pwm_bl.c revision 1dea1fd09246ada581a99d0669108eea94b7bfee 
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.h>
14#include <linux/of_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	int			enable_gpio;
36	unsigned long		enable_gpio_flags;
37	unsigned int		scale;
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 duty_cycle, 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 (gpio_is_valid(pb->enable_gpio)) {
58		if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
59			gpio_set_value(pb->enable_gpio, 0);
60		else
61			gpio_set_value(pb->enable_gpio, 1);
62	}
63
64	pwm_enable(pb->pwm);
65	pb->enabled = true;
66}
67
68static void pwm_backlight_power_off(struct pwm_bl_data *pb)
69{
70	if (!pb->enabled)
71		return;
72
73	pwm_config(pb->pwm, 0, pb->period);
74	pwm_disable(pb->pwm);
75
76	if (gpio_is_valid(pb->enable_gpio)) {
77		if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
78			gpio_set_value(pb->enable_gpio, 1);
79		else
80			gpio_set_value(pb->enable_gpio, 0);
81	}
82
83	regulator_disable(pb->power_supply);
84	pb->enabled = false;
85}
86
87static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
88{
89	unsigned int lth = pb->lth_brightness;
90	int duty_cycle;
91
92	if (pb->levels)
93		duty_cycle = pb->levels[brightness];
94	else
95		duty_cycle = brightness;
96
97	return (duty_cycle * (pb->period - lth) / pb->scale) + lth;
98}
99
100static int pwm_backlight_update_status(struct backlight_device *bl)
101{
102	struct pwm_bl_data *pb = bl_get_data(bl);
103	int brightness = bl->props.brightness;
104	int duty_cycle;
105
106	if (bl->props.power != FB_BLANK_UNBLANK ||
107	    bl->props.fb_blank != FB_BLANK_UNBLANK ||
108	    bl->props.state & BL_CORE_FBBLANK)
109		brightness = 0;
110
111	if (pb->notify)
112		brightness = pb->notify(pb->dev, brightness);
113
114	if (brightness > 0) {
115		duty_cycle = compute_duty_cycle(pb, brightness);
116		pwm_config(pb->pwm, duty_cycle, pb->period);
117		pwm_backlight_power_on(pb, brightness);
118	} else
119		pwm_backlight_power_off(pb);
120
121	if (pb->notify_after)
122		pb->notify_after(pb->dev, brightness);
123
124	return 0;
125}
126
127static int pwm_backlight_get_brightness(struct backlight_device *bl)
128{
129	return bl->props.brightness;
130}
131
132static int pwm_backlight_check_fb(struct backlight_device *bl,
133				  struct fb_info *info)
134{
135	struct pwm_bl_data *pb = bl_get_data(bl);
136
137	return !pb->check_fb || pb->check_fb(pb->dev, info);
138}
139
140static const struct backlight_ops pwm_backlight_ops = {
141	.update_status	= pwm_backlight_update_status,
142	.get_brightness	= pwm_backlight_get_brightness,
143	.check_fb	= pwm_backlight_check_fb,
144};
145
146#ifdef CONFIG_OF
147static int pwm_backlight_parse_dt(struct device *dev,
148				  struct platform_pwm_backlight_data *data)
149{
150	struct device_node *node = dev->of_node;
151	enum of_gpio_flags flags;
152	struct property *prop;
153	int length;
154	u32 value;
155	int ret;
156
157	if (!node)
158		return -ENODEV;
159
160	memset(data, 0, sizeof(*data));
161
162	/* determine the number of brightness levels */
163	prop = of_find_property(node, "brightness-levels", &length);
164	if (!prop)
165		return -EINVAL;
166
167	data->max_brightness = length / sizeof(u32);
168
169	/* read brightness levels from DT property */
170	if (data->max_brightness > 0) {
171		size_t size = sizeof(*data->levels) * data->max_brightness;
172
173		data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
174		if (!data->levels)
175			return -ENOMEM;
176
177		ret = of_property_read_u32_array(node, "brightness-levels",
178						 data->levels,
179						 data->max_brightness);
180		if (ret < 0)
181			return ret;
182
183		ret = of_property_read_u32(node, "default-brightness-level",
184					   &value);
185		if (ret < 0)
186			return ret;
187
188		data->dft_brightness = value;
189		data->max_brightness--;
190	}
191
192	data->enable_gpio = of_get_named_gpio_flags(node, "enable-gpios", 0,
193						    &flags);
194	if (data->enable_gpio == -EPROBE_DEFER)
195		return -EPROBE_DEFER;
196
197	if (gpio_is_valid(data->enable_gpio) && (flags & OF_GPIO_ACTIVE_LOW))
198		data->enable_gpio_flags |= PWM_BACKLIGHT_GPIO_ACTIVE_LOW;
199
200	return 0;
201}
202
203static struct of_device_id pwm_backlight_of_match[] = {
204	{ .compatible = "pwm-backlight" },
205	{ }
206};
207
208MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
209#else
210static int pwm_backlight_parse_dt(struct device *dev,
211				  struct platform_pwm_backlight_data *data)
212{
213	return -ENODEV;
214}
215#endif
216
217static int pwm_backlight_probe(struct platform_device *pdev)
218{
219	struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
220	struct platform_pwm_backlight_data defdata;
221	struct backlight_properties props;
222	struct backlight_device *bl;
223	struct pwm_bl_data *pb;
224	int ret;
225
226	if (!data) {
227		ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
228		if (ret < 0) {
229			dev_err(&pdev->dev, "failed to find platform data\n");
230			return ret;
231		}
232
233		data = &defdata;
234	}
235
236	if (data->init) {
237		ret = data->init(&pdev->dev);
238		if (ret < 0)
239			return ret;
240	}
241
242	pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
243	if (!pb) {
244		dev_err(&pdev->dev, "no memory for state\n");
245		ret = -ENOMEM;
246		goto err_alloc;
247	}
248
249	if (data->levels) {
250		unsigned int i;
251
252		for (i = 0; i <= data->max_brightness; i++)
253			if (data->levels[i] > pb->scale)
254				pb->scale = data->levels[i];
255
256		pb->levels = data->levels;
257	} else
258		pb->scale = data->max_brightness;
259
260	pb->enable_gpio = data->enable_gpio;
261	pb->enable_gpio_flags = data->enable_gpio_flags;
262	pb->notify = data->notify;
263	pb->notify_after = data->notify_after;
264	pb->check_fb = data->check_fb;
265	pb->exit = data->exit;
266	pb->dev = &pdev->dev;
267	pb->enabled = false;
268
269	if (gpio_is_valid(pb->enable_gpio)) {
270		unsigned long flags;
271
272		if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
273			flags = GPIOF_OUT_INIT_HIGH;
274		else
275			flags = GPIOF_OUT_INIT_LOW;
276
277		ret = gpio_request_one(pb->enable_gpio, flags, "enable");
278		if (ret < 0) {
279			dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
280				pb->enable_gpio, ret);
281			goto err_alloc;
282		}
283	}
284
285	pb->power_supply = devm_regulator_get(&pdev->dev, "power");
286	if (IS_ERR(pb->power_supply)) {
287		ret = PTR_ERR(pb->power_supply);
288		goto err_gpio;
289	}
290
291	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
292	if (IS_ERR(pb->pwm)) {
293		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
294
295		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
296		if (IS_ERR(pb->pwm)) {
297			dev_err(&pdev->dev, "unable to request legacy PWM\n");
298			ret = PTR_ERR(pb->pwm);
299			goto err_gpio;
300		}
301	}
302
303	dev_dbg(&pdev->dev, "got pwm for backlight\n");
304
305	/*
306	 * The DT case will set the pwm_period_ns field to 0 and store the
307	 * period, parsed from the DT, in the PWM device. For the non-DT case,
308	 * set the period from platform data.
309	 */
310	if (data->pwm_period_ns > 0)
311		pwm_set_period(pb->pwm, data->pwm_period_ns);
312
313	pb->period = pwm_get_period(pb->pwm);
314	pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
315
316	memset(&props, 0, sizeof(struct backlight_properties));
317	props.type = BACKLIGHT_RAW;
318	props.max_brightness = data->max_brightness;
319	bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
320				       &pwm_backlight_ops, &props);
321	if (IS_ERR(bl)) {
322		dev_err(&pdev->dev, "failed to register backlight\n");
323		ret = PTR_ERR(bl);
324		goto err_gpio;
325	}
326
327	if (data->dft_brightness > data->max_brightness) {
328		dev_warn(&pdev->dev,
329			 "invalid default brightness level: %u, using %u\n",
330			 data->dft_brightness, data->max_brightness);
331		data->dft_brightness = data->max_brightness;
332	}
333
334	bl->props.brightness = data->dft_brightness;
335	backlight_update_status(bl);
336
337	platform_set_drvdata(pdev, bl);
338	return 0;
339
340err_gpio:
341	if (gpio_is_valid(pb->enable_gpio))
342		gpio_free(pb->enable_gpio);
343err_alloc:
344	if (data->exit)
345		data->exit(&pdev->dev);
346	return ret;
347}
348
349static int pwm_backlight_remove(struct platform_device *pdev)
350{
351	struct backlight_device *bl = platform_get_drvdata(pdev);
352	struct pwm_bl_data *pb = bl_get_data(bl);
353
354	backlight_device_unregister(bl);
355	pwm_backlight_power_off(pb);
356
357	if (pb->exit)
358		pb->exit(&pdev->dev);
359
360	return 0;
361}
362
363#ifdef CONFIG_PM_SLEEP
364static int pwm_backlight_suspend(struct device *dev)
365{
366	struct backlight_device *bl = dev_get_drvdata(dev);
367	struct pwm_bl_data *pb = bl_get_data(bl);
368
369	if (pb->notify)
370		pb->notify(pb->dev, 0);
371
372	pwm_backlight_power_off(pb);
373
374	if (pb->notify_after)
375		pb->notify_after(pb->dev, 0);
376
377	return 0;
378}
379
380static int pwm_backlight_resume(struct device *dev)
381{
382	struct backlight_device *bl = dev_get_drvdata(dev);
383
384	backlight_update_status(bl);
385
386	return 0;
387}
388#endif
389
390static const struct dev_pm_ops pwm_backlight_pm_ops = {
391#ifdef CONFIG_PM_SLEEP
392	.suspend = pwm_backlight_suspend,
393	.resume = pwm_backlight_resume,
394	.poweroff = pwm_backlight_suspend,
395	.restore = pwm_backlight_resume,
396#endif
397};
398
399static struct platform_driver pwm_backlight_driver = {
400	.driver		= {
401		.name		= "pwm-backlight",
402		.owner		= THIS_MODULE,
403		.pm		= &pwm_backlight_pm_ops,
404		.of_match_table	= of_match_ptr(pwm_backlight_of_match),
405	},
406	.probe		= pwm_backlight_probe,
407	.remove		= pwm_backlight_remove,
408};
409
410module_platform_driver(pwm_backlight_driver);
411
412MODULE_DESCRIPTION("PWM based Backlight Driver");
413MODULE_LICENSE("GPL");
414MODULE_ALIAS("platform:pwm-backlight");
415