2 * ADS7846 based touchscreen and sensor driver
4 * Copyright (c) 2005 David Brownell
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
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.
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>
29 #include <asm/mach-types.h>
30 #ifdef CONFIG_ARCH_OMAP
31 #include <asm/arch/gpio.h>
37 * This code has been lightly tested on an ads7846.
38 * Support for ads7843 and ads7845 has only been stubbed in.
40 * Not yet done: investigate the values reported. Are x/y/pressure
41 * event values sane enough for X11? How accurate are the temperature
42 * and voltage readings? (System-specific calibration should support
43 * accuracy of 0.3 degrees C; otherwise it's 2.0 degrees.)
45 * app note sbaa036 talks in more detail about accurate sampling...
46 * that ought to help in situations like LCDs inducing noise (which
47 * can also be helped by using synch signals) and more generally.
50 #define TS_POLL_PERIOD msecs_to_jiffies(10)
52 /* this driver doesn't aim at the peak continuous sample rate */
53 #define SAMPLE_BITS (8 /*cmd*/ + 16 /*sample*/ + 2 /* before, after */)
56 /* For portability, we can't read 12 bit values using SPI (which
57 * would make the controller deliver them as native byteorder u16
58 * with msbs zeroed). Instead, we read them as two 8-bit values,
59 * which need byteswapping then range adjustment.
67 struct input_dev *input;
70 struct spi_device *spi;
75 u8 read_x, read_y, read_z1, read_z2, pwrdown;
76 u16 dummy; /* for the pwrdown read */
79 struct spi_transfer xfer[10];
80 struct spi_message msg;
83 struct timer_list timer; /* P: lock */
84 unsigned pendown:1; /* P: lock */
85 unsigned pending:1; /* P: lock */
86 // FIXME remove "irq_disabled"
87 unsigned irq_disabled:1; /* P: lock */
90 /* leave chip selected when we're done, for quicker re-select? */
92 #define CS_CHANGE(xfer) ((xfer).cs_change = 1)
94 #define CS_CHANGE(xfer) ((xfer).cs_change = 0)
97 /*--------------------------------------------------------------------------*/
99 /* The ADS7846 has touchscreen and other sensors.
100 * Earlier ads784x chips are somewhat compatible.
102 #define ADS_START (1 << 7)
103 #define ADS_A2A1A0_d_y (1 << 4) /* differential */
104 #define ADS_A2A1A0_d_z1 (3 << 4) /* differential */
105 #define ADS_A2A1A0_d_z2 (4 << 4) /* differential */
106 #define ADS_A2A1A0_d_x (5 << 4) /* differential */
107 #define ADS_A2A1A0_temp0 (0 << 4) /* non-differential */
108 #define ADS_A2A1A0_vbatt (2 << 4) /* non-differential */
109 #define ADS_A2A1A0_vaux (6 << 4) /* non-differential */
110 #define ADS_A2A1A0_temp1 (7 << 4) /* non-differential */
111 #define ADS_8_BIT (1 << 3)
112 #define ADS_12_BIT (0 << 3)
113 #define ADS_SER (1 << 2) /* non-differential */
114 #define ADS_DFR (0 << 2) /* differential */
115 #define ADS_PD10_PDOWN (0 << 0) /* lowpower mode + penirq */
116 #define ADS_PD10_ADC_ON (1 << 0) /* ADC on */
117 #define ADS_PD10_REF_ON (2 << 0) /* vREF on + penirq */
118 #define ADS_PD10_ALL_ON (3 << 0) /* ADC + vREF on */
120 #define MAX_12BIT ((1<<12)-1)
122 /* leave ADC powered up (disables penirq) between differential samples */
123 #define READ_12BIT_DFR(x) (ADS_START | ADS_A2A1A0_d_ ## x \
124 | ADS_12_BIT | ADS_DFR)
126 #define READ_Y (READ_12BIT_DFR(y) | ADS_PD10_ADC_ON)
127 #define READ_Z1 (READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON)
128 #define READ_Z2 (READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON)
130 #define READ_X (READ_12BIT_DFR(x) | ADS_PD10_ADC_ON)
131 #define PWRDOWN (READ_12BIT_DFR(y) | ADS_PD10_PDOWN) /* LAST */
133 /* single-ended samples need to first power up reference voltage;
134 * we leave both ADC and VREF powered
136 #define READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
137 | ADS_12_BIT | ADS_SER)
139 #define REF_ON (READ_12BIT_DFR(x) | ADS_PD10_ALL_ON)
140 #define REF_OFF (READ_12BIT_DFR(y) | ADS_PD10_PDOWN)
142 /*--------------------------------------------------------------------------*/
145 * Non-touchscreen sensors only use single-ended conversions.
154 struct spi_message msg;
155 struct spi_transfer xfer[6];
158 static int ads7846_read12_ser(struct device *dev, unsigned command)
160 struct spi_device *spi = to_spi_device(dev);
161 struct ads7846 *ts = dev_get_drvdata(dev);
162 struct ser_req *req = kzalloc(sizeof *req, SLAB_KERNEL);
170 INIT_LIST_HEAD(&req->msg.transfers);
172 /* activate reference, so it has time to settle; */
173 req->ref_on = REF_ON;
174 req->xfer[0].tx_buf = &req->ref_on;
175 req->xfer[0].len = 1;
176 req->xfer[1].rx_buf = &req->scratch;
177 req->xfer[1].len = 2;
180 * for external VREF, 0 usec (and assume it's always on);
181 * for 1uF, use 800 usec;
184 req->xfer[1].delay_usecs = ts->vref_delay_usecs;
187 req->command = (u8) command;
188 req->xfer[2].tx_buf = &req->command;
189 req->xfer[2].len = 1;
190 req->xfer[3].rx_buf = &req->sample;
191 req->xfer[3].len = 2;
193 /* REVISIT: take a few more samples, and compare ... */
195 /* turn off reference */
196 req->ref_off = REF_OFF;
197 req->xfer[4].tx_buf = &req->ref_off;
198 req->xfer[4].len = 1;
199 req->xfer[5].rx_buf = &req->scratch;
200 req->xfer[5].len = 2;
202 CS_CHANGE(req->xfer[5]);
204 /* group all the transfers together, so we can't interfere with
205 * reading touchscreen state; disable penirq while sampling
207 for (i = 0; i < 6; i++)
208 spi_message_add_tail(&req->xfer[i], &req->msg);
210 disable_irq(spi->irq);
211 status = spi_sync(spi, &req->msg);
212 enable_irq(spi->irq);
215 status = req->msg.status;
216 sample = be16_to_cpu(req->sample);
217 sample = sample >> 4;
220 return status ? status : sample;
223 #define SHOW(name) static ssize_t \
224 name ## _show(struct device *dev, struct device_attribute *attr, char *buf) \
226 ssize_t v = ads7846_read12_ser(dev, \
227 READ_12BIT_SER(name) | ADS_PD10_ALL_ON); \
230 return sprintf(buf, "%u\n", (unsigned) v); \
232 static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);
239 static int is_pen_down(struct device *dev)
241 struct ads7846 *ts = dev_get_drvdata(dev);
246 static ssize_t ads7846_pen_down_show(struct device *dev,
247 struct device_attribute *attr, char *buf)
249 return sprintf(buf, "%u\n", is_pen_down(dev));
252 static DEVICE_ATTR(pen_down, S_IRUGO, ads7846_pen_down_show, NULL);
254 /*--------------------------------------------------------------------------*/
257 * PENIRQ only kicks the timer. The timer only reissues the SPI transfer,
258 * to retrieve touchscreen status.
260 * The SPI transfer completion callback does the real work. It reports
261 * touchscreen events and reactivates the timer (or IRQ) as appropriate.
264 static void ads7846_rx(void *ads)
266 struct ads7846 *ts = ads;
267 struct input_dev *input_dev = ts->input;
273 /* adjust: 12 bit samples (left aligned), built from
274 * two 8 bit values writen msb-first.
276 x = be16_to_cpu(ts->tc.x) >> 4;
277 y = be16_to_cpu(ts->tc.y) >> 4;
278 z1 = be16_to_cpu(ts->tc.z1) >> 4;
279 z2 = be16_to_cpu(ts->tc.z2) >> 4;
281 /* range filtering */
285 if (x && z1 && ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
286 /* compute touch pressure resistance using equation #2 */
290 Rt *= ts->x_plate_ohms;
292 Rt = (Rt + 2047) >> 12;
296 /* NOTE: "pendown" is inferred from pressure; we don't rely on
297 * being able to check nPENIRQ status, or "friendly" trigger modes
298 * (both-edges is much better than just-falling or low-level).
300 * REVISIT: some boards may require reading nPENIRQ; it's
301 * needed on 7843. and 7845 reads pressure differently...
303 * REVISIT: the touchscreen might not be connected; this code
304 * won't notice that, even if nPENIRQ never fires ...
306 if (!ts->pendown && Rt != 0) {
307 input_report_key(input_dev, BTN_TOUCH, 1);
309 } else if (ts->pendown && Rt == 0) {
310 input_report_key(input_dev, BTN_TOUCH, 0);
315 input_report_abs(input_dev, ABS_X, x);
316 input_report_abs(input_dev, ABS_Y, y);
317 input_report_abs(input_dev, ABS_PRESSURE, Rt);
321 input_sync(input_dev);
324 if (Rt || ts->pendown)
325 pr_debug("%s: %d/%d/%d%s\n", ts->spi->dev.bus_id,
326 x, y, Rt, Rt ? "" : " UP");
329 /* don't retrigger while we're suspended */
330 spin_lock_irqsave(&ts->lock, flags);
332 ts->pendown = (Rt != 0);
335 if (ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
337 mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
338 else if (ts->irq_disabled) {
339 ts->irq_disabled = 0;
340 enable_irq(ts->spi->irq);
344 spin_unlock_irqrestore(&ts->lock, flags);
347 static void ads7846_timer(unsigned long handle)
349 struct ads7846 *ts = (void *)handle;
353 spin_lock_irqsave(&ts->lock, flags);
356 if (!ts->irq_disabled) {
357 ts->irq_disabled = 1;
358 disable_irq(ts->spi->irq);
360 status = spi_async(ts->spi, &ts->msg);
362 dev_err(&ts->spi->dev, "spi_async --> %d\n",
365 spin_unlock_irqrestore(&ts->lock, flags);
368 static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
370 ads7846_timer((unsigned long) handle);
374 /*--------------------------------------------------------------------------*/
377 ads7846_suspend(struct spi_device *spi, pm_message_t message)
379 struct ads7846 *ts = dev_get_drvdata(&spi->dev);
382 spin_lock_irqsave(&ts->lock, flags);
384 spi->dev.power.power_state = message;
386 /* are we waiting for IRQ, or polling? */
388 if (!ts->irq_disabled) {
389 ts->irq_disabled = 1;
390 disable_irq(ts->spi->irq);
393 /* polling; force a final SPI completion;
394 * that will clean things up neatly
397 mod_timer(&ts->timer, jiffies);
399 while (ts->pendown || ts->pending) {
400 spin_unlock_irqrestore(&ts->lock, flags);
402 spin_lock_irqsave(&ts->lock, flags);
406 /* we know the chip's in lowpower mode since we always
407 * leave it that way after every request
410 spin_unlock_irqrestore(&ts->lock, flags);
414 static int ads7846_resume(struct spi_device *spi)
416 struct ads7846 *ts = dev_get_drvdata(&spi->dev);
418 ts->irq_disabled = 0;
419 enable_irq(ts->spi->irq);
420 spi->dev.power.power_state = PMSG_ON;
424 static int __devinit ads7846_probe(struct spi_device *spi)
427 struct input_dev *input_dev;
428 struct ads7846_platform_data *pdata = spi->dev.platform_data;
429 struct spi_transfer *x;
433 dev_dbg(&spi->dev, "no IRQ?\n");
438 dev_dbg(&spi->dev, "no platform data?\n");
442 /* don't exceed max specified sample rate */
443 if (spi->max_speed_hz > (125000 * SAMPLE_BITS)) {
444 dev_dbg(&spi->dev, "f(sample) %d KHz?\n",
445 (spi->max_speed_hz/SAMPLE_BITS)/1000);
449 /* We'd set the wordsize to 12 bits ... except that some controllers
450 * will then treat the 8 bit command words as 12 bits (and drop the
451 * four MSBs of the 12 bit result). Result: inputs must be shifted
452 * to discard the four garbage LSBs.
455 ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL);
456 input_dev = input_allocate_device();
457 if (!ts || !input_dev) {
462 dev_set_drvdata(&spi->dev, ts);
463 spi->dev.power.power_state = PMSG_ON;
466 ts->input = input_dev;
468 init_timer(&ts->timer);
469 ts->timer.data = (unsigned long) ts;
470 ts->timer.function = ads7846_timer;
472 ts->model = pdata->model ? : 7846;
473 ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
474 ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
476 snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
478 input_dev->name = "ADS784x Touchscreen";
479 input_dev->phys = ts->phys;
480 input_dev->cdev.dev = &spi->dev;
482 input_dev->evbit[0] = BIT(EV_KEY) | BIT(EV_ABS);
483 input_dev->keybit[LONG(BTN_TOUCH)] = BIT(BTN_TOUCH);
484 input_set_abs_params(input_dev, ABS_X,
486 pdata->x_max ? : MAX_12BIT,
488 input_set_abs_params(input_dev, ABS_Y,
490 pdata->y_max ? : MAX_12BIT,
492 input_set_abs_params(input_dev, ABS_PRESSURE,
493 pdata->pressure_min, pdata->pressure_max, 0, 0);
495 /* set up the transfers to read touchscreen state; this assumes we
496 * use formula #2 for pressure, not #3.
498 INIT_LIST_HEAD(&ts->msg.transfers);
501 /* y- still on; turn on only y+ (and ADC) */
503 x->tx_buf = &ts->read_y;
505 spi_message_add_tail(x, &ts->msg);
508 x->rx_buf = &ts->tc.y;
510 spi_message_add_tail(x, &ts->msg);
512 /* turn y+ off, x- on; we'll use formula #2 */
513 if (ts->model == 7846) {
515 ts->read_z1 = READ_Z1;
516 x->tx_buf = &ts->read_z1;
518 spi_message_add_tail(x, &ts->msg);
521 x->rx_buf = &ts->tc.z1;
523 spi_message_add_tail(x, &ts->msg);
526 ts->read_z2 = READ_Z2;
527 x->tx_buf = &ts->read_z2;
529 spi_message_add_tail(x, &ts->msg);
532 x->rx_buf = &ts->tc.z2;
534 spi_message_add_tail(x, &ts->msg);
537 /* turn y- off, x+ on, then leave in lowpower */
540 x->tx_buf = &ts->read_x;
542 spi_message_add_tail(x, &ts->msg);
545 x->rx_buf = &ts->tc.x;
547 spi_message_add_tail(x, &ts->msg);
551 ts->pwrdown = PWRDOWN;
552 x->tx_buf = &ts->pwrdown;
554 spi_message_add_tail(x, &ts->msg);
557 x->rx_buf = &ts->dummy;
560 spi_message_add_tail(x, &ts->msg);
562 ts->msg.complete = ads7846_rx;
563 ts->msg.context = ts;
565 if (request_irq(spi->irq, ads7846_irq,
566 SA_SAMPLE_RANDOM | SA_TRIGGER_FALLING,
567 spi->dev.bus_id, ts)) {
568 dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
573 dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);
575 /* take a first sample, leaving nPENIRQ active; avoid
576 * the touchscreen, in case it's not connected.
578 (void) ads7846_read12_ser(&spi->dev,
579 READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);
581 /* ads7843/7845 don't have temperature sensors, and
582 * use the other sensors a bit differently too
584 if (ts->model == 7846) {
585 device_create_file(&spi->dev, &dev_attr_temp0);
586 device_create_file(&spi->dev, &dev_attr_temp1);
588 if (ts->model != 7845)
589 device_create_file(&spi->dev, &dev_attr_vbatt);
590 device_create_file(&spi->dev, &dev_attr_vaux);
592 device_create_file(&spi->dev, &dev_attr_pen_down);
594 err = input_register_device(input_dev);
601 free_irq(spi->irq, ts);
603 input_free_device(input_dev);
608 static int __devexit ads7846_remove(struct spi_device *spi)
610 struct ads7846 *ts = dev_get_drvdata(&spi->dev);
612 ads7846_suspend(spi, PMSG_SUSPEND);
613 free_irq(ts->spi->irq, ts);
614 if (ts->irq_disabled)
615 enable_irq(ts->spi->irq);
617 device_remove_file(&spi->dev, &dev_attr_pen_down);
619 if (ts->model == 7846) {
620 device_remove_file(&spi->dev, &dev_attr_temp0);
621 device_remove_file(&spi->dev, &dev_attr_temp1);
623 if (ts->model != 7845)
624 device_remove_file(&spi->dev, &dev_attr_vbatt);
625 device_remove_file(&spi->dev, &dev_attr_vaux);
627 input_unregister_device(ts->input);
630 dev_dbg(&spi->dev, "unregistered touchscreen\n");
634 static struct spi_driver ads7846_driver = {
637 .bus = &spi_bus_type,
638 .owner = THIS_MODULE,
640 .probe = ads7846_probe,
641 .remove = __devexit_p(ads7846_remove),
642 .suspend = ads7846_suspend,
643 .resume = ads7846_resume,
646 static int __init ads7846_init(void)
648 /* grr, board-specific init should stay out of drivers!! */
650 #ifdef CONFIG_ARCH_OMAP
651 if (machine_is_omap_osk()) {
652 /* GPIO4 = PENIRQ; GPIO6 = BUSY */
653 omap_request_gpio(4);
654 omap_set_gpio_direction(4, 1);
655 omap_request_gpio(6);
656 omap_set_gpio_direction(6, 1);
658 // also TI 1510 Innovator, bitbanging through FPGA
660 // also Palm Tungsten T2
664 // also Dell Axim X50
665 // also HP iPaq H191x/H192x/H415x/H435x
666 // also Intel Lubbock (additional to UCB1400; as temperature sensor)
667 // also Sharp Zaurus C7xx, C8xx (corgi/sheperd/husky)
669 // Atmel at91sam9261-EK uses ads7843
671 // also various AMD Au1x00 devel boards
673 return spi_register_driver(&ads7846_driver);
675 module_init(ads7846_init);
677 static void __exit ads7846_exit(void)
679 spi_unregister_driver(&ads7846_driver);
681 #ifdef CONFIG_ARCH_OMAP
682 if (machine_is_omap_osk()) {
689 module_exit(ads7846_exit);
691 MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
692 MODULE_LICENSE("GPL");