summaryrefslogtreecommitdiffstats
path: root/drivers/net/can/c_can/c_can.c
blob: 31552959aed7baa4895ac386d390b0a331abde6e (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
/*
 * CAN bus driver for Bosch C_CAN controller
 *
 * Copyright (C) 2010 ST Microelectronics
 * Bhupesh Sharma <bhupesh.sharma@st.com>
 *
 * Borrowed heavily from the C_CAN driver originally written by:
 * Copyright (C) 2007
 * - Sascha Hauer, Marc Kleine-Budde, Pengutronix <s.hauer@pengutronix.de>
 * - Simon Kallweit, intefo AG <simon.kallweit@intefo.ch>
 *
 * TX and RX NAPI implementation has been borrowed from at91 CAN driver
 * written by:
 * Copyright
 * (C) 2007 by Hans J. Koch <hjk@hansjkoch.de>
 * (C) 2008, 2009 by Marc Kleine-Budde <kernel@pengutronix.de>
 *
 * Bosch C_CAN controller is compliant to CAN protocol version 2.0 part A and B.
 * Bosch C_CAN user manual can be obtained from:
 * http://www.semiconductors.bosch.de/media/en/pdf/ipmodules_1/c_can/
 * users_manual_c_can.pdf
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/kernel.h>
#include <linux/version.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/list.h>
#include <linux/delay.h>
#include <linux/io.h>

#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>

#include "c_can.h"

/* control register */
#define CONTROL_TEST		BIT(7)
#define CONTROL_CCE		BIT(6)
#define CONTROL_DISABLE_AR	BIT(5)
#define CONTROL_ENABLE_AR	(0 << 5)
#define CONTROL_EIE		BIT(3)
#define CONTROL_SIE		BIT(2)
#define CONTROL_IE		BIT(1)
#define CONTROL_INIT		BIT(0)

/* test register */
#define TEST_RX			BIT(7)
#define TEST_TX1		BIT(6)
#define TEST_TX2		BIT(5)
#define TEST_LBACK		BIT(4)
#define TEST_SILENT		BIT(3)
#define TEST_BASIC		BIT(2)

/* status register */
#define STATUS_BOFF		BIT(7)
#define STATUS_EWARN		BIT(6)
#define STATUS_EPASS		BIT(5)
#define STATUS_RXOK		BIT(4)
#define STATUS_TXOK		BIT(3)

/* error counter register */
#define ERR_CNT_TEC_MASK	0xff
#define ERR_CNT_TEC_SHIFT	0
#define ERR_CNT_REC_SHIFT	8
#define ERR_CNT_REC_MASK	(0x7f << ERR_CNT_REC_SHIFT)
#define ERR_CNT_RP_SHIFT	15
#define ERR_CNT_RP_MASK		(0x1 << ERR_CNT_RP_SHIFT)

/* bit-timing register */
#define BTR_BRP_MASK		0x3f
#define BTR_BRP_SHIFT		0
#define BTR_SJW_SHIFT		6
#define BTR_SJW_MASK		(0x3 << BTR_SJW_SHIFT)
#define BTR_TSEG1_SHIFT		8
#define BTR_TSEG1_MASK		(0xf << BTR_TSEG1_SHIFT)
#define BTR_TSEG2_SHIFT		12
#define BTR_TSEG2_MASK		(0x7 << BTR_TSEG2_SHIFT)

/* brp extension register */
#define BRP_EXT_BRPE_MASK	0x0f
#define BRP_EXT_BRPE_SHIFT	0

/* IFx command request */
#define IF_COMR_BUSY		BIT(15)

/* IFx command mask */
#define IF_COMM_WR		BIT(7)
#define IF_COMM_MASK		BIT(6)
#define IF_COMM_ARB		BIT(5)
#define IF_COMM_CONTROL		BIT(4)
#define IF_COMM_CLR_INT_PND	BIT(3)
#define IF_COMM_TXRQST		BIT(2)
#define IF_COMM_DATAA		BIT(1)
#define IF_COMM_DATAB		BIT(0)
#define IF_COMM_ALL		(IF_COMM_MASK | IF_COMM_ARB | \
				IF_COMM_CONTROL | IF_COMM_TXRQST | \
				IF_COMM_DATAA | IF_COMM_DATAB)

/* IFx arbitration */
#define IF_ARB_MSGVAL		BIT(15)
#define IF_ARB_MSGXTD		BIT(14)
#define IF_ARB_TRANSMIT		BIT(13)

/* IFx message control */
#define IF_MCONT_NEWDAT		BIT(15)
#define IF_MCONT_MSGLST		BIT(14)
#define IF_MCONT_CLR_MSGLST	(0 << 14)
#define IF_MCONT_INTPND		BIT(13)
#define IF_MCONT_UMASK		BIT(12)
#define IF_MCONT_TXIE		BIT(11)
#define IF_MCONT_RXIE		BIT(10)
#define IF_MCONT_RMTEN		BIT(9)
#define IF_MCONT_TXRQST		BIT(8)
#define IF_MCONT_EOB		BIT(7)
#define IF_MCONT_DLC_MASK	0xf

/*
 * IFx register masks:
 * allow easy operation on 16-bit registers when the
 * argument is 32-bit instead
 */
#define IFX_WRITE_LOW_16BIT(x)	((x) & 0xFFFF)
#define IFX_WRITE_HIGH_16BIT(x)	(((x) & 0xFFFF0000) >> 16)

/* message object split */
#define C_CAN_NO_OF_OBJECTS	32
#define C_CAN_MSG_OBJ_RX_NUM	16
#define C_CAN_MSG_OBJ_TX_NUM	16

#define C_CAN_MSG_OBJ_RX_FIRST	1
#define C_CAN_MSG_OBJ_RX_LAST	(C_CAN_MSG_OBJ_RX_FIRST + \
				C_CAN_MSG_OBJ_RX_NUM - 1)

#define C_CAN_MSG_OBJ_TX_FIRST	(C_CAN_MSG_OBJ_RX_LAST + 1)
#define C_CAN_MSG_OBJ_TX_LAST	(C_CAN_MSG_OBJ_TX_FIRST + \
				C_CAN_MSG_OBJ_TX_NUM - 1)

#define C_CAN_MSG_OBJ_RX_SPLIT	9
#define C_CAN_MSG_RX_LOW_LAST	(C_CAN_MSG_OBJ_RX_SPLIT - 1)

#define C_CAN_NEXT_MSG_OBJ_MASK	(C_CAN_MSG_OBJ_TX_NUM - 1)
#define RECEIVE_OBJECT_BITS	0x0000ffff

/* status interrupt */
#define STATUS_INTERRUPT	0x8000

/* global interrupt masks */
#define ENABLE_ALL_INTERRUPTS	1
#define DISABLE_ALL_INTERRUPTS	0

/* minimum timeout for checking BUSY status */
#define MIN_TIMEOUT_VALUE	6

/* napi related */
#define C_CAN_NAPI_WEIGHT	C_CAN_MSG_OBJ_RX_NUM

/* c_can lec values */
enum c_can_lec_type {
	LEC_NO_ERROR = 0,
	LEC_STUFF_ERROR,
	LEC_FORM_ERROR,
	LEC_ACK_ERROR,
	LEC_BIT1_ERROR,
	LEC_BIT0_ERROR,
	LEC_CRC_ERROR,
	LEC_UNUSED,
};

/*
 * c_can error types:
 * Bus errors (BUS_OFF, ERROR_WARNING, ERROR_PASSIVE) are supported
 */
enum c_can_bus_error_types {
	C_CAN_NO_ERROR = 0,
	C_CAN_BUS_OFF,
	C_CAN_ERROR_WARNING,
	C_CAN_ERROR_PASSIVE,
};

static struct can_bittiming_const c_can_bittiming_const = {
	.name = KBUILD_MODNAME,
	.tseg1_min = 2,		/* Time segment 1 = prop_seg + phase_seg1 */
	.tseg1_max = 16,
	.tseg2_min = 1,		/* Time segment 2 = phase_seg2 */
	.tseg2_max = 8,
	.sjw_max = 4,
	.brp_min = 1,
	.brp_max = 1024,	/* 6-bit BRP field + 4-bit BRPE field*/
	.brp_inc = 1,
};

static inline int get_tx_next_msg_obj(const struct c_can_priv *priv)
{
	return (priv->tx_next & C_CAN_NEXT_MSG_OBJ_MASK) +
			C_CAN_MSG_OBJ_TX_FIRST;
}

static inline int get_tx_echo_msg_obj(const struct c_can_priv *priv)
{
	return (priv->tx_echo & C_CAN_NEXT_MSG_OBJ_MASK) +
			C_CAN_MSG_OBJ_TX_FIRST;
}

static u32 c_can_read_reg32(struct c_can_priv *priv, void *reg)
{
	u32 val = priv->read_reg(priv, reg);
	val |= ((u32) priv->read_reg(priv, reg + 2)) << 16;
	return val;
}

static void c_can_enable_all_interrupts(struct c_can_priv *priv,
						int enable)
{
	unsigned int cntrl_save = priv->read_reg(priv,
						&priv->regs->control);

	if (enable)
		cntrl_save |= (CONTROL_SIE | CONTROL_EIE | CONTROL_IE);
	else
		cntrl_save &= ~(CONTROL_EIE | CONTROL_IE | CONTROL_SIE);

	priv->write_reg(priv, &priv->regs->control, cntrl_save);
}

static inline int c_can_msg_obj_is_busy(struct c_can_priv *priv, int iface)
{
	int count = MIN_TIMEOUT_VALUE;

	while (count && priv->read_reg(priv,
				&priv->regs->ifregs[iface].com_req) &
				IF_COMR_BUSY) {
		count--;
		udelay(1);
	}

	if (!count)
		return 1;

	return 0;
}

static inline void c_can_object_get(struct net_device *dev,
					int iface, int objno, int mask)
{
	struct c_can_priv *priv = netdev_priv(dev);

	/*
	 * As per specs, after writting the message object number in the
	 * IF command request register the transfer b/w interface
	 * register and message RAM must be complete in 6 CAN-CLK
	 * period.
	 */
	priv->write_reg(priv, &priv->regs->ifregs[iface].com_mask,
			IFX_WRITE_LOW_16BIT(mask));
	priv->write_reg(priv, &priv->regs->ifregs[iface].com_req,
			IFX_WRITE_LOW_16BIT(objno));

	if (c_can_msg_obj_is_busy(priv, iface))
		netdev_err(dev, "timed out in object get\n");
}

static inline void c_can_object_put(struct net_device *dev,
					int iface, int objno, int mask)
{
	struct c_can_priv *priv = netdev_priv(dev);

	/*
	 * As per specs, after writting the message object number in the
	 * IF command request register the transfer b/w interface
	 * register and message RAM must be complete in 6 CAN-CLK
	 * period.
	 */
	priv->write_reg(priv, &priv->regs->ifregs[iface].com_mask,
			(IF_COMM_WR | IFX_WRITE_LOW_16BIT(mask)));
	priv->write_reg(priv, &priv->regs->ifregs[iface].com_req,
			IFX_WRITE_LOW_16BIT(objno));

	if (c_can_msg_obj_is_busy(priv, iface))
		netdev_err(dev, "timed out in object put\n");
}

static void c_can_write_msg_object(struct net_device *dev,
			int iface, struct can_frame *frame, int objno)
{
	int i;
	u16 flags = 0;
	unsigned int id;
	struct c_can_priv *priv = netdev_priv(dev);

	if (!(frame->can_id & CAN_RTR_FLAG))
		flags |= IF_ARB_TRANSMIT;

	if (frame->can_id & CAN_EFF_FLAG) {
		id = frame->can_id & CAN_EFF_MASK;
		flags |= IF_ARB_MSGXTD;
	} else
		id = ((frame->can_id & CAN_SFF_MASK) << 18);

	flags |= IF_ARB_MSGVAL;

	priv->write_reg(priv, &priv->regs->ifregs[iface].arb1,
				IFX_WRITE_LOW_16BIT(id));
	priv->write_reg(priv, &priv->regs->ifregs[iface].arb2, flags |
				IFX_WRITE_HIGH_16BIT(id));

	for (i = 0; i < frame->can_dlc; i += 2) {
		priv->write_reg(priv, &priv->regs->ifregs[iface].data[i / 2],
				frame->data[i] | (frame->data[i + 1] << 8));
	}

	/* enable interrupt for this message object */
	priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl,
			IF_MCONT_TXIE | IF_MCONT_TXRQST | IF_MCONT_EOB |
			frame->can_dlc);
	c_can_object_put(dev, iface, objno, IF_COMM_ALL);
}

static inline void c_can_mark_rx_msg_obj(struct net_device *dev,
						int iface, int ctrl_mask,
						int obj)
{
	struct c_can_priv *priv = netdev_priv(dev);

	priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl,
			ctrl_mask & ~(IF_MCONT_MSGLST | IF_MCONT_INTPND));
	c_can_object_put(dev, iface, obj, IF_COMM_CONTROL);

}

static inline void c_can_activate_all_lower_rx_msg_obj(struct net_device *dev,
						int iface,
						int ctrl_mask)
{
	int i;
	struct c_can_priv *priv = netdev_priv(dev);

	for (i = C_CAN_MSG_OBJ_RX_FIRST; i <= C_CAN_MSG_RX_LOW_LAST; i++) {
		priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl,
				ctrl_mask & ~(IF_MCONT_MSGLST |
					IF_MCONT_INTPND | IF_MCONT_NEWDAT));
		c_can_object_put(dev, iface, i, IF_COMM_CONTROL);
	}
}

static inline void c_can_activate_rx_msg_obj(struct net_device *dev,
						int iface, int ctrl_mask,
						int obj)
{
	struct c_can_priv *priv = netdev_priv(dev);

	priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl,
			ctrl_mask & ~(IF_MCONT_MSGLST |
				IF_MCONT_INTPND | IF_MCONT_NEWDAT));
	c_can_object_put(dev, iface, obj, IF_COMM_CONTROL);
}

static void c_can_handle_lost_msg_obj(struct net_device *dev,
					int iface, int objno)
{
	struct c_can_priv *priv = netdev_priv(dev);
	struct net_device_stats *stats = &dev->stats;
	struct sk_buff *skb;
	struct can_frame *frame;

	netdev_err(dev, "msg lost in buffer %d\n", objno);

	c_can_object_get(dev, iface, objno, IF_COMM_ALL & ~IF_COMM_TXRQST);

	priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl,
			IF_MCONT_CLR_MSGLST);

	c_can_object_put(dev, 0, objno, IF_COMM_CONTROL);

	/* create an error msg */
	skb = alloc_can_err_skb(dev, &frame);
	if (unlikely(!skb))
		return;

	frame->can_id |= CAN_ERR_CRTL;
	frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
	stats->rx_errors++;
	stats->rx_over_errors++;

	netif_receive_skb(skb);
}

static int c_can_read_msg_object(struct net_device *dev, int iface, int ctrl)
{
	u16 flags, data;
	int i;
	unsigned int val;
	struct c_can_priv *priv = netdev_priv(dev);
	struct net_device_stats *stats = &dev->stats;
	struct sk_buff *skb;
	struct can_frame *frame;

	skb = alloc_can_skb(dev, &frame);
	if (!skb) {
		stats->rx_dropped++;
		return -ENOMEM;
	}

	frame->can_dlc = get_can_dlc(ctrl & 0x0F);

	flags =	priv->read_reg(priv, &priv->regs->ifregs[iface].arb2);
	val = priv->read_reg(priv, &priv->regs->ifregs[iface].arb1) |
		(flags << 16);

	if (flags & IF_ARB_MSGXTD)
		frame->can_id = (val & CAN_EFF_MASK) | CAN_EFF_FLAG;
	else
		frame->can_id = (val >> 18) & CAN_SFF_MASK;

	if (flags & IF_ARB_TRANSMIT)
		frame->can_id |= CAN_RTR_FLAG;
	else {
		for (i = 0; i < frame->can_dlc; i += 2) {
			data = priv->read_reg(priv,
				&priv->regs->ifregs[iface].data[i / 2]);
			frame->data[i] = data;
			frame->data[i + 1] = data >> 8;
		}
	}

	netif_receive_skb(skb);

	stats->rx_packets++;
	stats->rx_bytes += frame->can_dlc;

	return 0;
}

static void c_can_setup_receive_object(struct net_device *dev, int iface,
					int objno, unsigned int mask,
					unsigned int id, unsigned int mcont)
{
	struct c_can_priv *priv = netdev_priv(dev);

	priv->write_reg(priv, &priv->regs->ifregs[iface].mask1,
			IFX_WRITE_LOW_16BIT(mask));
	priv->write_reg(priv, &priv->regs->ifregs[iface].mask2,
			IFX_WRITE_HIGH_16BIT(mask));

	priv->write_reg(priv, &priv->regs->ifregs[iface].arb1,
			IFX_WRITE_LOW_16BIT(id));
	priv->write_reg(priv, &priv->regs->ifregs[iface].arb2,
			(IF_ARB_MSGVAL | IFX_WRITE_HIGH_16BIT(id)));

	priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl, mcont);
	c_can_object_put(dev, iface, objno, IF_COMM_ALL & ~IF_COMM_TXRQST);

	netdev_dbg(dev, "obj no:%d, msgval:0x%08x\n", objno,
			c_can_read_reg32(priv, &priv->regs->msgval1));
}

static void c_can_inval_msg_object(struct net_device *dev, int iface, int objno)
{
	struct c_can_priv *priv = netdev_priv(dev);

	priv->write_reg(priv, &priv->regs->ifregs[iface].arb1, 0);
	priv->write_reg(priv, &priv->regs->ifregs[iface].arb2, 0);
	priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl, 0);

	c_can_object_put(dev, iface, objno, IF_COMM_ARB | IF_COMM_CONTROL);

	netdev_dbg(dev, "obj no:%d, msgval:0x%08x\n", objno,
			c_can_read_reg32(priv, &priv->regs->msgval1));
}

static inline int c_can_is_next_tx_obj_busy(struct c_can_priv *priv, int objno)
{
	int val = c_can_read_reg32(priv, &priv->regs->txrqst1);

	/*
	 * as transmission request register's bit n-1 corresponds to
	 * message object n, we need to handle the same properly.
	 */
	if (val & (1 << (objno - 1)))
		return 1;

	return 0;
}

static netdev_tx_t c_can_start_xmit(struct sk_buff *skb,
					struct net_device *dev)
{
	u32 msg_obj_no;
	struct c_can_priv *priv = netdev_priv(dev);
	struct can_frame *frame = (struct can_frame *)skb->data;

	if (can_dropped_invalid_skb(dev, skb))
		return NETDEV_TX_OK;

	msg_obj_no = get_tx_next_msg_obj(priv);

	/* prepare message object for transmission */
	c_can_write_msg_object(dev, 0, frame, msg_obj_no);
	can_put_echo_skb(skb, dev, msg_obj_no - C_CAN_MSG_OBJ_TX_FIRST);

	/*
	 * we have to stop the queue in case of a wrap around or
	 * if the next TX message object is still in use
	 */
	priv->tx_next++;
	if (c_can_is_next_tx_obj_busy(priv, get_tx_next_msg_obj(priv)) ||
			(priv->tx_next & C_CAN_NEXT_MSG_OBJ_MASK) == 0)
		netif_stop_queue(dev);

	return NETDEV_TX_OK;
}

static int c_can_set_bittiming(struct net_device *dev)
{
	unsigned int reg_btr, reg_brpe, ctrl_save;
	u8 brp, brpe, sjw, tseg1, tseg2;
	u32 ten_bit_brp;
	struct c_can_priv *priv = netdev_priv(dev);
	const struct can_bittiming *bt = &priv->can.bittiming;

	/* c_can provides a 6-bit brp and 4-bit brpe fields */
	ten_bit_brp = bt->brp - 1;
	brp = ten_bit_brp & BTR_BRP_MASK;
	brpe = ten_bit_brp >> 6;

	sjw = bt->sjw - 1;
	tseg1 = bt->prop_seg + bt->phase_seg1 - 1;
	tseg2 = bt->phase_seg2 - 1;
	reg_btr = brp | (sjw << BTR_SJW_SHIFT) | (tseg1 << BTR_TSEG1_SHIFT) |
			(tseg2 << BTR_TSEG2_SHIFT);
	reg_brpe = brpe & BRP_EXT_BRPE_MASK;

	netdev_info(dev,
		"setting BTR=%04x BRPE=%04x\n", reg_btr, reg_brpe);

	ctrl_save = priv->read_reg(priv, &priv->regs->control);
	priv->write_reg(priv, &priv->regs->control,
			ctrl_save | CONTROL_CCE | CONTROL_INIT);
	priv->write_reg(priv, &priv->regs->btr, reg_btr);
	priv->write_reg(priv, &priv->regs->brp_ext, reg_brpe);
	priv->write_reg(priv, &priv->regs->control, ctrl_save);

	return 0;
}

/*
 * Configure C_CAN message objects for Tx and Rx purposes:
 * C_CAN provides a total of 32 message objects that can be configured
 * either for Tx or Rx purposes. Here the first 16 message objects are used as
 * a reception FIFO. The end of reception FIFO is signified by the EoB bit
 * being SET. The remaining 16 message objects are kept aside for Tx purposes.
 * See user guide document for further details on configuring message
 * objects.
 */
static void c_can_configure_msg_objects(struct net_device *dev)
{
	int i;

	/* first invalidate all message objects */
	for (i = C_CAN_MSG_OBJ_RX_FIRST; i <= C_CAN_NO_OF_OBJECTS; i++)
		c_can_inval_msg_object(dev, 0, i);

	/* setup receive message objects */
	for (i = C_CAN_MSG_OBJ_RX_FIRST; i < C_CAN_MSG_OBJ_RX_LAST; i++)
		c_can_setup_receive_object(dev, 0, i, 0, 0,
			(IF_MCONT_RXIE | IF_MCONT_UMASK) & ~IF_MCONT_EOB);

	c_can_setup_receive_object(dev, 0, C_CAN_MSG_OBJ_RX_LAST, 0, 0,
			IF_MCONT_EOB | IF_MCONT_RXIE | IF_MCONT_UMASK);
}

/*
 * Configure C_CAN chip:
 * - enable/disable auto-retransmission
 * - set operating mode
 * - configure message objects
 */
static void c_can_chip_config(struct net_device *dev)
{
	struct c_can_priv *priv = netdev_priv(dev);

	/* enable automatic retransmission */
	priv->write_reg(priv, &priv->regs->control,
			CONTROL_ENABLE_AR);

	if (priv->can.ctrlmode & (CAN_CTRLMODE_LISTENONLY &
					CAN_CTRLMODE_LOOPBACK)) {
		/* loopback + silent mode : useful for hot self-test */
		priv->write_reg(priv, &priv->regs->control, CONTROL_EIE |
				CONTROL_SIE | CONTROL_IE | CONTROL_TEST);
		priv->write_reg(priv, &priv->regs->test,
				TEST_LBACK | TEST_SILENT);
	} else if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK) {
		/* loopback mode : useful for self-test function */
		priv->write_reg(priv, &priv->regs->control, CONTROL_EIE |
				CONTROL_SIE | CONTROL_IE | CONTROL_TEST);
		priv->write_reg(priv, &priv->regs->test, TEST_LBACK);
	} else if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
		/* silent mode : bus-monitoring mode */
		priv->write_reg(priv, &priv->regs->control, CONTROL_EIE |
				CONTROL_SIE | CONTROL_IE | CONTROL_TEST);
		priv->write_reg(priv, &priv->regs->test, TEST_SILENT);
	} else
		/* normal mode*/
		priv->write_reg(priv, &priv->regs->control,
				CONTROL_EIE | CONTROL_SIE | CONTROL_IE);

	/* configure message objects */
	c_can_configure_msg_objects(dev);

	/* set a `lec` value so that we can check for updates later */
	priv->write_reg(priv, &priv->regs->status, LEC_UNUSED);

	/* set bittiming params */
	c_can_set_bittiming(dev);
}

static void c_can_start(struct net_device *dev)
{
	struct c_can_priv *priv = netdev_priv(dev);

	/* basic c_can configuration */
	c_can_chip_config(dev);

	priv->can.state = CAN_STATE_ERROR_ACTIVE;

	/* reset tx helper pointers */
	priv->tx_next = priv->tx_echo = 0;

	/* enable status change, error and module interrupts */
	c_can_enable_all_interrupts(priv, ENABLE_ALL_INTERRUPTS);
}

static void c_can_stop(struct net_device *dev)
{
	struct c_can_priv *priv = netdev_priv(dev);

	/* disable all interrupts */
	c_can_enable_all_interrupts(priv, DISABLE_ALL_INTERRUPTS);

	/* set the state as STOPPED */
	priv->can.state = CAN_STATE_STOPPED;
}

static int c_can_set_mode(struct net_device *dev, enum can_mode mode)
{
	switch (mode) {
	case CAN_MODE_START:
		c_can_start(dev);
		netif_wake_queue(dev);
		break;
	default:
		return -EOPNOTSUPP;
	}

	return 0;
}

static int c_can_get_berr_counter(const struct net_device *dev,
					struct can_berr_counter *bec)
{
	unsigned int reg_err_counter;
	struct c_can_priv *priv = netdev_priv(dev);

	reg_err_counter = priv->read_reg(priv, &priv->regs->err_cnt);
	bec->rxerr = (reg_err_counter & ERR_CNT_REC_MASK) >>
				ERR_CNT_REC_SHIFT;
	bec->txerr = reg_err_counter & ERR_CNT_TEC_MASK;

	return 0;
}

/*
 * theory of operation:
 *
 * priv->tx_echo holds the number of the oldest can_frame put for
 * transmission into the hardware, but not yet ACKed by the CAN tx
 * complete IRQ.
 *
 * We iterate from priv->tx_echo to priv->tx_next and check if the
 * packet has been transmitted, echo it back to the CAN framework.
 * If we discover a not yet transmitted package, stop looking for more.
 */
static void c_can_do_tx(struct net_device *dev)
{
	u32 val;
	u32 msg_obj_no;
	struct c_can_priv *priv = netdev_priv(dev);
	struct net_device_stats *stats = &dev->stats;

	for (/* nix */; (priv->tx_next - priv->tx_echo) > 0; priv->tx_echo++) {
		msg_obj_no = get_tx_echo_msg_obj(priv);
		val = c_can_read_reg32(priv, &priv->regs->txrqst1);
		if (!(val & (1 << msg_obj_no))) {
			can_get_echo_skb(dev,
					msg_obj_no - C_CAN_MSG_OBJ_TX_FIRST);
			stats->tx_bytes += priv->read_reg(priv,
					&priv->regs->ifregs[0].msg_cntrl)
					& IF_MCONT_DLC_MASK;
			stats->tx_packets++;
			c_can_inval_msg_object(dev, 0, msg_obj_no);
		}
	}

	/* restart queue if wrap-up or if queue stalled on last pkt */
	if (((priv->tx_next & C_CAN_NEXT_MSG_OBJ_MASK) != 0) ||
			((priv->tx_echo & C_CAN_NEXT_MSG_OBJ_MASK) == 0))
		netif_wake_queue(dev);
}

/*
 * theory of operation:
 *
 * c_can core saves a received CAN message into the first free message
 * object it finds free (starting with the lowest). Bits NEWDAT and
 * INTPND are set for this message object indicating that a new message
 * has arrived. To work-around this issue, we keep two groups of message
 * objects whose partitioning is defined by C_CAN_MSG_OBJ_RX_SPLIT.
 *
 * To ensure in-order frame reception we use the following
 * approach while re-activating a message object to receive further
 * frames:
 * - if the current message object number is lower than
 *   C_CAN_MSG_RX_LOW_LAST, do not clear the NEWDAT bit while clearing
 *   the INTPND bit.
 * - if the current message object number is equal to
 *   C_CAN_MSG_RX_LOW_LAST then clear the NEWDAT bit of all lower
 *   receive message objects.
 * - if the current message object number is greater than
 *   C_CAN_MSG_RX_LOW_LAST then clear the NEWDAT bit of
 *   only this message object.
 */
static int c_can_do_rx_poll(struct net_device *dev, int quota)
{
	u32 num_rx_pkts = 0;
	unsigned int msg_obj, msg_ctrl_save;
	struct c_can_priv *priv = netdev_priv(dev);
	u32 val = c_can_read_reg32(priv, &priv->regs->intpnd1);

	for (msg_obj = C_CAN_MSG_OBJ_RX_FIRST;
			msg_obj <= C_CAN_MSG_OBJ_RX_LAST && quota > 0;
			val = c_can_read_reg32(priv, &priv->regs->intpnd1),
			msg_obj++) {
		/*
		 * as interrupt pending register's bit n-1 corresponds to
		 * message object n, we need to handle the same properly.
		 */
		if (val & (1 << (msg_obj - 1))) {
			c_can_object_get(dev, 0, msg_obj, IF_COMM_ALL &
					~IF_COMM_TXRQST);
			msg_ctrl_save = priv->read_reg(priv,
					&priv->regs->ifregs[0].msg_cntrl);

			if (msg_ctrl_save & IF_MCONT_EOB)
				return num_rx_pkts;

			if (msg_ctrl_save & IF_MCONT_MSGLST) {
				c_can_handle_lost_msg_obj(dev, 0, msg_obj);
				num_rx_pkts++;
				quota--;
				continue;
			}

			if (!(msg_ctrl_save & IF_MCONT_NEWDAT))
				continue;

			/* read the data from the message object */
			c_can_read_msg_object(dev, 0, msg_ctrl_save);

			if (msg_obj < C_CAN_MSG_RX_LOW_LAST)
				c_can_mark_rx_msg_obj(dev, 0,
						msg_ctrl_save, msg_obj);
			else if (msg_obj > C_CAN_MSG_RX_LOW_LAST)
				/* activate this msg obj */
				c_can_activate_rx_msg_obj(dev, 0,
						msg_ctrl_save, msg_obj);
			else if (msg_obj == C_CAN_MSG_RX_LOW_LAST)
				/* activate all lower message objects */
				c_can_activate_all_lower_rx_msg_obj(dev,
						0, msg_ctrl_save);

			num_rx_pkts++;
			quota--;
		}
	}

	return num_rx_pkts;
}

static inline int c_can_has_and_handle_berr(struct c_can_priv *priv)
{
	return (priv->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) &&
		(priv->current_status & LEC_UNUSED);
}

static int c_can_handle_state_change(struct net_device *dev,
				enum c_can_bus_error_types error_type)
{
	unsigned int reg_err_counter;
	unsigned int rx_err_passive;
	struct c_can_priv *priv = netdev_priv(dev);
	struct net_device_stats *stats = &dev->stats;
	struct can_frame *cf;
	struct sk_buff *skb;
	struct can_berr_counter bec;

	/* propogate the error condition to the CAN stack */
	skb = alloc_can_err_skb(dev, &cf);
	if (unlikely(!skb))
		return 0;

	c_can_get_berr_counter(dev, &bec);
	reg_err_counter = priv->read_reg(priv, &priv->regs->err_cnt);
	rx_err_passive = (reg_err_counter & ERR_CNT_RP_MASK) >>
				ERR_CNT_RP_SHIFT;

	switch (error_type) {
	case C_CAN_ERROR_WARNING:
		/* error warning state */
		priv->can.can_stats.error_warning++;
		priv->can.state = CAN_STATE_ERROR_WARNING;
		cf->can_id |= CAN_ERR_CRTL;
		cf->data[1] = (bec.txerr > bec.rxerr) ?
			CAN_ERR_CRTL_TX_WARNING :
			CAN_ERR_CRTL_RX_WARNING;
		cf->data[6] = bec.txerr;
		cf->data[7] = bec.rxerr;

		break;
	case C_CAN_ERROR_PASSIVE:
		/* error passive state */
		priv->can.can_stats.error_passive++;
		priv->can.state = CAN_STATE_ERROR_PASSIVE;
		cf->can_id |= CAN_ERR_CRTL;
		if (rx_err_passive)
			cf->data[1] |= CAN_ERR_CRTL_RX_PASSIVE;
		if (bec.txerr > 127)
			cf->data[1] |= CAN_ERR_CRTL_TX_PASSIVE;

		cf->data[6] = bec.txerr;
		cf->data[7] = bec.rxerr;
		break;
	case C_CAN_BUS_OFF:
		/* bus-off state */
		priv->can.state = CAN_STATE_BUS_OFF;
		cf->can_id |= CAN_ERR_BUSOFF;
		/*
		 * disable all interrupts in bus-off mode to ensure that
		 * the CPU is not hogged down
		 */
		c_can_enable_all_interrupts(priv, DISABLE_ALL_INTERRUPTS);
		can_bus_off(dev);
		break;
	default:
		break;
	}

	netif_receive_skb(skb);
	stats->rx_packets++;
	stats->rx_bytes += cf->can_dlc;

	return 1;
}

static int c_can_handle_bus_err(struct net_device *dev,
				enum c_can_lec_type lec_type)
{
	struct c_can_priv *priv = netdev_priv(dev);
	struct net_device_stats *stats = &dev->stats;
	struct can_frame *cf;
	struct sk_buff *skb;

	/*
	 * early exit if no lec update or no error.
	 * no lec update means that no CAN bus event has been detected
	 * since CPU wrote 0x7 value to status reg.
	 */
	if (lec_type == LEC_UNUSED || lec_type == LEC_NO_ERROR)
		return 0;

	/* propogate the error condition to the CAN stack */
	skb = alloc_can_err_skb(dev, &cf);
	if (unlikely(!skb))
		return 0;

	/*
	 * check for 'last error code' which tells us the
	 * type of the last error to occur on the CAN bus
	 */

	/* common for all type of bus errors */
	priv->can.can_stats.bus_error++;
	stats->rx_errors++;
	cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
	cf->data[2] |= CAN_ERR_PROT_UNSPEC;

	switch (lec_type) {
	case LEC_STUFF_ERROR:
		netdev_dbg(dev, "stuff error\n");
		cf->data[2] |= CAN_ERR_PROT_STUFF;
		break;
	case LEC_FORM_ERROR:
		netdev_dbg(dev, "form error\n");
		cf->data[2] |= CAN_ERR_PROT_FORM;
		break;
	case LEC_ACK_ERROR:
		netdev_dbg(dev, "ack error\n");
		cf->data[2] |= (CAN_ERR_PROT_LOC_ACK |
				CAN_ERR_PROT_LOC_ACK_DEL);
		break;
	case LEC_BIT1_ERROR:
		netdev_dbg(dev, "bit1 error\n");
		cf->data[2] |= CAN_ERR_PROT_BIT1;
		break;
	case LEC_BIT0_ERROR:
		netdev_dbg(dev, "bit0 error\n");
		cf->data[2] |= CAN_ERR_PROT_BIT0;
		break;
	case LEC_CRC_ERROR:
		netdev_dbg(dev, "CRC error\n");
		cf->data[2] |= (CAN_ERR_PROT_LOC_CRC_SEQ |
				CAN_ERR_PROT_LOC_CRC_DEL);
		break;
	default:
		break;
	}

	/* set a `lec` value so that we can check for updates later */
	priv->write_reg(priv, &priv->regs->status, LEC_UNUSED);

	netif_receive_skb(skb);
	stats->rx_packets++;
	stats->rx_bytes += cf->can_dlc;

	return 1;
}

static int c_can_poll(struct napi_struct *napi, int quota)
{
	u16 irqstatus;
	int lec_type = 0;
	int work_done = 0;
	struct net_device *dev = napi->dev;
	struct c_can_priv *priv = netdev_priv(dev);

	irqstatus = priv->read_reg(priv, &priv->regs->interrupt);
	if (!irqstatus)
		goto end;

	/* status events have the highest priority */
	if (irqstatus == STATUS_INTERRUPT) {
		priv->current_status = priv->read_reg(priv,
					&priv->regs->status);

		/* handle Tx/Rx events */
		if (priv->current_status & STATUS_TXOK)
			priv->write_reg(priv, &priv->regs->status,
					priv->current_status & ~STATUS_TXOK);

		if (priv->current_status & STATUS_RXOK)
			priv->write_reg(priv, &priv->regs->status,
					priv->current_status & ~STATUS_RXOK);

		/* handle state changes */
		if ((priv->current_status & STATUS_EWARN) &&
				(!(priv->last_status & STATUS_EWARN))) {
			netdev_dbg(dev, "entered error warning state\n");
			work_done += c_can_handle_state_change(dev,
						C_CAN_ERROR_WARNING);
		}
		if ((priv->current_status & STATUS_EPASS) &&
				(!(priv->last_status & STATUS_EPASS))) {
			netdev_dbg(dev, "entered error passive state\n");
			work_done += c_can_handle_state_change(dev,
						C_CAN_ERROR_PASSIVE);
		}
		if ((priv->current_status & STATUS_BOFF) &&
				(!(priv->last_status & STATUS_BOFF))) {
			netdev_dbg(dev, "entered bus off state\n");
			work_done += c_can_handle_state_change(dev,
						C_CAN_BUS_OFF);
		}

		/* handle bus recovery events */
		if ((!(priv->current_status & STATUS_BOFF)) &&
				(priv->last_status & STATUS_BOFF)) {
			netdev_dbg(dev, "left bus off state\n");
			priv->can.state = CAN_STATE_ERROR_ACTIVE;
		}
		if ((!(priv->current_status & STATUS_EPASS)) &&
				(priv->last_status & STATUS_EPASS)) {
			netdev_dbg(dev, "left error passive state\n");
			priv->can.state = CAN_STATE_ERROR_ACTIVE;
		}

		priv->last_status = priv->current_status;

		/* handle lec errors on the bus */
		lec_type = c_can_has_and_handle_berr(priv);
		if (lec_type)
			work_done += c_can_handle_bus_err(dev, lec_type);
	} else if ((irqstatus >= C_CAN_MSG_OBJ_RX_FIRST) &&
			(irqstatus <= C_CAN_MSG_OBJ_RX_LAST)) {
		/* handle events corresponding to receive message objects */
		work_done += c_can_do_rx_poll(dev, (quota - work_done));
	} else if ((irqstatus >= C_CAN_MSG_OBJ_TX_FIRST) &&
			(irqstatus <= C_CAN_MSG_OBJ_TX_LAST)) {
		/* handle events corresponding to transmit message objects */
		c_can_do_tx(dev);
	}

end:
	if (work_done < quota) {
		napi_complete(napi);
		/* enable all IRQs */
		c_can_enable_all_interrupts(priv, ENABLE_ALL_INTERRUPTS);
	}

	return work_done;
}

static irqreturn_t c_can_isr(int irq, void *dev_id)
{
	u16 irqstatus;
	struct net_device *dev = (struct net_device *)dev_id;
	struct c_can_priv *priv = netdev_priv(dev);

	irqstatus = priv->read_reg(priv, &priv->regs->interrupt);
	if (!irqstatus)
		return IRQ_NONE;

	/* disable all interrupts and schedule the NAPI */
	c_can_enable_all_interrupts(priv, DISABLE_ALL_INTERRUPTS);
	napi_schedule(&priv->napi);

	return IRQ_HANDLED;
}

static int c_can_open(struct net_device *dev)
{
	int err;
	struct c_can_priv *priv = netdev_priv(dev);

	/* open the can device */
	err = open_candev(dev);
	if (err) {
		netdev_err(dev, "failed to open can device\n");
		return err;
	}

	/* register interrupt handler */
	err = request_irq(dev->irq, &c_can_isr, IRQF_SHARED, dev->name,
				dev);
	if (err < 0) {
		netdev_err(dev, "failed to request interrupt\n");
		goto exit_irq_fail;
	}

	/* start the c_can controller */
	c_can_start(dev);

	napi_enable(&priv->napi);
	netif_start_queue(dev);

	return 0;

exit_irq_fail:
	close_candev(dev);
	return err;
}

static int c_can_close(struct net_device *dev)
{
	struct c_can_priv *priv = netdev_priv(dev);

	netif_stop_queue(dev);
	napi_disable(&priv->napi);
	c_can_stop(dev);
	free_irq(dev->irq, dev);
	close_candev(dev);

	return 0;
}

struct net_device *alloc_c_can_dev(void)
{
	struct net_device *dev;
	struct c_can_priv *priv;

	dev = alloc_candev(sizeof(struct c_can_priv), C_CAN_MSG_OBJ_TX_NUM);
	if (!dev)
		return NULL;

	priv = netdev_priv(dev);
	netif_napi_add(dev, &priv->napi, c_can_poll, C_CAN_NAPI_WEIGHT);

	priv->dev = dev;
	priv->can.bittiming_const = &c_can_bittiming_const;
	priv->can.do_set_mode = c_can_set_mode;
	priv->can.do_get_berr_counter = c_can_get_berr_counter;
	priv->can.ctrlmode_supported = CAN_CTRLMODE_LOOPBACK |
					CAN_CTRLMODE_LISTENONLY |
					CAN_CTRLMODE_BERR_REPORTING;

	return dev;
}
EXPORT_SYMBOL_GPL(alloc_c_can_dev);

void free_c_can_dev(struct net_device *dev)
{
	free_candev(dev);
}
EXPORT_SYMBOL_GPL(free_c_can_dev);

static const struct net_device_ops c_can_netdev_ops = {
	.ndo_open = c_can_open,
	.ndo_stop = c_can_close,
	.ndo_start_xmit = c_can_start_xmit,
};

int register_c_can_dev(struct net_device *dev)
{
	dev->flags |= IFF_ECHO;	/* we support local echo */
	dev->netdev_ops = &c_can_netdev_ops;

	return register_candev(dev);
}
EXPORT_SYMBOL_GPL(register_c_can_dev);

void unregister_c_can_dev(struct net_device *dev)
{
	struct c_can_priv *priv = netdev_priv(dev);

	/* disable all interrupts */
	c_can_enable_all_interrupts(priv, DISABLE_ALL_INTERRUPTS);

	unregister_candev(dev);
}
EXPORT_SYMBOL_GPL(unregister_c_can_dev);

MODULE_AUTHOR("Bhupesh Sharma <bhupesh.sharma@st.com>");
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("CAN bus driver for Bosch C_CAN controller");