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
  33 #else
  34 #define set_irq_type(irq,type)  do{}while(0)
  35 #endif
  36
  37
  38 /*
  39  * This code has been lightly tested on an ads7846.
  40  * Support for ads7843 and ads7845 has only been stubbed in.
  41  *
  42  * Not yet done:  investigate the values reported.  Are x/y/pressure
  43  * event values sane enough for X11?  How accurate are the temperature
  44  * and voltage readings?  (System-specific calibration should support
  45  * accuracy of 0.3 degrees C; otherwise it's 2.0 degrees.)
  46  *
  47  * app note sbaa036 talks in more detail about accurate sampling...
  48  * that ought to help in situations like LCDs inducing noise (which
  49  * can also be helped by using synch signals) and more generally.
  50  */
  51
  52 #define TS_POLL_PERIOD  msecs_to_jiffies(10)
  53
  54 struct ts_event {
  55         /* For portability, we can't read 12 bit values using SPI (which
  56          * would make the controller deliver them as native byteorder u16
  57          * with msbs zeroed).  Instead, we read them as two 8-byte values,
  58          * which need byteswapping then range adjustment.
  59          */
  60         __be16 x;
  61         __be16 y;
  62         __be16 z1, z2;
  63 };
  64
  65 struct ads7846 {
  66         struct input_dev        input;
  67         char                    phys[32];
  68
  69         struct spi_device       *spi;
  70         u16                     model;
  71         u16                     vref_delay_usecs;
  72         u16                     x_plate_ohms;
  73
  74         struct ts_event         tc;
  75
  76         struct spi_transfer     xfer[8];
  77         struct spi_message      msg;
  78
  79         spinlock_t              lock;
  80         struct timer_list       timer;          /* P: lock */
  81         unsigned                pendown:1;      /* P: lock */
  82         unsigned                pending:1;      /* P: lock */
  83 // FIXME remove "irq_disabled"
  84         unsigned                irq_disabled:1; /* P: lock */
  85 };
  86
  87 /* leave chip selected when we're done, for quicker re-select? */
  88 #if     0
  89 #define CS_CHANGE(xfer) ((xfer).cs_change = 1)
  90 #else
  91 #define CS_CHANGE(xfer) ((xfer).cs_change = 0)
  92 #endif
  93
  94 /*--------------------------------------------------------------------------*/
  95
  96 /* The ADS7846 has touchscreen and other sensors.
  97  * Earlier ads784x chips are somewhat compatible.
  98  */
  99 #define ADS_START               (1 << 7)
 100 #define ADS_A2A1A0_d_y          (1 << 4)        /* differential */
 101 #define ADS_A2A1A0_d_z1         (3 << 4)        /* differential */
 102 #define ADS_A2A1A0_d_z2         (4 << 4)        /* differential */
 103 #define ADS_A2A1A0_d_x          (5 << 4)        /* differential */
 104 #define ADS_A2A1A0_temp0        (0 << 4)        /* non-differential */
 105 #define ADS_A2A1A0_vbatt        (2 << 4)        /* non-differential */
 106 #define ADS_A2A1A0_vaux         (6 << 4)        /* non-differential */
 107 #define ADS_A2A1A0_temp1        (7 << 4)        /* non-differential */
 108 #define ADS_8_BIT               (1 << 3)
 109 #define ADS_12_BIT              (0 << 3)
 110 #define ADS_SER                 (1 << 2)        /* non-differential */
 111 #define ADS_DFR                 (0 << 2)        /* differential */
 112 #define ADS_PD10_PDOWN          (0 << 0)        /* lowpower mode + penirq */
 113 #define ADS_PD10_ADC_ON         (1 << 0)        /* ADC on */
 114 #define ADS_PD10_REF_ON         (2 << 0)        /* vREF on + penirq */
 115 #define ADS_PD10_ALL_ON         (3 << 0)        /* ADC + vREF on */
 116
 117 #define MAX_12BIT       ((1<<12)-1)
 118
 119 /* leave ADC powered up (disables penirq) between differential samples */
 120 #define READ_12BIT_DFR(x) (ADS_START | ADS_A2A1A0_d_ ## x \
 121         | ADS_12_BIT | ADS_DFR)
 122
 123 static const u8 read_y  = READ_12BIT_DFR(y)  | ADS_PD10_ADC_ON;
 124 static const u8 read_z1 = READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON;
 125 static const u8 read_z2 = READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON;
 126 static const u8 read_x  = READ_12BIT_DFR(x)  | ADS_PD10_PDOWN;  /* LAST */
 127
 128 /* single-ended samples need to first power up reference voltage;
 129  * we leave both ADC and VREF powered
 130  */
 131 #define READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
 132         | ADS_12_BIT | ADS_SER)
 133
 134 static const u8 ref_on = READ_12BIT_DFR(x) | ADS_PD10_ALL_ON;
 135 static const u8 ref_off = READ_12BIT_DFR(y) | ADS_PD10_PDOWN;
 136
 137 /*--------------------------------------------------------------------------*/
 138
 139 /*
 140  * Non-touchscreen sensors only use single-ended conversions.
 141  */
 142
 143 struct ser_req {
 144         u8                      command;
 145         u16                     scratch;
 146         __be16                  sample;
 147         struct spi_message      msg;
 148         struct spi_transfer     xfer[6];
 149 };
 150
 151 static int ads7846_read12_ser(struct device *dev, unsigned command)
 152 {
 153         struct spi_device       *spi = to_spi_device(dev);
 154         struct ads7846          *ts = dev_get_drvdata(dev);
 155         struct ser_req          *req = kzalloc(sizeof *req, SLAB_KERNEL);
 156         int                     status;
 157         int                     sample;
 158         int                     i;
 159
 160         if (!req)
 161                 return -ENOMEM;
 162
 163         INIT_LIST_HEAD(&req->msg.transfers);
 164
 165         /* activate reference, so it has time to settle; */
 166         req->xfer[0].tx_buf = &ref_on;
 167         req->xfer[0].len = 1;
 168         req->xfer[1].rx_buf = &req->scratch;
 169         req->xfer[1].len = 2;
 170
 171         /*
 172          * for external VREF, 0 usec (and assume it's always on);
 173          * for 1uF, use 800 usec;
 174          * no cap, 100 usec.
 175          */
 176         req->xfer[1].delay_usecs = ts->vref_delay_usecs;
 177
 178         /* take sample */
 179         req->command = (u8) command;
 180         req->xfer[2].tx_buf = &req->command;
 181         req->xfer[2].len = 1;
 182         req->xfer[3].rx_buf = &req->sample;
 183         req->xfer[3].len = 2;
 184
 185         /* REVISIT:  take a few more samples, and compare ... */
 186
 187         /* turn off reference */
 188         req->xfer[4].tx_buf = &ref_off;
 189         req->xfer[4].len = 1;
 190         req->xfer[5].rx_buf = &req->scratch;
 191         req->xfer[5].len = 2;
 192
 193         CS_CHANGE(req->xfer[5]);
 194
 195         /* group all the transfers together, so we can't interfere with
 196          * reading touchscreen state; disable penirq while sampling
 197          */
 198         for (i = 0; i < 6; i++)
 199                 spi_message_add_tail(&req->xfer[i], &req->msg);
 200
 201         disable_irq(spi->irq);
 202         status = spi_sync(spi, &req->msg);
 203         enable_irq(spi->irq);
 204
 205         if (req->msg.status)
 206                 status = req->msg.status;
 207         sample = be16_to_cpu(req->sample);
 208         sample = sample >> 4;
 209         kfree(req);
 210
 211         return status ? status : sample;
 212 }
 213
 214 #define SHOW(name) static ssize_t \
 215 name ## _show(struct device *dev, struct device_attribute *attr, char *buf) \
 216 { \
 217         ssize_t v = ads7846_read12_ser(dev, \
 218                         READ_12BIT_SER(name) | ADS_PD10_ALL_ON); \
 219         if (v < 0) \
 220                 return v; \
 221         return sprintf(buf, "%u\n", (unsigned) v); \
 222 } \
 223 static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);
 224
 225 SHOW(temp0)
 226 SHOW(temp1)
 227 SHOW(vaux)
 228 SHOW(vbatt)
 229
 230 /*--------------------------------------------------------------------------*/
 231
 232 /*
 233  * PENIRQ only kicks the timer.  The timer only reissues the SPI transfer,
 234  * to retrieve touchscreen status.
 235  *
 236  * The SPI transfer completion callback does the real work.  It reports
 237  * touchscreen events and reactivates the timer (or IRQ) as appropriate.
 238  */
 239
 240 static void ads7846_rx(void *ads)
 241 {
 242         struct ads7846  *ts = ads;
 243         unsigned        Rt;
 244         unsigned        sync = 0;
 245         u16             x, y, z1, z2;
 246         unsigned long   flags;
 247
 248         /* adjust:  12 bit samples (left aligned), built from
 249          * two 8 bit values writen msb-first.
 250          */
 251         x = be16_to_cpu(ts->tc.x) >> 4;
 252         y = be16_to_cpu(ts->tc.y) >> 4;
 253         z1 = be16_to_cpu(ts->tc.z1) >> 4;
 254         z2 = be16_to_cpu(ts->tc.z2) >> 4;
 255
 256         /* range filtering */
 257         if (x == MAX_12BIT)
 258                 x = 0;
 259
 260         if (x && z1 && ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
 261                 /* compute touch pressure resistance using equation #2 */
 262                 Rt = z2;
 263                 Rt -= z1;
 264                 Rt *= x;
 265                 Rt *= ts->x_plate_ohms;
 266                 Rt /= z1;
 267                 Rt = (Rt + 2047) >> 12;
 268         } else
 269                 Rt = 0;
 270
 271         /* NOTE:  "pendown" is inferred from pressure; we don't rely on
 272          * being able to check nPENIRQ status, or "friendly" trigger modes
 273          * (both-edges is much better than just-falling or low-level).
 274          *
 275          * REVISIT:  some boards may require reading nPENIRQ; it's
 276          * needed on 7843.  and 7845 reads pressure differently...
 277          *
 278          * REVISIT:  the touchscreen might not be connected; this code
 279          * won't notice that, even if nPENIRQ never fires ...
 280          */
 281         if (!ts->pendown && Rt != 0) {
 282                 input_report_key(&ts->input, BTN_TOUCH, 1);
 283                 sync = 1;
 284         } else if (ts->pendown && Rt == 0) {
 285                 input_report_key(&ts->input, BTN_TOUCH, 0);
 286                 sync = 1;
 287         }
 288
 289         if (Rt) {
 290                 input_report_abs(&ts->input, ABS_X, x);
 291                 input_report_abs(&ts->input, ABS_Y, y);
 292                 input_report_abs(&ts->input, ABS_PRESSURE, Rt);
 293                 sync = 1;
 294         }
 295         if (sync)
 296                 input_sync(&ts->input);
 297
 298 #ifdef  VERBOSE
 299         if (Rt || ts->pendown)
 300                 pr_debug("%s: %d/%d/%d%s\n", ts->spi->dev.bus_id,
 301                         x, y, Rt, Rt ? "" : " UP");
 302 #endif
 303
 304         /* don't retrigger while we're suspended */
 305         spin_lock_irqsave(&ts->lock, flags);
 306
 307         ts->pendown = (Rt != 0);
 308         ts->pending = 0;
 309
 310         if (ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
 311                 if (ts->pendown)
 312                         mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
 313                 else if (ts->irq_disabled) {
 314                         ts->irq_disabled = 0;
 315                         enable_irq(ts->spi->irq);
 316                 }
 317         }
 318
 319         spin_unlock_irqrestore(&ts->lock, flags);
 320 }
 321
 322 static void ads7846_timer(unsigned long handle)
 323 {
 324         struct ads7846  *ts = (void *)handle;
 325         int             status = 0;
 326         unsigned long   flags;
 327
 328         spin_lock_irqsave(&ts->lock, flags);
 329         if (!ts->pending) {
 330                 ts->pending = 1;
 331                 if (!ts->irq_disabled) {
 332                         ts->irq_disabled = 1;
 333                         disable_irq(ts->spi->irq);
 334                 }
 335                 status = spi_async(ts->spi, &ts->msg);
 336                 if (status)
 337                         dev_err(&ts->spi->dev, "spi_async --> %d\n",
 338                                         status);
 339         }
 340         spin_unlock_irqrestore(&ts->lock, flags);
 341 }
 342
 343 static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
 344 {
 345         ads7846_timer((unsigned long) handle);
 346         return IRQ_HANDLED;
 347 }
 348
 349 /*--------------------------------------------------------------------------*/
 350
 351 static int
 352 ads7846_suspend(struct spi_device *spi, pm_message_t message)
 353 {
 354         struct ads7846 *ts = dev_get_drvdata(&spi->dev);
 355         unsigned long   flags;
 356
 357         spin_lock_irqsave(&ts->lock, flags);
 358
 359         spi->dev.power.power_state = message;
 360
 361         /* are we waiting for IRQ, or polling? */
 362         if (!ts->pendown) {
 363                 if (!ts->irq_disabled) {
 364                         ts->irq_disabled = 1;
 365                         disable_irq(ts->spi->irq);
 366                 }
 367         } else {
 368                 /* polling; force a final SPI completion;
 369                  * that will clean things up neatly
 370                  */
 371                 if (!ts->pending)
 372                         mod_timer(&ts->timer, jiffies);
 373
 374                 while (ts->pendown || ts->pending) {
 375                         spin_unlock_irqrestore(&ts->lock, flags);
 376                         udelay(10);
 377                         spin_lock_irqsave(&ts->lock, flags);
 378                 }
 379         }
 380
 381         /* we know the chip's in lowpower mode since we always
 382          * leave it that way after every request
 383          */
 384
 385         spin_unlock_irqrestore(&ts->lock, flags);
 386         return 0;
 387 }
 388
 389 static int ads7846_resume(struct spi_device *spi)
 390 {
 391         struct ads7846 *ts = dev_get_drvdata(&spi->dev);
 392
 393         ts->irq_disabled = 0;
 394         enable_irq(ts->spi->irq);
 395         spi->dev.power.power_state = PMSG_ON;
 396         return 0;
 397 }
 398
 399 static int __devinit ads7846_probe(struct spi_device *spi)
 400 {
 401         struct ads7846                  *ts;
 402         struct ads7846_platform_data    *pdata = spi->dev.platform_data;
 403         struct spi_transfer             *x;
 404         int                             i;
 405
 406         if (!spi->irq) {
 407                 dev_dbg(&spi->dev, "no IRQ?\n");
 408                 return -ENODEV;
 409         }
 410
 411         if (!pdata) {
 412                 dev_dbg(&spi->dev, "no platform data?\n");
 413                 return -ENODEV;
 414         }
 415
 416         /* don't exceed max specified sample rate */
 417         if (spi->max_speed_hz > (125000 * 16)) {
 418                 dev_dbg(&spi->dev, "f(sample) %d KHz?\n",
 419                                 (spi->max_speed_hz/16)/1000);
 420                 return -EINVAL;
 421         }
 422
 423         /* We'd set the wordsize to 12 bits ... except that some controllers
 424          * will then treat the 8 bit command words as 12 bits (and drop the
 425          * four MSBs of the 12 bit result).  Result: inputs must be shifted
 426          * to discard the four garbage LSBs.
 427          */
 428
 429         if (!(ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL)))
 430                 return -ENOMEM;
 431
 432         dev_set_drvdata(&spi->dev, ts);
 433
 434         ts->spi = spi;
 435         spi->dev.power.power_state = PMSG_ON;
 436
 437         init_timer(&ts->timer);
 438         ts->timer.data = (unsigned long) ts;
 439         ts->timer.function = ads7846_timer;
 440
 441         ts->model = pdata->model ? : 7846;
 442         ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
 443         ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
 444
 445         init_input_dev(&ts->input);
 446
 447         ts->input.dev = &spi->dev;
 448         ts->input.name = "ADS784x Touchscreen";
 449         snprintf(ts->phys, sizeof ts->phys, "%s/input0", spi->dev.bus_id);
 450         ts->input.phys = ts->phys;
 451
 452         ts->input.evbit[0] = BIT(EV_KEY) | BIT(EV_ABS);
 453         ts->input.keybit[LONG(BTN_TOUCH)] = BIT(BTN_TOUCH);
 454         input_set_abs_params(&ts->input, ABS_X,
 455                         pdata->x_min ? : 0,
 456                         pdata->x_max ? : MAX_12BIT,
 457                         0, 0);
 458         input_set_abs_params(&ts->input, ABS_Y,
 459                         pdata->y_min ? : 0,
 460                         pdata->y_max ? : MAX_12BIT,
 461                         0, 0);
 462         input_set_abs_params(&ts->input, ABS_PRESSURE,
 463                         pdata->pressure_min, pdata->pressure_max, 0, 0);
 464
 465         input_register_device(&ts->input);
 466
 467         /* set up the transfers to read touchscreen state; this assumes we
 468          * use formula #2 for pressure, not #3.
 469          */
 470         x = ts->xfer;
 471
 472         /* y- still on; turn on only y+ (and ADC) */
 473         x->tx_buf = &read_y;
 474         x->len = 1;
 475         x++;
 476         x->rx_buf = &ts->tc.y;
 477         x->len = 2;
 478         x++;
 479
 480         /* turn y+ off, x- on; we'll use formula #2 */
 481         if (ts->model == 7846) {
 482                 x->tx_buf = &read_z1;
 483                 x->len = 1;
 484                 x++;
 485                 x->rx_buf = &ts->tc.z1;
 486                 x->len = 2;
 487                 x++;
 488
 489                 x->tx_buf = &read_z2;
 490                 x->len = 1;
 491                 x++;
 492                 x->rx_buf = &ts->tc.z2;
 493                 x->len = 2;
 494                 x++;
 495         }
 496
 497         /* turn y- off, x+ on, then leave in lowpower */
 498         x->tx_buf = &read_x;
 499         x->len = 1;
 500         x++;
 501         x->rx_buf = &ts->tc.x;
 502         x->len = 2;
 503         x++;
 504
 505         CS_CHANGE(x[-1]);
 506
 507         for (i = 0; i < x - ts->xfer; i++)
 508                 spi_message_add_tail(&ts->xfer[i], &ts->msg);
 509         ts->msg.complete = ads7846_rx;
 510         ts->msg.context = ts;
 511
 512         if (request_irq(spi->irq, ads7846_irq, SA_SAMPLE_RANDOM,
 513                                 spi->dev.bus_id, ts)) {
 514                 dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
 515                 input_unregister_device(&ts->input);
 516                 kfree(ts);
 517                 return -EBUSY;
 518         }
 519         set_irq_type(spi->irq, IRQT_FALLING);
 520
 521         dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);
 522
 523         /* take a first sample, leaving nPENIRQ active; avoid
 524          * the touchscreen, in case it's not connected.
 525          */
 526         (void) ads7846_read12_ser(&spi->dev,
 527                           READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);
 528
 529         /* ads7843/7845 don't have temperature sensors, and
 530          * use the other sensors a bit differently too
 531          */
 532         if (ts->model == 7846) {
 533                 device_create_file(&spi->dev, &dev_attr_temp0);
 534                 device_create_file(&spi->dev, &dev_attr_temp1);
 535         }
 536         if (ts->model != 7845)
 537                 device_create_file(&spi->dev, &dev_attr_vbatt);
 538         device_create_file(&spi->dev, &dev_attr_vaux);
 539
 540         return 0;
 541 }
 542
 543 static int __devexit ads7846_remove(struct spi_device *spi)
 544 {
 545         struct ads7846          *ts = dev_get_drvdata(&spi->dev);
 546
 547         ads7846_suspend(spi, PMSG_SUSPEND);
 548         free_irq(ts->spi->irq, ts);
 549         if (ts->irq_disabled)
 550                 enable_irq(ts->spi->irq);
 551
 552         if (ts->model == 7846) {
 553                 device_remove_file(&spi->dev, &dev_attr_temp0);
 554                 device_remove_file(&spi->dev, &dev_attr_temp1);
 555         }
 556         if (ts->model != 7845)
 557                 device_remove_file(&spi->dev, &dev_attr_vbatt);
 558         device_remove_file(&spi->dev, &dev_attr_vaux);
 559
 560         input_unregister_device(&ts->input);
 561         kfree(ts);
 562
 563         dev_dbg(&spi->dev, "unregistered touchscreen\n");
 564         return 0;
 565 }
 566
 567 static struct spi_driver ads7846_driver = {
 568         .driver = {
 569                 .name   = "ads7846",
 570                 .bus    = &spi_bus_type,
 571                 .owner  = THIS_MODULE,
 572         },
 573         .probe          = ads7846_probe,
 574         .remove         = __devexit_p(ads7846_remove),
 575         .suspend        = ads7846_suspend,
 576         .resume         = ads7846_resume,
 577 };
 578
 579 static int __init ads7846_init(void)
 580 {
 581         /* grr, board-specific init should stay out of drivers!! */
 582
 583 #ifdef  CONFIG_ARCH_OMAP
 584         if (machine_is_omap_osk()) {
 585                 /* GPIO4 = PENIRQ; GPIO6 = BUSY */
 586                 omap_request_gpio(4);
 587                 omap_set_gpio_direction(4, 1);
 588                 omap_request_gpio(6);
 589                 omap_set_gpio_direction(6, 1);
 590         }
 591         // also TI 1510 Innovator, bitbanging through FPGA
 592         // also Nokia 770
 593         // also Palm Tungsten T2
 594 #endif
 595
 596         // PXA:
 597         // also Dell Axim X50
 598         // also HP iPaq H191x/H192x/H415x/H435x
 599         // also Intel Lubbock (additional to UCB1400; as temperature sensor)
 600         // also Sharp Zaurus C7xx, C8xx (corgi/sheperd/husky)
 601
 602         // Atmel at91sam9261-EK uses ads7843
 603
 604         // also various AMD Au1x00 devel boards
 605
 606         return spi_register_driver(&ads7846_driver);
 607 }
 608 module_init(ads7846_init);
 609
 610 static void __exit ads7846_exit(void)
 611 {
 612         spi_unregister_driver(&ads7846_driver);
 613
 614 #ifdef  CONFIG_ARCH_OMAP
 615         if (machine_is_omap_osk()) {
 616                 omap_free_gpio(4);
 617                 omap_free_gpio(6);
 618         }
 619 #endif
 620
 621 }
 622 module_exit(ads7846_exit);
 623
 624 MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
 625 MODULE_LICENSE("GPL");