drivers/input/touchscreen/colibri-vf50-ts.c

   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/of.h>
  25 #include <linux/pinctrl/consumer.h>
  26 #include <linux/platform_device.h>
  27 #include <linux/slab.h>
  28 #include <linux/types.h>
  29
  30 #define DRIVER_NAME                     "colibri-vf50-ts"
  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
  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;
  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  */
  57 static 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
  80 error_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  */
  90 static 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  */
 108 static 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
 210 static 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
 226 static 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
 244 static 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
 259 static void vf50_ts_channel_release(void *data)
 260 {
 261         struct iio_channel *channels = data;
 262
 263         iio_channel_release_all(channels);
 264 }
 265
 266 static 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         input->name = DRIVER_NAME;
 314         input->id.bustype = BUS_HOST;
 315         input->dev.parent = dev;
 316         input->open = vf50_ts_open;
 317         input->close = vf50_ts_close;
 318
 319         input_set_capability(input, EV_KEY, BTN_TOUCH);
 320         input_set_abs_params(input, ABS_X, 0, VF_ADC_MAX, 0, 0);
 321         input_set_abs_params(input, ABS_Y, 0, VF_ADC_MAX, 0, 0);
 322         input_set_abs_params(input, ABS_PRESSURE, 0, VF_ADC_MAX, 0, 0);
 323
 324         touchdev->ts_input = input;
 325         input_set_drvdata(input, touchdev);
 326
 327         error = input_register_device(input);
 328         if (error) {
 329                 dev_err(dev, "Failed to register input device\n");
 330                 return error;
 331         }
 332
 333         error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xp, "xp", GPIOD_OUT_LOW);
 334         if (error)
 335                 return error;
 336
 337         error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xm,
 338                                 "xm", GPIOD_OUT_LOW);
 339         if (error)
 340                 return error;
 341
 342         error = vf50_ts_get_gpiod(dev, &touchdev->gpio_yp, "yp", GPIOD_OUT_LOW);
 343         if (error)
 344                 return error;
 345
 346         error = vf50_ts_get_gpiod(dev, &touchdev->gpio_ym, "ym", GPIOD_OUT_LOW);
 347         if (error)
 348                 return error;
 349
 350         touchdev->pen_irq = platform_get_irq(pdev, 0);
 351         if (touchdev->pen_irq < 0)
 352                 return touchdev->pen_irq;
 353
 354         error = devm_request_threaded_irq(dev, touchdev->pen_irq,
 355                                           NULL, vf50_ts_irq_bh, IRQF_ONESHOT,
 356                                           "vf50 touch", touchdev);
 357         if (error) {
 358                 dev_err(dev, "Failed to request IRQ %d: %d\n",
 359                         touchdev->pen_irq, error);
 360                 return error;
 361         }
 362
 363         return 0;
 364 }
 365
 366 static const struct of_device_id vf50_touch_of_match[] = {
 367         { .compatible = "toradex,vf50-touchscreen", },
 368         { }
 369 };
 370 MODULE_DEVICE_TABLE(of, vf50_touch_of_match);
 371
 372 static struct platform_driver vf50_touch_driver = {
 373         .driver = {
 374                 .name = "toradex,vf50_touchctrl",
 375                 .of_match_table = vf50_touch_of_match,
 376         },
 377         .probe = vf50_ts_probe,
 378 };
 379 module_platform_driver(vf50_touch_driver);
 380
 381 MODULE_AUTHOR("Sanchayan Maity");
 382 MODULE_DESCRIPTION("Colibri VF50 Touchscreen driver");
 383 MODULE_LICENSE("GPL");