aboutsummaryrefslogtreecommitdiff
path: root/drivers/input/touchscreen/ads7846.c
blob: 7c27c8b9b6d0e1b8d23199f584332119b541ba06 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
/*
 * ADS7846 based touchscreen and sensor driver
 *
 * Copyright (c) 2005 David Brownell
 * Copyright (c) 2006 Nokia Corporation
 * Various changes: Imre Deak <imre.deak@nokia.com>
 *
 * Using code from:
 *  - corgi_ts.c
 *	Copyright (C) 2004-2005 Richard Purdie
 *  - omap_ts.[hc], ads7846.h, ts_osk.c
 *	Copyright (C) 2002 MontaVista Software
 *	Copyright (C) 2004 Texas Instruments
 *	Copyright (C) 2005 Dirk Behme
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 */
#include <linux/hwmon.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/input.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/gpio.h>
#include <linux/spi/spi.h>
#include <linux/spi/ads7846.h>
#include <asm/irq.h>


/*
 * This code has been heavily tested on a Nokia 770, and lightly
 * tested on other ads7846 devices (OSK/Mistral, Lubbock).
 * TSC2046 is just newer ads7846 silicon.
 * Support for ads7843 tested on Atmel at91sam926x-EK.
 * Support for ads7845 has only been stubbed in.
 *
 * IRQ handling needs a workaround because of a shortcoming in handling
 * edge triggered IRQs on some platforms like the OMAP1/2. These
 * platforms don't handle the ARM lazy IRQ disabling properly, thus we
 * have to maintain our own SW IRQ disabled status. This should be
 * removed as soon as the affected platform's IRQ handling is fixed.
 *
 * app note sbaa036 talks in more detail about accurate sampling...
 * that ought to help in situations like LCDs inducing noise (which
 * can also be helped by using synch signals) and more generally.
 * This driver tries to utilize the measures described in the app
 * note. The strength of filtering can be set in the board-* specific
 * files.
 */

#define TS_POLL_DELAY	(1 * 1000000)	/* ns delay before the first sample */
#define TS_POLL_PERIOD	(5 * 1000000)	/* ns delay between samples */

/* this driver doesn't aim at the peak continuous sample rate */
#define	SAMPLE_BITS	(8 /*cmd*/ + 16 /*sample*/ + 2 /* before, after */)

struct ts_event {
	/* For portability, we can't read 12 bit values using SPI (which
	 * would make the controller deliver them as native byteorder u16
	 * with msbs zeroed).  Instead, we read them as two 8-bit values,
	 * *** WHICH NEED BYTESWAPPING *** and range adjustment.
	 */
	u16	x;
	u16	y;
	u16	z1, z2;
	int	ignore;
};

/*
 * We allocate this separately to avoid cache line sharing issues when
 * driver is used with DMA-based SPI controllers (like atmel_spi) on
 * systems where main memory is not DMA-coherent (most non-x86 boards).
 */
struct ads7846_packet {
	u8			read_x, read_y, read_z1, read_z2, pwrdown;
	u16			dummy;		/* for the pwrdown read */
	struct ts_event		tc;
};

struct ads7846 {
	struct input_dev	*input;
	char			phys[32];

	struct spi_device	*spi;

#if defined(CONFIG_HWMON) || defined(CONFIG_HWMON_MODULE)
	struct attribute_group	*attr_group;
	struct device		*hwmon;
#endif

	u16			model;
	u16			vref_mv;
	u16			vref_delay_usecs;
	u16			x_plate_ohms;
	u16			pressure_max;

	struct ads7846_packet	*packet;

	struct spi_transfer	xfer[18];
	struct spi_message	msg[5];
	struct spi_message	*last_msg;
	int			msg_idx;
	int			read_cnt;
	int			read_rep;
	int			last_read;

	u16			debounce_max;
	u16			debounce_tol;
	u16			debounce_rep;

	u16			penirq_recheck_delay_usecs;

	spinlock_t		lock;
	struct hrtimer		timer;
	unsigned		pendown:1;	/* P: lock */
	unsigned		pending:1;	/* P: lock */
// FIXME remove "irq_disabled"
	unsigned		irq_disabled:1;	/* P: lock */
	unsigned		disabled:1;
	unsigned		is_suspended:1;

	int			(*filter)(void *data, int data_idx, int *val);
	void			*filter_data;
	void			(*filter_cleanup)(void *data);
	int			(*get_pendown_state)(void);
	int			gpio_pendown;
};

/* leave chip selected when we're done, for quicker re-select? */
#if	0
#define	CS_CHANGE(xfer)	((xfer).cs_change = 1)
#else
#define	CS_CHANGE(xfer)	((xfer).cs_change = 0)
#endif

/*--------------------------------------------------------------------------*/

/* The ADS7846 has touchscreen and other sensors.
 * Earlier ads784x chips are somewhat compatible.
 */
#define	ADS_START		(1 << 7)
#define	ADS_A2A1A0_d_y		(1 << 4)	/* differential */
#define	ADS_A2A1A0_d_z1		(3 << 4)	/* differential */
#define	ADS_A2A1A0_d_z2		(4 << 4)	/* differential */
#define	ADS_A2A1A0_d_x		(5 << 4)	/* differential */
#define	ADS_A2A1A0_temp0	(0 << 4)	/* non-differential */
#define	ADS_A2A1A0_vbatt	(2 << 4)	/* non-differential */
#define	ADS_A2A1A0_vaux		(6 << 4)	/* non-differential */
#define	ADS_A2A1A0_temp1	(7 << 4)	/* non-differential */
#define	ADS_8_BIT		(1 << 3)
#define	ADS_12_BIT		(0 << 3)
#define	ADS_SER			(1 << 2)	/* non-differential */
#define	ADS_DFR			(0 << 2)	/* differential */
#define	ADS_PD10_PDOWN		(0 << 0)	/* lowpower mode + penirq */
#define	ADS_PD10_ADC_ON		(1 << 0)	/* ADC on */
#define	ADS_PD10_REF_ON		(2 << 0)	/* vREF on + penirq */
#define	ADS_PD10_ALL_ON		(3 << 0)	/* ADC + vREF on */

#define	MAX_12BIT	((1<<12)-1)

/* leave ADC powered up (disables penirq) between differential samples */
#define	READ_12BIT_DFR(x, adc, vref) (ADS_START | ADS_A2A1A0_d_ ## x \
	| ADS_12_BIT | ADS_DFR | \
	(adc ? ADS_PD10_ADC_ON : 0) | (vref ? ADS_PD10_REF_ON : 0))

#define	READ_Y(vref)	(READ_12BIT_DFR(y,  1, vref))
#define	READ_Z1(vref)	(READ_12BIT_DFR(z1, 1, vref))
#define	READ_Z2(vref)	(READ_12BIT_DFR(z2, 1, vref))

#define	READ_X(vref)	(READ_12BIT_DFR(x,  1, vref))
#define	PWRDOWN		(READ_12BIT_DFR(y,  0, 0))	/* LAST */

/* single-ended samples need to first power up reference voltage;
 * we leave both ADC and VREF powered
 */
#define	READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
	| ADS_12_BIT | ADS_SER)

#define	REF_ON	(READ_12BIT_DFR(x, 1, 1))
#define	REF_OFF	(READ_12BIT_DFR(y, 0, 0))

/*--------------------------------------------------------------------------*/

/*
 * Non-touchscreen sensors only use single-ended conversions.
 * The range is GND..vREF. The ads7843 and ads7835 must use external vREF;
 * ads7846 lets that pin be unconnected, to use internal vREF.
 */

struct ser_req {
	u8			ref_on;
	u8			command;
	u8			ref_off;
	u16			scratch;
	__be16			sample;
	struct spi_message	msg;
	struct spi_transfer	xfer[6];
};

static void ads7846_enable(struct ads7846 *ts);
static void ads7846_disable(struct ads7846 *ts);

static int device_suspended(struct device *dev)
{
	struct ads7846 *ts = dev_get_drvdata(dev);
	return ts->is_suspended || ts->disabled;
}

static int ads7846_read12_ser(struct device *dev, unsigned command)
{
	struct spi_device	*spi = to_spi_device(dev);
	struct ads7846		*ts = dev_get_drvdata(dev);
	struct ser_req		*req = kzalloc(sizeof *req, GFP_KERNEL);
	int			status;
	int			use_internal;

	if (!req)
		return -ENOMEM;

	spi_message_init(&req->msg);

	/* FIXME boards with ads7846 might use external vref instead ... */
	use_internal = (ts->model == 7846);

	/* maybe turn on internal vREF, and let it settle */
	if (use_internal) {
		req->ref_on = REF_ON;
		req->xfer[0].tx_buf = &req->ref_on;
		req->xfer[0].len = 1;
		spi_message_add_tail(&req->xfer[0], &req->msg);

		req->xfer[1].rx_buf = &req->scratch;
		req->xfer[1].len = 2;

		/* for 1uF, settle for 800 usec; no cap, 100 usec.  */
		req->xfer[1].delay_usecs = ts->vref_delay_usecs;
		spi_message_add_tail(&req->xfer[1], &req->msg);
	}

	/* take sample */
	req->command = (u8) command;
	req->xfer[2].tx_buf = &req->command;
	req->xfer[2].len = 1;
	spi_message_add_tail(&req->xfer[2], &req->msg);

	req->xfer[3].rx_buf = &req->sample;
	req->xfer[3].len = 2;
	spi_message_add_tail(&req->xfer[3], &req->msg);

	/* REVISIT:  take a few more samples, and compare ... */

	/* converter in low power mode & enable PENIRQ */
	req->ref_off = PWRDOWN;
	req->xfer[4].tx_buf = &req->ref_off;
	req->xfer[4].len = 1;
	spi_message_add_tail(&req->xfer[4], &req->msg);

	req->xfer[5].rx_buf = &req->scratch;
	req->xfer[5].len = 2;
	CS_CHANGE(req->xfer[5]);
	spi_message_add_tail(&req->xfer[5], &req->msg);

	ts->irq_disabled = 1;
	disable_irq(spi->irq);
	status = spi_sync(spi, &req->msg);
	ts->irq_disabled = 0;
	enable_irq(spi->irq);

	if (status == 0) {
		/* on-wire is a must-ignore bit, a BE12 value, then padding */
		status = be16_to_cpu(req->sample);
		status = status >> 3;
		status &= 0x0fff;
	}

	kfree(req);
	return status;
}

#if defined(CONFIG_HWMON) || defined(CONFIG_HWMON_MODULE)

#define SHOW(name, var, adjust) static ssize_t \
name ## _show(struct device *dev, struct device_attribute *attr, char *buf) \
{ \
	struct ads7846 *ts = dev_get_drvdata(dev); \
	ssize_t v = ads7846_read12_ser(dev, \
			READ_12BIT_SER(var) | ADS_PD10_ALL_ON); \
	if (v < 0) \
		return v; \
	return sprintf(buf, "%u\n", adjust(ts, v)); \
} \
static DEVICE_ATTR(name, S_IRUGO, name ## _show, NULL);


/* Sysfs conventions report temperatures in millidegrees Celcius.
 * ADS7846 could use the low-accuracy two-sample scheme, but can't do the high
 * accuracy scheme without calibration data.  For now we won't try either;
 * userspace sees raw sensor values, and must scale/calibrate appropriately.
 */
static inline unsigned null_adjust(struct ads7846 *ts, ssize_t v)
{
	return v;
}

SHOW(temp0, temp0, null_adjust)		/* temp1_input */
SHOW(temp1, temp1, null_adjust)		/* temp2_input */


/* sysfs conventions report voltages in millivolts.  We can convert voltages
 * if we know vREF.  userspace may need to scale vAUX to match the board's
 * external resistors; we assume that vBATT only uses the internal ones.
 */
static inline unsigned vaux_adjust(struct ads7846 *ts, ssize_t v)
{
	unsigned retval = v;

	/* external resistors may scale vAUX into 0..vREF */
	retval *= ts->vref_mv;
	retval = retval >> 12;
	return retval;
}

static inline unsigned vbatt_adjust(struct ads7846 *ts, ssize_t v)
{
	unsigned retval = vaux_adjust(ts, v);

	/* ads7846 has a resistor ladder to scale this signal down */
	if (ts->model == 7846)
		retval *= 4;
	return retval;
}

SHOW(in0_input, vaux, vaux_adjust)
SHOW(in1_input, vbatt, vbatt_adjust)


static struct attribute *ads7846_attributes[] = {
	&dev_attr_temp0.attr,
	&dev_attr_temp1.attr,
	&dev_attr_in0_input.attr,
	&dev_attr_in1_input.attr,
	NULL,
};

static struct attribute_group ads7846_attr_group = {
	.attrs = ads7846_attributes,
};

static struct attribute *ads7843_attributes[] = {
	&dev_attr_in0_input.attr,
	&dev_attr_in1_input.attr,
	NULL,
};

static struct attribute_group ads7843_attr_group = {
	.attrs = ads7843_attributes,
};

static struct attribute *ads7845_attributes[] = {
	&dev_attr_in0_input.attr,
	NULL,
};

static struct attribute_group ads7845_attr_group = {
	.attrs = ads7845_attributes,
};

static int ads784x_hwmon_register(struct spi_device *spi, struct ads7846 *ts)
{
	struct device *hwmon;
	int err;

	/* hwmon sensors need a reference voltage */
	switch (ts->model) {
	case 7846:
		if (!ts->vref_mv) {
			dev_dbg(&spi->dev, "assuming 2.5V internal vREF\n");
			ts->vref_mv = 2500;
		}
		break;
	case 7845:
	case 7843:
		if (!ts->vref_mv) {
			dev_warn(&spi->dev,
				"external vREF for ADS%d not specified\n",
				ts->model);
			return 0;
		}
		break;
	}

	/* different chips have different sensor groups */
	switch (ts->model) {
	case 7846:
		ts->attr_group = &ads7846_attr_group;
		break;
	case 7845:
		ts->attr_group = &ads7845_attr_group;
		break;
	case 7843:
		ts->attr_group = &ads7843_attr_group;
		break;
	default:
		dev_dbg(&spi->dev, "ADS%d not recognized\n", ts->model);
		return 0;
	}

	err = sysfs_create_group(&spi->dev.kobj, ts->attr_group);
	if (err)
		return err;

	hwmon = hwmon_device_register(&spi->dev);
	if (IS_ERR(hwmon)) {
		sysfs_remove_group(&spi->dev.kobj, ts->attr_group);
		return PTR_ERR(hwmon);
	}

	ts->hwmon = hwmon;
	return 0;
}

static void ads784x_hwmon_unregister(struct spi_device *spi,
				     struct ads7846 *ts)
{
	if (ts->hwmon) {
		sysfs_remove_group(&spi->dev.kobj, ts->attr_group);
		hwmon_device_unregister(ts->hwmon);
	}
}

#else
static inline int ads784x_hwmon_register(struct spi_device *spi,
					 struct ads7846 *ts)
{
	return 0;
}

static inline void ads784x_hwmon_unregister(struct spi_device *spi,
					    struct ads7846 *ts)
{
}
#endif

static int is_pen_down(struct device *dev)
{
	struct ads7846	*ts = dev_get_drvdata(dev);

	return ts->pendown;
}

static ssize_t ads7846_pen_down_show(struct device *dev,
				     struct device_attribute *attr, char *buf)
{
	return sprintf(buf, "%u\n", is_pen_down(dev));
}

static DEVICE_ATTR(pen_down, S_IRUGO, ads7846_pen_down_show, NULL);

static ssize_t ads7846_disable_show(struct device *dev,
				     struct device_attribute *attr, char *buf)
{
	struct ads7846	*ts = dev_get_drvdata(dev);

	return sprintf(buf, "%u\n", ts->disabled);
}

static ssize_t ads7846_disable_store(struct device *dev,
				     struct device_attribute *attr,
				     const char *buf, size_t count)
{
	struct ads7846 *ts = dev_get_drvdata(dev);
	unsigned long i;

	if (strict_strtoul(buf, 10, &i))
		return -EINVAL;

	spin_lock_irq(&ts->lock);

	if (i)
		ads7846_disable(ts);
	else
		ads7846_enable(ts);

	spin_unlock_irq(&ts->lock);

	return count;
}

static DEVICE_ATTR(disable, 0664, ads7846_disable_show, ads7846_disable_store);

static struct attribute *ads784x_attributes[] = {
	&dev_attr_pen_down.attr,
	&dev_attr_disable.attr,
	NULL,
};

static struct attribute_group ads784x_attr_group = {
	.attrs = ads784x_attributes,
};

/*--------------------------------------------------------------------------*/

static int get_pendown_state(struct ads7846 *ts)
{
	if (ts->get_pendown_state)
		return ts->get_pendown_state();

	return !gpio_get_value(ts->gpio_pendown);
}

/*
 * PENIRQ only kicks the timer.  The timer only reissues the SPI transfer,
 * to retrieve touchscreen status.
 *
 * The SPI transfer completion callback does the real work.  It reports
 * touchscreen events and reactivates the timer (or IRQ) as appropriate.
 */

static void ads7846_rx(void *ads)
{
	struct ads7846		*ts = ads;
	struct ads7846_packet	*packet = ts->packet;
	unsigned		Rt;
	u16			x, y, z1, z2;

	/* ads7846_rx_val() did in-place conversion (including byteswap) from
	 * on-the-wire format as part of debouncing to get stable readings.
	 */
	x = packet->tc.x;
	y = packet->tc.y;
	z1 = packet->tc.z1;
	z2 = packet->tc.z2;

	/* range filtering */
	if (x == MAX_12BIT)
		x = 0;

	if (ts->model == 7843) {
		Rt = ts->pressure_max / 2;
	} else if (likely(x && z1)) {
		/* compute touch pressure resistance using equation #2 */
		Rt = z2;
		Rt -= z1;
		Rt *= x;
		Rt *= ts->x_plate_ohms;
		Rt /= z1;
		Rt = (Rt + 2047) >> 12;
	} else {
		Rt = 0;
	}

	/* Sample found inconsistent by debouncing or pressure is beyond
	 * the maximum. Don't report it to user space, repeat at least
	 * once more the measurement
	 */
	if (packet->tc.ignore || Rt > ts->pressure_max) {
#ifdef VERBOSE
		pr_debug("%s: ignored %d pressure %d\n",
			dev_name(&ts->spi->dev), packet->tc.ignore, Rt);
#endif
		hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_PERIOD),
			      HRTIMER_MODE_REL);
		return;
	}

	/* Maybe check the pendown state before reporting. This discards
	 * false readings when the pen is lifted.
	 */
	if (ts->penirq_recheck_delay_usecs) {
		udelay(ts->penirq_recheck_delay_usecs);
		if (!get_pendown_state(ts))
			Rt = 0;
	}

	/* NOTE: We can't rely on the pressure to determine the pen down
	 * state, even this controller has a pressure sensor.  The pressure
	 * value can fluctuate for quite a while after lifting the pen and
	 * in some cases may not even settle at the expected value.
	 *
	 * The only safe way to check for the pen up condition is in the
	 * timer by reading the pen signal state (it's a GPIO _and_ IRQ).
	 */
	if (Rt) {
		struct input_dev *input = ts->input;

		if (!ts->pendown) {
			input_report_key(input, BTN_TOUCH, 1);
			ts->pendown = 1;
#ifdef VERBOSE
			dev_dbg(&ts->spi->dev, "DOWN\n");
#endif
		}
		input_report_abs(input, ABS_X, x);
		input_report_abs(input, ABS_Y, y);
		input_report_abs(input, ABS_PRESSURE, Rt);

		input_sync(input);
#ifdef VERBOSE
		dev_dbg(&ts->spi->dev, "%4d/%4d/%4d\n", x, y, Rt);
#endif
	}

	hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_PERIOD),
			HRTIMER_MODE_REL);
}

static int ads7846_debounce(void *ads, int data_idx, int *val)
{
	struct ads7846		*ts = ads;

	if (!ts->read_cnt || (abs(ts->last_read - *val) > ts->debounce_tol)) {
		/* Start over collecting consistent readings. */
		ts->read_rep = 0;
		/* Repeat it, if this was the first read or the read
		 * wasn't consistent enough. */
		if (ts->read_cnt < ts->debounce_max) {
			ts->last_read = *val;
			ts->read_cnt++;
			return ADS7846_FILTER_REPEAT;
		} else {
			/* Maximum number of debouncing reached and still
			 * not enough number of consistent readings. Abort
			 * the whole sample, repeat it in the next sampling
			 * period.
			 */
			ts->read_cnt = 0;
			return ADS7846_FILTER_IGNORE;
		}
	} else {
		if (++ts->read_rep > ts->debounce_rep) {
			/* Got a good reading for this coordinate,
			 * go for the next one. */
			ts->read_cnt = 0;
			ts->read_rep = 0;
			return ADS7846_FILTER_OK;
		} else {
			/* Read more values that are consistent. */
			ts->read_cnt++;
			return ADS7846_FILTER_REPEAT;
		}
	}
}

static int ads7846_no_filter(void *ads, int data_idx, int *val)
{
	return ADS7846_FILTER_OK;
}

static void ads7846_rx_val(void *ads)
{
	struct ads7846 *ts = ads;
	struct ads7846_packet *packet = ts->packet;
	struct spi_message *m;
	struct spi_transfer *t;
	int val;
	int action;
	int status;

	m = &ts->msg[ts->msg_idx];
	t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);

	/* adjust:  on-wire is a must-ignore bit, a BE12 value, then padding;
	 * built from two 8 bit values written msb-first.
	 */
	val = be16_to_cpup((__be16 *)t->rx_buf) >> 3;

	action = ts->filter(ts->filter_data, ts->msg_idx, &val);
	switch (action) {
	case ADS7846_FILTER_REPEAT:
		break;
	case ADS7846_FILTER_IGNORE:
		packet->tc.ignore = 1;
		/* Last message will contain ads7846_rx() as the
		 * completion function.
		 */
		m = ts->last_msg;
		break;
	case ADS7846_FILTER_OK:
		*(u16 *)t->rx_buf = val;
		packet->tc.ignore = 0;
		m = &ts->msg[++ts->msg_idx];
		break;
	default:
		BUG();
	}
	status = spi_async(ts->spi, m);
	if (status)
		dev_err(&ts->spi->dev, "spi_async --> %d\n",
				status);
}

static enum hrtimer_restart ads7846_timer(struct hrtimer *handle)
{
	struct ads7846	*ts = container_of(handle, struct ads7846, timer);
	int		status = 0;

	spin_lock(&ts->lock);

	if (unlikely(!get_pendown_state(ts) ||
		     device_suspended(&ts->spi->dev))) {
		if (ts->pendown) {
			struct input_dev *input = ts->input;

			input_report_key(input, BTN_TOUCH, 0);
			input_report_abs(input, ABS_PRESSURE, 0);
			input_sync(input);

			ts->pendown = 0;
#ifdef VERBOSE
			dev_dbg(&ts->spi->dev, "UP\n");
#endif
		}

		/* measurement cycle ended */
		if (!device_suspended(&ts->spi->dev)) {
			ts->irq_disabled = 0;
			enable_irq(ts->spi->irq);
		}
		ts->pending = 0;
	} else {
		/* pen is still down, continue with the measurement */
		ts->msg_idx = 0;
		status = spi_async(ts->spi, &ts->msg[0]);
		if (status)
			dev_err(&ts->spi->dev, "spi_async --> %d\n", status);
	}

	spin_unlock(&ts->lock);
	return HRTIMER_NORESTART;
}

static irqreturn_t ads7846_irq(int irq, void *handle)
{
	struct ads7846 *ts = handle;
	unsigned long flags;

	spin_lock_irqsave(&ts->lock, flags);
	if (likely(get_pendown_state(ts))) {
		if (!ts->irq_disabled) {
			/* The ARM do_simple_IRQ() dispatcher doesn't act
			 * like the other dispatchers:  it will report IRQs
			 * even after they've been disabled.  We work around
			 * that here.  (The "generic irq" framework may help...)
			 */
			ts->irq_disabled = 1;
			disable_irq(ts->spi->irq);
			ts->pending = 1;
			hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_DELAY),
					HRTIMER_MODE_REL);
		}
	}
	spin_unlock_irqrestore(&ts->lock, flags);

	return IRQ_HANDLED;
}

/*--------------------------------------------------------------------------*/

/* Must be called with ts->lock held */
static void ads7846_disable(struct ads7846 *ts)
{
	if (ts->disabled)
		return;

	ts->disabled = 1;

	/* are we waiting for IRQ, or polling? */
	if (!ts->pending) {
		ts->irq_disabled = 1;
		disable_irq(ts->spi->irq);
	} else {
		/* the timer will run at least once more, and
		 * leave everything in a clean state, IRQ disabled
		 */
		while (ts->pending) {
			spin_unlock_irq(&ts->lock);
			msleep(1);
			spin_lock_irq(&ts->lock);
		}
	}

	/* we know the chip's in lowpower mode since we always
	 * leave it that way after every request
	 */
}

/* Must be called with ts->lock held */
static void ads7846_enable(struct ads7846 *ts)
{
	if (!ts->disabled)
		return;

	ts->disabled = 0;
	ts->irq_disabled = 0;
	enable_irq(ts->spi->irq);
}

static int ads7846_suspend(struct spi_device *spi, pm_message_t message)
{
	struct ads7846 *ts = dev_get_drvdata(&spi->dev);

	spin_lock_irq(&ts->lock);

	ts->is_suspended = 1;
	ads7846_disable(ts);

	spin_unlock_irq(&ts->lock);

	return 0;

}

static int ads7846_resume(struct spi_device *spi)
{
	struct ads7846 *ts = dev_get_drvdata(&spi->dev);

	spin_lock_irq(&ts->lock);

	ts->is_suspended = 0;
	ads7846_enable(ts);

	spin_unlock_irq(&ts->lock);

	return 0;
}

static int __devinit setup_pendown(struct spi_device *spi, struct ads7846 *ts)
{
	struct ads7846_platform_data *pdata = spi->dev.platform_data;
	int err;

	/* REVISIT when the irq can be triggered active-low, or if for some
	 * reason the touchscreen isn't hooked up, we don't need to access
	 * the pendown state.
	 */
	if (!pdata->get_pendown_state && !gpio_is_valid(pdata->gpio_pendown)) {
		dev_err(&spi->dev, "no get_pendown_state nor gpio_pendown?\n");
		return -EINVAL;
	}

	if (pdata->get_pendown_state) {
		ts->get_pendown_state = pdata->get_pendown_state;
		return 0;
	}

	err = gpio_request(pdata->gpio_pendown, "ads7846_pendown");
	if (err) {
		dev_err(&spi->dev, "failed to request pendown GPIO%d\n",
				pdata->gpio_pendown);
		return err;
	}

	ts->gpio_pendown = pdata->gpio_pendown;
	return 0;
}

static int __devinit ads7846_probe(struct spi_device *spi)
{
	struct ads7846			*ts;
	struct ads7846_packet		*packet;
	struct input_dev		*input_dev;
	struct ads7846_platform_data	*pdata = spi->dev.platform_data;
	struct spi_message		*m;
	struct spi_transfer		*x;
	int				vref;
	int				err;

	if (!spi->irq) {
		dev_dbg(&spi->dev, "no IRQ?\n");
		return -ENODEV;
	}

	if (!pdata) {
		dev_dbg(&spi->dev, "no platform data?\n");
		return -ENODEV;
	}

	/* don't exceed max specified sample rate */
	if (spi->max_speed_hz > (125000 * SAMPLE_BITS)) {
		dev_dbg(&spi->dev, "f(sample) %d KHz?\n",
				(spi->max_speed_hz/SAMPLE_BITS)/1000);
		return -EINVAL;
	}

	/* We'd set TX wordsize 8 bits and RX wordsize to 13 bits ... except
	 * that even if the hardware can do that, the SPI controller driver
	 * may not.  So we stick to very-portable 8 bit words, both RX and TX.
	 */
	spi->bits_per_word = 8;
	spi->mode = SPI_MODE_0;
	err = spi_setup(spi);
	if (err < 0)
		return err;

	ts = kzalloc(sizeof(struct ads7846), GFP_KERNEL);
	packet = kzalloc(sizeof(struct ads7846_packet), GFP_KERNEL);
	input_dev = input_allocate_device();
	if (!ts || !packet || !input_dev) {
		err = -ENOMEM;
		goto err_free_mem;
	}

	dev_set_drvdata(&spi->dev, ts);

	ts->packet = packet;
	ts->spi = spi;
	ts->input = input_dev;
	ts->vref_mv = pdata->vref_mv;

	hrtimer_init(&ts->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	ts->timer.function = ads7846_timer;

	spin_lock_init(&ts->lock);

	ts->model = pdata->model ? : 7846;
	ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
	ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
	ts->pressure_max = pdata->pressure_max ? : ~0;

	if (pdata->filter != NULL) {
		if (pdata->filter_init != NULL) {
			err = pdata->filter_init(pdata, &ts->filter_data);
			if (err < 0)
				goto err_free_mem;
		}
		ts->filter = pdata->filter;
		ts->filter_cleanup = pdata->filter_cleanup;
	} else if (pdata->debounce_max) {
		ts->debounce_max = pdata->debounce_max;
		if (ts->debounce_max < 2)
			ts->debounce_max = 2;
		ts->debounce_tol = pdata->debounce_tol;
		ts->debounce_rep = pdata->debounce_rep;
		ts->filter = ads7846_debounce;
		ts->filter_data = ts;
	} else
		ts->filter = ads7846_no_filter;

	err = setup_pendown(spi, ts);
	if (err)
		goto err_cleanup_filter;

	if (pdata->penirq_recheck_delay_usecs)
		ts->penirq_recheck_delay_usecs =
				pdata->penirq_recheck_delay_usecs;

	snprintf(ts->phys, sizeof(ts->phys), "%s/input0", dev_name(&spi->dev));

	input_dev->name = "ADS784x Touchscreen";
	input_dev->phys = ts->phys;
	input_dev->dev.parent = &spi->dev;

	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
	input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
	input_set_abs_params(input_dev, ABS_X,
			pdata->x_min ? : 0,
			pdata->x_max ? : MAX_12BIT,
			0, 0);
	input_set_abs_params(input_dev, ABS_Y,
			pdata->y_min ? : 0,
			pdata->y_max ? : MAX_12BIT,
			0, 0);
	input_set_abs_params(input_dev, ABS_PRESSURE,
			pdata->pressure_min, pdata->pressure_max, 0, 0);

	vref = pdata->keep_vref_on;

	/* set up the transfers to read touchscreen state; this assumes we
	 * use formula #2 for pressure, not #3.
	 */
	m = &ts->msg[0];
	x = ts->xfer;

	spi_message_init(m);

	/* y- still on; turn on only y+ (and ADC) */
	packet->read_y = READ_Y(vref);
	x->tx_buf = &packet->read_y;
	x->len = 1;
	spi_message_add_tail(x, m);

	x++;
	x->rx_buf = &packet->tc.y;
	x->len = 2;
	spi_message_add_tail(x, m);

	/* the first sample after switching drivers can be low quality;
	 * optionally discard it, using a second one after the signals
	 * have had enough time to stabilize.
	 */
	if (pdata->settle_delay_usecs) {
		x->delay_usecs = pdata->settle_delay_usecs;

		x++;
		x->tx_buf = &packet->read_y;
		x->len = 1;
		spi_message_add_tail(x, m);

		x++;
		x->rx_buf = &packet->tc.y;
		x->len = 2;
		spi_message_add_tail(x, m);
	}

	m->complete = ads7846_rx_val;
	m->context = ts;

	m++;
	spi_message_init(m);

	/* turn y- off, x+ on, then leave in lowpower */
	x++;
	packet->read_x = READ_X(vref);
	x->tx_buf = &packet->read_x;
	x->len = 1;
	spi_message_add_tail(x, m);

	x++;
	x->rx_buf = &packet->tc.x;
	x->len = 2;
	spi_message_add_tail(x, m);

	/* ... maybe discard first sample ... */
	if (pdata->settle_delay_usecs) {
		x->delay_usecs = pdata->settle_delay_usecs;

		x++;
		x->tx_buf = &packet->read_x;
		x->len = 1;
		spi_message_add_tail(x, m);

		x++;
		x->rx_buf = &packet->tc.x;
		x->len = 2;
		spi_message_add_tail(x, m);
	}

	m->complete = ads7846_rx_val;
	m->context = ts;

	/* turn y+ off, x- on; we'll use formula #2 */
	if (ts->model == 7846) {
		m++;
		spi_message_init(m);

		x++;
		packet->read_z1 = READ_Z1(vref);
		x->tx_buf = &packet->read_z1;
		x->len = 1;
		spi_message_add_tail(x, m);

		x++;
		x->rx_buf = &packet->tc.z1;
		x->len = 2;
		spi_message_add_tail(x, m);

		/* ... maybe discard first sample ... */
		if (pdata->settle_delay_usecs) {
			x->delay_usecs = pdata->settle_delay_usecs;

			x++;
			x->tx_buf = &packet->read_z1;
			x->len = 1;
			spi_message_add_tail(x, m);

			x++;
			x->rx_buf = &packet->tc.z1;
			x->len = 2;
			spi_message_add_tail(x, m);
		}

		m->complete = ads7846_rx_val;
		m->context = ts;

		m++;
		spi_message_init(m);

		x++;
		packet->read_z2 = READ_Z2(vref);
		x->tx_buf = &packet->read_z2;
		x->len = 1;
		spi_message_add_tail(x, m);

		x++;
		x->rx_buf = &packet->tc.z2;
		x->len = 2;
		spi_message_add_tail(x, m);

		/* ... maybe discard first sample ... */
		if (pdata->settle_delay_usecs) {
			x->delay_usecs = pdata->settle_delay_usecs;

			x++;
			x->tx_buf = &packet->read_z2;
			x->len = 1;
			spi_message_add_tail(x, m);

			x++;
			x->rx_buf = &packet->tc.z2;
			x->len = 2;
			spi_message_add_tail(x, m);
		}

		m->complete = ads7846_rx_val;
		m->context = ts;
	}

	/* power down */
	m++;
	spi_message_init(m);

	x++;
	packet->pwrdown = PWRDOWN;
	x->tx_buf = &packet->pwrdown;
	x->len = 1;
	spi_message_add_tail(x, m);

	x++;
	x->rx_buf = &packet->dummy;
	x->len = 2;
	CS_CHANGE(*x);
	spi_message_add_tail(x, m);

	m->complete = ads7846_rx;
	m->context = ts;

	ts->last_msg = m;

	if (request_irq(spi->irq, ads7846_irq, IRQF_TRIGGER_FALLING,
			spi->dev.driver->name, ts)) {
		dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
		err = -EBUSY;
		goto err_free_gpio;
	}

	err = ads784x_hwmon_register(spi, ts);
	if (err)
		goto err_free_irq;

	dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);

	/* take a first sample, leaving nPENIRQ active and vREF off; avoid
	 * the touchscreen, in case it's not connected.
	 */
	(void) ads7846_read12_ser(&spi->dev,
			  READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);

	err = sysfs_create_group(&spi->dev.kobj, &ads784x_attr_group);
	if (err)
		goto err_remove_hwmon;

	err = input_register_device(input_dev);
	if (err)
		goto err_remove_attr_group;

	return 0;

 err_remove_attr_group:
	sysfs_remove_group(&spi->dev.kobj, &ads784x_attr_group);
 err_remove_hwmon:
	ads784x_hwmon_unregister(spi, ts);
 err_free_irq:
	free_irq(spi->irq, ts);
 err_free_gpio:
	if (ts->gpio_pendown != -1)
		gpio_free(ts->gpio_pendown);
 err_cleanup_filter:
	if (ts->filter_cleanup)
		ts->filter_cleanup(ts->filter_data);
 err_free_mem:
	input_free_device(input_dev);
	kfree(packet);
	kfree(ts);
	return err;
}

static int __devexit ads7846_remove(struct spi_device *spi)
{
	struct ads7846		*ts = dev_get_drvdata(&spi->dev);

	ads784x_hwmon_unregister(spi, ts);
	input_unregister_device(ts->input);

	ads7846_suspend(spi, PMSG_SUSPEND);

	sysfs_remove_group(&spi->dev.kobj, &ads784x_attr_group);

	free_irq(ts->spi->irq, ts);
	/* suspend left the IRQ disabled */
	enable_irq(ts->spi->irq);

	if (ts->gpio_pendown != -1)
		gpio_free(ts->gpio_pendown);

	if (ts->filter_cleanup)
		ts->filter_cleanup(ts->filter_data);

	kfree(ts->packet);
	kfree(ts);

	dev_dbg(&spi->dev, "unregistered touchscreen\n");
	return 0;
}

static struct spi_driver ads7846_driver = {
	.driver = {
		.name	= "ads7846",
		.bus	= &spi_bus_type,
		.owner	= THIS_MODULE,
	},
	.probe		= ads7846_probe,
	.remove		= __devexit_p(ads7846_remove),
	.suspend	= ads7846_suspend,
	.resume		= ads7846_resume,
};

static int __init ads7846_init(void)
{
	return spi_register_driver(&ads7846_driver);
}
module_init(ads7846_init);

static void __exit ads7846_exit(void)
{
	spi_unregister_driver(&ads7846_driver);
}
module_exit(ads7846_exit);

MODULE_DESCRIPTION("ADS7846 TouchScreen Driver");
MODULE_LICENSE("GPL");