drivers/input/touchscreen/ads7846.c

   1 /*
   2  * ADS7846 based touchscreen and sensor driver
   3  *
   4  * Copyright (c) 2005 David Brownell
   5  *
   6  * Using code from:
   7  *  - corgi_ts.c
   8  *      Copyright (C) 2004-2005 Richard Purdie
   9  *  - omap_ts.[hc], ads7846.h, ts_osk.c
  10  *      Copyright (C) 2002 MontaVista Software
  11  *      Copyright (C) 2004 Texas Instruments
  12  *      Copyright (C) 2005 Dirk Behme
  13  *
  14  *  This program is free software; you can redistribute it and/or modify
  15  *  it under the terms of the GNU General Public License version 2 as
  16  *  published by the Free Software Foundation.
  17  */
  18 #include <linux/device.h>
  19 #include <linux/init.h>
  20 #include <linux/delay.h>
  21 #include <linux/input.h>
  22 #include <linux/interrupt.h>
  23 #include <linux/slab.h>
  24 #include <linux/spi/spi.h>
  25 #include <linux/spi/ads7846.h>
  26
  27 #ifdef  CONFIG_ARM
  28 #include <asm/mach-types.h>
  29 #ifdef  CONFIG_ARCH_OMAP
  30 #include <asm/arch/gpio.h>
  31 #endif
  32 #endif
  33
  34
  35 /*
  36  * This code has been lightly tested on an ads7846.
  37  * Support for ads7843 and ads7845 has only been stubbed in.
  38  *
  39  * Not yet done:  investigate the values reported.  Are x/y/pressure
  40  * event values sane enough for X11?  How accurate are the temperature
  41  * and voltage readings?  (System-specific calibration should support
  42  * accuracy of 0.3 degrees C; otherwise it's 2.0 degrees.)
  43  *
  44  * app note sbaa036 talks in more detail about accurate sampling...
  45  * that ought to help in situations like LCDs inducing noise (which
  46  * can also be helped by using synch signals) and more generally.
  47  */
  48
  49 #define TS_POLL_PERIOD  msecs_to_jiffies(10)
  50
  51 struct ts_event {
  52         /* For portability, we can't read 12 bit values using SPI (which
  53          * would make the controller deliver them as native byteorder u16
  54          * with msbs zeroed).  Instead, we read them as two 8-byte values,
  55          * which need byteswapping then range adjustment.
  56          */
  57         __be16 x;
  58         __be16 y;
  59         __be16 z1, z2;
  60 };
  61
  62 struct ads7846 {
  63         struct input_dev        input;
  64         char                    phys[32];
  65
  66         struct spi_device       *spi;
  67         u16                     model;
  68         u16                     vref_delay_usecs;
  69         u16                     x_plate_ohms;
  70
  71         struct ts_event         tc;
  72
  73         struct spi_transfer     xfer[8];
  74         struct spi_message      msg;
  75
  76         spinlock_t              lock;
  77         struct timer_list       timer;          /* P: lock */
  78         unsigned                pendown:1;      /* P: lock */
  79         unsigned                pending:1;      /* P: lock */
  80 // FIXME remove "irq_disabled"
  81         unsigned                irq_disabled:1; /* P: lock */
  82 };
  83
  84 /* leave chip selected when we're done, for quicker re-select? */
  85 #if     0
  86 #define CS_CHANGE(xfer) ((xfer).cs_change = 1)
  87 #else
  88 #define CS_CHANGE(xfer) ((xfer).cs_change = 0)
  89 #endif
  90
  91 /*--------------------------------------------------------------------------*/
  92
  93 /* The ADS7846 has touchscreen and other sensors.
  94  * Earlier ads784x chips are somewhat compatible.
  95  */
  96 #define ADS_START               (1 << 7)
  97 #define ADS_A2A1A0_d_y          (1 << 4)        /* differential */
  98 #define ADS_A2A1A0_d_z1         (3 << 4)        /* differential */
  99 #define ADS_A2A1A0_d_z2         (4 << 4)        /* differential */
 100 #define ADS_A2A1A0_d_x          (5 << 4)        /* differential */
 101 #define ADS_A2A1A0_temp0        (0 << 4)        /* non-differential */
 102 #define ADS_A2A1A0_vbatt        (2 << 4)        /* non-differential */
 103 #define ADS_A2A1A0_vaux         (6 << 4)        /* non-differential */
 104 #define ADS_A2A1A0_temp1        (7 << 4)        /* non-differential */
 105 #define ADS_8_BIT               (1 << 3)
 106 #define ADS_12_BIT              (0 << 3)
 107 #define ADS_SER                 (1 << 2)        /* non-differential */
 108 #define ADS_DFR                 (0 << 2)        /* differential */
 109 #define ADS_PD10_PDOWN          (0 << 0)        /* lowpower mode + penirq */
 110 #define ADS_PD10_ADC_ON         (1 << 0)        /* ADC on */
 111 #define ADS_PD10_REF_ON         (2 << 0)        /* vREF on + penirq */
 112 #define ADS_PD10_ALL_ON         (3 << 0)        /* ADC + vREF on */
 113
 114 #define MAX_12BIT       ((1<<12)-1)
 115
 116 /* leave ADC powered up (disables penirq) between differential samples */
 117 #define READ_12BIT_DFR(x) (ADS_START | ADS_A2A1A0_d_ ## x \
 118         | ADS_12_BIT | ADS_DFR)
 119
 120 static const u8 read_y  = READ_12BIT_DFR(y)  | ADS_PD10_ADC_ON;
 121 static const u8 read_z1 = READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON;
 122 static const u8 read_z2 = READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON;
 123 static const u8 read_x  = READ_12BIT_DFR(x)  | ADS_PD10_PDOWN;  /* LAST */
 124
 125 /* single-ended samples need to first power up reference voltage;
 126  * we leave both ADC and VREF powered
 127  */
 128 #define READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
 129         | ADS_12_BIT | ADS_SER)
 130
 131 static const u8 ref_on = READ_12BIT_DFR(x) | ADS_PD10_ALL_ON;
 132 static const u8 ref_off = READ_12BIT_DFR(y) | ADS_PD10_PDOWN;
 133
 134 /*--------------------------------------------------------------------------*/
 135
 136 /*
 137  * Non-touchscreen sensors only use single-ended conversions.
 138  */
 139
 140 struct ser_req {
 141         u8                      command;
 142         u16                     scratch;
 143         __be16                  sample;
 144         struct spi_message      msg;
 145         struct spi_transfer     xfer[6];
 146 };
 147
 148 static int ads7846_read12_ser(struct device *dev, unsigned command)
 149 {
 150         struct spi_device       *spi = to_spi_device(dev);
 151         struct ads7846          *ts = dev_get_drvdata(dev);
 152         struct ser_req          *req = kzalloc(sizeof *req, SLAB_KERNEL);
 153         int                     status;
 154         int                     sample;
 155         int                     i;
 156
 157         if (!req)
 158                 return -ENOMEM;
 159
 160         INIT_LIST_HEAD(&req->msg.transfers);
 161
 162         /* activate reference, so it has time to settle; */
 163         req->xfer[0].tx_buf = &ref_on;
 164         req->xfer[0].len = 1;
 165         req->xfer[1].rx_buf = &req->scratch;
 166         req->xfer[1].len = 2;
 167
 168         /*
 169          * for external VREF, 0 usec (and assume it's always on);
 170          * for 1uF, use 800 usec;
 171          * no cap, 100 usec.
 172          */
 173         req->xfer[1].delay_usecs = ts->vref_delay_usecs;
 174
 175         /* take sample */
 176         req->command = (u8) command;
 177         req->xfer[2].tx_buf = &req->command;
 178         req->xfer[2].len = 1;
 179         req->xfer[3].rx_buf = &req->sample;
 180         req->xfer[3].len = 2;
 181
 182         /* REVISIT:  take a few more samples, and compare ... */
 183
 184         /* turn off reference */
 185         req->xfer[4].tx_buf = &ref_off;
 186         req->xfer[4].len = 1;
 187         req->xfer[5].rx_buf = &req->scratch;
 188         req->xfer[5].len = 2;
 189
 190         CS_CHANGE(req->xfer[5]);
 191
 192         /* group all the transfers together, so we can't interfere with
 193          * reading touchscreen state; disable penirq while sampling
 194          */
 195         for (i = 0; i < 6; i++)
 196                 spi_message_add_tail(&req->xfer[i], &req->msg);
 197
 198         disable_irq(spi->irq);
 199         status = spi_sync(spi, &req->msg);
 200         enable_irq(spi->irq);
 201
 202         if (req->msg.status)
 203                 status = req->msg.status;
 204         sample = be16_to_cpu(req->sample);
 205         sample = sample >> 4;
 206         kfree(req);
 207
 208         return status ? status : sample;
 209 }
 210
 211 #define SHOW(name) static ssize_t \
 212 name ## _show(struct device *dev, struct device_attribute *attr, char *buf) \
 213 { \
 214         ssize_t v = ads7846_read12_ser(dev, \
 215                         READ_12BIT_SER(name) | ADS_PD10_ALL_ON); \
 216         if (v < 0) \
 217                 return v; \
 218         return sprintf(buf, "%u\n", (unsigned) v); \
 219 } \
 220 static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);
 221
 222 SHOW(temp0)
 223 SHOW(temp1)
 224 SHOW(vaux)
 225 SHOW(vbatt)
 226
 227 /*--------------------------------------------------------------------------*/
 228
 229 /*
 230  * PENIRQ only kicks the timer.  The timer only reissues the SPI transfer,
 231  * to retrieve touchscreen status.
 232  *
 233  * The SPI transfer completion callback does the real work.  It reports
 234  * touchscreen events and reactivates the timer (or IRQ) as appropriate.
 235  */
 236
 237 static void ads7846_rx(void *ads)
 238 {
 239         struct ads7846  *ts = ads;
 240         unsigned        Rt;
 241         unsigned        sync = 0;
 242         u16             x, y, z1, z2;
 243         unsigned long   flags;
 244
 245         /* adjust:  12 bit samples (left aligned), built from
 246          * two 8 bit values writen msb-first.
 247          */
 248         x = be16_to_cpu(ts->tc.x) >> 4;
 249         y = be16_to_cpu(ts->tc.y) >> 4;
 250         z1 = be16_to_cpu(ts->tc.z1) >> 4;
 251         z2 = be16_to_cpu(ts->tc.z2) >> 4;
 252
 253         /* range filtering */
 254         if (x == MAX_12BIT)
 255                 x = 0;
 256
 257         if (x && z1 && ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
 258                 /* compute touch pressure resistance using equation #2 */
 259                 Rt = z2;
 260                 Rt -= z1;
 261                 Rt *= x;
 262                 Rt *= ts->x_plate_ohms;
 263                 Rt /= z1;
 264                 Rt = (Rt + 2047) >> 12;
 265         } else
 266                 Rt = 0;
 267
 268         /* NOTE:  "pendown" is inferred from pressure; we don't rely on
 269          * being able to check nPENIRQ status, or "friendly" trigger modes
 270          * (both-edges is much better than just-falling or low-level).
 271          *
 272          * REVISIT:  some boards may require reading nPENIRQ; it's
 273          * needed on 7843.  and 7845 reads pressure differently...
 274          *
 275          * REVISIT:  the touchscreen might not be connected; this code
 276          * won't notice that, even if nPENIRQ never fires ...
 277          */
 278         if (!ts->pendown && Rt != 0) {
 279                 input_report_key(&ts->input, BTN_TOUCH, 1);
 280                 sync = 1;
 281         } else if (ts->pendown && Rt == 0) {
 282                 input_report_key(&ts->input, BTN_TOUCH, 0);
 283                 sync = 1;
 284         }
 285
 286         if (Rt) {
 287                 input_report_abs(&ts->input, ABS_X, x);
 288                 input_report_abs(&ts->input, ABS_Y, y);
 289                 input_report_abs(&ts->input, ABS_PRESSURE, Rt);
 290                 sync = 1;
 291         }
 292         if (sync)
 293                 input_sync(&ts->input);
 294
 295 #ifdef  VERBOSE
 296         if (Rt || ts->pendown)
 297                 pr_debug("%s: %d/%d/%d%s\n", ts->spi->dev.bus_id,
 298                         x, y, Rt, Rt ? "" : " UP");
 299 #endif
 300
 301         /* don't retrigger while we're suspended */
 302         spin_lock_irqsave(&ts->lock, flags);
 303
 304         ts->pendown = (Rt != 0);
 305         ts->pending = 0;
 306
 307         if (ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
 308                 if (ts->pendown)
 309                         mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
 310                 else if (ts->irq_disabled) {
 311                         ts->irq_disabled = 0;
 312                         enable_irq(ts->spi->irq);
 313                 }
 314         }
 315
 316         spin_unlock_irqrestore(&ts->lock, flags);
 317 }
 318
 319 static void ads7846_timer(unsigned long handle)
 320 {
 321         struct ads7846  *ts = (void *)handle;
 322         int             status = 0;
 323         unsigned long   flags;
 324
 325         spin_lock_irqsave(&ts->lock, flags);
 326         if (!ts->pending) {
 327                 ts->pending = 1;
 328                 if (!ts->irq_disabled) {
 329                         ts->irq_disabled = 1;
 330                         disable_irq(ts->spi->irq);
 331                 }
 332                 status = spi_async(ts->spi, &ts->msg);
 333                 if (status)
 334                         dev_err(&ts->spi->dev, "spi_async --> %d\n",
 335                                         status);
 336         }
 337         spin_unlock_irqrestore(&ts->lock, flags);
 338 }
 339
 340 static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
 341 {
 342         ads7846_timer((unsigned long) handle);
 343         return IRQ_HANDLED;
 344 }
 345
 346 /*--------------------------------------------------------------------------*/
 347
 348 static int
 349 ads7846_suspend(struct spi_device *spi, pm_message_t message)
 350 {
 351         struct ads7846 *ts = dev_get_drvdata(&spi->dev);
 352         unsigned long   flags;
 353
 354         spin_lock_irqsave(&ts->lock, flags);
 355
 356         spi->dev.power.power_state = message;
 357
 358         /* are we waiting for IRQ, or polling? */
 359         if (!ts->pendown) {
 360                 if (!ts->irq_disabled) {
 361                         ts->irq_disabled = 1;
 362                         disable_irq(ts->spi->irq);
 363                 }
 364         } else {
 365                 /* polling; force a final SPI completion;
 366                  * that will clean things up neatly
 367                  */
 368                 if (!ts->pending)
 369                         mod_timer(&ts->timer, jiffies);
 370
 371                 while (ts->pendown || ts->pending) {
 372                         spin_unlock_irqrestore(&ts->lock, flags);
 373                         udelay(10);
 374                         spin_lock_irqsave(&ts->lock, flags);
 375                 }
 376         }
 377
 378         /* we know the chip's in lowpower mode since we always
 379          * leave it that way after every request
 380          */
 381
 382         spin_unlock_irqrestore(&ts->lock, flags);
 383         return 0;
 384 }
 385
 386 static int ads7846_resume(struct spi_device *spi)
 387 {
 388         struct ads7846 *ts = dev_get_drvdata(&spi->dev);
 389
 390         ts->irq_disabled = 0;
 391         enable_irq(ts->spi->irq);
 392         spi->dev.power.power_state = PMSG_ON;
 393         return 0;
 394 }
 395
 396 static int __devinit ads7846_probe(struct spi_device *spi)
 397 {
 398         struct ads7846                  *ts;
 399         struct ads7846_platform_data    *pdata = spi->dev.platform_data;
 400         struct spi_transfer             *x;
 401         int                             i;
 402
 403         if (!spi->irq) {
 404                 dev_dbg(&spi->dev, "no IRQ?\n");
 405                 return -ENODEV;
 406         }
 407
 408         if (!pdata) {
 409                 dev_dbg(&spi->dev, "no platform data?\n");
 410                 return -ENODEV;
 411         }
 412
 413         /* don't exceed max specified sample rate */
 414         if (spi->max_speed_hz > (125000 * 16)) {
 415                 dev_dbg(&spi->dev, "f(sample) %d KHz?\n",
 416                                 (spi->max_speed_hz/16)/1000);
 417                 return -EINVAL;
 418         }
 419
 420         /* We'd set the wordsize to 12 bits ... except that some controllers
 421          * will then treat the 8 bit command words as 12 bits (and drop the
 422          * four MSBs of the 12 bit result).  Result: inputs must be shifted
 423          * to discard the four garbage LSBs.
 424          */
 425
 426         if (!(ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL)))
 427                 return -ENOMEM;
 428
 429         dev_set_drvdata(&spi->dev, ts);
 430
 431         ts->spi = spi;
 432         spi->dev.power.power_state = PMSG_ON;
 433
 434         init_timer(&ts->timer);
 435         ts->timer.data = (unsigned long) ts;
 436         ts->timer.function = ads7846_timer;
 437
 438         ts->model = pdata->model ? : 7846;
 439         ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
 440         ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
 441
 442         init_input_dev(&ts->input);
 443
 444         ts->input.dev = &spi->dev;
 445         ts->input.name = "ADS784x Touchscreen";
 446         snprintf(ts->phys, sizeof ts->phys, "%s/input0", spi->dev.bus_id);
 447         ts->input.phys = ts->phys;
 448
 449         ts->input.evbit[0] = BIT(EV_KEY) | BIT(EV_ABS);
 450         ts->input.keybit[LONG(BTN_TOUCH)] = BIT(BTN_TOUCH);
 451         input_set_abs_params(&ts->input, ABS_X,
 452                         pdata->x_min ? : 0,
 453                         pdata->x_max ? : MAX_12BIT,
 454                         0, 0);
 455         input_set_abs_params(&ts->input, ABS_Y,
 456                         pdata->y_min ? : 0,
 457                         pdata->y_max ? : MAX_12BIT,
 458                         0, 0);
 459         input_set_abs_params(&ts->input, ABS_PRESSURE,
 460                         pdata->pressure_min, pdata->pressure_max, 0, 0);
 461
 462         input_register_device(&ts->input);
 463
 464         /* set up the transfers to read touchscreen state; this assumes we
 465          * use formula #2 for pressure, not #3.
 466          */
 467         x = ts->xfer;
 468
 469         /* y- still on; turn on only y+ (and ADC) */
 470         x->tx_buf = &read_y;
 471         x->len = 1;
 472         x++;
 473         x->rx_buf = &ts->tc.y;
 474         x->len = 2;
 475         x++;
 476
 477         /* turn y+ off, x- on; we'll use formula #2 */
 478         if (ts->model == 7846) {
 479                 x->tx_buf = &read_z1;
 480                 x->len = 1;
 481                 x++;
 482                 x->rx_buf = &ts->tc.z1;
 483                 x->len = 2;
 484                 x++;
 485
 486                 x->tx_buf = &read_z2;
 487                 x->len = 1;
 488                 x++;
 489                 x->rx_buf = &ts->tc.z2;
 490                 x->len = 2;
 491                 x++;
 492         }
 493
 494         /* turn y- off, x+ on, then leave in lowpower */
 495         x->tx_buf = &read_x;
 496         x->len = 1;
 497         x++;
 498         x->rx_buf = &ts->tc.x;
 499         x->len = 2;
 500         x++;
 501
 502         CS_CHANGE(x[-1]);
 503
 504         for (i = 0; i < x - ts->xfer; i++)
 505                 spi_message_add_tail(&ts->xfer[i], &ts->msg);
 506         ts->msg.complete = ads7846_rx;
 507         ts->msg.context = ts;
 508
 509         if (request_irq(spi->irq, ads7846_irq,
 510                         SA_SAMPLE_RANDOM | SA_TRIGGER_FALLING,
 511                         spi->dev.bus_id, ts)) {
 512                 dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
 513                 input_unregister_device(&ts->input);
 514                 kfree(ts);
 515                 return -EBUSY;
 516         }
 517
 518         dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);
 519
 520         /* take a first sample, leaving nPENIRQ active; avoid
 521          * the touchscreen, in case it's not connected.
 522          */
 523         (void) ads7846_read12_ser(&spi->dev,
 524                           READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);
 525
 526         /* ads7843/7845 don't have temperature sensors, and
 527          * use the other sensors a bit differently too
 528          */
 529         if (ts->model == 7846) {
 530                 device_create_file(&spi->dev, &dev_attr_temp0);
 531                 device_create_file(&spi->dev, &dev_attr_temp1);
 532         }
 533         if (ts->model != 7845)
 534                 device_create_file(&spi->dev, &dev_attr_vbatt);
 535         device_create_file(&spi->dev, &dev_attr_vaux);
 536
 537         return 0;
 538 }
 539
 540 static int __devexit ads7846_remove(struct spi_device *spi)
 541 {
 542         struct ads7846          *ts = dev_get_drvdata(&spi->dev);
 543
 544         ads7846_suspend(spi, PMSG_SUSPEND);
 545         free_irq(ts->spi->irq, ts);
 546         if (ts->irq_disabled)
 547                 enable_irq(ts->spi->irq);
 548
 549         if (ts->model == 7846) {
 550                 device_remove_file(&spi->dev, &dev_attr_temp0);
 551                 device_remove_file(&spi->dev, &dev_attr_temp1);
 552         }
 553         if (ts->model != 7845)
 554                 device_remove_file(&spi->dev, &dev_attr_vbatt);
 555         device_remove_file(&spi->dev, &dev_attr_vaux);
 556
 557         input_unregister_device(&ts->input);
 558         kfree(ts);
 559
 560         dev_dbg(&spi->dev, "unregistered touchscreen\n");
 561         return 0;
 562 }
 563
 564 static struct spi_driver ads7846_driver = {
 565         .driver = {
 566                 .name   = "ads7846",
 567                 .bus    = &spi_bus_type,
 568                 .owner  = THIS_MODULE,
 569         },
 570         .probe          = ads7846_probe,
 571         .remove         = __devexit_p(ads7846_remove),
 572         .suspend        = ads7846_suspend,
 573         .resume         = ads7846_resume,
 574 };
 575
 576 static int __init ads7846_init(void)
 577 {
 578         /* grr, board-specific init should stay out of drivers!! */
 579
 580 #ifdef  CONFIG_ARCH_OMAP
 581         if (machine_is_omap_osk()) {
 582                 /* GPIO4 = PENIRQ; GPIO6 = BUSY */
 583                 omap_request_gpio(4);
 584                 omap_set_gpio_direction(4, 1);
 585                 omap_request_gpio(6);
 586                 omap_set_gpio_direction(6, 1);
 587         }
 588         // also TI 1510 Innovator, bitbanging through FPGA
 589         // also Nokia 770
 590         // also Palm Tungsten T2
 591 #endif
 592
 593         // PXA:
 594         // also Dell Axim X50
 595         // also HP iPaq H191x/H192x/H415x/H435x
 596         // also Intel Lubbock (additional to UCB1400; as temperature sensor)
 597         // also Sharp Zaurus C7xx, C8xx (corgi/sheperd/husky)
 598
 599         // Atmel at91sam9261-EK uses ads7843
 600
 601         // also various AMD Au1x00 devel boards
 602
 603         return spi_register_driver(&ads7846_driver);
 604 }
 605 module_init(ads7846_init);
 606
 607 static void __exit ads7846_exit(void)
 608 {
 609         spi_unregister_driver(&ads7846_driver);
 610
 611 #ifdef  CONFIG_ARCH_OMAP
 612         if (machine_is_omap_osk()) {
 613                 omap_free_gpio(4);
 614                 omap_free_gpio(6);
 615         }
 616 #endif
 617
 618 }
 619 module_exit(ads7846_exit);
 620
 621 MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
 622 MODULE_LICENSE("GPL");