1/*
2 * Toradex Colibri VF50 Touchscreen driver
3 *
4 * Copyright 2015 Toradex AG
5 *
6 * Originally authored by Stefan Agner for 3.0 kernel
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 as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 */
13
14#include <linux/delay.h>
15#include <linux/err.h>
16#include <linux/gpio.h>
17#include <linux/gpio/consumer.h>
18#include <linux/iio/consumer.h>
19#include <linux/iio/types.h>
20#include <linux/input.h>
21#include <linux/interrupt.h>
22#include <linux/kernel.h>
23#include <linux/module.h>
24#include <linux/pinctrl/consumer.h>
25#include <linux/platform_device.h>
26#include <linux/slab.h>
27#include <linux/types.h>
28
29#define DRIVER_NAME			"colibri-vf50-ts"
30#define DRV_VERSION			"1.0"
31
32#define VF_ADC_MAX			((1 << 12) - 1)
33
34#define COLI_TOUCH_MIN_DELAY_US		1000
35#define COLI_TOUCH_MAX_DELAY_US		2000
36#define COLI_PULLUP_MIN_DELAY_US	10000
37#define COLI_PULLUP_MAX_DELAY_US	11000
38#define COLI_TOUCH_NO_OF_AVGS		5
39#define COLI_TOUCH_REQ_ADC_CHAN		4
40
41struct vf50_touch_device {
42	struct platform_device *pdev;
43	struct input_dev *ts_input;
44	struct iio_channel *channels;
45	struct gpio_desc *gpio_xp;
46	struct gpio_desc *gpio_xm;
47	struct gpio_desc *gpio_yp;
48	struct gpio_desc *gpio_ym;
49	int pen_irq;
50	int min_pressure;
51	bool stop_touchscreen;
52};
53
54/*
55 * Enables given plates and measures touch parameters using ADC
56 */
57static int adc_ts_measure(struct iio_channel *channel,
58			  struct gpio_desc *plate_p, struct gpio_desc *plate_m)
59{
60	int i, value = 0, val = 0;
61	int error;
62
63	gpiod_set_value(plate_p, 1);
64	gpiod_set_value(plate_m, 1);
65
66	usleep_range(COLI_TOUCH_MIN_DELAY_US, COLI_TOUCH_MAX_DELAY_US);
67
68	for (i = 0; i < COLI_TOUCH_NO_OF_AVGS; i++) {
69		error = iio_read_channel_raw(channel, &val);
70		if (error < 0) {
71			value = error;
72			goto error_iio_read;
73		}
74
75		value += val;
76	}
77
78	value /= COLI_TOUCH_NO_OF_AVGS;
79
80error_iio_read:
81	gpiod_set_value(plate_p, 0);
82	gpiod_set_value(plate_m, 0);
83
84	return value;
85}
86
87/*
88 * Enable touch detection using falling edge detection on XM
89 */
90static void vf50_ts_enable_touch_detection(struct vf50_touch_device *vf50_ts)
91{
92	/* Enable plate YM (needs to be strong GND, high active) */
93	gpiod_set_value(vf50_ts->gpio_ym, 1);
94
95	/*
96	 * Let the platform mux to idle state in order to enable
97	 * Pull-Up on GPIO
98	 */
99	pinctrl_pm_select_idle_state(&vf50_ts->pdev->dev);
100
101	/* Wait for the pull-up to be stable on high */
102	usleep_range(COLI_PULLUP_MIN_DELAY_US, COLI_PULLUP_MAX_DELAY_US);
103}
104
105/*
106 * ADC touch screen sampling bottom half irq handler
107 */
108static irqreturn_t vf50_ts_irq_bh(int irq, void *private)
109{
110	struct vf50_touch_device *vf50_ts = private;
111	struct device *dev = &vf50_ts->pdev->dev;
112	int val_x, val_y, val_z1, val_z2, val_p = 0;
113	bool discard_val_on_start = true;
114
115	/* Disable the touch detection plates */
116	gpiod_set_value(vf50_ts->gpio_ym, 0);
117
118	/* Let the platform mux to default state in order to mux as ADC */
119	pinctrl_pm_select_default_state(dev);
120
121	while (!vf50_ts->stop_touchscreen) {
122		/* X-Direction */
123		val_x = adc_ts_measure(&vf50_ts->channels[0],
124				vf50_ts->gpio_xp, vf50_ts->gpio_xm);
125		if (val_x < 0)
126			break;
127
128		/* Y-Direction */
129		val_y = adc_ts_measure(&vf50_ts->channels[1],
130				vf50_ts->gpio_yp, vf50_ts->gpio_ym);
131		if (val_y < 0)
132			break;
133
134		/*
135		 * Touch pressure
136		 * Measure on XP/YM
137		 */
138		val_z1 = adc_ts_measure(&vf50_ts->channels[2],
139				vf50_ts->gpio_yp, vf50_ts->gpio_xm);
140		if (val_z1 < 0)
141			break;
142		val_z2 = adc_ts_measure(&vf50_ts->channels[3],
143				vf50_ts->gpio_yp, vf50_ts->gpio_xm);
144		if (val_z2 < 0)
145			break;
146
147		/* Validate signal (avoid calculation using noise) */
148		if (val_z1 > 64 && val_x > 64) {
149			/*
150			 * Calculate resistance between the plates
151			 * lower resistance means higher pressure
152			 */
153			int r_x = (1000 * val_x) / VF_ADC_MAX;
154
155			val_p = (r_x * val_z2) / val_z1 - r_x;
156
157		} else {
158			val_p = 2000;
159		}
160
161		val_p = 2000 - val_p;
162		dev_dbg(dev,
163			"Measured values: x: %d, y: %d, z1: %d, z2: %d, p: %d\n",
164			val_x, val_y, val_z1, val_z2, val_p);
165
166		/*
167		 * If touch pressure is too low, stop measuring and reenable
168		 * touch detection
169		 */
170		if (val_p < vf50_ts->min_pressure || val_p > 2000)
171			break;
172
173		/*
174		 * The pressure may not be enough for the first x and the
175		 * second y measurement, but, the pressure is ok when the
176		 * driver is doing the third and fourth measurement. To
177		 * take care of this, we drop the first measurement always.
178		 */
179		if (discard_val_on_start) {
180			discard_val_on_start = false;
181		} else {
182			/*
183			 * Report touch position and sleep for
184			 * the next measurement.
185			 */
186			input_report_abs(vf50_ts->ts_input,
187					ABS_X, VF_ADC_MAX - val_x);
188			input_report_abs(vf50_ts->ts_input,
189					ABS_Y, VF_ADC_MAX - val_y);
190			input_report_abs(vf50_ts->ts_input,
191					ABS_PRESSURE, val_p);
192			input_report_key(vf50_ts->ts_input, BTN_TOUCH, 1);
193			input_sync(vf50_ts->ts_input);
194		}
195
196		usleep_range(COLI_PULLUP_MIN_DELAY_US,
197			     COLI_PULLUP_MAX_DELAY_US);
198	}
199
200	/* Report no more touch, re-enable touch detection */
201	input_report_abs(vf50_ts->ts_input, ABS_PRESSURE, 0);
202	input_report_key(vf50_ts->ts_input, BTN_TOUCH, 0);
203	input_sync(vf50_ts->ts_input);
204
205	vf50_ts_enable_touch_detection(vf50_ts);
206
207	return IRQ_HANDLED;
208}
209
210static int vf50_ts_open(struct input_dev *dev_input)
211{
212	struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
213	struct device *dev = &touchdev->pdev->dev;
214
215	dev_dbg(dev, "Input device %s opened, starting touch detection\n",
216		dev_input->name);
217
218	touchdev->stop_touchscreen = false;
219
220	/* Mux detection before request IRQ, wait for pull-up to settle */
221	vf50_ts_enable_touch_detection(touchdev);
222
223	return 0;
224}
225
226static void vf50_ts_close(struct input_dev *dev_input)
227{
228	struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
229	struct device *dev = &touchdev->pdev->dev;
230
231	touchdev->stop_touchscreen = true;
232
233	/* Make sure IRQ is not running past close */
234	mb();
235	synchronize_irq(touchdev->pen_irq);
236
237	gpiod_set_value(touchdev->gpio_ym, 0);
238	pinctrl_pm_select_default_state(dev);
239
240	dev_dbg(dev, "Input device %s closed, disable touch detection\n",
241		dev_input->name);
242}
243
244static int vf50_ts_get_gpiod(struct device *dev, struct gpio_desc **gpio_d,
245			     const char *con_id, enum gpiod_flags flags)
246{
247	int error;
248
249	*gpio_d = devm_gpiod_get(dev, con_id, flags);
250	if (IS_ERR(*gpio_d)) {
251		error = PTR_ERR(*gpio_d);
252		dev_err(dev, "Could not get gpio_%s %d\n", con_id, error);
253		return error;
254	}
255
256	return 0;
257}
258
259static void vf50_ts_channel_release(void *data)
260{
261	struct iio_channel *channels = data;
262
263	iio_channel_release_all(channels);
264}
265
266static int vf50_ts_probe(struct platform_device *pdev)
267{
268	struct input_dev *input;
269	struct iio_channel *channels;
270	struct device *dev = &pdev->dev;
271	struct vf50_touch_device *touchdev;
272	int num_adc_channels;
273	int error;
274
275	channels = iio_channel_get_all(dev);
276	if (IS_ERR(channels))
277		return PTR_ERR(channels);
278
279	error = devm_add_action(dev, vf50_ts_channel_release, channels);
280	if (error) {
281		iio_channel_release_all(channels);
282		dev_err(dev, "Failed to register iio channel release action");
283		return error;
284	}
285
286	num_adc_channels = 0;
287	while (channels[num_adc_channels].indio_dev)
288		num_adc_channels++;
289
290	if (num_adc_channels != COLI_TOUCH_REQ_ADC_CHAN) {
291		dev_err(dev, "Inadequate ADC channels specified\n");
292		return -EINVAL;
293	}
294
295	touchdev = devm_kzalloc(dev, sizeof(*touchdev), GFP_KERNEL);
296	if (!touchdev)
297		return -ENOMEM;
298
299	touchdev->pdev = pdev;
300	touchdev->channels = channels;
301
302	error = of_property_read_u32(dev->of_node, "vf50-ts-min-pressure",
303				 &touchdev->min_pressure);
304	if (error)
305		return error;
306
307	input = devm_input_allocate_device(dev);
308	if (!input) {
309		dev_err(dev, "Failed to allocate TS input device\n");
310		return -ENOMEM;
311	}
312
313	platform_set_drvdata(pdev, touchdev);
314
315	input->name = DRIVER_NAME;
316	input->id.bustype = BUS_HOST;
317	input->dev.parent = dev;
318	input->open = vf50_ts_open;
319	input->close = vf50_ts_close;
320
321	input_set_capability(input, EV_KEY, BTN_TOUCH);
322	input_set_abs_params(input, ABS_X, 0, VF_ADC_MAX, 0, 0);
323	input_set_abs_params(input, ABS_Y, 0, VF_ADC_MAX, 0, 0);
324	input_set_abs_params(input, ABS_PRESSURE, 0, VF_ADC_MAX, 0, 0);
325
326	touchdev->ts_input = input;
327	input_set_drvdata(input, touchdev);
328
329	error = input_register_device(input);
330	if (error) {
331		dev_err(dev, "Failed to register input device\n");
332		return error;
333	}
334
335	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xp, "xp", GPIOD_OUT_LOW);
336	if (error)
337		return error;
338
339	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xm,
340				"xm", GPIOD_OUT_LOW);
341	if (error)
342		return error;
343
344	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_yp, "yp", GPIOD_OUT_LOW);
345	if (error)
346		return error;
347
348	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_ym, "ym", GPIOD_OUT_LOW);
349	if (error)
350		return error;
351
352	touchdev->pen_irq = platform_get_irq(pdev, 0);
353	if (touchdev->pen_irq < 0)
354		return touchdev->pen_irq;
355
356	error = devm_request_threaded_irq(dev, touchdev->pen_irq,
357					  NULL, vf50_ts_irq_bh, IRQF_ONESHOT,
358					  "vf50 touch", touchdev);
359	if (error) {
360		dev_err(dev, "Failed to request IRQ %d: %d\n",
361			touchdev->pen_irq, error);
362		return error;
363	}
364
365	return 0;
366}
367
368static const struct of_device_id vf50_touch_of_match[] = {
369	{ .compatible = "toradex,vf50-touchscreen", },
370	{ }
371};
372MODULE_DEVICE_TABLE(of, vf50_touch_of_match);
373
374static struct platform_driver vf50_touch_driver = {
375	.driver = {
376		.name = "toradex,vf50_touchctrl",
377		.of_match_table = vf50_touch_of_match,
378	},
379	.probe = vf50_ts_probe,
380};
381module_platform_driver(vf50_touch_driver);
382
383MODULE_AUTHOR("Sanchayan Maity");
384MODULE_DESCRIPTION("Colibri VF50 Touchscreen driver");
385MODULE_LICENSE("GPL");
386MODULE_VERSION(DRV_VERSION);
387