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/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  */
  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  */
  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  */
 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
 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
 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
 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
 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
 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");