	pwm_backlight_power_off(pb);
371
372	if (pb->notify_after)
373		pb->notify_after(pb->dev, 0);
374
375	return 0;
376}
377
378static int pwm_backlight_resume(struct device *dev)
379{
380	struct backlight_device *bl = dev_get_drvdata(dev);
381
382	backlight_update_status(bl);
383
384	return 0;
385}
386#endif
387
388static 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,
394#endif
395};
396
397static struct platform_driver pwm_backlight_driver = {
398	.driver		= {
399		.name		= "pwm-backlight",
400		.pm		= &pwm_backlight_pm_ops,
401		.of_match_table	= of_match_ptr(pwm_backlight_of_match),
402	},
403	.probe		= pwm_backlight_probe,
404	.remove		= pwm_backlight_remove,
405	.shutdown	= pwm_backlight_shutdown,
406};
407
408module_platform_driver(pwm_backlight_driver);
409
410MODULE_DESCRIPTION("PWM based Backlight Driver");
411MODULE_LICENSE("GPL");
412MODULE_ALIAS("platform:pwm-backlight");
413