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>
28 #include <asm/mach-types.h>
29 #ifdef CONFIG_ARCH_OMAP
30 #include <asm/arch/gpio.h>
36 * This code has been lightly tested on an ads7846.
37 * Support for ads7843 and ads7845 has only been stubbed in.
39 * Not yet done: investigate the values reported. Are x/y/pressure
40 * event values sane enough for X11? How accurate are the temperature
41 * and voltage readings? (System-specific calibration should support
42 * accuracy of 0.3 degrees C; otherwise it's 2.0 degrees.)
44 * app note sbaa036 talks in more detail about accurate sampling...
45 * that ought to help in situations like LCDs inducing noise (which
46 * can also be helped by using synch signals) and more generally.
49 #define TS_POLL_PERIOD msecs_to_jiffies(10)
52 /* For portability, we can't read 12 bit values using SPI (which
53 * would make the controller deliver them as native byteorder u16
54 * with msbs zeroed). Instead, we read them as two 8-byte values,
55 * which need byteswapping then range adjustment.
63 struct input_dev *input;
66 struct spi_device *spi;
73 struct spi_transfer xfer[8];
74 struct spi_message msg;
77 struct timer_list timer; /* P: lock */
78 unsigned pendown:1; /* P: lock */
79 unsigned pending:1; /* P: lock */
80 // FIXME remove "irq_disabled"
81 unsigned irq_disabled:1; /* P: lock */
84 /* leave chip selected when we're done, for quicker re-select? */
86 #define CS_CHANGE(xfer) ((xfer).cs_change = 1)
88 #define CS_CHANGE(xfer) ((xfer).cs_change = 0)
91 /*--------------------------------------------------------------------------*/
93 /* The ADS7846 has touchscreen and other sensors.
94 * Earlier ads784x chips are somewhat compatible.
96 #define ADS_START (1 << 7)
97 #define ADS_A2A1A0_d_y (1 << 4) /* differential */
98 #define ADS_A2A1A0_d_z1 (3 << 4) /* differential */
99 #define ADS_A2A1A0_d_z2 (4 << 4) /* differential */
100 #define ADS_A2A1A0_d_x (5 << 4) /* differential */
101 #define ADS_A2A1A0_temp0 (0 << 4) /* non-differential */
102 #define ADS_A2A1A0_vbatt (2 << 4) /* non-differential */
103 #define ADS_A2A1A0_vaux (6 << 4) /* non-differential */
104 #define ADS_A2A1A0_temp1 (7 << 4) /* non-differential */
105 #define ADS_8_BIT (1 << 3)
106 #define ADS_12_BIT (0 << 3)
107 #define ADS_SER (1 << 2) /* non-differential */
108 #define ADS_DFR (0 << 2) /* differential */
109 #define ADS_PD10_PDOWN (0 << 0) /* lowpower mode + penirq */
110 #define ADS_PD10_ADC_ON (1 << 0) /* ADC on */
111 #define ADS_PD10_REF_ON (2 << 0) /* vREF on + penirq */
112 #define ADS_PD10_ALL_ON (3 << 0) /* ADC + vREF on */
114 #define MAX_12BIT ((1<<12)-1)
116 /* leave ADC powered up (disables penirq) between differential samples */
117 #define READ_12BIT_DFR(x) (ADS_START | ADS_A2A1A0_d_ ## x \
118 | ADS_12_BIT | ADS_DFR)
120 static const u8 read_y = READ_12BIT_DFR(y) | ADS_PD10_ADC_ON;
121 static const u8 read_z1 = READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON;
122 static const u8 read_z2 = READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON;
123 static const u8 read_x = READ_12BIT_DFR(x) | ADS_PD10_PDOWN; /* LAST */
125 /* single-ended samples need to first power up reference voltage;
126 * we leave both ADC and VREF powered
128 #define READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
129 | ADS_12_BIT | ADS_SER)
131 static const u8 ref_on = READ_12BIT_DFR(x) | ADS_PD10_ALL_ON;
132 static const u8 ref_off = READ_12BIT_DFR(y) | ADS_PD10_PDOWN;
134 /*--------------------------------------------------------------------------*/
137 * Non-touchscreen sensors only use single-ended conversions.
144 struct spi_message msg;
145 struct spi_transfer xfer[6];
148 static int ads7846_read12_ser(struct device *dev, unsigned command)
150 struct spi_device *spi = to_spi_device(dev);
151 struct ads7846 *ts = dev_get_drvdata(dev);
152 struct ser_req *req = kzalloc(sizeof *req, SLAB_KERNEL);
160 INIT_LIST_HEAD(&req->msg.transfers);
162 /* activate reference, so it has time to settle; */
163 req->xfer[0].tx_buf = &ref_on;
164 req->xfer[0].len = 1;
165 req->xfer[1].rx_buf = &req->scratch;
166 req->xfer[1].len = 2;
169 * for external VREF, 0 usec (and assume it's always on);
170 * for 1uF, use 800 usec;
173 req->xfer[1].delay_usecs = ts->vref_delay_usecs;
176 req->command = (u8) command;
177 req->xfer[2].tx_buf = &req->command;
178 req->xfer[2].len = 1;
179 req->xfer[3].rx_buf = &req->sample;
180 req->xfer[3].len = 2;
182 /* REVISIT: take a few more samples, and compare ... */
184 /* turn off reference */
185 req->xfer[4].tx_buf = &ref_off;
186 req->xfer[4].len = 1;
187 req->xfer[5].rx_buf = &req->scratch;
188 req->xfer[5].len = 2;
190 CS_CHANGE(req->xfer[5]);
192 /* group all the transfers together, so we can't interfere with
193 * reading touchscreen state; disable penirq while sampling
195 for (i = 0; i < 6; i++)
196 spi_message_add_tail(&req->xfer[i], &req->msg);
198 disable_irq(spi->irq);
199 status = spi_sync(spi, &req->msg);
200 enable_irq(spi->irq);
203 status = req->msg.status;
204 sample = be16_to_cpu(req->sample);
205 sample = sample >> 4;
208 return status ? status : sample;
211 #define SHOW(name) static ssize_t \
212 name ## _show(struct device *dev, struct device_attribute *attr, char *buf) \
214 ssize_t v = ads7846_read12_ser(dev, \
215 READ_12BIT_SER(name) | ADS_PD10_ALL_ON); \
218 return sprintf(buf, "%u\n", (unsigned) v); \
220 static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);
227 /*--------------------------------------------------------------------------*/
230 * PENIRQ only kicks the timer. The timer only reissues the SPI transfer,
231 * to retrieve touchscreen status.
233 * The SPI transfer completion callback does the real work. It reports
234 * touchscreen events and reactivates the timer (or IRQ) as appropriate.
237 static void ads7846_rx(void *ads)
239 struct ads7846 *ts = ads;
240 struct input_dev *input_dev = ts->input;
246 /* adjust: 12 bit samples (left aligned), built from
247 * two 8 bit values writen msb-first.
249 x = be16_to_cpu(ts->tc.x) >> 4;
250 y = be16_to_cpu(ts->tc.y) >> 4;
251 z1 = be16_to_cpu(ts->tc.z1) >> 4;
252 z2 = be16_to_cpu(ts->tc.z2) >> 4;
254 /* range filtering */
258 if (x && z1 && ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
259 /* compute touch pressure resistance using equation #2 */
263 Rt *= ts->x_plate_ohms;
265 Rt = (Rt + 2047) >> 12;
269 /* NOTE: "pendown" is inferred from pressure; we don't rely on
270 * being able to check nPENIRQ status, or "friendly" trigger modes
271 * (both-edges is much better than just-falling or low-level).
273 * REVISIT: some boards may require reading nPENIRQ; it's
274 * needed on 7843. and 7845 reads pressure differently...
276 * REVISIT: the touchscreen might not be connected; this code
277 * won't notice that, even if nPENIRQ never fires ...
279 if (!ts->pendown && Rt != 0) {
280 input_report_key(input_dev, BTN_TOUCH, 1);
282 } else if (ts->pendown && Rt == 0) {
283 input_report_key(input_dev, BTN_TOUCH, 0);
288 input_report_abs(input_dev, ABS_X, x);
289 input_report_abs(input_dev, ABS_Y, y);
290 input_report_abs(input_dev, ABS_PRESSURE, Rt);
294 input_sync(input_dev);
297 if (Rt || ts->pendown)
298 pr_debug("%s: %d/%d/%d%s\n", ts->spi->dev.bus_id,
299 x, y, Rt, Rt ? "" : " UP");
302 /* don't retrigger while we're suspended */
303 spin_lock_irqsave(&ts->lock, flags);
305 ts->pendown = (Rt != 0);
308 if (ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
310 mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
311 else if (ts->irq_disabled) {
312 ts->irq_disabled = 0;
313 enable_irq(ts->spi->irq);
317 spin_unlock_irqrestore(&ts->lock, flags);
320 static void ads7846_timer(unsigned long handle)
322 struct ads7846 *ts = (void *)handle;
326 spin_lock_irqsave(&ts->lock, flags);
329 if (!ts->irq_disabled) {
330 ts->irq_disabled = 1;
331 disable_irq(ts->spi->irq);
333 status = spi_async(ts->spi, &ts->msg);
335 dev_err(&ts->spi->dev, "spi_async --> %d\n",
338 spin_unlock_irqrestore(&ts->lock, flags);
341 static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
343 ads7846_timer((unsigned long) handle);
347 /*--------------------------------------------------------------------------*/
350 ads7846_suspend(struct spi_device *spi, pm_message_t message)
352 struct ads7846 *ts = dev_get_drvdata(&spi->dev);
355 spin_lock_irqsave(&ts->lock, flags);
357 spi->dev.power.power_state = message;
359 /* are we waiting for IRQ, or polling? */
361 if (!ts->irq_disabled) {
362 ts->irq_disabled = 1;
363 disable_irq(ts->spi->irq);
366 /* polling; force a final SPI completion;
367 * that will clean things up neatly
370 mod_timer(&ts->timer, jiffies);
372 while (ts->pendown || ts->pending) {
373 spin_unlock_irqrestore(&ts->lock, flags);
375 spin_lock_irqsave(&ts->lock, flags);
379 /* we know the chip's in lowpower mode since we always
380 * leave it that way after every request
383 spin_unlock_irqrestore(&ts->lock, flags);
387 static int ads7846_resume(struct spi_device *spi)
389 struct ads7846 *ts = dev_get_drvdata(&spi->dev);
391 ts->irq_disabled = 0;
392 enable_irq(ts->spi->irq);
393 spi->dev.power.power_state = PMSG_ON;
397 static int __devinit ads7846_probe(struct spi_device *spi)
400 struct input_dev *input_dev;
401 struct ads7846_platform_data *pdata = spi->dev.platform_data;
402 struct spi_transfer *x;
407 dev_dbg(&spi->dev, "no IRQ?\n");
412 dev_dbg(&spi->dev, "no platform data?\n");
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);
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.
429 ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL);
430 input_dev = input_allocate_device();
431 if (!ts || !input_dev) {
436 dev_set_drvdata(&spi->dev, ts);
437 spi->dev.power.power_state = PMSG_ON;
440 ts->input = input_dev;
442 init_timer(&ts->timer);
443 ts->timer.data = (unsigned long) ts;
444 ts->timer.function = ads7846_timer;
446 ts->model = pdata->model ? : 7846;
447 ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
448 ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
450 snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
452 input_dev->name = "ADS784x Touchscreen";
453 input_dev->phys = ts->phys;
454 input_dev->cdev.dev = &spi->dev;
456 input_dev->evbit[0] = BIT(EV_KEY) | BIT(EV_ABS);
457 input_dev->keybit[LONG(BTN_TOUCH)] = BIT(BTN_TOUCH);
458 input_set_abs_params(input_dev, ABS_X,
460 pdata->x_max ? : MAX_12BIT,
462 input_set_abs_params(input_dev, ABS_Y,
464 pdata->y_max ? : MAX_12BIT,
466 input_set_abs_params(input_dev, ABS_PRESSURE,
467 pdata->pressure_min, pdata->pressure_max, 0, 0);
469 /* set up the transfers to read touchscreen state; this assumes we
470 * use formula #2 for pressure, not #3.
474 /* y- still on; turn on only y+ (and ADC) */
478 x->rx_buf = &ts->tc.y;
482 /* turn y+ off, x- on; we'll use formula #2 */
483 if (ts->model == 7846) {
484 x->tx_buf = &read_z1;
487 x->rx_buf = &ts->tc.z1;
491 x->tx_buf = &read_z2;
494 x->rx_buf = &ts->tc.z2;
499 /* turn y- off, x+ on, then leave in lowpower */
503 x->rx_buf = &ts->tc.x;
509 for (i = 0; i < x - ts->xfer; i++)
510 spi_message_add_tail(&ts->xfer[i], &ts->msg);
511 ts->msg.complete = ads7846_rx;
512 ts->msg.context = ts;
514 if (request_irq(spi->irq, ads7846_irq,
515 SA_SAMPLE_RANDOM | SA_TRIGGER_FALLING,
516 spi->dev.bus_id, ts)) {
517 dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
522 dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);
524 /* take a first sample, leaving nPENIRQ active; avoid
525 * the touchscreen, in case it's not connected.
527 (void) ads7846_read12_ser(&spi->dev,
528 READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);
530 /* ads7843/7845 don't have temperature sensors, and
531 * use the other sensors a bit differently too
533 if (ts->model == 7846) {
534 device_create_file(&spi->dev, &dev_attr_temp0);
535 device_create_file(&spi->dev, &dev_attr_temp1);
537 if (ts->model != 7845)
538 device_create_file(&spi->dev, &dev_attr_vbatt);
539 device_create_file(&spi->dev, &dev_attr_vaux);
541 err = input_register_device(input_dev);
548 free_irq(spi->irq, ts);
550 input_free_device(input_dev);
555 static int __devexit ads7846_remove(struct spi_device *spi)
557 struct ads7846 *ts = dev_get_drvdata(&spi->dev);
559 ads7846_suspend(spi, PMSG_SUSPEND);
560 free_irq(ts->spi->irq, ts);
561 if (ts->irq_disabled)
562 enable_irq(ts->spi->irq);
564 if (ts->model == 7846) {
565 device_remove_file(&spi->dev, &dev_attr_temp0);
566 device_remove_file(&spi->dev, &dev_attr_temp1);
568 if (ts->model != 7845)
569 device_remove_file(&spi->dev, &dev_attr_vbatt);
570 device_remove_file(&spi->dev, &dev_attr_vaux);
572 input_unregister_device(ts->input);
575 dev_dbg(&spi->dev, "unregistered touchscreen\n");
579 static struct spi_driver ads7846_driver = {
582 .bus = &spi_bus_type,
583 .owner = THIS_MODULE,
585 .probe = ads7846_probe,
586 .remove = __devexit_p(ads7846_remove),
587 .suspend = ads7846_suspend,
588 .resume = ads7846_resume,
591 static int __init ads7846_init(void)
593 /* grr, board-specific init should stay out of drivers!! */
595 #ifdef CONFIG_ARCH_OMAP
596 if (machine_is_omap_osk()) {
597 /* GPIO4 = PENIRQ; GPIO6 = BUSY */
598 omap_request_gpio(4);
599 omap_set_gpio_direction(4, 1);
600 omap_request_gpio(6);
601 omap_set_gpio_direction(6, 1);
603 // also TI 1510 Innovator, bitbanging through FPGA
605 // also Palm Tungsten T2
609 // also Dell Axim X50
610 // also HP iPaq H191x/H192x/H415x/H435x
611 // also Intel Lubbock (additional to UCB1400; as temperature sensor)
612 // also Sharp Zaurus C7xx, C8xx (corgi/sheperd/husky)
614 // Atmel at91sam9261-EK uses ads7843
616 // also various AMD Au1x00 devel boards
618 return spi_register_driver(&ads7846_driver);
620 module_init(ads7846_init);
622 static void __exit ads7846_exit(void)
624 spi_unregister_driver(&ads7846_driver);
626 #ifdef CONFIG_ARCH_OMAP
627 if (machine_is_omap_osk()) {
634 module_exit(ads7846_exit);
636 MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
637 MODULE_LICENSE("GPL");