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	*gpio_d = devm_gpiod_get(dev, con_id, flags);
243	if (IS_ERR(*gpio_d))
244		return dev_err_probe(dev, PTR_ERR(*gpio_d),
245				     "Could not get gpio_%s\n", con_id);
246
247	return 0;
248}
249
250static void vf50_ts_channel_release(void *data)
251{
252	struct iio_channel *channels = data;
253
254	iio_channel_release_all(channels);
255}
256
257static int vf50_ts_probe(struct platform_device *pdev)
258{
259	struct input_dev *input;
260	struct iio_channel *channels;
261	struct device *dev = &pdev->dev;
262	struct vf50_touch_device *touchdev;
263	int num_adc_channels;
264	int error;
265
266	channels = iio_channel_get_all(dev);
267	if (IS_ERR(channels))
268		return PTR_ERR(channels);
269
270	error = devm_add_action(dev, vf50_ts_channel_release, channels);
271	if (error) {
272		iio_channel_release_all(channels);
273		dev_err(dev, "Failed to register iio channel release action");
274		return error;
275	}
276
277	num_adc_channels = 0;
278	while (channels[num_adc_channels].indio_dev)
279		num_adc_channels++;
280
281	if (num_adc_channels != COLI_TOUCH_REQ_ADC_CHAN) {
282		dev_err(dev, "Inadequate ADC channels specified\n");
283		return -EINVAL;
284	}
285
286	touchdev = devm_kzalloc(dev, sizeof(*touchdev), GFP_KERNEL);
287	if (!touchdev)
288		return -ENOMEM;
289
290	touchdev->pdev = pdev;
291	touchdev->channels = channels;
292
293	error = of_property_read_u32(dev->of_node, "vf50-ts-min-pressure",
294				 &touchdev->min_pressure);
295	if (error)
296		return error;
297
298	input = devm_input_allocate_device(dev);
299	if (!input) {
300		dev_err(dev, "Failed to allocate TS input device\n");
301		return -ENOMEM;
302	}
303
304	input->name = DRIVER_NAME;
305	input->id.bustype = BUS_HOST;
306	input->dev.parent = dev;
307	input->open = vf50_ts_open;
308	input->close = vf50_ts_close;
309
310	input_set_capability(input, EV_KEY, BTN_TOUCH);
311	input_set_abs_params(input, ABS_X, 0, VF_ADC_MAX, 0, 0);
312	input_set_abs_params(input, ABS_Y, 0, VF_ADC_MAX, 0, 0);
313	input_set_abs_params(input, ABS_PRESSURE, 0, VF_ADC_MAX, 0, 0);
314
315	touchdev->ts_input = input;
316	input_set_drvdata(input, touchdev);
317
318	error = input_register_device(input);
319	if (error) {
320		dev_err(dev, "Failed to register input device\n");
321		return error;
322	}
323
324	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xp, "xp", GPIOD_OUT_LOW);
325	if (error)
326		return error;
327
328	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xm,
329				"xm", GPIOD_OUT_LOW);
330	if (error)
331		return error;
332
333	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_yp, "yp", GPIOD_OUT_LOW);
334	if (error)
335		return error;
336
337	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_ym, "ym", GPIOD_OUT_LOW);
338	if (error)
339		return error;
340
341	touchdev->pen_irq = platform_get_irq(pdev, 0);
342	if (touchdev->pen_irq < 0)
343		return touchdev->pen_irq;
344
345	error = devm_request_threaded_irq(dev, touchdev->pen_irq,
346					  NULL, vf50_ts_irq_bh, IRQF_ONESHOT,
347					  "vf50 touch", touchdev);
348	if (error) {
349		dev_err(dev, "Failed to request IRQ %d: %d\n",
350			touchdev->pen_irq, error);
351		return error;
352	}
353
354	return 0;
355}
356
357static const struct of_device_id vf50_touch_of_match[] = {
358	{ .compatible = "toradex,vf50-touchscreen", },
359	{ }
360};
361MODULE_DEVICE_TABLE(of, vf50_touch_of_match);
362
363static struct platform_driver vf50_touch_driver = {
364	.driver = {
365		.name = "toradex,vf50_touchctrl",
366		.of_match_table = vf50_touch_of_match,
367	},
368	.probe = vf50_ts_probe,
369};
370module_platform_driver(vf50_touch_driver);
371
372MODULE_AUTHOR("Sanchayan Maity");
373MODULE_DESCRIPTION("Colibri VF50 Touchscreen driver");
374MODULE_LICENSE("GPL");