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

   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.h>
  13 #include <linux/gpio/consumer.h>
  14 #include <linux/iio/consumer.h>
  15 #include <linux/iio/types.h>
  16 #include <linux/input.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/kernel.h>
  19 #include <linux/module.h>
  20 #include <linux/of.h>
  21 #include <linux/pinctrl/consumer.h>
  22 #include <linux/platform_device.h>
  23 #include <linux/slab.h>
  24 #include <linux/types.h>
  25
  26 #define DRIVER_NAME                     "colibri-vf50-ts"
  27
  28 #define VF_ADC_MAX                      ((1 << 12) - 1)
  29
  30 #define COLI_TOUCH_MIN_DELAY_US         1000
  31 #define COLI_TOUCH_MAX_DELAY_US         2000
  32 #define COLI_PULLUP_MIN_DELAY_US        10000
  33 #define COLI_PULLUP_MAX_DELAY_US        11000
  34 #define COLI_TOUCH_NO_OF_AVGS           5
  35 #define COLI_TOUCH_REQ_ADC_CHAN         4
  36
  37 struct vf50_touch_device {
  38         struct platform_device *pdev;
  39         struct input_dev *ts_input;
  40         struct iio_channel *channels;
  41         struct gpio_desc *gpio_xp;
  42         struct gpio_desc *gpio_xm;
  43         struct gpio_desc *gpio_yp;
  44         struct gpio_desc *gpio_ym;
  45         int pen_irq;
  46         int min_pressure;
  47         bool stop_touchscreen;
  48 };
  49
  50 /*
  51  * Enables given plates and measures touch parameters using ADC
  52  */
  53 static int adc_ts_measure(struct iio_channel *channel,
  54                           struct gpio_desc *plate_p, struct gpio_desc *plate_m)
  55 {
  56         int i, value = 0, val = 0;
  57         int error;
  58
  59         gpiod_set_value(plate_p, 1);
  60         gpiod_set_value(plate_m, 1);
  61
  62         usleep_range(COLI_TOUCH_MIN_DELAY_US, COLI_TOUCH_MAX_DELAY_US);
  63
  64         for (i = 0; i < COLI_TOUCH_NO_OF_AVGS; i++) {
  65                 error = iio_read_channel_raw(channel, &val);
  66                 if (error < 0) {
  67                         value = error;
  68                         goto error_iio_read;
  69                 }
  70
  71                 value += val;
  72         }
  73
  74         value /= COLI_TOUCH_NO_OF_AVGS;
  75
  76 error_iio_read:
  77         gpiod_set_value(plate_p, 0);
  78         gpiod_set_value(plate_m, 0);
  79
  80         return value;
  81 }
  82
  83 /*
  84  * Enable touch detection using falling edge detection on XM
  85  */
  86 static void vf50_ts_enable_touch_detection(struct vf50_touch_device *vf50_ts)
  87 {
  88         /* Enable plate YM (needs to be strong GND, high active) */
  89         gpiod_set_value(vf50_ts->gpio_ym, 1);
  90
  91         /*
  92          * Let the platform mux to idle state in order to enable
  93          * Pull-Up on GPIO
  94          */
  95         pinctrl_pm_select_idle_state(&vf50_ts->pdev->dev);
  96
  97         /* Wait for the pull-up to be stable on high */
  98         usleep_range(COLI_PULLUP_MIN_DELAY_US, COLI_PULLUP_MAX_DELAY_US);
  99 }
 100
 101 /*
 102  * ADC touch screen sampling bottom half irq handler
 103  */
 104 static irqreturn_t vf50_ts_irq_bh(int irq, void *private)
 105 {
 106         struct vf50_touch_device *vf50_ts = private;
 107         struct device *dev = &vf50_ts->pdev->dev;
 108         int val_x, val_y, val_z1, val_z2, val_p = 0;
 109         bool discard_val_on_start = true;
 110
 111         /* Disable the touch detection plates */
 112         gpiod_set_value(vf50_ts->gpio_ym, 0);
 113
 114         /* Let the platform mux to default state in order to mux as ADC */
 115         pinctrl_pm_select_default_state(dev);
 116
 117         while (!vf50_ts->stop_touchscreen) {
 118                 /* X-Direction */
 119                 val_x = adc_ts_measure(&vf50_ts->channels[0],
 120                                 vf50_ts->gpio_xp, vf50_ts->gpio_xm);
 121                 if (val_x < 0)
 122                         break;
 123
 124                 /* Y-Direction */
 125                 val_y = adc_ts_measure(&vf50_ts->channels[1],
 126                                 vf50_ts->gpio_yp, vf50_ts->gpio_ym);
 127                 if (val_y < 0)
 128                         break;
 129
 130                 /*
 131                  * Touch pressure
 132                  * Measure on XP/YM
 133                  */
 134                 val_z1 = adc_ts_measure(&vf50_ts->channels[2],
 135                                 vf50_ts->gpio_yp, vf50_ts->gpio_xm);
 136                 if (val_z1 < 0)
 137                         break;
 138                 val_z2 = adc_ts_measure(&vf50_ts->channels[3],
 139                                 vf50_ts->gpio_yp, vf50_ts->gpio_xm);
 140                 if (val_z2 < 0)
 141                         break;
 142
 143                 /* Validate signal (avoid calculation using noise) */
 144                 if (val_z1 > 64 && val_x > 64) {
 145                         /*
 146                          * Calculate resistance between the plates
 147                          * lower resistance means higher pressure
 148                          */
 149                         int r_x = (1000 * val_x) / VF_ADC_MAX;
 150
 151                         val_p = (r_x * val_z2) / val_z1 - r_x;
 152
 153                 } else {
 154                         val_p = 2000;
 155                 }
 156
 157                 val_p = 2000 - val_p;
 158                 dev_dbg(dev,
 159                         "Measured values: x: %d, y: %d, z1: %d, z2: %d, p: %d\n",
 160                         val_x, val_y, val_z1, val_z2, val_p);
 161
 162                 /*
 163                  * If touch pressure is too low, stop measuring and reenable
 164                  * touch detection
 165                  */
 166                 if (val_p < vf50_ts->min_pressure || val_p > 2000)
 167                         break;
 168
 169                 /*
 170                  * The pressure may not be enough for the first x and the
 171                  * second y measurement, but, the pressure is ok when the
 172                  * driver is doing the third and fourth measurement. To
 173                  * take care of this, we drop the first measurement always.
 174                  */
 175                 if (discard_val_on_start) {
 176                         discard_val_on_start = false;
 177                 } else {
 178                         /*
 179                          * Report touch position and sleep for
 180                          * the next measurement.
 181                          */
 182                         input_report_abs(vf50_ts->ts_input,
 183                                         ABS_X, VF_ADC_MAX - val_x);
 184                         input_report_abs(vf50_ts->ts_input,
 185                                         ABS_Y, VF_ADC_MAX - val_y);
 186                         input_report_abs(vf50_ts->ts_input,
 187                                         ABS_PRESSURE, val_p);
 188                         input_report_key(vf50_ts->ts_input, BTN_TOUCH, 1);
 189                         input_sync(vf50_ts->ts_input);
 190                 }
 191
 192                 usleep_range(COLI_PULLUP_MIN_DELAY_US,
 193                              COLI_PULLUP_MAX_DELAY_US);
 194         }
 195
 196         /* Report no more touch, re-enable touch detection */
 197         input_report_abs(vf50_ts->ts_input, ABS_PRESSURE, 0);
 198         input_report_key(vf50_ts->ts_input, BTN_TOUCH, 0);
 199         input_sync(vf50_ts->ts_input);
 200
 201         vf50_ts_enable_touch_detection(vf50_ts);
 202
 203         return IRQ_HANDLED;
 204 }
 205
 206 static int vf50_ts_open(struct input_dev *dev_input)
 207 {
 208         struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
 209         struct device *dev = &touchdev->pdev->dev;
 210
 211         dev_dbg(dev, "Input device %s opened, starting touch detection\n",
 212                 dev_input->name);
 213
 214         touchdev->stop_touchscreen = false;
 215
 216         /* Mux detection before request IRQ, wait for pull-up to settle */
 217         vf50_ts_enable_touch_detection(touchdev);
 218
 219         return 0;
 220 }
 221
 222 static void vf50_ts_close(struct input_dev *dev_input)
 223 {
 224         struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
 225         struct device *dev = &touchdev->pdev->dev;
 226
 227         touchdev->stop_touchscreen = true;
 228
 229         /* Make sure IRQ is not running past close */
 230         mb();
 231         synchronize_irq(touchdev->pen_irq);
 232
 233         gpiod_set_value(touchdev->gpio_ym, 0);
 234         pinctrl_pm_select_default_state(dev);
 235
 236         dev_dbg(dev, "Input device %s closed, disable touch detection\n",
 237                 dev_input->name);
 238 }
 239
 240 static int vf50_ts_get_gpiod(struct device *dev, struct gpio_desc **gpio_d,
 241                              const char *con_id, enum gpiod_flags flags)
 242 {
 243         int error;
 244
 245         *gpio_d = devm_gpiod_get(dev, con_id, flags);
 246         if (IS_ERR(*gpio_d)) {
 247                 error = PTR_ERR(*gpio_d);
 248                 dev_err(dev, "Could not get gpio_%s %d\n", con_id, error);
 249                 return error;
 250         }
 251
 252         return 0;
 253 }
 254
 255 static void vf50_ts_channel_release(void *data)
 256 {
 257         struct iio_channel *channels = data;
 258
 259         iio_channel_release_all(channels);
 260 }
 261
 262 static int vf50_ts_probe(struct platform_device *pdev)
 263 {
 264         struct input_dev *input;
 265         struct iio_channel *channels;
 266         struct device *dev = &pdev->dev;
 267         struct vf50_touch_device *touchdev;
 268         int num_adc_channels;
 269         int error;
 270
 271         channels = iio_channel_get_all(dev);
 272         if (IS_ERR(channels))
 273                 return PTR_ERR(channels);
 274
 275         error = devm_add_action(dev, vf50_ts_channel_release, channels);
 276         if (error) {
 277                 iio_channel_release_all(channels);
 278                 dev_err(dev, "Failed to register iio channel release action");
 279                 return error;
 280         }
 281
 282         num_adc_channels = 0;
 283         while (channels[num_adc_channels].indio_dev)
 284                 num_adc_channels++;
 285
 286         if (num_adc_channels != COLI_TOUCH_REQ_ADC_CHAN) {
 287                 dev_err(dev, "Inadequate ADC channels specified\n");
 288                 return -EINVAL;
 289         }
 290
 291         touchdev = devm_kzalloc(dev, sizeof(*touchdev), GFP_KERNEL);
 292         if (!touchdev)
 293                 return -ENOMEM;
 294
 295         touchdev->pdev = pdev;
 296         touchdev->channels = channels;
 297
 298         error = of_property_read_u32(dev->of_node, "vf50-ts-min-pressure",
 299                                  &touchdev->min_pressure);
 300         if (error)
 301                 return error;
 302
 303         input = devm_input_allocate_device(dev);
 304         if (!input) {
 305                 dev_err(dev, "Failed to allocate TS input device\n");
 306                 return -ENOMEM;
 307         }
 308
 309         input->name = DRIVER_NAME;
 310         input->id.bustype = BUS_HOST;
 311         input->dev.parent = dev;
 312         input->open = vf50_ts_open;
 313         input->close = vf50_ts_close;
 314
 315         input_set_capability(input, EV_KEY, BTN_TOUCH);
 316         input_set_abs_params(input, ABS_X, 0, VF_ADC_MAX, 0, 0);
 317         input_set_abs_params(input, ABS_Y, 0, VF_ADC_MAX, 0, 0);
 318         input_set_abs_params(input, ABS_PRESSURE, 0, VF_ADC_MAX, 0, 0);
 319
 320         touchdev->ts_input = input;
 321         input_set_drvdata(input, touchdev);
 322
 323         error = input_register_device(input);
 324         if (error) {
 325                 dev_err(dev, "Failed to register input device\n");
 326                 return error;
 327         }
 328
 329         error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xp, "xp", GPIOD_OUT_LOW);
 330         if (error)
 331                 return error;
 332
 333         error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xm,
 334                                 "xm", GPIOD_OUT_LOW);
 335         if (error)
 336                 return error;
 337
 338         error = vf50_ts_get_gpiod(dev, &touchdev->gpio_yp, "yp", GPIOD_OUT_LOW);
 339         if (error)
 340                 return error;
 341
 342         error = vf50_ts_get_gpiod(dev, &touchdev->gpio_ym, "ym", GPIOD_OUT_LOW);
 343         if (error)
 344                 return error;
 345
 346         touchdev->pen_irq = platform_get_irq(pdev, 0);
 347         if (touchdev->pen_irq < 0)
 348                 return touchdev->pen_irq;
 349
 350         error = devm_request_threaded_irq(dev, touchdev->pen_irq,
 351                                           NULL, vf50_ts_irq_bh, IRQF_ONESHOT,
 352                                           "vf50 touch", touchdev);
 353         if (error) {
 354                 dev_err(dev, "Failed to request IRQ %d: %d\n",
 355                         touchdev->pen_irq, error);
 356                 return error;
 357         }
 358
 359         return 0;
 360 }
 361
 362 static const struct of_device_id vf50_touch_of_match[] = {
 363         { .compatible = "toradex,vf50-touchscreen", },
 364         { }
 365 };
 366 MODULE_DEVICE_TABLE(of, vf50_touch_of_match);
 367
 368 static struct platform_driver vf50_touch_driver = {
 369         .driver = {
 370                 .name = "toradex,vf50_touchctrl",
 371                 .of_match_table = vf50_touch_of_match,
 372         },
 373         .probe = vf50_ts_probe,
 374 };
 375 module_platform_driver(vf50_touch_driver);
 376
 377 MODULE_AUTHOR("Sanchayan Maity");
 378 MODULE_DESCRIPTION("Colibri VF50 Touchscreen driver");
 379 MODULE_LICENSE("GPL");