drivers/input/touchscreen/ads7846.c

   1 /*
   2  * ADS7846 based touchscreen and sensor driver
   3  *
   4  * Copyright (c) 2005 David Brownell
   5  * Copyright (c) 2006 Nokia Corporation
   6  * Various changes: Imre Deak <imre.deak@nokia.com>
   7  *
   8  * Using code from:
   9  *  - corgi_ts.c
  10  *      Copyright (C) 2004-2005 Richard Purdie
  11  *  - omap_ts.[hc], ads7846.h, ts_osk.c
  12  *      Copyright (C) 2002 MontaVista Software
  13  *      Copyright (C) 2004 Texas Instruments
  14  *      Copyright (C) 2005 Dirk Behme
  15  *
  16  *  This program is free software; you can redistribute it and/or modify
  17  *  it under the terms of the GNU General Public License version 2 as
  18  *  published by the Free Software Foundation.
  19  */
  20 #include <linux/device.h>
  21 #include <linux/init.h>
  22 #include <linux/delay.h>
  23 #include <linux/input.h>
  24 #include <linux/interrupt.h>
  25 #include <linux/slab.h>
  26 #include <linux/spi/spi.h>
  27 #include <linux/spi/ads7846.h>
  28 #include <asm/irq.h>
  29
  30 #ifdef  CONFIG_ARM
  31 #include <asm/mach-types.h>
  32 #ifdef  CONFIG_ARCH_OMAP
  33 #include <asm/arch/gpio.h>
  34 #endif
  35 #endif
  36
  37
  38 /*
  39  * This code has been tested on an ads7846 / N770 device.
  40  * Support for ads7843 and ads7845 has only been stubbed in.
  41  *
  42  * Not yet done:  How accurate are the temperature and voltage
  43  * readings? (System-specific calibration should support
  44  * accuracy of 0.3 degrees C; otherwise it's 2.0 degrees.)
  45  *
  46  * IRQ handling needs a workaround because of a shortcoming in handling
  47  * edge triggered IRQs on some platforms like the OMAP1/2. These
  48  * platforms don't handle the ARM lazy IRQ disabling properly, thus we
  49  * have to maintain our own SW IRQ disabled status. This should be
  50  * removed as soon as the affected platform's IRQ handling is fixed.
  51  *
  52  * app note sbaa036 talks in more detail about accurate sampling...
  53  * that ought to help in situations like LCDs inducing noise (which
  54  * can also be helped by using synch signals) and more generally.
  55  * This driver tries to utilize the measures described in the app
  56  * note. The strength of filtering can be set in the board-* specific
  57  * files.
  58  */
  59
  60 #define TS_POLL_PERIOD  msecs_to_jiffies(10)
  61
  62 /* this driver doesn't aim at the peak continuous sample rate */
  63 #define SAMPLE_BITS     (8 /*cmd*/ + 16 /*sample*/ + 2 /* before, after */)
  64
  65 struct ts_event {
  66         /* For portability, we can't read 12 bit values using SPI (which
  67          * would make the controller deliver them as native byteorder u16
  68          * with msbs zeroed).  Instead, we read them as two 8-bit values,
  69          * which need byteswapping then range adjustment.
  70          */
  71         __be16 x;
  72         __be16 y;
  73         __be16 z1, z2;
  74 };
  75
  76 struct ads7846 {
  77         struct input_dev        *input;
  78         char                    phys[32];
  79
  80         struct spi_device       *spi;
  81         u16                     model;
  82         u16                     vref_delay_usecs;
  83         u16                     x_plate_ohms;
  84
  85         u8                      read_x, read_y, read_z1, read_z2, pwrdown;
  86         u16                     dummy;          /* for the pwrdown read */
  87         struct ts_event         tc;
  88
  89         struct spi_transfer     xfer[10];
  90         struct spi_message      msg[5];
  91         int                     msg_idx;
  92         int                     read_cnt;
  93         int                     last_read;
  94
  95         u16                     debounce_max;
  96         u16                     debounce_tol;
  97
  98         spinlock_t              lock;
  99         struct timer_list       timer;          /* P: lock */
 100         unsigned                pendown:1;      /* P: lock */
 101         unsigned                pending:1;      /* P: lock */
 102 // FIXME remove "irq_disabled"
 103         unsigned                irq_disabled:1; /* P: lock */
 104         unsigned                disabled:1;
 105
 106         int                     (*get_pendown_state)(void);
 107 };
 108
 109 /* leave chip selected when we're done, for quicker re-select? */
 110 #if     0
 111 #define CS_CHANGE(xfer) ((xfer).cs_change = 1)
 112 #else
 113 #define CS_CHANGE(xfer) ((xfer).cs_change = 0)
 114 #endif
 115
 116 /*--------------------------------------------------------------------------*/
 117
 118 /* The ADS7846 has touchscreen and other sensors.
 119  * Earlier ads784x chips are somewhat compatible.
 120  */
 121 #define ADS_START               (1 << 7)
 122 #define ADS_A2A1A0_d_y          (1 << 4)        /* differential */
 123 #define ADS_A2A1A0_d_z1         (3 << 4)        /* differential */
 124 #define ADS_A2A1A0_d_z2         (4 << 4)        /* differential */
 125 #define ADS_A2A1A0_d_x          (5 << 4)        /* differential */
 126 #define ADS_A2A1A0_temp0        (0 << 4)        /* non-differential */
 127 #define ADS_A2A1A0_vbatt        (2 << 4)        /* non-differential */
 128 #define ADS_A2A1A0_vaux         (6 << 4)        /* non-differential */
 129 #define ADS_A2A1A0_temp1        (7 << 4)        /* non-differential */
 130 #define ADS_8_BIT               (1 << 3)
 131 #define ADS_12_BIT              (0 << 3)
 132 #define ADS_SER                 (1 << 2)        /* non-differential */
 133 #define ADS_DFR                 (0 << 2)        /* differential */
 134 #define ADS_PD10_PDOWN          (0 << 0)        /* lowpower mode + penirq */
 135 #define ADS_PD10_ADC_ON         (1 << 0)        /* ADC on */
 136 #define ADS_PD10_REF_ON         (2 << 0)        /* vREF on + penirq */
 137 #define ADS_PD10_ALL_ON         (3 << 0)        /* ADC + vREF on */
 138
 139 #define MAX_12BIT       ((1<<12)-1)
 140
 141 /* leave ADC powered up (disables penirq) between differential samples */
 142 #define READ_12BIT_DFR(x) (ADS_START | ADS_A2A1A0_d_ ## x \
 143         | ADS_12_BIT | ADS_DFR)
 144
 145 #define READ_Y  (READ_12BIT_DFR(y)  | ADS_PD10_ADC_ON)
 146 #define READ_Z1 (READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON)
 147 #define READ_Z2 (READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON)
 148
 149 #define READ_X  (READ_12BIT_DFR(x)  | ADS_PD10_ADC_ON)
 150 #define PWRDOWN (READ_12BIT_DFR(y)  | ADS_PD10_PDOWN)   /* LAST */
 151
 152 /* single-ended samples need to first power up reference voltage;
 153  * we leave both ADC and VREF powered
 154  */
 155 #define READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
 156         | ADS_12_BIT | ADS_SER)
 157
 158 #define REF_ON  (READ_12BIT_DFR(x) | ADS_PD10_ALL_ON)
 159 #define REF_OFF (READ_12BIT_DFR(y) | ADS_PD10_PDOWN)
 160
 161 /*--------------------------------------------------------------------------*/
 162
 163 /*
 164  * Non-touchscreen sensors only use single-ended conversions.
 165  */
 166
 167 struct ser_req {
 168         u8                      ref_on;
 169         u8                      command;
 170         u8                      ref_off;
 171         u16                     scratch;
 172         __be16                  sample;
 173         struct spi_message      msg;
 174         struct spi_transfer     xfer[6];
 175 };
 176
 177 static void ads7846_enable(struct ads7846 *ts);
 178 static void ads7846_disable(struct ads7846 *ts);
 179
 180 static int device_suspended(struct device *dev)
 181 {
 182         struct ads7846 *ts = dev_get_drvdata(dev);
 183         return dev->power.power_state.event != PM_EVENT_ON || ts->disabled;
 184 }
 185
 186 static int ads7846_read12_ser(struct device *dev, unsigned command)
 187 {
 188         struct spi_device       *spi = to_spi_device(dev);
 189         struct ads7846          *ts = dev_get_drvdata(dev);
 190         struct ser_req          *req = kzalloc(sizeof *req, SLAB_KERNEL);
 191         int                     status;
 192         int                     sample;
 193         int                     i;
 194
 195         if (!req)
 196                 return -ENOMEM;
 197
 198         spi_message_init(&req->msg);
 199
 200         /* activate reference, so it has time to settle; */
 201         req->ref_on = REF_ON;
 202         req->xfer[0].tx_buf = &req->ref_on;
 203         req->xfer[0].len = 1;
 204         req->xfer[1].rx_buf = &req->scratch;
 205         req->xfer[1].len = 2;
 206
 207         /*
 208          * for external VREF, 0 usec (and assume it's always on);
 209          * for 1uF, use 800 usec;
 210          * no cap, 100 usec.
 211          */
 212         req->xfer[1].delay_usecs = ts->vref_delay_usecs;
 213
 214         /* take sample */
 215         req->command = (u8) command;
 216         req->xfer[2].tx_buf = &req->command;
 217         req->xfer[2].len = 1;
 218         req->xfer[3].rx_buf = &req->sample;
 219         req->xfer[3].len = 2;
 220
 221         /* REVISIT:  take a few more samples, and compare ... */
 222
 223         /* turn off reference */
 224         req->ref_off = REF_OFF;
 225         req->xfer[4].tx_buf = &req->ref_off;
 226         req->xfer[4].len = 1;
 227         req->xfer[5].rx_buf = &req->scratch;
 228         req->xfer[5].len = 2;
 229
 230         CS_CHANGE(req->xfer[5]);
 231
 232         /* group all the transfers together, so we can't interfere with
 233          * reading touchscreen state; disable penirq while sampling
 234          */
 235         for (i = 0; i < 6; i++)
 236                 spi_message_add_tail(&req->xfer[i], &req->msg);
 237
 238         ts->irq_disabled = 1;
 239         disable_irq(spi->irq);
 240         status = spi_sync(spi, &req->msg);
 241         ts->irq_disabled = 0;
 242         enable_irq(spi->irq);
 243
 244         if (req->msg.status)
 245                 status = req->msg.status;
 246         sample = be16_to_cpu(req->sample);
 247         sample = sample >> 4;
 248         kfree(req);
 249
 250         return status ? status : sample;
 251 }
 252
 253 #define SHOW(name) static ssize_t \
 254 name ## _show(struct device *dev, struct device_attribute *attr, char *buf) \
 255 { \
 256         ssize_t v = ads7846_read12_ser(dev, \
 257                         READ_12BIT_SER(name) | ADS_PD10_ALL_ON); \
 258         if (v < 0) \
 259                 return v; \
 260         return sprintf(buf, "%u\n", (unsigned) v); \
 261 } \
 262 static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);
 263
 264 SHOW(temp0)
 265 SHOW(temp1)
 266 SHOW(vaux)
 267 SHOW(vbatt)
 268
 269 static int is_pen_down(struct device *dev)
 270 {
 271         struct ads7846          *ts = dev_get_drvdata(dev);
 272
 273         return ts->pendown;
 274 }
 275
 276 static ssize_t ads7846_pen_down_show(struct device *dev,
 277                                      struct device_attribute *attr, char *buf)
 278 {
 279         return sprintf(buf, "%u\n", is_pen_down(dev));
 280 }
 281
 282 static DEVICE_ATTR(pen_down, S_IRUGO, ads7846_pen_down_show, NULL);
 283
 284 static ssize_t ads7846_disable_show(struct device *dev,
 285                                      struct device_attribute *attr, char *buf)
 286 {
 287         struct ads7846  *ts = dev_get_drvdata(dev);
 288
 289         return sprintf(buf, "%u\n", ts->disabled);
 290 }
 291
 292 static ssize_t ads7846_disable_store(struct device *dev,
 293                                      struct device_attribute *attr,
 294                                      const char *buf, size_t count)
 295 {
 296         struct ads7846 *ts = dev_get_drvdata(dev);
 297         char *endp;
 298         int i;
 299
 300         i = simple_strtoul(buf, &endp, 10);
 301         spin_lock_irq(&ts->lock);
 302
 303         if (i)
 304                 ads7846_disable(ts);
 305         else
 306                 ads7846_enable(ts);
 307
 308         spin_unlock_irq(&ts->lock);
 309
 310         return count;
 311 }
 312
 313 static DEVICE_ATTR(disable, 0664, ads7846_disable_show, ads7846_disable_store);
 314
 315 /*--------------------------------------------------------------------------*/
 316
 317 /*
 318  * PENIRQ only kicks the timer.  The timer only reissues the SPI transfer,
 319  * to retrieve touchscreen status.
 320  *
 321  * The SPI transfer completion callback does the real work.  It reports
 322  * touchscreen events and reactivates the timer (or IRQ) as appropriate.
 323  */
 324
 325 static void ads7846_rx(void *ads)
 326 {
 327         struct ads7846          *ts = ads;
 328         struct input_dev        *input_dev = ts->input;
 329         unsigned                Rt;
 330         unsigned                sync = 0;
 331         u16                     x, y, z1, z2;
 332         unsigned long           flags;
 333
 334         /* adjust:  12 bit samples (left aligned), built from
 335          * two 8 bit values writen msb-first.
 336          */
 337         x = be16_to_cpu(ts->tc.x) >> 4;
 338         y = be16_to_cpu(ts->tc.y) >> 4;
 339         z1 = be16_to_cpu(ts->tc.z1) >> 4;
 340         z2 = be16_to_cpu(ts->tc.z2) >> 4;
 341
 342         /* range filtering */
 343         if (x == MAX_12BIT)
 344                 x = 0;
 345
 346         if (likely(x && z1 && !device_suspended(&ts->spi->dev))) {
 347                 /* compute touch pressure resistance using equation #2 */
 348                 Rt = z2;
 349                 Rt -= z1;
 350                 Rt *= x;
 351                 Rt *= ts->x_plate_ohms;
 352                 Rt /= z1;
 353                 Rt = (Rt + 2047) >> 12;
 354         } else
 355                 Rt = 0;
 356
 357         /* NOTE:  "pendown" is inferred from pressure; we don't rely on
 358          * being able to check nPENIRQ status, or "friendly" trigger modes
 359          * (both-edges is much better than just-falling or low-level).
 360          *
 361          * REVISIT:  some boards may require reading nPENIRQ; it's
 362          * needed on 7843.  and 7845 reads pressure differently...
 363          *
 364          * REVISIT:  the touchscreen might not be connected; this code
 365          * won't notice that, even if nPENIRQ never fires ...
 366          */
 367         if (!ts->pendown && Rt != 0) {
 368                 input_report_key(input_dev, BTN_TOUCH, 1);
 369                 sync = 1;
 370         } else if (ts->pendown && Rt == 0) {
 371                 input_report_key(input_dev, BTN_TOUCH, 0);
 372                 sync = 1;
 373         }
 374
 375         if (Rt) {
 376                 input_report_abs(input_dev, ABS_X, x);
 377                 input_report_abs(input_dev, ABS_Y, y);
 378                 sync = 1;
 379         }
 380
 381         if (sync) {
 382                 input_report_abs(input_dev, ABS_PRESSURE, Rt);
 383                 input_sync(input_dev);
 384         }
 385
 386 #ifdef  VERBOSE
 387         if (Rt || ts->pendown)
 388                 pr_debug("%s: %d/%d/%d%s\n", ts->spi->dev.bus_id,
 389                         x, y, Rt, Rt ? "" : " UP");
 390 #endif
 391
 392         spin_lock_irqsave(&ts->lock, flags);
 393
 394         ts->pendown = (Rt != 0);
 395         mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
 396
 397         spin_unlock_irqrestore(&ts->lock, flags);
 398 }
 399
 400 static void ads7846_debounce(void *ads)
 401 {
 402         struct ads7846          *ts = ads;
 403         struct spi_message      *m;
 404         struct spi_transfer     *t;
 405         u16                     val;
 406         int                     status;
 407
 408         m = &ts->msg[ts->msg_idx];
 409         t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);
 410         val = (*(u16 *)t->rx_buf) >> 3;
 411
 412         if (!ts->read_cnt || (abs(ts->last_read - val) > ts->debounce_tol
 413                                 && ts->read_cnt < ts->debounce_max)) {
 414                 /* Repeat it, if this was the first read or the read wasn't
 415                  * consistent enough
 416                  */
 417                 ts->read_cnt++;
 418                 ts->last_read = val;
 419         } else {
 420                 /* Go for the next read */
 421                 ts->msg_idx++;
 422                 ts->read_cnt = 0;
 423                 m++;
 424         }
 425         status = spi_async(ts->spi, m);
 426         if (status)
 427                 dev_err(&ts->spi->dev, "spi_async --> %d\n",
 428                                 status);
 429 }
 430
 431 static void ads7846_timer(unsigned long handle)
 432 {
 433         struct ads7846  *ts = (void *)handle;
 434         int             status = 0;
 435
 436         spin_lock_irq(&ts->lock);
 437
 438         if (unlikely(ts->msg_idx && !ts->pendown)) {
 439                 /* measurment cycle ended */
 440                 if (!device_suspended(&ts->spi->dev)) {
 441                         ts->irq_disabled = 0;
 442                         enable_irq(ts->spi->irq);
 443                 }
 444                 ts->pending = 0;
 445                 ts->msg_idx = 0;
 446         } else {
 447                 /* pen is still down, continue with the measurement */
 448                 ts->msg_idx = 0;
 449                 status = spi_async(ts->spi, &ts->msg[0]);
 450                 if (status)
 451                         dev_err(&ts->spi->dev, "spi_async --> %d\n", status);
 452         }
 453
 454         spin_unlock_irq(&ts->lock);
 455 }
 456
 457 static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
 458 {
 459         struct ads7846 *ts = handle;
 460         unsigned long flags;
 461
 462         spin_lock_irqsave(&ts->lock, flags);
 463         if (likely(ts->get_pendown_state())) {
 464                 if (!ts->irq_disabled) {
 465                         /* REVISIT irq logic for many ARM chips has cloned a
 466                          * bug wherein disabling an irq in its handler won't
 467                          * work;(it's disabled lazily, and too late to work.
 468                          * until all their irq logic is fixed, we must shadow
 469                          * that state here.
 470                          */
 471                         ts->irq_disabled = 1;
 472                         disable_irq(ts->spi->irq);
 473                         ts->pending = 1;
 474                         mod_timer(&ts->timer, jiffies);
 475                 }
 476         }
 477         spin_unlock_irqrestore(&ts->lock, flags);
 478
 479         return IRQ_HANDLED;
 480 }
 481
 482 /*--------------------------------------------------------------------------*/
 483
 484 /* Must be called with ts->lock held */
 485 static void ads7846_disable(struct ads7846 *ts)
 486 {
 487         if (ts->disabled)
 488                 return;
 489
 490         ts->disabled = 1;
 491
 492         /* are we waiting for IRQ, or polling? */
 493         if (!ts->pending) {
 494                 ts->irq_disabled = 1;
 495                 disable_irq(ts->spi->irq);
 496         } else {
 497                 /* the timer will run at least once more, and
 498                  * leave everything in a clean state, IRQ disabled
 499                  */
 500                 while (ts->pending) {
 501                         spin_unlock_irq(&ts->lock);
 502                         msleep(1);
 503                         spin_lock_irq(&ts->lock);
 504                 }
 505         }
 506
 507         /* we know the chip's in lowpower mode since we always
 508          * leave it that way after every request
 509          */
 510
 511 }
 512
 513 /* Must be called with ts->lock held */
 514 static void ads7846_enable(struct ads7846 *ts)
 515 {
 516         if (!ts->disabled)
 517                 return;
 518
 519         ts->disabled = 0;
 520         ts->irq_disabled = 0;
 521         enable_irq(ts->spi->irq);
 522 }
 523
 524 static int ads7846_suspend(struct spi_device *spi, pm_message_t message)
 525 {
 526         struct ads7846 *ts = dev_get_drvdata(&spi->dev);
 527
 528         spin_lock_irq(&ts->lock);
 529
 530         spi->dev.power.power_state = message;
 531         ads7846_disable(ts);
 532
 533         spin_unlock_irq(&ts->lock);
 534
 535         return 0;
 536
 537 }
 538
 539 static int ads7846_resume(struct spi_device *spi)
 540 {
 541         struct ads7846 *ts = dev_get_drvdata(&spi->dev);
 542
 543         spin_lock_irq(&ts->lock);
 544
 545         spi->dev.power.power_state = PMSG_ON;
 546         ads7846_enable(ts);
 547
 548         spin_unlock_irq(&ts->lock);
 549
 550         return 0;
 551 }
 552
 553 static int __devinit ads7846_probe(struct spi_device *spi)
 554 {
 555         struct ads7846                  *ts;
 556         struct input_dev                *input_dev;
 557         struct ads7846_platform_data    *pdata = spi->dev.platform_data;
 558         struct spi_message              *m;
 559         struct spi_transfer             *x;
 560         int                             err;
 561
 562         if (!spi->irq) {
 563                 dev_dbg(&spi->dev, "no IRQ?\n");
 564                 return -ENODEV;
 565         }
 566
 567         if (!pdata) {
 568                 dev_dbg(&spi->dev, "no platform data?\n");
 569                 return -ENODEV;
 570         }
 571
 572         /* don't exceed max specified sample rate */
 573         if (spi->max_speed_hz > (125000 * SAMPLE_BITS)) {
 574                 dev_dbg(&spi->dev, "f(sample) %d KHz?\n",
 575                                 (spi->max_speed_hz/SAMPLE_BITS)/1000);
 576                 return -EINVAL;
 577         }
 578
 579         if (pdata->get_pendown_state == NULL) {
 580                 dev_dbg(&spi->dev, "no get_pendown_state function?\n");
 581                 return -EINVAL;
 582         }
 583
 584         /* We'd set the wordsize to 12 bits ... except that some controllers
 585          * will then treat the 8 bit command words as 12 bits (and drop the
 586          * four MSBs of the 12 bit result).  Result: inputs must be shifted
 587          * to discard the four garbage LSBs.
 588          */
 589
 590         ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL);
 591         input_dev = input_allocate_device();
 592         if (!ts || !input_dev) {
 593                 err = -ENOMEM;
 594                 goto err_free_mem;
 595         }
 596
 597         dev_set_drvdata(&spi->dev, ts);
 598         spi->dev.power.power_state = PMSG_ON;
 599
 600         ts->spi = spi;
 601         ts->input = input_dev;
 602
 603         init_timer(&ts->timer);
 604         ts->timer.data = (unsigned long) ts;
 605         ts->timer.function = ads7846_timer;
 606
 607         spin_lock_init(&ts->lock);
 608
 609         ts->model = pdata->model ? : 7846;
 610         ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
 611         ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
 612         ts->debounce_max = pdata->debounce_max ? : 1;
 613         ts->debounce_tol = pdata->debounce_tol ? : 10;
 614         ts->get_pendown_state = pdata->get_pendown_state;
 615
 616         snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
 617
 618         input_dev->name = "ADS784x Touchscreen";
 619         input_dev->phys = ts->phys;
 620         input_dev->cdev.dev = &spi->dev;
 621
 622         input_dev->evbit[0] = BIT(EV_KEY) | BIT(EV_ABS);
 623         input_dev->keybit[LONG(BTN_TOUCH)] = BIT(BTN_TOUCH);
 624         input_set_abs_params(input_dev, ABS_X,
 625                         pdata->x_min ? : 0,
 626                         pdata->x_max ? : MAX_12BIT,
 627                         0, 0);
 628         input_set_abs_params(input_dev, ABS_Y,
 629                         pdata->y_min ? : 0,
 630                         pdata->y_max ? : MAX_12BIT,
 631                         0, 0);
 632         input_set_abs_params(input_dev, ABS_PRESSURE,
 633                         pdata->pressure_min, pdata->pressure_max, 0, 0);
 634
 635         /* set up the transfers to read touchscreen state; this assumes we
 636          * use formula #2 for pressure, not #3.
 637          */
 638         m = &ts->msg[0];
 639         x = ts->xfer;
 640
 641         spi_message_init(m);
 642
 643         /* y- still on; turn on only y+ (and ADC) */
 644         ts->read_y = READ_Y;
 645         x->tx_buf = &ts->read_y;
 646         x->len = 1;
 647         spi_message_add_tail(x, m);
 648
 649         x++;
 650         x->rx_buf = &ts->tc.y;
 651         x->len = 2;
 652         spi_message_add_tail(x, m);
 653
 654         m->complete = ads7846_debounce;
 655         m->context = ts;
 656
 657         m++;
 658         spi_message_init(m);
 659
 660         /* turn y- off, x+ on, then leave in lowpower */
 661         x++;
 662         ts->read_x = READ_X;
 663         x->tx_buf = &ts->read_x;
 664         x->len = 1;
 665         spi_message_add_tail(x, m);
 666
 667         x++;
 668         x->rx_buf = &ts->tc.x;
 669         x->len = 2;
 670         spi_message_add_tail(x, m);
 671
 672         m->complete = ads7846_debounce;
 673         m->context = ts;
 674
 675         /* turn y+ off, x- on; we'll use formula #2 */
 676         if (ts->model == 7846) {
 677                 m++;
 678                 spi_message_init(m);
 679
 680                 x++;
 681                 ts->read_z1 = READ_Z1;
 682                 x->tx_buf = &ts->read_z1;
 683                 x->len = 1;
 684                 spi_message_add_tail(x, m);
 685
 686                 x++;
 687                 x->rx_buf = &ts->tc.z1;
 688                 x->len = 2;
 689                 spi_message_add_tail(x, m);
 690
 691                 m->complete = ads7846_debounce;
 692                 m->context = ts;
 693
 694                 m++;
 695                 spi_message_init(m);
 696
 697                 x++;
 698                 ts->read_z2 = READ_Z2;
 699                 x->tx_buf = &ts->read_z2;
 700                 x->len = 1;
 701                 spi_message_add_tail(x, m);
 702
 703                 x++;
 704                 x->rx_buf = &ts->tc.z2;
 705                 x->len = 2;
 706                 spi_message_add_tail(x, m);
 707
 708                 m->complete = ads7846_debounce;
 709                 m->context = ts;
 710         }
 711
 712         /* power down */
 713         m++;
 714         spi_message_init(m);
 715
 716         x++;
 717         ts->pwrdown = PWRDOWN;
 718         x->tx_buf = &ts->pwrdown;
 719         x->len = 1;
 720         spi_message_add_tail(x, m);
 721
 722         x++;
 723         x->rx_buf = &ts->dummy;
 724         x->len = 2;
 725         CS_CHANGE(*x);
 726         spi_message_add_tail(x, m);
 727
 728         m->complete = ads7846_rx;
 729         m->context = ts;
 730
 731         if (request_irq(spi->irq, ads7846_irq,
 732                         SA_SAMPLE_RANDOM | SA_TRIGGER_FALLING,
 733                         spi->dev.bus_id, ts)) {
 734                 dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
 735                 err = -EBUSY;
 736                 goto err_free_mem;
 737         }
 738
 739         dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);
 740
 741         /* take a first sample, leaving nPENIRQ active; avoid
 742          * the touchscreen, in case it's not connected.
 743          */
 744         (void) ads7846_read12_ser(&spi->dev,
 745                           READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);
 746
 747         /* ads7843/7845 don't have temperature sensors, and
 748          * use the other sensors a bit differently too
 749          */
 750         if (ts->model == 7846) {
 751                 device_create_file(&spi->dev, &dev_attr_temp0);
 752                 device_create_file(&spi->dev, &dev_attr_temp1);
 753         }
 754         if (ts->model != 7845)
 755                 device_create_file(&spi->dev, &dev_attr_vbatt);
 756         device_create_file(&spi->dev, &dev_attr_vaux);
 757
 758         device_create_file(&spi->dev, &dev_attr_pen_down);
 759
 760         device_create_file(&spi->dev, &dev_attr_disable);
 761
 762         err = input_register_device(input_dev);
 763         if (err)
 764                 goto err_remove_attr;
 765
 766         return 0;
 767
 768  err_remove_attr:
 769         device_remove_file(&spi->dev, &dev_attr_disable);
 770         device_remove_file(&spi->dev, &dev_attr_pen_down);
 771         if (ts->model == 7846) {
 772                 device_remove_file(&spi->dev, &dev_attr_temp1);
 773                 device_remove_file(&spi->dev, &dev_attr_temp0);
 774         }
 775         if (ts->model != 7845)
 776                 device_remove_file(&spi->dev, &dev_attr_vbatt);
 777         device_remove_file(&spi->dev, &dev_attr_vaux);
 778
 779         free_irq(spi->irq, ts);
 780  err_free_mem:
 781         input_free_device(input_dev);
 782         kfree(ts);
 783         return err;
 784 }
 785
 786 static int __devexit ads7846_remove(struct spi_device *spi)
 787 {
 788         struct ads7846          *ts = dev_get_drvdata(&spi->dev);
 789
 790         input_unregister_device(ts->input);
 791
 792         ads7846_suspend(spi, PMSG_SUSPEND);
 793
 794         device_remove_file(&spi->dev, &dev_attr_disable);
 795         device_remove_file(&spi->dev, &dev_attr_pen_down);
 796         if (ts->model == 7846) {
 797                 device_remove_file(&spi->dev, &dev_attr_temp1);
 798                 device_remove_file(&spi->dev, &dev_attr_temp0);
 799         }
 800         if (ts->model != 7845)
 801                 device_remove_file(&spi->dev, &dev_attr_vbatt);
 802         device_remove_file(&spi->dev, &dev_attr_vaux);
 803
 804         free_irq(ts->spi->irq, ts);
 805         /* suspend left the IRQ disabled */
 806         enable_irq(ts->spi->irq);
 807
 808         kfree(ts);
 809
 810         dev_dbg(&spi->dev, "unregistered touchscreen\n");
 811         return 0;
 812 }
 813
 814 static struct spi_driver ads7846_driver = {
 815         .driver = {
 816                 .name   = "ads7846",
 817                 .bus    = &spi_bus_type,
 818                 .owner  = THIS_MODULE,
 819         },
 820         .probe          = ads7846_probe,
 821         .remove         = __devexit_p(ads7846_remove),
 822         .suspend        = ads7846_suspend,
 823         .resume         = ads7846_resume,
 824 };
 825
 826 static int __init ads7846_init(void)
 827 {
 828         /* grr, board-specific init should stay out of drivers!! */
 829
 830 #ifdef  CONFIG_ARCH_OMAP
 831         if (machine_is_omap_osk()) {
 832                 /* GPIO4 = PENIRQ; GPIO6 = BUSY */
 833                 omap_request_gpio(4);
 834                 omap_set_gpio_direction(4, 1);
 835                 omap_request_gpio(6);
 836                 omap_set_gpio_direction(6, 1);
 837         }
 838         // also TI 1510 Innovator, bitbanging through FPGA
 839         // also Nokia 770
 840         // also Palm Tungsten T2
 841 #endif
 842
 843         // PXA:
 844         // also Dell Axim X50
 845         // also HP iPaq H191x/H192x/H415x/H435x
 846         // also Intel Lubbock (additional to UCB1400; as temperature sensor)
 847         // also Sharp Zaurus C7xx, C8xx (corgi/sheperd/husky)
 848
 849         // Atmel at91sam9261-EK uses ads7843
 850
 851         // also various AMD Au1x00 devel boards
 852
 853         return spi_register_driver(&ads7846_driver);
 854 }
 855 module_init(ads7846_init);
 856
 857 static void __exit ads7846_exit(void)
 858 {
 859         spi_unregister_driver(&ads7846_driver);
 860
 861 #ifdef  CONFIG_ARCH_OMAP
 862         if (machine_is_omap_osk()) {
 863                 omap_free_gpio(4);
 864                 omap_free_gpio(6);
 865         }
 866 #endif
 867
 868 }
 869 module_exit(ads7846_exit);
 870
 871 MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
 872 MODULE_LICENSE("GPL");