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[5];
89 struct timer_list timer; /* P: lock */
90 unsigned pendown:1; /* P: lock */
91 unsigned pending:1; /* P: lock */
92 // FIXME remove "irq_disabled"
93 unsigned irq_disabled:1; /* P: lock */
96 /* leave chip selected when we're done, for quicker re-select? */
98 #define CS_CHANGE(xfer) ((xfer).cs_change = 1)
100 #define CS_CHANGE(xfer) ((xfer).cs_change = 0)
103 /*--------------------------------------------------------------------------*/
105 /* The ADS7846 has touchscreen and other sensors.
106 * Earlier ads784x chips are somewhat compatible.
108 #define ADS_START (1 << 7)
109 #define ADS_A2A1A0_d_y (1 << 4) /* differential */
110 #define ADS_A2A1A0_d_z1 (3 << 4) /* differential */
111 #define ADS_A2A1A0_d_z2 (4 << 4) /* differential */
112 #define ADS_A2A1A0_d_x (5 << 4) /* differential */
113 #define ADS_A2A1A0_temp0 (0 << 4) /* non-differential */
114 #define ADS_A2A1A0_vbatt (2 << 4) /* non-differential */
115 #define ADS_A2A1A0_vaux (6 << 4) /* non-differential */
116 #define ADS_A2A1A0_temp1 (7 << 4) /* non-differential */
117 #define ADS_8_BIT (1 << 3)
118 #define ADS_12_BIT (0 << 3)
119 #define ADS_SER (1 << 2) /* non-differential */
120 #define ADS_DFR (0 << 2) /* differential */
121 #define ADS_PD10_PDOWN (0 << 0) /* lowpower mode + penirq */
122 #define ADS_PD10_ADC_ON (1 << 0) /* ADC on */
123 #define ADS_PD10_REF_ON (2 << 0) /* vREF on + penirq */
124 #define ADS_PD10_ALL_ON (3 << 0) /* ADC + vREF on */
126 #define MAX_12BIT ((1<<12)-1)
128 /* leave ADC powered up (disables penirq) between differential samples */
129 #define READ_12BIT_DFR(x) (ADS_START | ADS_A2A1A0_d_ ## x \
130 | ADS_12_BIT | ADS_DFR)
132 #define READ_Y (READ_12BIT_DFR(y) | ADS_PD10_ADC_ON)
133 #define READ_Z1 (READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON)
134 #define READ_Z2 (READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON)
136 #define READ_X (READ_12BIT_DFR(x) | ADS_PD10_ADC_ON)
137 #define PWRDOWN (READ_12BIT_DFR(y) | ADS_PD10_PDOWN) /* LAST */
139 /* single-ended samples need to first power up reference voltage;
140 * we leave both ADC and VREF powered
142 #define READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
143 | ADS_12_BIT | ADS_SER)
145 #define REF_ON (READ_12BIT_DFR(x) | ADS_PD10_ALL_ON)
146 #define REF_OFF (READ_12BIT_DFR(y) | ADS_PD10_PDOWN)
148 /*--------------------------------------------------------------------------*/
151 * Non-touchscreen sensors only use single-ended conversions.
160 struct spi_message msg;
161 struct spi_transfer xfer[6];
164 static int ads7846_read12_ser(struct device *dev, unsigned command)
166 struct spi_device *spi = to_spi_device(dev);
167 struct ads7846 *ts = dev_get_drvdata(dev);
168 struct ser_req *req = kzalloc(sizeof *req, SLAB_KERNEL);
176 spi_message_init(&req->msg);
178 /* activate reference, so it has time to settle; */
179 req->ref_on = REF_ON;
180 req->xfer[0].tx_buf = &req->ref_on;
181 req->xfer[0].len = 1;
182 req->xfer[1].rx_buf = &req->scratch;
183 req->xfer[1].len = 2;
186 * for external VREF, 0 usec (and assume it's always on);
187 * for 1uF, use 800 usec;
190 req->xfer[1].delay_usecs = ts->vref_delay_usecs;
193 req->command = (u8) command;
194 req->xfer[2].tx_buf = &req->command;
195 req->xfer[2].len = 1;
196 req->xfer[3].rx_buf = &req->sample;
197 req->xfer[3].len = 2;
199 /* REVISIT: take a few more samples, and compare ... */
201 /* turn off reference */
202 req->ref_off = REF_OFF;
203 req->xfer[4].tx_buf = &req->ref_off;
204 req->xfer[4].len = 1;
205 req->xfer[5].rx_buf = &req->scratch;
206 req->xfer[5].len = 2;
208 CS_CHANGE(req->xfer[5]);
210 /* group all the transfers together, so we can't interfere with
211 * reading touchscreen state; disable penirq while sampling
213 for (i = 0; i < 6; i++)
214 spi_message_add_tail(&req->xfer[i], &req->msg);
216 disable_irq(spi->irq);
217 status = spi_sync(spi, &req->msg);
218 enable_irq(spi->irq);
221 status = req->msg.status;
222 sample = be16_to_cpu(req->sample);
223 sample = sample >> 4;
226 return status ? status : sample;
229 #define SHOW(name) static ssize_t \
230 name ## _show(struct device *dev, struct device_attribute *attr, char *buf) \
232 ssize_t v = ads7846_read12_ser(dev, \
233 READ_12BIT_SER(name) | ADS_PD10_ALL_ON); \
236 return sprintf(buf, "%u\n", (unsigned) v); \
238 static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);
245 static int is_pen_down(struct device *dev)
247 struct ads7846 *ts = dev_get_drvdata(dev);
252 static ssize_t ads7846_pen_down_show(struct device *dev,
253 struct device_attribute *attr, char *buf)
255 return sprintf(buf, "%u\n", is_pen_down(dev));
258 static DEVICE_ATTR(pen_down, S_IRUGO, ads7846_pen_down_show, NULL);
260 /*--------------------------------------------------------------------------*/
263 * PENIRQ only kicks the timer. The timer only reissues the SPI transfer,
264 * to retrieve touchscreen status.
266 * The SPI transfer completion callback does the real work. It reports
267 * touchscreen events and reactivates the timer (or IRQ) as appropriate.
270 static void ads7846_rx(void *ads)
272 struct ads7846 *ts = ads;
273 struct input_dev *input_dev = ts->input;
279 /* adjust: 12 bit samples (left aligned), built from
280 * two 8 bit values writen msb-first.
282 x = be16_to_cpu(ts->tc.x) >> 4;
283 y = be16_to_cpu(ts->tc.y) >> 4;
284 z1 = be16_to_cpu(ts->tc.z1) >> 4;
285 z2 = be16_to_cpu(ts->tc.z2) >> 4;
287 /* range filtering */
291 if (x && z1 && ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
292 /* compute touch pressure resistance using equation #2 */
296 Rt *= ts->x_plate_ohms;
298 Rt = (Rt + 2047) >> 12;
302 /* NOTE: "pendown" is inferred from pressure; we don't rely on
303 * being able to check nPENIRQ status, or "friendly" trigger modes
304 * (both-edges is much better than just-falling or low-level).
306 * REVISIT: some boards may require reading nPENIRQ; it's
307 * needed on 7843. and 7845 reads pressure differently...
309 * REVISIT: the touchscreen might not be connected; this code
310 * won't notice that, even if nPENIRQ never fires ...
312 if (!ts->pendown && Rt != 0) {
313 input_report_key(input_dev, BTN_TOUCH, 1);
315 } else if (ts->pendown && Rt == 0) {
316 input_report_key(input_dev, BTN_TOUCH, 0);
321 input_report_abs(input_dev, ABS_X, x);
322 input_report_abs(input_dev, ABS_Y, y);
323 input_report_abs(input_dev, ABS_PRESSURE, Rt);
327 input_sync(input_dev);
330 if (Rt || ts->pendown)
331 pr_debug("%s: %d/%d/%d%s\n", ts->spi->dev.bus_id,
332 x, y, Rt, Rt ? "" : " UP");
335 /* don't retrigger while we're suspended */
336 spin_lock_irqsave(&ts->lock, flags);
338 ts->pendown = (Rt != 0);
341 if (ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
343 mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
344 else if (ts->irq_disabled) {
345 ts->irq_disabled = 0;
346 enable_irq(ts->spi->irq);
350 spin_unlock_irqrestore(&ts->lock, flags);
353 static void ads7846_debounce(void *ads)
355 struct ads7846 *ts = ads;
356 struct spi_message *m;
357 struct spi_transfer *t;
361 m = &ts->msg[ts->msg_idx];
362 t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);
363 val = (*(u16 *)t->rx_buf) >> 3;
365 if (!ts->read_cnt || (abs(ts->last_read - val) > ts->debounce_tol
366 && ts->read_cnt < ts->debounce_max)) {
367 /* Repeat it, if this was the first read or the read wasn't
373 /* Go for the next read */
378 status = spi_async(ts->spi, m);
380 dev_err(&ts->spi->dev, "spi_async --> %d\n",
384 static void ads7846_timer(unsigned long handle)
386 struct ads7846 *ts = (void *)handle;
390 status = spi_async(ts->spi, &ts->msg[0]);
392 dev_err(&ts->spi->dev, "spi_async --> %d\n", status);
395 static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
397 struct ads7846 *ts = handle;
401 spin_lock_irqsave(&ts->lock, flags);
402 if (ts->irq_disabled)
405 if (!ts->irq_disabled) {
406 /* REVISIT irq logic for many ARM chips has cloned a
407 * bug wherein disabling an irq in its handler won't
408 * work;(it's disabled lazily, and too late to work.
409 * until all their irq logic is fixed, we must shadow
412 ts->irq_disabled = 1;
414 disable_irq(ts->spi->irq);
418 mod_timer(&ts->timer, jiffies);
421 spin_unlock_irqrestore(&ts->lock, flags);
425 /*--------------------------------------------------------------------------*/
428 ads7846_suspend(struct spi_device *spi, pm_message_t message)
430 struct ads7846 *ts = dev_get_drvdata(&spi->dev);
433 spin_lock_irqsave(&ts->lock, flags);
435 spi->dev.power.power_state = message;
437 /* are we waiting for IRQ, or polling? */
439 if (!ts->irq_disabled) {
440 ts->irq_disabled = 1;
441 disable_irq(ts->spi->irq);
444 /* polling; force a final SPI completion;
445 * that will clean things up neatly
448 mod_timer(&ts->timer, jiffies);
450 while (ts->pendown || ts->pending) {
451 spin_unlock_irqrestore(&ts->lock, flags);
453 spin_lock_irqsave(&ts->lock, flags);
457 /* we know the chip's in lowpower mode since we always
458 * leave it that way after every request
461 spin_unlock_irqrestore(&ts->lock, flags);
465 static int ads7846_resume(struct spi_device *spi)
467 struct ads7846 *ts = dev_get_drvdata(&spi->dev);
469 ts->irq_disabled = 0;
470 enable_irq(ts->spi->irq);
471 spi->dev.power.power_state = PMSG_ON;
475 static int __devinit ads7846_probe(struct spi_device *spi)
478 struct input_dev *input_dev;
479 struct ads7846_platform_data *pdata = spi->dev.platform_data;
480 struct spi_message *m;
481 struct spi_transfer *x;
485 dev_dbg(&spi->dev, "no IRQ?\n");
490 dev_dbg(&spi->dev, "no platform data?\n");
494 /* don't exceed max specified sample rate */
495 if (spi->max_speed_hz > (125000 * SAMPLE_BITS)) {
496 dev_dbg(&spi->dev, "f(sample) %d KHz?\n",
497 (spi->max_speed_hz/SAMPLE_BITS)/1000);
501 /* We'd set the wordsize to 12 bits ... except that some controllers
502 * will then treat the 8 bit command words as 12 bits (and drop the
503 * four MSBs of the 12 bit result). Result: inputs must be shifted
504 * to discard the four garbage LSBs.
507 ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL);
508 input_dev = input_allocate_device();
509 if (!ts || !input_dev) {
514 dev_set_drvdata(&spi->dev, ts);
515 spi->dev.power.power_state = PMSG_ON;
518 ts->input = input_dev;
520 init_timer(&ts->timer);
521 ts->timer.data = (unsigned long) ts;
522 ts->timer.function = ads7846_timer;
524 ts->model = pdata->model ? : 7846;
525 ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
526 ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
527 ts->debounce_max = pdata->debounce_max ? : 1;
528 ts->debounce_tol = pdata->debounce_tol ? : 10;
530 snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
532 input_dev->name = "ADS784x Touchscreen";
533 input_dev->phys = ts->phys;
534 input_dev->cdev.dev = &spi->dev;
536 input_dev->evbit[0] = BIT(EV_KEY) | BIT(EV_ABS);
537 input_dev->keybit[LONG(BTN_TOUCH)] = BIT(BTN_TOUCH);
538 input_set_abs_params(input_dev, ABS_X,
540 pdata->x_max ? : MAX_12BIT,
542 input_set_abs_params(input_dev, ABS_Y,
544 pdata->y_max ? : MAX_12BIT,
546 input_set_abs_params(input_dev, ABS_PRESSURE,
547 pdata->pressure_min, pdata->pressure_max, 0, 0);
549 /* set up the transfers to read touchscreen state; this assumes we
550 * use formula #2 for pressure, not #3.
557 /* y- still on; turn on only y+ (and ADC) */
559 x->tx_buf = &ts->read_y;
561 spi_message_add_tail(x, m);
564 x->rx_buf = &ts->tc.y;
566 spi_message_add_tail(x, m);
568 m->complete = ads7846_debounce;
574 /* turn y- off, x+ on, then leave in lowpower */
577 x->tx_buf = &ts->read_x;
579 spi_message_add_tail(x, m);
582 x->rx_buf = &ts->tc.x;
584 spi_message_add_tail(x, m);
586 m->complete = ads7846_debounce;
589 /* turn y+ off, x- on; we'll use formula #2 */
590 if (ts->model == 7846) {
595 ts->read_z1 = READ_Z1;
596 x->tx_buf = &ts->read_z1;
598 spi_message_add_tail(x, m);
601 x->rx_buf = &ts->tc.z1;
603 spi_message_add_tail(x, m);
605 m->complete = ads7846_debounce;
612 ts->read_z2 = READ_Z2;
613 x->tx_buf = &ts->read_z2;
615 spi_message_add_tail(x, m);
618 x->rx_buf = &ts->tc.z2;
620 spi_message_add_tail(x, m);
622 m->complete = ads7846_debounce;
631 ts->pwrdown = PWRDOWN;
632 x->tx_buf = &ts->pwrdown;
634 spi_message_add_tail(x, m);
637 x->rx_buf = &ts->dummy;
640 spi_message_add_tail(x, m);
642 m->complete = ads7846_rx;
645 if (request_irq(spi->irq, ads7846_irq,
646 SA_SAMPLE_RANDOM | SA_TRIGGER_FALLING,
647 spi->dev.bus_id, ts)) {
648 dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
653 dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);
655 /* take a first sample, leaving nPENIRQ active; avoid
656 * the touchscreen, in case it's not connected.
658 (void) ads7846_read12_ser(&spi->dev,
659 READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);
661 /* ads7843/7845 don't have temperature sensors, and
662 * use the other sensors a bit differently too
664 if (ts->model == 7846) {
665 device_create_file(&spi->dev, &dev_attr_temp0);
666 device_create_file(&spi->dev, &dev_attr_temp1);
668 if (ts->model != 7845)
669 device_create_file(&spi->dev, &dev_attr_vbatt);
670 device_create_file(&spi->dev, &dev_attr_vaux);
672 device_create_file(&spi->dev, &dev_attr_pen_down);
674 err = input_register_device(input_dev);
681 free_irq(spi->irq, ts);
683 input_free_device(input_dev);
688 static int __devexit ads7846_remove(struct spi_device *spi)
690 struct ads7846 *ts = dev_get_drvdata(&spi->dev);
692 ads7846_suspend(spi, PMSG_SUSPEND);
693 free_irq(ts->spi->irq, ts);
694 if (ts->irq_disabled)
695 enable_irq(ts->spi->irq);
697 device_remove_file(&spi->dev, &dev_attr_pen_down);
699 if (ts->model == 7846) {
700 device_remove_file(&spi->dev, &dev_attr_temp0);
701 device_remove_file(&spi->dev, &dev_attr_temp1);
703 if (ts->model != 7845)
704 device_remove_file(&spi->dev, &dev_attr_vbatt);
705 device_remove_file(&spi->dev, &dev_attr_vaux);
707 input_unregister_device(ts->input);
710 dev_dbg(&spi->dev, "unregistered touchscreen\n");
714 static struct spi_driver ads7846_driver = {
717 .bus = &spi_bus_type,
718 .owner = THIS_MODULE,
720 .probe = ads7846_probe,
721 .remove = __devexit_p(ads7846_remove),
722 .suspend = ads7846_suspend,
723 .resume = ads7846_resume,
726 static int __init ads7846_init(void)
728 /* grr, board-specific init should stay out of drivers!! */
730 #ifdef CONFIG_ARCH_OMAP
731 if (machine_is_omap_osk()) {
732 /* GPIO4 = PENIRQ; GPIO6 = BUSY */
733 omap_request_gpio(4);
734 omap_set_gpio_direction(4, 1);
735 omap_request_gpio(6);
736 omap_set_gpio_direction(6, 1);
738 // also TI 1510 Innovator, bitbanging through FPGA
740 // also Palm Tungsten T2
744 // also Dell Axim X50
745 // also HP iPaq H191x/H192x/H415x/H435x
746 // also Intel Lubbock (additional to UCB1400; as temperature sensor)
747 // also Sharp Zaurus C7xx, C8xx (corgi/sheperd/husky)
749 // Atmel at91sam9261-EK uses ads7843
751 // also various AMD Au1x00 devel boards
753 return spi_register_driver(&ads7846_driver);
755 module_init(ads7846_init);
757 static void __exit ads7846_exit(void)
759 spi_unregister_driver(&ads7846_driver);
761 #ifdef CONFIG_ARCH_OMAP
762 if (machine_is_omap_osk()) {
769 module_exit(ads7846_exit);
771 MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
772 MODULE_LICENSE("GPL");