1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * rotary_encoder.c
4 *
5 * (c) 2009 Daniel Mack <daniel@caiaq.de>
6 * Copyright (C) 2011 Johan Hovold <jhovold@gmail.com>
7 *
8 * state machine code inspired by code from Tim Ruetz
9 *
10 * A generic driver for rotary encoders connected to GPIO lines.
11 * See file:Documentation/input/devices/rotary-encoder.rst for more information
12 */
13
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/interrupt.h>
17#include <linux/input.h>
18#include <linux/device.h>
19#include <linux/platform_device.h>
20#include <linux/gpio/consumer.h>
21#include <linux/slab.h>
22#include <linux/of.h>
23#include <linux/pm.h>
24#include <linux/property.h>
25
26#define DRV_NAME "rotary-encoder"
27
28enum rotary_encoder_encoding {
29	ROTENC_GRAY,
30	ROTENC_BINARY,
31};
32
33struct rotary_encoder {
34	struct input_dev *input;
35
36	struct mutex access_mutex;
37
38	u32 steps;
39	u32 axis;
40	bool relative_axis;
41	bool rollover;
42	enum rotary_encoder_encoding encoding;
43
44	unsigned int pos;
45
46	struct gpio_descs *gpios;
47
48	unsigned int *irq;
49
50	bool armed;
51	signed char dir;	/* 1 - clockwise, -1 - CCW */
52
53	unsigned int last_stable;
54};
55
56static unsigned int rotary_encoder_get_state(struct rotary_encoder *encoder)
57{
58	int i;
59	unsigned int ret = 0;
60
61	for (i = 0; i < encoder->gpios->ndescs; ++i) {
62		int val = gpiod_get_value_cansleep(encoder->gpios->desc[i]);
63
64		/* convert from gray encoding to normal */
65		if (encoder->encoding == ROTENC_GRAY && ret & 1)
66			val = !val;
67
68		ret = ret << 1 | val;
69	}
70
71	return ret & 3;
72}
73
74static void rotary_encoder_report_event(struct rotary_encoder *encoder)
75{
76	if (encoder->relative_axis) {
77		input_report_rel(encoder->input,
78				 encoder->axis, encoder->dir);
79	} else {
80		unsigned int pos = encoder->pos;
81
82		if (encoder->dir < 0) {
83			/* turning counter-clockwise */
84			if (encoder->rollover)
85				pos += encoder->steps;
86			if (pos)
87				pos--;
88		} else {
89			/* turning clockwise */
90			if (encoder->rollover || pos < encoder->steps)
91				pos++;
92		}
93
94		if (encoder->rollover)
95			pos %= encoder->steps;
96
97		encoder->pos = pos;
98		input_report_abs(encoder->input, encoder->axis, encoder->pos);
99	}
100
101	input_sync(encoder->input);
102}
103
104static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
105{
106	struct rotary_encoder *encoder = dev_id;
107	unsigned int state;
108
109	mutex_lock(&encoder->access_mutex);
110
111	state = rotary_encoder_get_state(encoder);
112
113	switch (state) {
114	case 0x0:
115		if (encoder->armed) {
116			rotary_encoder_report_event(encoder);
117			encoder->armed = false;
118		}
119		break;
120
121	case 0x1:
122	case 0x3:
123		if (encoder->armed)
124			encoder->dir = 2 - state;
125		break;
126
127	case 0x2:
128		encoder->armed = true;
129		break;
130	}
131
132	mutex_unlock(&encoder->access_mutex);
133
134	return IRQ_HANDLED;
135}
136
137static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
138{
139	struct rotary_encoder *encoder = dev_id;
140	unsigned int state;
141
142	mutex_lock(&encoder->access_mutex);
143
144	state = rotary_encoder_get_state(encoder);
145
146	if (state & 1) {
147		encoder->dir = ((encoder->last_stable - state + 1) % 4) - 1;
148	} else {
149		if (state != encoder->last_stable) {
150			rotary_encoder_report_event(encoder);
151			encoder->last_stable = state;
152		}
153	}
154
155	mutex_unlock(&encoder->access_mutex);
156
157	return IRQ_HANDLED;
158}
159
160static irqreturn_t rotary_encoder_quarter_period_irq(int irq, void *dev_id)
161{
162	struct rotary_encoder *encoder = dev_id;
163	unsigned int state;
164
165	mutex_lock(&encoder->access_mutex);
166
167	state = rotary_encoder_get_state(encoder);
168
169	if ((encoder->last_stable + 1) % 4 == state)
170		encoder->dir = 1;
171	else if (encoder->last_stable == (state + 1) % 4)
172		encoder->dir = -1;
173	else
174		goto out;
175
176	rotary_encoder_report_event(encoder);
177
178out:
179	encoder->last_stable = state;
180	mutex_unlock(&encoder->access_mutex);
181
182	return IRQ_HANDLED;
183}
184
185static int rotary_encoder_probe(struct platform_device *pdev)
186{
187	struct device *dev = &pdev->dev;
188	struct rotary_encoder *encoder;
189	struct input_dev *input;
190	irq_handler_t handler;
191	u32 steps_per_period;
192	unsigned int i;
193	int err;
194
195	encoder = devm_kzalloc(dev, sizeof(struct rotary_encoder), GFP_KERNEL);
196	if (!encoder)
197		return -ENOMEM;
198
199	mutex_init(&encoder->access_mutex);
200
201	device_property_read_u32(dev, "rotary-encoder,steps", &encoder->steps);
202
203	err = device_property_read_u32(dev, "rotary-encoder,steps-per-period",
204				       &steps_per_period);
205	if (err) {
206		/*
207		 * The 'half-period' property has been deprecated, you must
208		 * use 'steps-per-period' and set an appropriate value, but
209		 * we still need to parse it to maintain compatibility. If
210		 * neither property is present we fall back to the one step
211		 * per period behavior.
212		 */
213		steps_per_period = device_property_read_bool(dev,
214					"rotary-encoder,half-period") ? 2 : 1;
215	}
216
217	encoder->rollover =
218		device_property_read_bool(dev, "rotary-encoder,rollover");
219
220	if (!device_property_present(dev, "rotary-encoder,encoding") ||
221	    !device_property_match_string(dev, "rotary-encoder,encoding",
222					  "gray")) {
223		dev_info(dev, "gray");
224		encoder->encoding = ROTENC_GRAY;
225	} else if (!device_property_match_string(dev, "rotary-encoder,encoding",
226						 "binary")) {
227		dev_info(dev, "binary");
228		encoder->encoding = ROTENC_BINARY;
229	} else {
230		dev_err(dev, "unknown encoding setting\n");
231		return -EINVAL;
232	}
233
234	device_property_read_u32(dev, "linux,axis", &encoder->axis);
235	encoder->relative_axis =
236		device_property_read_bool(dev, "rotary-encoder,relative-axis");
237
238	encoder->gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
239	if (IS_ERR(encoder->gpios))
240		return dev_err_probe(dev, PTR_ERR(encoder->gpios), "unable to get gpios\n");
241	if (encoder->gpios->ndescs < 2) {
242		dev_err(dev, "not enough gpios found\n");
243		return -EINVAL;
244	}
245
246	input = devm_input_allocate_device(dev);
247	if (!input)
248		return -ENOMEM;
249
250	encoder->input = input;
251
252	input->name = pdev->name;
253	input->id.bustype = BUS_HOST;
254
255	if (encoder->relative_axis)
256		input_set_capability(input, EV_REL, encoder->axis);
257	else
258		input_set_abs_params(input,
259				     encoder->axis, 0, encoder->steps, 0, 1);
260
261	switch (steps_per_period >> (encoder->gpios->ndescs - 2)) {
262	case 4:
263		handler = &rotary_encoder_quarter_period_irq;
264		encoder->last_stable = rotary_encoder_get_state(encoder);
265		break;
266	case 2:
267		handler = &rotary_encoder_half_period_irq;
268		encoder->last_stable = rotary_encoder_get_state(encoder);
269		break;
270	case 1:
271		handler = &rotary_encoder_irq;
272		break;
273	default:
274		dev_err(dev, "'%d' is not a valid steps-per-period value\n",
275			steps_per_period);
276		return -EINVAL;
277	}
278
279	encoder->irq =
280		devm_kcalloc(dev,
281			     encoder->gpios->ndescs, sizeof(*encoder->irq),
282			     GFP_KERNEL);
283	if (!encoder->irq)
284		return -ENOMEM;
285
286	for (i = 0; i < encoder->gpios->ndescs; ++i) {
287		encoder->irq[i] = gpiod_to_irq(encoder->gpios->desc[i]);
288
289		err = devm_request_threaded_irq(dev, encoder->irq[i],
290				NULL, handler,
291				IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
292				IRQF_ONESHOT,
293				DRV_NAME, encoder);
294		if (err) {
295			dev_err(dev, "unable to request IRQ %d (gpio#%d)\n",
296				encoder->irq[i], i);
297			return err;
298		}
299	}
300
301	err = input_register_device(input);
302	if (err) {
303		dev_err(dev, "failed to register input device\n");
304		return err;
305	}
306
307	device_init_wakeup(dev,
308			   device_property_read_bool(dev, "wakeup-source"));
309
310	platform_set_drvdata(pdev, encoder);
311
312	return 0;
313}
314
315static int rotary_encoder_suspend(struct device *dev)
316{
317	struct rotary_encoder *encoder = dev_get_drvdata(dev);
318	unsigned int i;
319
320	if (device_may_wakeup(dev)) {
321		for (i = 0; i < encoder->gpios->ndescs; ++i)
322			enable_irq_wake(encoder->irq[i]);
323	}
324
325	return 0;
326}
327
328static int rotary_encoder_resume(struct device *dev)
329{
330	struct rotary_encoder *encoder = dev_get_drvdata(dev);
331	unsigned int i;
332
333	if (device_may_wakeup(dev)) {
334		for (i = 0; i < encoder->gpios->ndescs; ++i)
335			disable_irq_wake(encoder->irq[i]);
336	}
337
338	return 0;
339}
340
341static DEFINE_SIMPLE_DEV_PM_OPS(rotary_encoder_pm_ops,
342				rotary_encoder_suspend, rotary_encoder_resume);
343
344#ifdef CONFIG_OF
345static const struct of_device_id rotary_encoder_of_match[] = {
346	{ .compatible = "rotary-encoder", },
347	{ },
348};
349MODULE_DEVICE_TABLE(of, rotary_encoder_of_match);
350#endif
351
352static struct platform_driver rotary_encoder_driver = {
353	.probe		= rotary_encoder_probe,
354	.driver		= {
355		.name	= DRV_NAME,
356		.pm	= pm_sleep_ptr(&rotary_encoder_pm_ops),
357		.of_match_table = of_match_ptr(rotary_encoder_of_match),
358	}
359};
360module_platform_driver(rotary_encoder_driver);
361
362MODULE_ALIAS("platform:" DRV_NAME);
363MODULE_DESCRIPTION("GPIO rotary encoder driver");
364MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
365MODULE_LICENSE("GPL v2");
366