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
36 struct 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 */
adc_ts_measure(struct iio_channel * channel,struct gpio_desc * plate_p,struct gpio_desc * plate_m)52 static 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
75 error_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 */
vf50_ts_enable_touch_detection(struct vf50_touch_device * vf50_ts)85 static 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 */
vf50_ts_irq_bh(int irq,void * private)103 static 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
vf50_ts_open(struct input_dev * dev_input)205 static 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
vf50_ts_close(struct input_dev * dev_input)221 static 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
vf50_ts_get_gpiod(struct device * dev,struct gpio_desc ** gpio_d,const char * con_id,enum gpiod_flags flags)239 static 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
vf50_ts_channel_release(void * data)250 static void vf50_ts_channel_release(void *data)
251 {
252 struct iio_channel *channels = data;
253
254 iio_channel_release_all(channels);
255 }
256
vf50_ts_probe(struct platform_device * pdev)257 static 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
357 static const struct of_device_id vf50_touch_of_match[] = {
358 { .compatible = "toradex,vf50-touchscreen", },
359 { }
360 };
361 MODULE_DEVICE_TABLE(of, vf50_touch_of_match);
362
363 static 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 };
370 module_platform_driver(vf50_touch_driver);
371
372 MODULE_AUTHOR("Sanchayan Maity");
373 MODULE_DESCRIPTION("Colibri VF50 Touchscreen driver");
374 MODULE_LICENSE("GPL");
375