summaryrefslogtreecommitdiff
path: root/drivers/video/backlight/pwm_bl.c
blob: 002f1ce22bd02032062924b19d645ebc25302c93 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
/*
 * linux/drivers/video/backlight/pwm_bl.c
 *
 * simple PWM based backlight control, board code has to setup
 * 1) pin configuration so PWM waveforms can output
 * 2) platform_data being correctly configured
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/gpio/consumer.h>
#include <linux/gpio.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/fb.h>
#include <linux/backlight.h>
#include <linux/err.h>
#include <linux/pwm.h>
#include <linux/pwm_backlight.h>
#include <linux/regulator/consumer.h>
#include <linux/slab.h>

struct pwm_bl_data {
	struct pwm_device	*pwm;
	struct device		*dev;
	unsigned int		period;
	unsigned int		lth_brightness;
	unsigned int		*levels;
	bool			enabled;
	struct regulator	*power_supply;
	struct gpio_desc	*enable_gpio;
	unsigned int		scale;
	bool			legacy;
	int			(*notify)(struct device *,
					  int brightness);
	void			(*notify_after)(struct device *,
					int brightness);
	int			(*check_fb)(struct device *, struct fb_info *);
	void			(*exit)(struct device *);
};

static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
{
	int err;

	if (pb->enabled)
		return;

	err = regulator_enable(pb->power_supply);
	if (err < 0)
		dev_err(pb->dev, "failed to enable power supply\n");

	if (pb->enable_gpio)
		gpiod_set_value_cansleep(pb->enable_gpio, 1);

	pwm_enable(pb->pwm);
	pb->enabled = true;
}

static void pwm_backlight_power_off(struct pwm_bl_data *pb)
{
	if (!pb->enabled)
		return;

	pwm_config(pb->pwm, 0, pb->period);
	pwm_disable(pb->pwm);

	if (pb->enable_gpio)
		gpiod_set_value_cansleep(pb->enable_gpio, 0);

	regulator_disable(pb->power_supply);
	pb->enabled = false;
}

static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness)
{
	unsigned int lth = pb->lth_brightness;
	int duty_cycle;

	if (pb->levels)
		duty_cycle = pb->levels[brightness];
	else
		duty_cycle = brightness;

	return (duty_cycle * (pb->period - lth) / pb->scale) + lth;
}

static int pwm_backlight_update_status(struct backlight_device *bl)
{
	struct pwm_bl_data *pb = bl_get_data(bl);
	int brightness = bl->props.brightness;
	int duty_cycle;

	if (bl->props.power != FB_BLANK_UNBLANK ||
	    bl->props.fb_blank != FB_BLANK_UNBLANK ||
	    bl->props.state & BL_CORE_FBBLANK)
		brightness = 0;

	if (pb->notify)
		brightness = pb->notify(pb->dev, brightness);

	if (brightness > 0) {
		duty_cycle = compute_duty_cycle(pb, brightness);
		pwm_config(pb->pwm, duty_cycle, pb->period);
		pwm_backlight_power_on(pb, brightness);
	} else
		pwm_backlight_power_off(pb);

	if (pb->notify_after)
		pb->notify_after(pb->dev, brightness);

	return 0;
}

static int pwm_backlight_check_fb(struct backlight_device *bl,
				  struct fb_info *info)
{
	struct pwm_bl_data *pb = bl_get_data(bl);

	return !pb->check_fb || pb->check_fb(pb->dev, info);
}

static const struct backlight_ops pwm_backlight_ops = {
	.update_status	= pwm_backlight_update_status,
	.check_fb	= pwm_backlight_check_fb,
};

#ifdef CONFIG_OF
static int pwm_backlight_parse_dt(struct device *dev,
				  struct platform_pwm_backlight_data *data)
{
	struct device_node *node = dev->of_node;
	struct property *prop;
	int length;
	u32 value;
	int ret;

	if (!node)
		return -ENODEV;

	memset(data, 0, sizeof(*data));

	/* determine the number of brightness levels */
	prop = of_find_property(node, "brightness-levels", &length);
	if (!prop)
		return -EINVAL;

	data->max_brightness = length / sizeof(u32);

	/* read brightness levels from DT property */
	if (data->max_brightness > 0) {
		size_t size = sizeof(*data->levels) * data->max_brightness;

		data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
		if (!data->levels)
			return -ENOMEM;

		ret = of_property_read_u32_array(node, "brightness-levels",
						 data->levels,
						 data->max_brightness);
		if (ret < 0)
			return ret;

		ret = of_property_read_u32(node, "default-brightness-level",
					   &value);
		if (ret < 0)
			return ret;

		data->dft_brightness = value;
		data->max_brightness--;
	}

	data->enable_gpio = -EINVAL;
	return 0;
}

static struct of_device_id pwm_backlight_of_match[] = {
	{ .compatible = "pwm-backlight" },
	{ }
};

MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
#else
static int pwm_backlight_parse_dt(struct device *dev,
				  struct platform_pwm_backlight_data *data)
{
	return -ENODEV;
}
#endif

static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
{
	struct device_node *node = pb->dev->of_node;

	/* Not booted with device tree or no phandle link to the node */
	if (!node || !node->phandle)
		return FB_BLANK_UNBLANK;

	/*
	 * If the driver is probed from the device tree and there is a
	 * phandle link pointing to the backlight node, it is safe to
	 * assume that another driver will enable the backlight at the
	 * appropriate time. Therefore, if it is disabled, keep it so.
	 */

	/* if the enable GPIO is disabled, do not enable the backlight */
	if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) == 0)
		return FB_BLANK_POWERDOWN;

	/* The regulator is disabled, do not enable the backlight */
	if (!regulator_is_enabled(pb->power_supply))
		return FB_BLANK_POWERDOWN;

	/* The PWM is disabled, keep it like this */
	if (!pwm_is_enabled(pb->pwm))
		return FB_BLANK_POWERDOWN;

	return FB_BLANK_UNBLANK;
}

static int pwm_backlight_probe(struct platform_device *pdev)
{
	struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
	struct platform_pwm_backlight_data defdata;
	struct backlight_properties props;
	struct backlight_device *bl;
	struct device_node *node = pdev->dev.of_node;
	struct pwm_bl_data *pb;
	struct pwm_args pargs;
	int ret;

	if (!data) {
		ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
		if (ret < 0) {
			dev_err(&pdev->dev, "failed to find platform data\n");
			return ret;
		}

		data = &defdata;
	}

	if (data->init) {
		ret = data->init(&pdev->dev);
		if (ret < 0)
			return ret;
	}

	pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
	if (!pb) {
		ret = -ENOMEM;
		goto err_alloc;
	}

	if (data->levels) {
		unsigned int i;

		for (i = 0; i <= data->max_brightness; i++)
			if (data->levels[i] > pb->scale)
				pb->scale = data->levels[i];

		pb->levels = data->levels;
	} else
		pb->scale = data->max_brightness;

	pb->notify = data->notify;
	pb->notify_after = data->notify_after;
	pb->check_fb = data->check_fb;
	pb->exit = data->exit;
	pb->dev = &pdev->dev;
	pb->enabled = false;

	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
						  GPIOD_ASIS);
	if (IS_ERR(pb->enable_gpio)) {
		ret = PTR_ERR(pb->enable_gpio);
		goto err_alloc;
	}

	/*
	 * Compatibility fallback for drivers still using the integer GPIO
	 * platform data. Must go away soon.
	 */
	if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) {
		ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio,
					    GPIOF_OUT_INIT_HIGH, "enable");
		if (ret < 0) {
			dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
				data->enable_gpio, ret);
			goto err_alloc;
		}

		pb->enable_gpio = gpio_to_desc(data->enable_gpio);
	}

	/*
	 * If the GPIO is not known to be already configured as output, that
	 * is, if gpiod_get_direction returns either GPIOF_DIR_IN or -EINVAL,
	 * change the direction to output and set the GPIO as active.
	 * Do not force the GPIO to active when it was already output as it
	 * could cause backlight flickering or we would enable the backlight too
	 * early. Leave the decision of the initial backlight state for later.
	 */
	if (pb->enable_gpio &&
	    gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
		gpiod_direction_output(pb->enable_gpio, 1);

	pb->power_supply = devm_regulator_get(&pdev->dev, "power");
	if (IS_ERR(pb->power_supply)) {
		ret = PTR_ERR(pb->power_supply);
		goto err_alloc;
	}

	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) {
		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
		pb->legacy = true;
		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
	}

	if (IS_ERR(pb->pwm)) {
		ret = PTR_ERR(pb->pwm);
		if (ret != -EPROBE_DEFER)
			dev_err(&pdev->dev, "unable to request PWM\n");
		goto err_alloc;
	}

	dev_dbg(&pdev->dev, "got pwm for backlight\n");

	/*
	 * FIXME: pwm_apply_args() should be removed when switching to
	 * the atomic PWM API.
	 */
	pwm_apply_args(pb->pwm);

	/*
	 * The DT case will set the pwm_period_ns field to 0 and store the
	 * period, parsed from the DT, in the PWM device. For the non-DT case,
	 * set the period from platform data if it has not already been set
	 * via the PWM lookup table.
	 */
	pwm_get_args(pb->pwm, &pargs);
	pb->period = pargs.period;
	if (!pb->period && (data->pwm_period_ns > 0))
		pb->period = data->pwm_period_ns;

	pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);

	memset(&props, 0, sizeof(struct backlight_properties));
	props.type = BACKLIGHT_RAW;
	props.max_brightness = data->max_brightness;
	bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
				       &pwm_backlight_ops, &props);
	if (IS_ERR(bl)) {
		dev_err(&pdev->dev, "failed to register backlight\n");
		ret = PTR_ERR(bl);
		if (pb->legacy)
			pwm_free(pb->pwm);
		goto err_alloc;
	}

	if (data->dft_brightness > data->max_brightness) {
		dev_warn(&pdev->dev,
			 "invalid default brightness level: %u, using %u\n",
			 data->dft_brightness, data->max_brightness);
		data->dft_brightness = data->max_brightness;
	}

	bl->props.brightness = data->dft_brightness;
	bl->props.power = pwm_backlight_initial_power_state(pb);
	backlight_update_status(bl);

	platform_set_drvdata(pdev, bl);
	return 0;

err_alloc:
	if (data->exit)
		data->exit(&pdev->dev);
	return ret;
}

static int pwm_backlight_remove(struct platform_device *pdev)
{
	struct backlight_device *bl = platform_get_drvdata(pdev);
	struct pwm_bl_data *pb = bl_get_data(bl);

	backlight_device_unregister(bl);
	pwm_backlight_power_off(pb);

	if (pb->exit)
		pb->exit(&pdev->dev);
	if (pb->legacy)
		pwm_free(pb->pwm);

	return 0;
}

static void pwm_backlight_shutdown(struct platform_device *pdev)
{
	struct backlight_device *bl = platform_get_drvdata(pdev);
	struct pwm_bl_data *pb = bl_get_data(bl);

	pwm_backlight_power_off(pb);
}

#ifdef CONFIG_PM_SLEEP
static int pwm_backlight_suspend(struct device *dev)
{
	struct backlight_device *bl = dev_get_drvdata(dev);
	struct pwm_bl_data *pb = bl_get_data(bl);

	if (pb->notify)
		pb->notify(pb->dev, 0);

	pwm_backlight_power_off(pb);

	if (pb->notify_after)
		pb->notify_after(pb->dev, 0);

	return 0;
}

static int pwm_backlight_resume(struct device *dev)
{
	struct backlight_device *bl = dev_get_drvdata(dev);

	backlight_update_status(bl);

	return 0;
}
#endif

static const struct dev_pm_ops pwm_backlight_pm_ops = {
#ifdef CONFIG_PM_SLEEP
	.suspend = pwm_backlight_suspend,
	.resume = pwm_backlight_resume,
	.poweroff = pwm_backlight_suspend,
	.restore = pwm_backlight_resume,
#endif
};

static struct platform_driver pwm_backlight_driver = {
	.driver		= {
		.name		= "pwm-backlight",
		.pm		= &pwm_backlight_pm_ops,
		.of_match_table	= of_match_ptr(pwm_backlight_of_match),
	},
	.probe		= pwm_backlight_probe,
	.remove		= pwm_backlight_remove,
	.shutdown	= pwm_backlight_shutdown,
};

module_platform_driver(pwm_backlight_driver);

MODULE_DESCRIPTION("PWM based Backlight Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:pwm-backlight");