1 /*
2  * rotary_encoder.c
3  *
4  * (c) 2009 Daniel Mack <daniel@caiaq.de>
5  * Copyright (C) 2011 Johan Hovold <jhovold@gmail.com>
6  *
7  * state machine code inspired by code from Tim Ruetz
8  *
9  * A generic driver for rotary encoders connected to GPIO lines.
10  * See file:Documentation/input/rotary-encoder.txt for more information
11  *
12  * This program is free software; you can redistribute it and/or modify
13  * it under the terms of the GNU General Public License version 2 as
14  * published by the Free Software Foundation.
15  */
16 
17 #include <linux/kernel.h>
18 #include <linux/module.h>
19 #include <linux/interrupt.h>
20 #include <linux/input.h>
21 #include <linux/device.h>
22 #include <linux/platform_device.h>
23 #include <linux/gpio/consumer.h>
24 #include <linux/rotary_encoder.h>
25 #include <linux/slab.h>
26 #include <linux/of.h>
27 #include <linux/of_platform.h>
28 #include <linux/pm.h>
29 
30 #define DRV_NAME "rotary-encoder"
31 
32 struct rotary_encoder {
33 	struct input_dev *input;
34 	const struct rotary_encoder_platform_data *pdata;
35 	struct mutex access_mutex;
36 
37 	unsigned int axis;
38 	unsigned int pos;
39 
40 	struct gpio_desc *gpio_a;
41 	struct gpio_desc *gpio_b;
42 
43 	unsigned int irq_a;
44 	unsigned int irq_b;
45 
46 	bool armed;
47 	unsigned char dir;	/* 0 - clockwise, 1 - CCW */
48 
49 	char last_stable;
50 };
51 
52 static int rotary_encoder_get_state(struct rotary_encoder *encoder)
53 {
54 	int a = !!gpiod_get_value_cansleep(encoder->gpio_a);
55 	int b = !!gpiod_get_value_cansleep(encoder->gpio_b);
56 
57 	return ((a << 1) | b);
58 }
59 
60 static void rotary_encoder_report_event(struct rotary_encoder *encoder)
61 {
62 	const struct rotary_encoder_platform_data *pdata = encoder->pdata;
63 
64 	if (pdata->relative_axis) {
65 		input_report_rel(encoder->input,
66 				 pdata->axis, encoder->dir ? -1 : 1);
67 	} else {
68 		unsigned int pos = encoder->pos;
69 
70 		if (encoder->dir) {
71 			/* turning counter-clockwise */
72 			if (pdata->rollover)
73 				pos += pdata->steps;
74 			if (pos)
75 				pos--;
76 		} else {
77 			/* turning clockwise */
78 			if (pdata->rollover || pos < pdata->steps)
79 				pos++;
80 		}
81 
82 		if (pdata->rollover)
83 			pos %= pdata->steps;
84 
85 		encoder->pos = pos;
86 		input_report_abs(encoder->input, pdata->axis, encoder->pos);
87 	}
88 
89 	input_sync(encoder->input);
90 }
91 
92 static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
93 {
94 	struct rotary_encoder *encoder = dev_id;
95 	int state;
96 
97 	mutex_lock(&encoder->access_mutex);
98 
99 	state = rotary_encoder_get_state(encoder);
100 
101 	switch (state) {
102 	case 0x0:
103 		if (encoder->armed) {
104 			rotary_encoder_report_event(encoder);
105 			encoder->armed = false;
106 		}
107 		break;
108 
109 	case 0x1:
110 	case 0x2:
111 		if (encoder->armed)
112 			encoder->dir = state - 1;
113 		break;
114 
115 	case 0x3:
116 		encoder->armed = true;
117 		break;
118 	}
119 
120 	mutex_unlock(&encoder->access_mutex);
121 
122 	return IRQ_HANDLED;
123 }
124 
125 static irqreturn_t rotary_encoder_half_period_irq(int irq, void *dev_id)
126 {
127 	struct rotary_encoder *encoder = dev_id;
128 	int state;
129 
130 	mutex_lock(&encoder->access_mutex);
131 
132 	state = rotary_encoder_get_state(encoder);
133 
134 	switch (state) {
135 	case 0x00:
136 	case 0x03:
137 		if (state != encoder->last_stable) {
138 			rotary_encoder_report_event(encoder);
139 			encoder->last_stable = state;
140 		}
141 		break;
142 
143 	case 0x01:
144 	case 0x02:
145 		encoder->dir = (encoder->last_stable + state) & 0x01;
146 		break;
147 	}
148 
149 	mutex_unlock(&encoder->access_mutex);
150 
151 	return IRQ_HANDLED;
152 }
153 
154 static irqreturn_t rotary_encoder_quarter_period_irq(int irq, void *dev_id)
155 {
156 	struct rotary_encoder *encoder = dev_id;
157 	unsigned char sum;
158 	int state;
159 
160 	mutex_lock(&encoder->access_mutex);
161 
162 	state = rotary_encoder_get_state(encoder);
163 
164 	/*
165 	 * We encode the previous and the current state using a byte.
166 	 * The previous state in the MSB nibble, the current state in the LSB
167 	 * nibble. Then use a table to decide the direction of the turn.
168 	 */
169 	sum = (encoder->last_stable << 4) + state;
170 	switch (sum) {
171 	case 0x31:
172 	case 0x10:
173 	case 0x02:
174 	case 0x23:
175 		encoder->dir = 0; /* clockwise */
176 		break;
177 
178 	case 0x13:
179 	case 0x01:
180 	case 0x20:
181 	case 0x32:
182 		encoder->dir = 1; /* counter-clockwise */
183 		break;
184 
185 	default:
186 		/*
187 		 * Ignore all other values. This covers the case when the
188 		 * state didn't change (a spurious interrupt) and the
189 		 * cases where the state changed by two steps, making it
190 		 * impossible to tell the direction.
191 		 *
192 		 * In either case, don't report any event and save the
193 		 * state for later.
194 		 */
195 		goto out;
196 	}
197 
198 	rotary_encoder_report_event(encoder);
199 
200 out:
201 	encoder->last_stable = state;
202 	mutex_unlock(&encoder->access_mutex);
203 
204 	return IRQ_HANDLED;
205 }
206 
207 #ifdef CONFIG_OF
208 static const struct of_device_id rotary_encoder_of_match[] = {
209 	{ .compatible = "rotary-encoder", },
210 	{ },
211 };
212 MODULE_DEVICE_TABLE(of, rotary_encoder_of_match);
213 
214 static struct rotary_encoder_platform_data *rotary_encoder_parse_dt(struct device *dev)
215 {
216 	const struct of_device_id *of_id =
217 				of_match_device(rotary_encoder_of_match, dev);
218 	struct device_node *np = dev->of_node;
219 	struct rotary_encoder_platform_data *pdata;
220 	int error;
221 
222 	if (!of_id || !np)
223 		return NULL;
224 
225 	pdata = devm_kzalloc(dev, sizeof(struct rotary_encoder_platform_data),
226 			     GFP_KERNEL);
227 	if (!pdata)
228 		return ERR_PTR(-ENOMEM);
229 
230 	of_property_read_u32(np, "rotary-encoder,steps", &pdata->steps);
231 	of_property_read_u32(np, "linux,axis", &pdata->axis);
232 
233 	pdata->relative_axis =
234 		of_property_read_bool(np, "rotary-encoder,relative-axis");
235 	pdata->rollover = of_property_read_bool(np, "rotary-encoder,rollover");
236 
237 	error = of_property_read_u32(np, "rotary-encoder,steps-per-period",
238 				     &pdata->steps_per_period);
239 	if (error) {
240 		/*
241 		 * The 'half-period' property has been deprecated, you must use
242 		 * 'steps-per-period' and set an appropriate value, but we still
243 		 * need to parse it to maintain compatibility.
244 		 */
245 		if (of_property_read_bool(np, "rotary-encoder,half-period")) {
246 			pdata->steps_per_period = 2;
247 		} else {
248 			/* Fallback to one step per period behavior */
249 			pdata->steps_per_period = 1;
250 		}
251 	}
252 
253 	pdata->wakeup_source = of_property_read_bool(np, "wakeup-source");
254 
255 	return pdata;
256 }
257 #else
258 static inline struct rotary_encoder_platform_data *
259 rotary_encoder_parse_dt(struct device *dev)
260 {
261 	return NULL;
262 }
263 #endif
264 
265 static int rotary_encoder_probe(struct platform_device *pdev)
266 {
267 	struct device *dev = &pdev->dev;
268 	const struct rotary_encoder_platform_data *pdata = dev_get_platdata(dev);
269 	struct rotary_encoder *encoder;
270 	struct input_dev *input;
271 	irq_handler_t handler;
272 	int err;
273 
274 	if (!pdata) {
275 		pdata = rotary_encoder_parse_dt(dev);
276 		if (IS_ERR(pdata))
277 			return PTR_ERR(pdata);
278 
279 		if (!pdata) {
280 			dev_err(dev, "missing platform data\n");
281 			return -EINVAL;
282 		}
283 	}
284 
285 	encoder = devm_kzalloc(dev, sizeof(struct rotary_encoder), GFP_KERNEL);
286 	if (!encoder)
287 		return -ENOMEM;
288 
289 	mutex_init(&encoder->access_mutex);
290 	encoder->pdata = pdata;
291 
292 	encoder->gpio_a = devm_gpiod_get_index(dev, NULL, 0, GPIOD_IN);
293 	if (IS_ERR(encoder->gpio_a)) {
294 		err = PTR_ERR(encoder->gpio_a);
295 		dev_err(dev, "unable to get GPIO at index 0: %d\n", err);
296 		return err;
297 	}
298 
299 	encoder->irq_a = gpiod_to_irq(encoder->gpio_a);
300 
301 	encoder->gpio_b = devm_gpiod_get_index(dev, NULL, 1, GPIOD_IN);
302 	if (IS_ERR(encoder->gpio_b)) {
303 		err = PTR_ERR(encoder->gpio_b);
304 		dev_err(dev, "unable to get GPIO at index 1: %d\n", err);
305 		return err;
306 	}
307 
308 	encoder->irq_b = gpiod_to_irq(encoder->gpio_b);
309 
310 	input = devm_input_allocate_device(dev);
311 	if (!input)
312 		return -ENOMEM;
313 
314 	encoder->input = input;
315 
316 	input->name = pdev->name;
317 	input->id.bustype = BUS_HOST;
318 	input->dev.parent = dev;
319 
320 	if (pdata->relative_axis) {
321 		input->evbit[0] = BIT_MASK(EV_REL);
322 		input->relbit[0] = BIT_MASK(pdata->axis);
323 	} else {
324 		input->evbit[0] = BIT_MASK(EV_ABS);
325 		input_set_abs_params(encoder->input,
326 				     pdata->axis, 0, pdata->steps, 0, 1);
327 	}
328 
329 	switch (pdata->steps_per_period) {
330 	case 4:
331 		handler = &rotary_encoder_quarter_period_irq;
332 		encoder->last_stable = rotary_encoder_get_state(encoder);
333 		break;
334 	case 2:
335 		handler = &rotary_encoder_half_period_irq;
336 		encoder->last_stable = rotary_encoder_get_state(encoder);
337 		break;
338 	case 1:
339 		handler = &rotary_encoder_irq;
340 		break;
341 	default:
342 		dev_err(dev, "'%d' is not a valid steps-per-period value\n",
343 			pdata->steps_per_period);
344 		return -EINVAL;
345 	}
346 
347 	err = devm_request_threaded_irq(dev, encoder->irq_a, NULL, handler,
348 				IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
349 				IRQF_ONESHOT,
350 				DRV_NAME, encoder);
351 	if (err) {
352 		dev_err(dev, "unable to request IRQ %d\n", encoder->irq_a);
353 		return err;
354 	}
355 
356 	err = devm_request_threaded_irq(dev, encoder->irq_b, NULL, handler,
357 				IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
358 				IRQF_ONESHOT,
359 				DRV_NAME, encoder);
360 	if (err) {
361 		dev_err(dev, "unable to request IRQ %d\n", encoder->irq_b);
362 		return err;
363 	}
364 
365 	err = input_register_device(input);
366 	if (err) {
367 		dev_err(dev, "failed to register input device\n");
368 		return err;
369 	}
370 
371 	device_init_wakeup(&pdev->dev, pdata->wakeup_source);
372 
373 	platform_set_drvdata(pdev, encoder);
374 
375 	return 0;
376 }
377 
378 static int __maybe_unused rotary_encoder_suspend(struct device *dev)
379 {
380 	struct rotary_encoder *encoder = dev_get_drvdata(dev);
381 
382 	if (device_may_wakeup(dev)) {
383 		enable_irq_wake(encoder->irq_a);
384 		enable_irq_wake(encoder->irq_b);
385 	}
386 
387 	return 0;
388 }
389 
390 static int __maybe_unused rotary_encoder_resume(struct device *dev)
391 {
392 	struct rotary_encoder *encoder = dev_get_drvdata(dev);
393 
394 	if (device_may_wakeup(dev)) {
395 		disable_irq_wake(encoder->irq_a);
396 		disable_irq_wake(encoder->irq_b);
397 	}
398 
399 	return 0;
400 }
401 
402 static SIMPLE_DEV_PM_OPS(rotary_encoder_pm_ops,
403 			 rotary_encoder_suspend, rotary_encoder_resume);
404 
405 static struct platform_driver rotary_encoder_driver = {
406 	.probe		= rotary_encoder_probe,
407 	.driver		= {
408 		.name	= DRV_NAME,
409 		.pm	= &rotary_encoder_pm_ops,
410 		.of_match_table = of_match_ptr(rotary_encoder_of_match),
411 	}
412 };
413 module_platform_driver(rotary_encoder_driver);
414 
415 MODULE_ALIAS("platform:" DRV_NAME);
416 MODULE_DESCRIPTION("GPIO rotary encoder driver");
417 MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>, Johan Hovold");
418 MODULE_LICENSE("GPL v2");
419