2 * ADS7846 based touchscreen and sensor driver
4 * Copyright (c) 2005 David Brownell
5 * Copyright (c) 2006 Nokia Corporation
6 * Various changes: Imre Deak <imre.deak@nokia.com>
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
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.
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>
31 #include <asm/mach-types.h>
32 #ifdef CONFIG_ARCH_OMAP
33 #include <asm/arch/gpio.h>
39 * This code has been tested on an ads7846 / N770 device.
40 * Support for ads7843 and ads7845 has only been stubbed in.
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.)
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.
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
60 #define TS_POLL_PERIOD msecs_to_jiffies(10)
62 /* this driver doesn't aim at the peak continuous sample rate */
63 #define SAMPLE_BITS (8 /*cmd*/ + 16 /*sample*/ + 2 /* before, after */)
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.
77 struct input_dev *input;
80 struct spi_device *spi;
85 u8 read_x, read_y, read_z1, read_z2, pwrdown;
86 u16 dummy; /* for the pwrdown read */
89 struct spi_transfer xfer[10];
90 struct spi_message msg[5];
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 */
106 int (*get_pendown_state)(void);
109 /* leave chip selected when we're done, for quicker re-select? */
111 #define CS_CHANGE(xfer) ((xfer).cs_change = 1)
113 #define CS_CHANGE(xfer) ((xfer).cs_change = 0)
116 /*--------------------------------------------------------------------------*/
118 /* The ADS7846 has touchscreen and other sensors.
119 * Earlier ads784x chips are somewhat compatible.
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 */
139 #define MAX_12BIT ((1<<12)-1)
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)
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)
149 #define READ_X (READ_12BIT_DFR(x) | ADS_PD10_ADC_ON)
150 #define PWRDOWN (READ_12BIT_DFR(y) | ADS_PD10_PDOWN) /* LAST */
152 /* single-ended samples need to first power up reference voltage;
153 * we leave both ADC and VREF powered
155 #define READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
156 | ADS_12_BIT | ADS_SER)
158 #define REF_ON (READ_12BIT_DFR(x) | ADS_PD10_ALL_ON)
159 #define REF_OFF (READ_12BIT_DFR(y) | ADS_PD10_PDOWN)
161 /*--------------------------------------------------------------------------*/
164 * Non-touchscreen sensors only use single-ended conversions.
173 struct spi_message msg;
174 struct spi_transfer xfer[6];
177 static void ads7846_enable(struct ads7846 *ts);
178 static void ads7846_disable(struct ads7846 *ts);
180 static int device_suspended(struct device *dev)
182 struct ads7846 *ts = dev_get_drvdata(dev);
183 return dev->power.power_state.event != PM_EVENT_ON || ts->disabled;
186 static int ads7846_read12_ser(struct device *dev, unsigned command)
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);
198 spi_message_init(&req->msg);
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;
208 * for external VREF, 0 usec (and assume it's always on);
209 * for 1uF, use 800 usec;
212 req->xfer[1].delay_usecs = ts->vref_delay_usecs;
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;
221 /* REVISIT: take a few more samples, and compare ... */
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;
230 CS_CHANGE(req->xfer[5]);
232 /* group all the transfers together, so we can't interfere with
233 * reading touchscreen state; disable penirq while sampling
235 for (i = 0; i < 6; i++)
236 spi_message_add_tail(&req->xfer[i], &req->msg);
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);
245 status = req->msg.status;
246 sample = be16_to_cpu(req->sample);
247 sample = sample >> 4;
250 return status ? status : sample;
253 #define SHOW(name) static ssize_t \
254 name ## _show(struct device *dev, struct device_attribute *attr, char *buf) \
256 ssize_t v = ads7846_read12_ser(dev, \
257 READ_12BIT_SER(name) | ADS_PD10_ALL_ON); \
260 return sprintf(buf, "%u\n", (unsigned) v); \
262 static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);
269 static int is_pen_down(struct device *dev)
271 struct ads7846 *ts = dev_get_drvdata(dev);
276 static ssize_t ads7846_pen_down_show(struct device *dev,
277 struct device_attribute *attr, char *buf)
279 return sprintf(buf, "%u\n", is_pen_down(dev));
282 static DEVICE_ATTR(pen_down, S_IRUGO, ads7846_pen_down_show, NULL);
284 static ssize_t ads7846_disable_show(struct device *dev,
285 struct device_attribute *attr, char *buf)
287 struct ads7846 *ts = dev_get_drvdata(dev);
289 return sprintf(buf, "%u\n", ts->disabled);
292 static ssize_t ads7846_disable_store(struct device *dev,
293 struct device_attribute *attr,
294 const char *buf, size_t count)
296 struct ads7846 *ts = dev_get_drvdata(dev);
300 i = simple_strtoul(buf, &endp, 10);
301 spin_lock_irq(&ts->lock);
308 spin_unlock_irq(&ts->lock);
313 static DEVICE_ATTR(disable, 0664, ads7846_disable_show, ads7846_disable_store);
315 /*--------------------------------------------------------------------------*/
318 * PENIRQ only kicks the timer. The timer only reissues the SPI transfer,
319 * to retrieve touchscreen status.
321 * The SPI transfer completion callback does the real work. It reports
322 * touchscreen events and reactivates the timer (or IRQ) as appropriate.
325 static void ads7846_rx(void *ads)
327 struct ads7846 *ts = ads;
328 struct input_dev *input_dev = ts->input;
334 /* adjust: 12 bit samples (left aligned), built from
335 * two 8 bit values writen msb-first.
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;
342 /* range filtering */
346 if (likely(x && z1 && !device_suspended(&ts->spi->dev))) {
347 /* compute touch pressure resistance using equation #2 */
351 Rt *= ts->x_plate_ohms;
353 Rt = (Rt + 2047) >> 12;
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).
361 * REVISIT: some boards may require reading nPENIRQ; it's
362 * needed on 7843. and 7845 reads pressure differently...
364 * REVISIT: the touchscreen might not be connected; this code
365 * won't notice that, even if nPENIRQ never fires ...
367 if (!ts->pendown && Rt != 0) {
368 input_report_key(input_dev, BTN_TOUCH, 1);
370 } else if (ts->pendown && Rt == 0) {
371 input_report_key(input_dev, BTN_TOUCH, 0);
376 input_report_abs(input_dev, ABS_X, x);
377 input_report_abs(input_dev, ABS_Y, y);
382 input_report_abs(input_dev, ABS_PRESSURE, Rt);
383 input_sync(input_dev);
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");
392 spin_lock_irqsave(&ts->lock, flags);
394 ts->pendown = (Rt != 0);
395 mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
397 spin_unlock_irqrestore(&ts->lock, flags);
400 static void ads7846_debounce(void *ads)
402 struct ads7846 *ts = ads;
403 struct spi_message *m;
404 struct spi_transfer *t;
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;
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
420 /* Go for the next read */
425 status = spi_async(ts->spi, m);
427 dev_err(&ts->spi->dev, "spi_async --> %d\n",
431 static void ads7846_timer(unsigned long handle)
433 struct ads7846 *ts = (void *)handle;
436 spin_lock_irq(&ts->lock);
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);
447 /* pen is still down, continue with the measurement */
449 status = spi_async(ts->spi, &ts->msg[0]);
451 dev_err(&ts->spi->dev, "spi_async --> %d\n", status);
454 spin_unlock_irq(&ts->lock);
457 static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
459 struct ads7846 *ts = handle;
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
471 ts->irq_disabled = 1;
472 disable_irq(ts->spi->irq);
474 mod_timer(&ts->timer, jiffies);
477 spin_unlock_irqrestore(&ts->lock, flags);
482 /*--------------------------------------------------------------------------*/
484 /* Must be called with ts->lock held */
485 static void ads7846_disable(struct ads7846 *ts)
492 /* are we waiting for IRQ, or polling? */
494 ts->irq_disabled = 1;
495 disable_irq(ts->spi->irq);
497 /* the timer will run at least once more, and
498 * leave everything in a clean state, IRQ disabled
500 while (ts->pending) {
501 spin_unlock_irq(&ts->lock);
503 spin_lock_irq(&ts->lock);
507 /* we know the chip's in lowpower mode since we always
508 * leave it that way after every request
513 /* Must be called with ts->lock held */
514 static void ads7846_enable(struct ads7846 *ts)
520 ts->irq_disabled = 0;
521 enable_irq(ts->spi->irq);
524 static int ads7846_suspend(struct spi_device *spi, pm_message_t message)
526 struct ads7846 *ts = dev_get_drvdata(&spi->dev);
528 spin_lock_irq(&ts->lock);
530 spi->dev.power.power_state = message;
533 spin_unlock_irq(&ts->lock);
539 static int ads7846_resume(struct spi_device *spi)
541 struct ads7846 *ts = dev_get_drvdata(&spi->dev);
543 spin_lock_irq(&ts->lock);
545 spi->dev.power.power_state = PMSG_ON;
548 spin_unlock_irq(&ts->lock);
553 static int __devinit ads7846_probe(struct spi_device *spi)
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;
563 dev_dbg(&spi->dev, "no IRQ?\n");
568 dev_dbg(&spi->dev, "no platform data?\n");
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);
579 if (pdata->get_pendown_state == NULL) {
580 dev_dbg(&spi->dev, "no get_pendown_state function?\n");
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.
590 ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL);
591 input_dev = input_allocate_device();
592 if (!ts || !input_dev) {
597 dev_set_drvdata(&spi->dev, ts);
598 spi->dev.power.power_state = PMSG_ON;
601 ts->input = input_dev;
603 init_timer(&ts->timer);
604 ts->timer.data = (unsigned long) ts;
605 ts->timer.function = ads7846_timer;
607 spin_lock_init(&ts->lock);
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;
616 snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
618 input_dev->name = "ADS784x Touchscreen";
619 input_dev->phys = ts->phys;
620 input_dev->cdev.dev = &spi->dev;
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,
626 pdata->x_max ? : MAX_12BIT,
628 input_set_abs_params(input_dev, ABS_Y,
630 pdata->y_max ? : MAX_12BIT,
632 input_set_abs_params(input_dev, ABS_PRESSURE,
633 pdata->pressure_min, pdata->pressure_max, 0, 0);
635 /* set up the transfers to read touchscreen state; this assumes we
636 * use formula #2 for pressure, not #3.
643 /* y- still on; turn on only y+ (and ADC) */
645 x->tx_buf = &ts->read_y;
647 spi_message_add_tail(x, m);
650 x->rx_buf = &ts->tc.y;
652 spi_message_add_tail(x, m);
654 m->complete = ads7846_debounce;
660 /* turn y- off, x+ on, then leave in lowpower */
663 x->tx_buf = &ts->read_x;
665 spi_message_add_tail(x, m);
668 x->rx_buf = &ts->tc.x;
670 spi_message_add_tail(x, m);
672 m->complete = ads7846_debounce;
675 /* turn y+ off, x- on; we'll use formula #2 */
676 if (ts->model == 7846) {
681 ts->read_z1 = READ_Z1;
682 x->tx_buf = &ts->read_z1;
684 spi_message_add_tail(x, m);
687 x->rx_buf = &ts->tc.z1;
689 spi_message_add_tail(x, m);
691 m->complete = ads7846_debounce;
698 ts->read_z2 = READ_Z2;
699 x->tx_buf = &ts->read_z2;
701 spi_message_add_tail(x, m);
704 x->rx_buf = &ts->tc.z2;
706 spi_message_add_tail(x, m);
708 m->complete = ads7846_debounce;
717 ts->pwrdown = PWRDOWN;
718 x->tx_buf = &ts->pwrdown;
720 spi_message_add_tail(x, m);
723 x->rx_buf = &ts->dummy;
726 spi_message_add_tail(x, m);
728 m->complete = ads7846_rx;
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);
739 dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);
741 /* take a first sample, leaving nPENIRQ active; avoid
742 * the touchscreen, in case it's not connected.
744 (void) ads7846_read12_ser(&spi->dev,
745 READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);
747 /* ads7843/7845 don't have temperature sensors, and
748 * use the other sensors a bit differently too
750 if (ts->model == 7846) {
751 device_create_file(&spi->dev, &dev_attr_temp0);
752 device_create_file(&spi->dev, &dev_attr_temp1);
754 if (ts->model != 7845)
755 device_create_file(&spi->dev, &dev_attr_vbatt);
756 device_create_file(&spi->dev, &dev_attr_vaux);
758 device_create_file(&spi->dev, &dev_attr_pen_down);
760 device_create_file(&spi->dev, &dev_attr_disable);
762 err = input_register_device(input_dev);
764 goto 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);
775 if (ts->model != 7845)
776 device_remove_file(&spi->dev, &dev_attr_vbatt);
777 device_remove_file(&spi->dev, &dev_attr_vaux);
779 free_irq(spi->irq, ts);
781 input_free_device(input_dev);
786 static int __devexit ads7846_remove(struct spi_device *spi)
788 struct ads7846 *ts = dev_get_drvdata(&spi->dev);
790 input_unregister_device(ts->input);
792 ads7846_suspend(spi, PMSG_SUSPEND);
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);
800 if (ts->model != 7845)
801 device_remove_file(&spi->dev, &dev_attr_vbatt);
802 device_remove_file(&spi->dev, &dev_attr_vaux);
804 free_irq(ts->spi->irq, ts);
805 /* suspend left the IRQ disabled */
806 enable_irq(ts->spi->irq);
810 dev_dbg(&spi->dev, "unregistered touchscreen\n");
814 static struct spi_driver ads7846_driver = {
817 .bus = &spi_bus_type,
818 .owner = THIS_MODULE,
820 .probe = ads7846_probe,
821 .remove = __devexit_p(ads7846_remove),
822 .suspend = ads7846_suspend,
823 .resume = ads7846_resume,
826 static int __init ads7846_init(void)
828 /* grr, board-specific init should stay out of drivers!! */
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);
838 // also TI 1510 Innovator, bitbanging through FPGA
840 // also Palm Tungsten T2
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)
849 // Atmel at91sam9261-EK uses ads7843
851 // also various AMD Au1x00 devel boards
853 return spi_register_driver(&ads7846_driver);
855 module_init(ads7846_init);
857 static void __exit ads7846_exit(void)
859 spi_unregister_driver(&ads7846_driver);
861 #ifdef CONFIG_ARCH_OMAP
862 if (machine_is_omap_osk()) {
869 module_exit(ads7846_exit);
871 MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
872 MODULE_LICENSE("GPL");