1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Toradex Colibri VF50 Touchscreen driver
4 *
5 * Copyright 2015 Toradex AG
6 *
7 * Originally authored by Stefan Agner for 3.0 kernel
8 */
9
10#include <linux/delay.h>
11#include <linux/err.h>
12#include <linux/gpio/consumer.h>
13#include <linux/iio/consumer.h>
14#include <linux/iio/types.h>
15#include <linux/input.h>
16#include <linux/interrupt.h>
17#include <linux/kernel.h>
18#include <linux/module.h>
19#include <linux/of.h>
20#include <linux/pinctrl/consumer.h>
21#include <linux/platform_device.h>
22#include <linux/slab.h>
23#include <linux/types.h>
24
25#define DRIVER_NAME			"colibri-vf50-ts"
26
27#define VF_ADC_MAX			((1 << 12) - 1)
28
29#define COLI_TOUCH_MIN_DELAY_US		1000
30#define COLI_TOUCH_MAX_DELAY_US		2000
31#define COLI_PULLUP_MIN_DELAY_US	10000
32#define COLI_PULLUP_MAX_DELAY_US	11000
33#define COLI_TOUCH_NO_OF_AVGS		5
34#define COLI_TOUCH_REQ_ADC_CHAN		4
35
36struct vf50_touch_device {
37	struct platform_device *pdev;
38	struct input_dev *ts_input;
39	struct iio_channel *channels;
40	struct gpio_desc *gpio_xp;
41	struct gpio_desc *gpio_xm;
42	struct gpio_desc *gpio_yp;
43	struct gpio_desc *gpio_ym;
44	int pen_irq;
45	int min_pressure;
46	bool stop_touchscreen;
47};
48
49/*
50 * Enables given plates and measures touch parameters using ADC
51 */
52static int adc_ts_measure(struct iio_channel *channel,
53			  struct gpio_desc *plate_p, struct gpio_desc *plate_m)
54{
55	int i, value = 0, val = 0;
56	int error;
57
58	gpiod_set_value(plate_p, 1);
59	gpiod_set_value(plate_m, 1);
60
61	usleep_range(COLI_TOUCH_MIN_DELAY_US, COLI_TOUCH_MAX_DELAY_US);
62
63	for (i = 0; i < COLI_TOUCH_NO_OF_AVGS; i++) {
64		error = iio_read_channel_raw(channel, &val);
65		if (error < 0) {
66			value = error;
67			goto error_iio_read;
68		}
69
70		value += val;
71	}
72
73	value /= COLI_TOUCH_NO_OF_AVGS;
74
75error_iio_read:
76	gpiod_set_value(plate_p, 0);
77	gpiod_set_value(plate_m, 0);
78
79	return value;
80}
81
82/*
83 * Enable touch detection using falling edge detection on XM
84 */
85static void vf50_ts_enable_touch_detection(struct vf50_touch_device *vf50_ts)
86{
87	/* Enable plate YM (needs to be strong GND, high active) */
88	gpiod_set_value(vf50_ts->gpio_ym, 1);
89
90	/*
91	 * Let the platform mux to idle state in order to enable
92	 * Pull-Up on GPIO
93	 */
94	pinctrl_pm_select_idle_state(&vf50_ts->pdev->dev);
95
96	/* Wait for the pull-up to be stable on high */
97	usleep_range(COLI_PULLUP_MIN_DELAY_US, COLI_PULLUP_MAX_DELAY_US);
98}
99
100/*
101 * ADC touch screen sampling bottom half irq handler
102 */
103static irqreturn_t vf50_ts_irq_bh(int irq, void *private)
104{
105	struct vf50_touch_device *vf50_ts = private;
106	struct device *dev = &vf50_ts->pdev->dev;
107	int val_x, val_y, val_z1, val_z2, val_p = 0;
108	bool discard_val_on_start = true;
109
110	/* Disable the touch detection plates */
111	gpiod_set_value(vf50_ts->gpio_ym, 0);
112
113	/* Let the platform mux to default state in order to mux as ADC */
114	pinctrl_pm_select_default_state(dev);
115
116	while (!vf50_ts->stop_touchscreen) {
117		/* X-Direction */
118		val_x = adc_ts_measure(&vf50_ts->channels[0],
119				vf50_ts->gpio_xp, vf50_ts->gpio_xm);
120		if (val_x < 0)
121			break;
122
123		/* Y-Direction */
124		val_y = adc_ts_measure(&vf50_ts->channels[1],
125				vf50_ts->gpio_yp, vf50_ts->gpio_ym);
126		if (val_y < 0)
127			break;
128
129		/*
130		 * Touch pressure
131		 * Measure on XP/YM
132		 */
133		val_z1 = adc_ts_measure(&vf50_ts->channels[2],
134				vf50_ts->gpio_yp, vf50_ts->gpio_xm);
135		if (val_z1 < 0)
136			break;
137		val_z2 = adc_ts_measure(&vf50_ts->channels[3],
138				vf50_ts->gpio_yp, vf50_ts->gpio_xm);
139		if (val_z2 < 0)
140			break;
141
142		/* Validate signal (avoid calculation using noise) */
143		if (val_z1 > 64 && val_x > 64) {
144			/*
145			 * Calculate resistance between the plates
146			 * lower resistance means higher pressure
147			 */
148			int r_x = (1000 * val_x) / VF_ADC_MAX;
149
150			val_p = (r_x * val_z2) / val_z1 - r_x;
151
152		} else {
153			val_p = 2000;
154		}
155
156		val_p = 2000 - val_p;
157		dev_dbg(dev,
158			"Measured values: x: %d, y: %d, z1: %d, z2: %d, p: %d\n",
159			val_x, val_y, val_z1, val_z2, val_p);
160
161		/*
162		 * If touch pressure is too low, stop measuring and reenable
163		 * touch detection
164		 */
165		if (val_p < vf50_ts->min_pressure || val_p > 2000)
166			break;
167
168		/*
169		 * The pressure may not be enough for the first x and the
170		 * second y measurement, but, the pressure is ok when the
171		 * driver is doing the third and fourth measurement. To
172		 * take care of this, we drop the first measurement always.
173		 */
174		if (discard_val_on_start) {
175			discard_val_on_start = false;
176		} else {
177			/*
178			 * Report touch position and sleep for
179			 * the next measurement.
180			 */
181			input_report_abs(vf50_ts->ts_input,
182					ABS_X, VF_ADC_MAX - val_x);
183			input_report_abs(vf50_ts->ts_input,
184					ABS_Y, VF_ADC_MAX - val_y);
185			input_report_abs(vf50_ts->ts_input,
186					ABS_PRESSURE, val_p);
187			input_report_key(vf50_ts->ts_input, BTN_TOUCH, 1);
188			input_sync(vf50_ts->ts_input);
189		}
190
191		usleep_range(COLI_PULLUP_MIN_DELAY_US,
192			     COLI_PULLUP_MAX_DELAY_US);
193	}
194
195	/* Report no more touch, re-enable touch detection */
196	input_report_abs(vf50_ts->ts_input, ABS_PRESSURE, 0);
197	input_report_key(vf50_ts->ts_input, BTN_TOUCH, 0);
198	input_sync(vf50_ts->ts_input);
199
200	vf50_ts_enable_touch_detection(vf50_ts);
201
202	return IRQ_HANDLED;
203}
204
205static int vf50_ts_open(struct input_dev *dev_input)
206{
207	struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
208	struct device *dev = &touchdev->pdev->dev;
209
210	dev_dbg(dev, "Input device %s opened, starting touch detection\n",
211		dev_input->name);
212
213	touchdev->stop_touchscreen = false;
214
215	/* Mux detection before request IRQ, wait for pull-up to settle */
216	vf50_ts_enable_touch_detection(touchdev);
217
218	return 0;
219}
220
221static void vf50_ts_close(struct input_dev *dev_input)
222{
223	struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
224	struct device *dev = &touchdev->pdev->dev;
225
226	touchdev->stop_touchscreen = true;
227
228	/* Make sure IRQ is not running past close */
229	mb();
230	synchronize_irq(touchdev->pen_irq);
231
232	gpiod_set_value(touchdev->gpio_ym, 0);
233	pinctrl_pm_select_default_state(dev);
234
235	dev_dbg(dev, "Input device %s closed, disable touch detection\n",
236		dev_input->name);
237}
238
239static int vf50_ts_get_gpiod(struct device *dev, struct gpio_desc **gpio_d,
240			     const char *con_id, enum gpiod_flags flags)
241{
242	int error;
243
244	*gpio_d = devm_gpiod_get(dev, con_id, flags);
245	if (IS_ERR(*gpio_d)) {
246		error = PTR_ERR(*gpio_d);
247		dev_err(dev, "Could not get gpio_%s %d\n", con_id, error);
248		return error;
249	}
250
251	return 0;
252}
253
254static void vf50_ts_channel_release(void *data)
255{
256	struct iio_channel *channels = data;
257
258	iio_channel_release_all(channels);
259}
260
261static int vf50_ts_probe(struct platform_device *pdev)
262{
263	struct input_dev *input;
264	struct iio_channel *channels;
265	struct device *dev = &pdev->dev;
266	struct vf50_touch_device *touchdev;
267	int num_adc_channels;
268	int error;
269
270	channels = iio_channel_get_all(dev);
271	if (IS_ERR(channels))
272		return PTR_ERR(channels);
273
274	error = devm_add_action(dev, vf50_ts_channel_release, channels);
275	if (error) {
276		iio_channel_release_all(channels);
277		dev_err(dev, "Failed to register iio channel release action");
278		return error;
279	}
280
281	num_adc_channels = 0;
282	while (channels[num_adc_channels].indio_dev)
283		num_adc_channels++;
284
285	if (num_adc_channels != COLI_TOUCH_REQ_ADC_CHAN) {
286		dev_err(dev, "Inadequate ADC channels specified\n");
287		return -EINVAL;
288	}
289
290	touchdev = devm_kzalloc(dev, sizeof(*touchdev), GFP_KERNEL);
291	if (!touchdev)
292		return -ENOMEM;
293
294	touchdev->pdev = pdev;
295	touchdev->channels = channels;
296
297	error = of_property_read_u32(dev->of_node, "vf50-ts-min-pressure",
298				 &touchdev->min_pressure);
299	if (error)
300		return error;
301
302	input = devm_input_allocate_device(dev);
303	if (!input) {
304		dev_err(dev, "Failed to allocate TS input device\n");
305		return -ENOMEM;
306	}
307
308	input->name = DRIVER_NAME;
309	input->id.bustype = BUS_HOST;
310	input->dev.parent = dev;
311	input->open = vf50_ts_open;
312	input->close = vf50_ts_close;
313
314	input_set_capability(input, EV_KEY, BTN_TOUCH);
315	input_set_abs_params(input, ABS_X, 0, VF_ADC_MAX, 0, 0);
316	input_set_abs_params(input, ABS_Y, 0, VF_ADC_MAX, 0, 0);
317	input_set_abs_params(input, ABS_PRESSURE, 0, VF_ADC_MAX, 0, 0);
318
319	touchdev->ts_input = input;
320	input_set_drvdata(input, touchdev);
321
322	error = input_register_device(input);
323	if (error) {
324		dev_err(dev, "Failed to register input device\n");
325		return error;
326	}
327
328	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xp, "xp", GPIOD_OUT_LOW);
329	if (error)
330		return error;
331
332	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xm,
333				"xm", GPIOD_OUT_LOW);
334	if (error)
335		return error;
336
337	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_yp, "yp", GPIOD_OUT_LOW);
338	if (error)
339		return error;
340
341	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_ym, "ym", GPIOD_OUT_LOW);
342	if (error)
343		return error;
344
345	touchdev->pen_irq = platform_get_irq(pdev, 0);
346	if (touchdev->pen_irq < 0)
347		return touchdev->pen_irq;
348
349	error = devm_request_threaded_irq(dev, touchdev->pen_irq,
350					  NULL, vf50_ts_irq_bh, IRQF_ONESHOT,
351					  "vf50 touch", touchdev);
352	if (error) {
353		dev_err(dev, "Failed to request IRQ %d: %d\n",
354			touchdev->pen_irq, error);
355		return error;
356	}
357
358	return 0;
359}
360
361static const struct of_device_id vf50_touch_of_match[] = {
362	{ .compatible = "toradex,vf50-touchscreen", },
363	{ }
364};
365MODULE_DEVICE_TABLE(of, vf50_touch_of_match);
366
367static struct platform_driver vf50_touch_driver = {
368	.driver = {
369		.name = "toradex,vf50_touchctrl",
370		.of_match_table = vf50_touch_of_match,
371	},
372	.probe = vf50_ts_probe,
373};
374module_platform_driver(vf50_touch_driver);
375
376MODULE_AUTHOR("Sanchayan Maity");
377MODULE_DESCRIPTION("Colibri VF50 Touchscreen driver");
378MODULE_LICENSE("GPL");
379