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 #define DRV_VERSION                     "1.0"
  32
  33 #define VF_ADC_MAX                      ((1 << 12) - 1)
  34
  35 #define COLI_TOUCH_MIN_DELAY_US         1000
  36 #define COLI_TOUCH_MAX_DELAY_US         2000
  37 #define COLI_PULLUP_MIN_DELAY_US        10000
  38 #define COLI_PULLUP_MAX_DELAY_US        11000
  39 #define COLI_TOUCH_NO_OF_AVGS           5
  40 #define COLI_TOUCH_REQ_ADC_CHAN         4
  41
  42 struct vf50_touch_device {
  43         struct platform_device *pdev;
  44         struct input_dev *ts_input;
  45         struct iio_channel *channels;
  46         struct gpio_desc *gpio_xp;
  47         struct gpio_desc *gpio_xm;
  48         struct gpio_desc *gpio_yp;
  49         struct gpio_desc *gpio_ym;
  50         int pen_irq;
  51         int min_pressure;
  52         bool stop_touchscreen;
  53 };
  54
  55 /*
  56  * Enables given plates and measures touch parameters using ADC
  57  */
  58 static int adc_ts_measure(struct iio_channel *channel,
  59                           struct gpio_desc *plate_p, struct gpio_desc *plate_m)
  60 {
  61         int i, value = 0, val = 0;
  62         int error;
  63
  64         gpiod_set_value(plate_p, 1);
  65         gpiod_set_value(plate_m, 1);
  66
  67         usleep_range(COLI_TOUCH_MIN_DELAY_US, COLI_TOUCH_MAX_DELAY_US);
  68
  69         for (i = 0; i < COLI_TOUCH_NO_OF_AVGS; i++) {
  70                 error = iio_read_channel_raw(channel, &val);
  71                 if (error < 0) {
  72                         value = error;
  73                         goto error_iio_read;
  74                 }
  75
  76                 value += val;
  77         }
  78
  79         value /= COLI_TOUCH_NO_OF_AVGS;
  80
  81 error_iio_read:
  82         gpiod_set_value(plate_p, 0);
  83         gpiod_set_value(plate_m, 0);
  84
  85         return value;
  86 }
  87
  88 /*
  89  * Enable touch detection using falling edge detection on XM
  90  */
  91 static void vf50_ts_enable_touch_detection(struct vf50_touch_device *vf50_ts)
  92 {
  93         /* Enable plate YM (needs to be strong GND, high active) */
  94         gpiod_set_value(vf50_ts->gpio_ym, 1);
  95
  96         /*
  97          * Let the platform mux to idle state in order to enable
  98          * Pull-Up on GPIO
  99          */
 100         pinctrl_pm_select_idle_state(&vf50_ts->pdev->dev);
 101
 102         /* Wait for the pull-up to be stable on high */
 103         usleep_range(COLI_PULLUP_MIN_DELAY_US, COLI_PULLUP_MAX_DELAY_US);
 104 }
 105
 106 /*
 107  * ADC touch screen sampling bottom half irq handler
 108  */
 109 static irqreturn_t vf50_ts_irq_bh(int irq, void *private)
 110 {
 111         struct vf50_touch_device *vf50_ts = private;
 112         struct device *dev = &vf50_ts->pdev->dev;
 113         int val_x, val_y, val_z1, val_z2, val_p = 0;
 114         bool discard_val_on_start = true;
 115
 116         /* Disable the touch detection plates */
 117         gpiod_set_value(vf50_ts->gpio_ym, 0);
 118
 119         /* Let the platform mux to default state in order to mux as ADC */
 120         pinctrl_pm_select_default_state(dev);
 121
 122         while (!vf50_ts->stop_touchscreen) {
 123                 /* X-Direction */
 124                 val_x = adc_ts_measure(&vf50_ts->channels[0],
 125                                 vf50_ts->gpio_xp, vf50_ts->gpio_xm);
 126                 if (val_x < 0)
 127                         break;
 128
 129                 /* Y-Direction */
 130                 val_y = adc_ts_measure(&vf50_ts->channels[1],
 131                                 vf50_ts->gpio_yp, vf50_ts->gpio_ym);
 132                 if (val_y < 0)
 133                         break;
 134
 135                 /*
 136                  * Touch pressure
 137                  * Measure on XP/YM
 138                  */
 139                 val_z1 = adc_ts_measure(&vf50_ts->channels[2],
 140                                 vf50_ts->gpio_yp, vf50_ts->gpio_xm);
 141                 if (val_z1 < 0)
 142                         break;
 143                 val_z2 = adc_ts_measure(&vf50_ts->channels[3],
 144                                 vf50_ts->gpio_yp, vf50_ts->gpio_xm);
 145                 if (val_z2 < 0)
 146                         break;
 147
 148                 /* Validate signal (avoid calculation using noise) */
 149                 if (val_z1 > 64 && val_x > 64) {
 150                         /*
 151                          * Calculate resistance between the plates
 152                          * lower resistance means higher pressure
 153                          */
 154                         int r_x = (1000 * val_x) / VF_ADC_MAX;
 155
 156                         val_p = (r_x * val_z2) / val_z1 - r_x;
 157
 158                 } else {
 159                         val_p = 2000;
 160                 }
 161
 162                 val_p = 2000 - val_p;
 163                 dev_dbg(dev,
 164                         "Measured values: x: %d, y: %d, z1: %d, z2: %d, p: %d\n",
 165                         val_x, val_y, val_z1, val_z2, val_p);
 166
 167                 /*
 168                  * If touch pressure is too low, stop measuring and reenable
 169                  * touch detection
 170                  */
 171                 if (val_p < vf50_ts->min_pressure || val_p > 2000)
 172                         break;
 173
 174                 /*
 175                  * The pressure may not be enough for the first x and the
 176                  * second y measurement, but, the pressure is ok when the
 177                  * driver is doing the third and fourth measurement. To
 178                  * take care of this, we drop the first measurement always.
 179                  */
 180                 if (discard_val_on_start) {
 181                         discard_val_on_start = false;
 182                 } else {
 183                         /*
 184                          * Report touch position and sleep for
 185                          * the next measurement.
 186                          */
 187                         input_report_abs(vf50_ts->ts_input,
 188                                         ABS_X, VF_ADC_MAX - val_x);
 189                         input_report_abs(vf50_ts->ts_input,
 190                                         ABS_Y, VF_ADC_MAX - val_y);
 191                         input_report_abs(vf50_ts->ts_input,
 192                                         ABS_PRESSURE, val_p);
 193                         input_report_key(vf50_ts->ts_input, BTN_TOUCH, 1);
 194                         input_sync(vf50_ts->ts_input);
 195                 }
 196
 197                 usleep_range(COLI_PULLUP_MIN_DELAY_US,
 198                              COLI_PULLUP_MAX_DELAY_US);
 199         }
 200
 201         /* Report no more touch, re-enable touch detection */
 202         input_report_abs(vf50_ts->ts_input, ABS_PRESSURE, 0);
 203         input_report_key(vf50_ts->ts_input, BTN_TOUCH, 0);
 204         input_sync(vf50_ts->ts_input);
 205
 206         vf50_ts_enable_touch_detection(vf50_ts);
 207
 208         return IRQ_HANDLED;
 209 }
 210
 211 static int vf50_ts_open(struct input_dev *dev_input)
 212 {
 213         struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
 214         struct device *dev = &touchdev->pdev->dev;
 215
 216         dev_dbg(dev, "Input device %s opened, starting touch detection\n",
 217                 dev_input->name);
 218
 219         touchdev->stop_touchscreen = false;
 220
 221         /* Mux detection before request IRQ, wait for pull-up to settle */
 222         vf50_ts_enable_touch_detection(touchdev);
 223
 224         return 0;
 225 }
 226
 227 static void vf50_ts_close(struct input_dev *dev_input)
 228 {
 229         struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
 230         struct device *dev = &touchdev->pdev->dev;
 231
 232         touchdev->stop_touchscreen = true;
 233
 234         /* Make sure IRQ is not running past close */
 235         mb();
 236         synchronize_irq(touchdev->pen_irq);
 237
 238         gpiod_set_value(touchdev->gpio_ym, 0);
 239         pinctrl_pm_select_default_state(dev);
 240
 241         dev_dbg(dev, "Input device %s closed, disable touch detection\n",
 242                 dev_input->name);
 243 }
 244
 245 static int vf50_ts_get_gpiod(struct device *dev, struct gpio_desc **gpio_d,
 246                              const char *con_id, enum gpiod_flags flags)
 247 {
 248         int error;
 249
 250         *gpio_d = devm_gpiod_get(dev, con_id, flags);
 251         if (IS_ERR(*gpio_d)) {
 252                 error = PTR_ERR(*gpio_d);
 253                 dev_err(dev, "Could not get gpio_%s %d\n", con_id, error);
 254                 return error;
 255         }
 256
 257         return 0;
 258 }
 259
 260 static void vf50_ts_channel_release(void *data)
 261 {
 262         struct iio_channel *channels = data;
 263
 264         iio_channel_release_all(channels);
 265 }
 266
 267 static int vf50_ts_probe(struct platform_device *pdev)
 268 {
 269         struct input_dev *input;
 270         struct iio_channel *channels;
 271         struct device *dev = &pdev->dev;
 272         struct vf50_touch_device *touchdev;
 273         int num_adc_channels;
 274         int error;
 275
 276         channels = iio_channel_get_all(dev);
 277         if (IS_ERR(channels))
 278                 return PTR_ERR(channels);
 279
 280         error = devm_add_action(dev, vf50_ts_channel_release, channels);
 281         if (error) {
 282                 iio_channel_release_all(channels);
 283                 dev_err(dev, "Failed to register iio channel release action");
 284                 return error;
 285         }
 286
 287         num_adc_channels = 0;
 288         while (channels[num_adc_channels].indio_dev)
 289                 num_adc_channels++;
 290
 291         if (num_adc_channels != COLI_TOUCH_REQ_ADC_CHAN) {
 292                 dev_err(dev, "Inadequate ADC channels specified\n");
 293                 return -EINVAL;
 294         }
 295
 296         touchdev = devm_kzalloc(dev, sizeof(*touchdev), GFP_KERNEL);
 297         if (!touchdev)
 298                 return -ENOMEM;
 299
 300         touchdev->pdev = pdev;
 301         touchdev->channels = channels;
 302
 303         error = of_property_read_u32(dev->of_node, "vf50-ts-min-pressure",
 304                                  &touchdev->min_pressure);
 305         if (error)
 306                 return error;
 307
 308         input = devm_input_allocate_device(dev);
 309         if (!input) {
 310                 dev_err(dev, "Failed to allocate TS input device\n");
 311                 return -ENOMEM;
 312         }
 313
 314         input->name = DRIVER_NAME;
 315         input->id.bustype = BUS_HOST;
 316         input->dev.parent = dev;
 317         input->open = vf50_ts_open;
 318         input->close = vf50_ts_close;
 319
 320         input_set_capability(input, EV_KEY, BTN_TOUCH);
 321         input_set_abs_params(input, ABS_X, 0, VF_ADC_MAX, 0, 0);
 322         input_set_abs_params(input, ABS_Y, 0, VF_ADC_MAX, 0, 0);
 323         input_set_abs_params(input, ABS_PRESSURE, 0, VF_ADC_MAX, 0, 0);
 324
 325         touchdev->ts_input = input;
 326         input_set_drvdata(input, touchdev);
 327
 328         error = input_register_device(input);
 329         if (error) {
 330                 dev_err(dev, "Failed to register input device\n");
 331                 return error;
 332         }
 333
 334         error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xp, "xp", GPIOD_OUT_LOW);
 335         if (error)
 336                 return error;
 337
 338         error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xm,
 339                                 "xm", GPIOD_OUT_LOW);
 340         if (error)
 341                 return error;
 342
 343         error = vf50_ts_get_gpiod(dev, &touchdev->gpio_yp, "yp", GPIOD_OUT_LOW);
 344         if (error)
 345                 return error;
 346
 347         error = vf50_ts_get_gpiod(dev, &touchdev->gpio_ym, "ym", GPIOD_OUT_LOW);
 348         if (error)
 349                 return error;
 350
 351         touchdev->pen_irq = platform_get_irq(pdev, 0);
 352         if (touchdev->pen_irq < 0)
 353                 return touchdev->pen_irq;
 354
 355         error = devm_request_threaded_irq(dev, touchdev->pen_irq,
 356                                           NULL, vf50_ts_irq_bh, IRQF_ONESHOT,
 357                                           "vf50 touch", touchdev);
 358         if (error) {
 359                 dev_err(dev, "Failed to request IRQ %d: %d\n",
 360                         touchdev->pen_irq, error);
 361                 return error;
 362         }
 363
 364         return 0;
 365 }
 366
 367 static const struct of_device_id vf50_touch_of_match[] = {
 368         { .compatible = "toradex,vf50-touchscreen", },
 369         { }
 370 };
 371 MODULE_DEVICE_TABLE(of, vf50_touch_of_match);
 372
 373 static struct platform_driver vf50_touch_driver = {
 374         .driver = {
 375                 .name = "toradex,vf50_touchctrl",
 376                 .of_match_table = vf50_touch_of_match,
 377         },
 378         .probe = vf50_ts_probe,
 379 };
 380 module_platform_driver(vf50_touch_driver);
 381
 382 MODULE_AUTHOR("Sanchayan Maity");
 383 MODULE_DESCRIPTION("Colibri VF50 Touchscreen driver");
 384 MODULE_LICENSE("GPL");
 385 MODULE_VERSION(DRV_VERSION);