2 * Toradex Colibri VF50 Touchscreen driver
4 * Copyright 2015 Toradex AG
6 * Originally authored by Stefan Agner for 3.0 kernel
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.
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>
29 #define DRIVER_NAME "colibri-vf50-ts"
30 #define DRV_VERSION "1.0"
32 #define VF_ADC_MAX ((1 << 12) - 1)
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
41 struct 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;
51 bool stop_touchscreen;
55 * Enables given plates and measures touch parameters using ADC
57 static int adc_ts_measure(struct iio_channel *channel,
58 struct gpio_desc *plate_p, struct gpio_desc *plate_m)
60 int i, value = 0, val = 0;
63 gpiod_set_value(plate_p, 1);
64 gpiod_set_value(plate_m, 1);
66 usleep_range(COLI_TOUCH_MIN_DELAY_US, COLI_TOUCH_MAX_DELAY_US);
68 for (i = 0; i < COLI_TOUCH_NO_OF_AVGS; i++) {
69 error = iio_read_channel_raw(channel, &val);
78 value /= COLI_TOUCH_NO_OF_AVGS;
81 gpiod_set_value(plate_p, 0);
82 gpiod_set_value(plate_m, 0);
88 * Enable touch detection using falling edge detection on XM
90 static void vf50_ts_enable_touch_detection(struct vf50_touch_device *vf50_ts)
92 /* Enable plate YM (needs to be strong GND, high active) */
93 gpiod_set_value(vf50_ts->gpio_ym, 1);
96 * Let the platform mux to idle state in order to enable
99 pinctrl_pm_select_idle_state(&vf50_ts->pdev->dev);
101 /* Wait for the pull-up to be stable on high */
102 usleep_range(COLI_PULLUP_MIN_DELAY_US, COLI_PULLUP_MAX_DELAY_US);
106 * ADC touch screen sampling bottom half irq handler
108 static irqreturn_t vf50_ts_irq_bh(int irq, void *private)
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;
115 /* Disable the touch detection plates */
116 gpiod_set_value(vf50_ts->gpio_ym, 0);
118 /* Let the platform mux to default state in order to mux as ADC */
119 pinctrl_pm_select_default_state(dev);
121 while (!vf50_ts->stop_touchscreen) {
123 val_x = adc_ts_measure(&vf50_ts->channels[0],
124 vf50_ts->gpio_xp, vf50_ts->gpio_xm);
129 val_y = adc_ts_measure(&vf50_ts->channels[1],
130 vf50_ts->gpio_yp, vf50_ts->gpio_ym);
138 val_z1 = adc_ts_measure(&vf50_ts->channels[2],
139 vf50_ts->gpio_yp, vf50_ts->gpio_xm);
142 val_z2 = adc_ts_measure(&vf50_ts->channels[3],
143 vf50_ts->gpio_yp, vf50_ts->gpio_xm);
147 /* Validate signal (avoid calculation using noise) */
148 if (val_z1 > 64 && val_x > 64) {
150 * Calculate resistance between the plates
151 * lower resistance means higher pressure
153 int r_x = (1000 * val_x) / VF_ADC_MAX;
155 val_p = (r_x * val_z2) / val_z1 - r_x;
161 val_p = 2000 - val_p;
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);
167 * If touch pressure is too low, stop measuring and reenable
170 if (val_p < vf50_ts->min_pressure || val_p > 2000)
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.
179 if (discard_val_on_start) {
180 discard_val_on_start = false;
183 * Report touch position and sleep for
184 * the next measurement.
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);
196 usleep_range(COLI_PULLUP_MIN_DELAY_US,
197 COLI_PULLUP_MAX_DELAY_US);
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);
205 vf50_ts_enable_touch_detection(vf50_ts);
210 static int vf50_ts_open(struct input_dev *dev_input)
212 struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
213 struct device *dev = &touchdev->pdev->dev;
215 dev_dbg(dev, "Input device %s opened, starting touch detection\n",
218 touchdev->stop_touchscreen = false;
220 /* Mux detection before request IRQ, wait for pull-up to settle */
221 vf50_ts_enable_touch_detection(touchdev);
226 static void vf50_ts_close(struct input_dev *dev_input)
228 struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
229 struct device *dev = &touchdev->pdev->dev;
231 touchdev->stop_touchscreen = true;
233 /* Make sure IRQ is not running past close */
235 synchronize_irq(touchdev->pen_irq);
237 gpiod_set_value(touchdev->gpio_ym, 0);
238 pinctrl_pm_select_default_state(dev);
240 dev_dbg(dev, "Input device %s closed, disable touch detection\n",
244 static int vf50_ts_get_gpiod(struct device *dev, struct gpio_desc **gpio_d,
245 const char *con_id, enum gpiod_flags flags)
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);
259 static void vf50_ts_channel_release(void *data)
261 struct iio_channel *channels = data;
263 iio_channel_release_all(channels);
266 static int vf50_ts_probe(struct platform_device *pdev)
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;
275 channels = iio_channel_get_all(dev);
276 if (IS_ERR(channels))
277 return PTR_ERR(channels);
279 error = devm_add_action(dev, vf50_ts_channel_release, channels);
281 iio_channel_release_all(channels);
282 dev_err(dev, "Failed to register iio channel release action");
286 num_adc_channels = 0;
287 while (channels[num_adc_channels].indio_dev)
290 if (num_adc_channels != COLI_TOUCH_REQ_ADC_CHAN) {
291 dev_err(dev, "Inadequate ADC channels specified\n");
295 touchdev = devm_kzalloc(dev, sizeof(*touchdev), GFP_KERNEL);
299 touchdev->pdev = pdev;
300 touchdev->channels = channels;
302 error = of_property_read_u32(dev->of_node, "vf50-ts-min-pressure",
303 &touchdev->min_pressure);
307 input = devm_input_allocate_device(dev);
309 dev_err(dev, "Failed to allocate TS input device\n");
313 platform_set_drvdata(pdev, touchdev);
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;
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);
326 touchdev->ts_input = input;
327 input_set_drvdata(input, touchdev);
329 error = input_register_device(input);
331 dev_err(dev, "Failed to register input device\n");
335 error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xp, "xp", GPIOD_OUT_LOW);
339 error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xm,
340 "xm", GPIOD_OUT_LOW);
344 error = vf50_ts_get_gpiod(dev, &touchdev->gpio_yp, "yp", GPIOD_OUT_LOW);
348 error = vf50_ts_get_gpiod(dev, &touchdev->gpio_ym, "ym", GPIOD_OUT_LOW);
352 touchdev->pen_irq = platform_get_irq(pdev, 0);
353 if (touchdev->pen_irq < 0)
354 return touchdev->pen_irq;
356 error = devm_request_threaded_irq(dev, touchdev->pen_irq,
357 NULL, vf50_ts_irq_bh, IRQF_ONESHOT,
358 "vf50 touch", touchdev);
360 dev_err(dev, "Failed to request IRQ %d: %d\n",
361 touchdev->pen_irq, error);
368 static const struct of_device_id vf50_touch_of_match[] = {
369 { .compatible = "toradex,vf50-touchscreen", },
372 MODULE_DEVICE_TABLE(of, vf50_touch_of_match);
374 static struct platform_driver vf50_touch_driver = {
376 .name = "toradex,vf50_touchctrl",
377 .of_match_table = vf50_touch_of_match,
379 .probe = vf50_ts_probe,
381 module_platform_driver(vf50_touch_driver);
383 MODULE_AUTHOR("Sanchayan Maity");
384 MODULE_DESCRIPTION("Colibri VF50 Touchscreen driver");
385 MODULE_LICENSE("GPL");
386 MODULE_VERSION(DRV_VERSION);