aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/usb/musb/cppi_dma.c
blob: ef2332a9941dec7a39c25d52a69b4fce3943771d (plain) (blame)
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
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
/*
 * Copyright (C) 2005-2006 by Texas Instruments
 *
 * This file implements a DMA  interface using TI's CPPI DMA.
 * For now it's DaVinci-only, but CPPI isn't specific to DaVinci or USB.
 * The TUSB6020, using VLYNQ, has CPPI that looks much like DaVinci.
 */

#include <linux/platform_device.h>
#include <linux/usb.h>

#include "musb_core.h"
#include "musb_debug.h"
#include "cppi_dma.h"


/* CPPI DMA status 7-mar-2006:
 *
 * - See musb_{host,gadget}.c for more info
 *
 * - Correct RX DMA generally forces the engine into irq-per-packet mode,
 *   which can easily saturate the CPU under non-mass-storage loads.
 *
 * NOTES 24-aug-2006 (2.6.18-rc4):
 *
 * - peripheral RXDMA wedged in a test with packets of length 512/512/1.
 *   evidently after the 1 byte packet was received and acked, the queue
 *   of BDs got garbaged so it wouldn't empty the fifo.  (rxcsr 0x2003,
 *   and RX DMA0: 4 left, 80000000 8feff880, 8feff860 8feff860; 8f321401
 *   004001ff 00000001 .. 8feff860)  Host was just getting NAKed on tx
 *   of its next (512 byte) packet.  IRQ issues?
 *
 * REVISIT:  the "transfer DMA" glue between CPPI and USB fifos will
 * evidently also directly update the RX and TX CSRs ... so audit all
 * host and peripheral side DMA code to avoid CSR access after DMA has
 * been started.
 */

/* REVISIT now we can avoid preallocating these descriptors; or
 * more simply, switch to a global freelist not per-channel ones.
 * Note: at full speed, 64 descriptors == 4K bulk data.
 */
#define NUM_TXCHAN_BD       64
#define NUM_RXCHAN_BD       64

static inline void cpu_drain_writebuffer(void)
{
	wmb();
#ifdef	CONFIG_CPU_ARM926T
	/* REVISIT this "should not be needed",
	 * but lack of it sure seemed to hurt ...
	 */
	asm("mcr p15, 0, r0, c7, c10, 4 @ drain write buffer\n");
#endif
}

static inline struct cppi_descriptor *cppi_bd_alloc(struct cppi_channel *c)
{
	struct cppi_descriptor	*bd = c->freelist;

	if (bd)
		c->freelist = bd->next;
	return bd;
}

static inline void
cppi_bd_free(struct cppi_channel *c, struct cppi_descriptor *bd)
{
	if (!bd)
		return;
	bd->next = c->freelist;
	c->freelist = bd;
}

/*
 *  Start DMA controller
 *
 *  Initialize the DMA controller as necessary.
 */

/* zero out entire rx state RAM entry for the channel */
static void cppi_reset_rx(struct cppi_rx_stateram __iomem *rx)
{
	musb_writel(&rx->rx_skipbytes, 0, 0);
	musb_writel(&rx->rx_head, 0, 0);
	musb_writel(&rx->rx_sop, 0, 0);
	musb_writel(&rx->rx_current, 0, 0);
	musb_writel(&rx->rx_buf_current, 0, 0);
	musb_writel(&rx->rx_len_len, 0, 0);
	musb_writel(&rx->rx_cnt_cnt, 0, 0);
}

/* zero out entire tx state RAM entry for the channel */
static void cppi_reset_tx(struct cppi_tx_stateram __iomem *tx, u32 ptr)
{
	musb_writel(&tx->tx_head, 0, 0);
	musb_writel(&tx->tx_buf, 0, 0);
	musb_writel(&tx->tx_current, 0, 0);
	musb_writel(&tx->tx_buf_current, 0, 0);
	musb_writel(&tx->tx_info, 0, 0);
	musb_writel(&tx->tx_rem_len, 0, 0);
	/* musb_writel(&tx->tx_dummy, 0, 0); */
	musb_writel(&tx->tx_complete, 0, ptr);
}

static void __init cppi_pool_init(struct cppi *cppi, struct cppi_channel *c)
{
	int	j;

	/* initialize channel fields */
	c->head = NULL;
	c->tail = NULL;
	c->last_processed = NULL;
	c->channel.status = MUSB_DMA_STATUS_UNKNOWN;
	c->controller = cppi;
	c->is_rndis = 0;
	c->freelist = NULL;

	/* build the BD Free list for the channel */
	for (j = 0; j < NUM_TXCHAN_BD + 1; j++) {
		struct cppi_descriptor	*bd;
		dma_addr_t		dma;

		bd = dma_pool_alloc(cppi->pool, GFP_KERNEL, &dma);
		bd->dma = dma;
		cppi_bd_free(c, bd);
	}
}

static int cppi_channel_abort(struct dma_channel *);

static void cppi_pool_free(struct cppi_channel *c)
{
	struct cppi		*cppi = c->controller;
	struct cppi_descriptor	*bd;

	(void) cppi_channel_abort(&c->channel);
	c->channel.status = MUSB_DMA_STATUS_UNKNOWN;
	c->controller = NULL;

	/* free all its bds */
	bd = c->last_processed;
	do {
		if (bd)
			dma_pool_free(cppi->pool, bd, bd->dma);
		bd = cppi_bd_alloc(c);
	} while (bd);
	c->last_processed = NULL;
}

static int __init cppi_controller_start(struct dma_controller *c)
{
	struct cppi	*controller;
	void __iomem	*tibase;
	int		i;

	controller = container_of(c, struct cppi, controller);

	/* do whatever is necessary to start controller */
	for (i = 0; i < ARRAY_SIZE(controller->tx); i++) {
		controller->tx[i].transmit = true;
		controller->tx[i].index = i;
	}
	for (i = 0; i < ARRAY_SIZE(controller->rx); i++) {
		controller->rx[i].transmit = false;
		controller->rx[i].index = i;
	}

	/* setup BD list on a per channel basis */
	for (i = 0; i < ARRAY_SIZE(controller->tx); i++)
		cppi_pool_init(controller, controller->tx + i);
	for (i = 0; i < ARRAY_SIZE(controller->rx); i++)
		cppi_pool_init(controller, controller->rx + i);

	tibase =  controller->tibase;
	INIT_LIST_HEAD(&controller->tx_complete);

	/* initialise tx/rx channel head pointers to zero */
	for (i = 0; i < ARRAY_SIZE(controller->tx); i++) {
		struct cppi_channel	*tx_ch = controller->tx + i;
		struct cppi_tx_stateram __iomem *tx;

		INIT_LIST_HEAD(&tx_ch->tx_complete);

		tx = tibase + DAVINCI_TXCPPI_STATERAM_OFFSET(i);
		tx_ch->state_ram = tx;
		cppi_reset_tx(tx, 0);
	}
	for (i = 0; i < ARRAY_SIZE(controller->rx); i++) {
		struct cppi_channel	*rx_ch = controller->rx + i;
		struct cppi_rx_stateram __iomem *rx;

		INIT_LIST_HEAD(&rx_ch->tx_complete);

		rx = tibase + DAVINCI_RXCPPI_STATERAM_OFFSET(i);
		rx_ch->state_ram = rx;
		cppi_reset_rx(rx);
	}

	/* enable individual cppi channels */
	musb_writel(tibase, DAVINCI_TXCPPI_INTENAB_REG,
			DAVINCI_DMA_ALL_CHANNELS_ENABLE);
	musb_writel(tibase, DAVINCI_RXCPPI_INTENAB_REG,
			DAVINCI_DMA_ALL_CHANNELS_ENABLE);

	/* enable tx/rx CPPI control */
	musb_writel(tibase, DAVINCI_TXCPPI_CTRL_REG, DAVINCI_DMA_CTRL_ENABLE);
	musb_writel(tibase, DAVINCI_RXCPPI_CTRL_REG, DAVINCI_DMA_CTRL_ENABLE);

	/* disable RNDIS mode, also host rx RNDIS autorequest */
	musb_writel(tibase, DAVINCI_RNDIS_REG, 0);
	musb_writel(tibase, DAVINCI_AUTOREQ_REG, 0);

	return 0;
}

/*
 *  Stop DMA controller
 *
 *  De-Init the DMA controller as necessary.
 */

static int cppi_controller_stop(struct dma_controller *c)
{
	struct cppi		*controller;
	void __iomem		*tibase;
	int			i;

	controller = container_of(c, struct cppi, controller);

	tibase = controller->tibase;
	/* DISABLE INDIVIDUAL CHANNEL Interrupts */
	musb_writel(tibase, DAVINCI_TXCPPI_INTCLR_REG,
			DAVINCI_DMA_ALL_CHANNELS_ENABLE);
	musb_writel(tibase, DAVINCI_RXCPPI_INTCLR_REG,
			DAVINCI_DMA_ALL_CHANNELS_ENABLE);

	DBG(1, "Tearing down RX and TX Channels\n");
	for (i = 0; i < ARRAY_SIZE(controller->tx); i++) {
		/* FIXME restructure of txdma to use bds like rxdma */
		controller->tx[i].last_processed = NULL;
		cppi_pool_free(controller->tx + i);
	}
	for (i = 0; i < ARRAY_SIZE(controller->rx); i++)
		cppi_pool_free(controller->rx + i);

	/* in Tx Case proper teardown is supported. We resort to disabling
	 * Tx/Rx CPPI after cleanup of Tx channels. Before TX teardown is
	 * complete TX CPPI cannot be disabled.
	 */
	/*disable tx/rx cppi */
	musb_writel(tibase, DAVINCI_TXCPPI_CTRL_REG, DAVINCI_DMA_CTRL_DISABLE);
	musb_writel(tibase, DAVINCI_RXCPPI_CTRL_REG, DAVINCI_DMA_CTRL_DISABLE);

	return 0;
}

/* While dma channel is allocated, we only want the core irqs active
 * for fault reports, otherwise we'd get irqs that we don't care about.
 * Except for TX irqs, where dma done != fifo empty and reusable ...
 *
 * NOTE: docs don't say either way, but irq masking **enables** irqs.
 *
 * REVISIT same issue applies to pure PIO usage too, and non-cppi dma...
 */
static inline void core_rxirq_disable(void __iomem *tibase, unsigned epnum)
{
	musb_writel(tibase, DAVINCI_USB_INT_MASK_CLR_REG, 1 << (epnum + 8));
}

static inline void core_rxirq_enable(void __iomem *tibase, unsigned epnum)
{
	musb_writel(tibase, DAVINCI_USB_INT_MASK_SET_REG, 1 << (epnum + 8));
}


/*
 * Allocate a CPPI Channel for DMA.  With CPPI, channels are bound to
 * each transfer direction of a non-control endpoint, so allocating
 * (and deallocating) is mostly a way to notice bad housekeeping on
 * the software side.  We assume the irqs are always active.
 */
static struct dma_channel *
cppi_channel_allocate(struct dma_controller *c,
		struct musb_hw_ep *ep, u8 transmit)
{
	struct cppi		*controller;
	u8			index;
	struct cppi_channel	*cppi_ch;
	void __iomem		*tibase;

	controller = container_of(c, struct cppi, controller);
	tibase = controller->tibase;

	/* ep0 doesn't use DMA; remember cppi indices are 0..N-1 */
	index = ep->epnum - 1;

	/* return the corresponding CPPI Channel Handle, and
	 * probably disable the non-CPPI irq until we need it.
	 */
	if (transmit) {
		if (index >= ARRAY_SIZE(controller->tx)) {
			DBG(1, "no %cX%d CPPI channel\n", 'T', index);
			return NULL;
		}
		cppi_ch = controller->tx + index;
	} else {
		if (index >= ARRAY_SIZE(controller->rx)) {
			DBG(1, "no %cX%d CPPI channel\n", 'R', index);
			return NULL;
		}
		cppi_ch = controller->rx + index;
		core_rxirq_disable(tibase, ep->epnum);
	}

	/* REVISIT make this an error later once the same driver code works
	 * with the other DMA engine too
	 */
	if (cppi_ch->hw_ep)
		DBG(1, "re-allocating DMA%d %cX channel %p\n",
				index, transmit ? 'T' : 'R', cppi_ch);
	cppi_ch->hw_ep = ep;
	cppi_ch->channel.status = MUSB_DMA_STATUS_FREE;

	DBG(4, "Allocate CPPI%d %cX\n", index, transmit ? 'T' : 'R');
	return &cppi_ch->channel;
}

/* Release a CPPI Channel.  */
static void cppi_channel_release(struct dma_channel *channel)
{
	struct cppi_channel	*c;
	void __iomem		*tibase;

	/* REVISIT:  for paranoia, check state and abort if needed... */

	c = container_of(channel, struct cppi_channel, channel);
	tibase = c->controller->tibase;
	if (!c->hw_ep)
		DBG(1, "releasing idle DMA channel %p\n", c);
	else if (!c->transmit)
		core_rxirq_enable(tibase, c->index + 1);

	/* for now, leave its cppi IRQ enabled (we won't trigger it) */
	c->hw_ep = NULL;
	channel->status = MUSB_DMA_STATUS_UNKNOWN;
}

/* Context: controller irqlocked */
static void
cppi_dump_rx(int level, struct cppi_channel *c, const char *tag)
{
	void __iomem			*base = c->controller->mregs;
	struct cppi_rx_stateram __iomem	*rx = c->state_ram;

	musb_ep_select(base, c->index + 1);

	DBG(level, "RX DMA%d%s: %d left, csr %04x, "
			"%08x H%08x S%08x C%08x, "
			"B%08x L%08x %08x .. %08x"
			"\n",
		c->index, tag,
		musb_readl(c->controller->tibase,
			DAVINCI_RXCPPI_BUFCNT0_REG + 4 * c->index),
		musb_readw(c->hw_ep->regs, MUSB_RXCSR),

		musb_readl(&rx->rx_skipbytes, 0),
		musb_readl(&rx->rx_head, 0),
		musb_readl(&rx->rx_sop, 0),
		musb_readl(&rx->rx_current, 0),

		musb_readl(&rx->rx_buf_current, 0),
		musb_readl(&rx->rx_len_len, 0),
		musb_readl(&rx->rx_cnt_cnt, 0),
		musb_readl(&rx->rx_complete, 0)
		);
}

/* Context: controller irqlocked */
static void
cppi_dump_tx(int level, struct cppi_channel *c, const char *tag)
{
	void __iomem			*base = c->controller->mregs;
	struct cppi_tx_stateram __iomem	*tx = c->state_ram;

	musb_ep_select(base, c->index + 1);

	DBG(level, "TX DMA%d%s: csr %04x, "
			"H%08x S%08x C%08x %08x, "
			"F%08x L%08x .. %08x"
			"\n",
		c->index, tag,
		musb_readw(c->hw_ep->regs, MUSB_TXCSR),

		musb_readl(&tx->tx_head, 0),
		musb_readl(&tx->tx_buf, 0),
		musb_readl(&tx->tx_current, 0),
		musb_readl(&tx->tx_buf_current, 0),

		musb_readl(&tx->tx_info, 0),
		musb_readl(&tx->tx_rem_len, 0),
		/* dummy/unused word 6 */
		musb_readl(&tx->tx_complete, 0)
		);
}

/* Context: controller irqlocked */
static inline void
cppi_rndis_update(struct cppi_channel *c, int is_rx,
		void __iomem *tibase, int is_rndis)
{
	/* we may need to change the rndis flag for this cppi channel */
	if (c->is_rndis != is_rndis) {
		u32	value = musb_readl(tibase, DAVINCI_RNDIS_REG);
		u32	temp = 1 << (c->index);

		if (is_rx)
			temp <<= 16;
		if (is_rndis)
			value |= temp;
		else
			value &= ~temp;
		musb_writel(tibase, DAVINCI_RNDIS_REG, value);
		c->is_rndis = is_rndis;
	}
}

#ifdef CONFIG_USB_MUSB_DEBUG
static void cppi_dump_rxbd(const char *tag, struct cppi_descriptor *bd)
{
	pr_debug("RXBD/%s %08x: "
			"nxt %08x buf %08x off.blen %08x opt.plen %08x\n",
			tag, bd->dma,
			bd->hw_next, bd->hw_bufp, bd->hw_off_len,
			bd->hw_options);
}
#endif

static void cppi_dump_rxq(int level, const char *tag, struct cppi_channel *rx)
{
#ifdef CONFIG_USB_MUSB_DEBUG
	struct cppi_descriptor	*bd;

	if (!_dbg_level(level))
		return;
	cppi_dump_rx(level, rx, tag);
	if (rx->last_processed)
		cppi_dump_rxbd("last", rx->last_processed);
	for (bd = rx->head; bd; bd = bd->next)
		cppi_dump_rxbd("active", bd);
#endif
}


/* NOTE:  DaVinci autoreq is ignored except for host side "RNDIS" mode RX;
 * so we won't ever use it (see "CPPI RX Woes" below).
 */
static inline int cppi_autoreq_update(struct cppi_channel *rx,
		void __iomem *tibase, int onepacket, unsigned n_bds)
{
	u32	val;

#ifdef	RNDIS_RX_IS_USABLE
	u32	tmp;
	/* assert(is_host_active(musb)) */

	/* start from "AutoReq never" */
	tmp = musb_readl(tibase, DAVINCI_AUTOREQ_REG);
	val = tmp & ~((0x3) << (rx->index * 2));

	/* HCD arranged reqpkt for packet #1.  we arrange int
	 * for all but the last one, maybe in two segments.
	 */
	if (!onepacket) {
#if 0
		/* use two segments, autoreq "all" then the last "never" */
		val |= ((0x3) << (rx->index * 2));
		n_bds--;
#else
		/* one segment, autoreq "all-but-last" */
		val |= ((0x1) << (rx->index * 2));
#endif
	}

	if (val != tmp) {
		int n = 100;

		/* make sure that autoreq is updated before continuing */
		musb_writel(tibase, DAVINCI_AUTOREQ_REG, val);
		do {
			tmp = musb_readl(tibase, DAVINCI_AUTOREQ_REG);
			if (tmp == val)
				break;
			cpu_relax();
		} while (n-- > 0);
	}
#endif

	/* REQPKT is turned off after each segment */
	if (n_bds && rx->channel.actual_len) {
		void __iomem	*regs = rx->hw_ep->regs;

		val = musb_readw(regs, MUSB_RXCSR);
		if (!(val & MUSB_RXCSR_H_REQPKT)) {
			val |= MUSB_RXCSR_H_REQPKT | MUSB_RXCSR_H_WZC_BITS;
			musb_writew(regs, MUSB_RXCSR, val);
			/* flush writebufer */
			val = musb_readw(regs, MUSB_RXCSR);
		}
	}
	return n_bds;
}


/* Buffer enqueuing Logic:
 *
 *  - RX builds new queues each time, to help handle routine "early
 *    termination" cases (faults, including errors and short reads)
 *    more correctly.
 *
 *  - for now, TX reuses the same queue of BDs every time
 *
 * REVISIT long term, we want a normal dynamic model.
 * ... the goal will be to append to the
 * existing queue, processing completed "dma buffers" (segments) on the fly.
 *
 * Otherwise we force an IRQ latency between requests, which slows us a lot
 * (especially in "transparent" dma).  Unfortunately that model seems to be
 * inherent in the DMA model from the Mentor code, except in the rare case
 * of transfers big enough (~128+ KB) that we could append "middle" segments
 * in the TX paths.  (RX can't do this, see below.)
 *
 * That's true even in the CPPI- friendly iso case, where most urbs have
 * several small segments provided in a group and where the "packet at a time"
 * "transparent" DMA model is always correct, even on the RX side.
 */

/*
 * CPPI TX:
 * ========
 * TX is a lot more reasonable than RX; it doesn't need to run in
 * irq-per-packet mode very often.  RNDIS mode seems to behave too
 * (except how it handles the exactly-N-packets case).  Building a
 * txdma queue with multiple requests (urb or usb_request) looks
 * like it would work ... but fault handling would need much testing.
 *
 * The main issue with TX mode RNDIS relates to transfer lengths that
 * are an exact multiple of the packet length.  It appears that there's
 * a hiccup in that case (maybe the DMA completes before the ZLP gets
 * written?) boiling down to not being able to rely on CPPI writing any
 * terminating zero length packet before the next transfer is written.
 * So that's punted to PIO; better yet, gadget drivers can avoid it.
 *
 * Plus, there's allegedly an undocumented constraint that rndis transfer
 * length be a multiple of 64 bytes ... but the chip doesn't act that
 * way, and we really don't _want_ that behavior anyway.
 *
 * On TX, "transparent" mode works ... although experiments have shown
 * problems trying to use the SOP/EOP bits in different USB packets.
 *
 * REVISIT try to handle terminating zero length packets using CPPI
 * instead of doing it by PIO after an IRQ.  (Meanwhile, make Ethernet
 * links avoid that issue by forcing them to avoid zlps.)
 */
static void
cppi_next_tx_segment(struct musb *musb, struct cppi_channel *tx)
{
	unsigned		maxpacket = tx->maxpacket;
	dma_addr_t		addr = tx->buf_dma + tx->offset;
	size_t			length = tx->buf_len - tx->offset;
	struct cppi_descriptor	*bd;
	unsigned		n_bds;
	unsigned		i;
	struct cppi_tx_stateram	__iomem *tx_ram = tx->state_ram;
	int			rndis;

	/* TX can use the CPPI "rndis" mode, where we can probably fit this
	 * transfer in one BD and one IRQ.  The only time we would NOT want
	 * to use it is when hardware constraints prevent it, or if we'd
	 * trigger the "send a ZLP?" confusion.
	 */
	rndis = (maxpacket & 0x3f) == 0
		&& length > maxpacket
		&& length < 0xffff
		&& (length % maxpacket) != 0;

	if (rndis) {
		maxpacket = length;
		n_bds = 1;
	} else {
		n_bds = length / maxpacket;
		if (!length || (length % maxpacket))
			n_bds++;
		n_bds = min(n_bds, (unsigned) NUM_TXCHAN_BD);
		length = min(n_bds * maxpacket, length);
	}

	DBG(4, "TX DMA%d, pktSz %d %s bds %d dma 0x%x len %u\n",
			tx->index,
			maxpacket,
			rndis ? "rndis" : "transparent",
			n_bds,
			addr, length);

	cppi_rndis_update(tx, 0, musb->ctrl_base, rndis);

	/* assuming here that channel_program is called during
	 * transfer initiation ... current code maintains state
	 * for one outstanding request only (no queues, not even
	 * the implicit ones of an iso urb).
	 */

	bd = tx->freelist;
	tx->head = bd;
	tx->last_processed = NULL;

	/* FIXME use BD pool like RX side does, and just queue
	 * the minimum number for this request.
	 */

	/* Prepare queue of BDs first, then hand it to hardware.
	 * All BDs except maybe the last should be of full packet
	 * size; for RNDIS there _is_ only that last packet.
	 */
	for (i = 0; i < n_bds; ) {
		if (++i < n_bds && bd->next)
			bd->hw_next = bd->next->dma;
		else
			bd->hw_next = 0;

		bd->hw_bufp = tx->buf_dma + tx->offset;

		/* FIXME set EOP only on the last packet,
		 * SOP only on the first ... avoid IRQs
		 */
		if ((tx->offset + maxpacket) <= tx->buf_len) {
			tx->offset += maxpacket;
			bd->hw_off_len = maxpacket;
			bd->hw_options = CPPI_SOP_SET | CPPI_EOP_SET
				| CPPI_OWN_SET | maxpacket;
		} else {
			/* only this one may be a partial USB Packet */
			u32		partial_len;

			partial_len = tx->buf_len - tx->offset;
			tx->offset = tx->buf_len;
			bd->hw_off_len = partial_len;

			bd->hw_options = CPPI_SOP_SET | CPPI_EOP_SET
				| CPPI_OWN_SET | partial_len;
			if (partial_len == 0)
				bd->hw_options |= CPPI_ZERO_SET;
		}

		DBG(5, "TXBD %p: nxt %08x buf %08x len %04x opt %08x\n",
				bd, bd->hw_next, bd->hw_bufp,
				bd->hw_off_len, bd->hw_options);

		/* update the last BD enqueued to the list */
		tx->tail = bd;
		bd = bd->next;
	}

	/* BDs live in DMA-coherent memory, but writes might be pending */
	cpu_drain_writebuffer();

	/* Write to the HeadPtr in state RAM to trigger */
	musb_writel(&tx_ram->tx_head, 0, (u32)tx->freelist->dma);

	cppi_dump_tx(5, tx, "/S");
}

/*
 * CPPI RX Woes:
 * =============
 * Consider a 1KB bulk RX buffer in two scenarios:  (a) it's fed two 300 byte
 * packets back-to-back, and (b) it's fed two 512 byte packets back-to-back.
 * (Full speed transfers have similar scenarios.)
 *
 * The correct behavior for Linux is that (a) fills the buffer with 300 bytes,
 * and the next packet goes into a buffer that's queued later; while (b) fills
 * the buffer with 1024 bytes.  How to do that with CPPI?
 *
 * - RX queues in "rndis" mode -- one single BD -- handle (a) correctly, but
 *   (b) loses **BADLY** because nothing (!) happens when that second packet
 *   fills the buffer, much less when a third one arrives.  (Which makes this
 *   not a "true" RNDIS mode.  In the RNDIS protocol short-packet termination
 *   is optional, and it's fine if peripherals -- not hosts! -- pad messages
 *   out to end-of-buffer.  Standard PCI host controller DMA descriptors
 *   implement that mode by default ... which is no accident.)
 *
 * - RX queues in "transparent" mode -- two BDs with 512 bytes each -- have
 *   converse problems:  (b) is handled right, but (a) loses badly.  CPPI RX
 *   ignores SOP/EOP markings and processes both of those BDs; so both packets
 *   are loaded into the buffer (with a 212 byte gap between them), and the next
 *   buffer queued will NOT get its 300 bytes of data. (It seems like SOP/EOP
 *   are intended as outputs for RX queues, not inputs...)
 *
 * - A variant of "transparent" mode -- one BD at a time -- is the only way to
 *   reliably make both cases work, with software handling both cases correctly
 *   and at the significant penalty of needing an IRQ per packet.  (The lack of
 *   I/O overlap can be slightly ameliorated by enabling double buffering.)
 *
 * So how to get rid of IRQ-per-packet?  The transparent multi-BD case could
 * be used in special cases like mass storage, which sets URB_SHORT_NOT_OK
 * (or maybe its peripheral side counterpart) to flag (a) scenarios as errors
 * with guaranteed driver level fault recovery and scrubbing out what's left
 * of that garbaged datastream.
 *
 * But there seems to be no way to identify the cases where CPPI RNDIS mode
 * is appropriate -- which do NOT include RNDIS host drivers, but do include
 * the CDC Ethernet driver! -- and the documentation is incomplete/wrong.
 * So we can't _ever_ use RX RNDIS mode ... except by using a heuristic
 * that applies best on the peripheral side (and which could fail rudely).
 *
 * Leaving only "transparent" mode; we avoid multi-bd modes in almost all
 * cases other than mass storage class.  Otherwise we're correct but slow,
 * since CPPI penalizes our need for a "true RNDIS" default mode.
 */


/* Heuristic, intended to kick in for ethernet/rndis peripheral ONLY
 *
 * IFF
 *  (a)	peripheral mode ... since rndis peripherals could pad their
 *	writes to hosts, causing i/o failure; or we'd have to cope with
 *	a largely unknowable variety of host side protocol variants
 *  (b)	and short reads are NOT errors ... since full reads would
 *	cause those same i/o failures
 *  (c)	and read length is
 *	- less than 64KB (max per cppi descriptor)
 *	- not a multiple of 4096 (g_zero default, full reads typical)
 *	- N (>1) packets long, ditto (full reads not EXPECTED)
 * THEN
 *   try rx rndis mode
 *
 * Cost of heuristic failing:  RXDMA wedges at the end of transfers that
 * fill out the whole buffer.  Buggy host side usb network drivers could
 * trigger that, but "in the field" such bugs seem to be all but unknown.
 *
 * So this module parameter lets the heuristic be disabled.  When using
 * gadgetfs, the heuristic will probably need to be disabled.
 */
static int cppi_rx_rndis = 1;

module_param(cppi_rx_rndis, bool, 0);
MODULE_PARM_DESC(cppi_rx_rndis, "enable/disable RX RNDIS heuristic");


/**
 * cppi_next_rx_segment - dma read for the next chunk of a buffer
 * @musb: the controller
 * @rx: dma channel
 * @onepacket: true unless caller treats short reads as errors, and
 *	performs fault recovery above usbcore.
 * Context: controller irqlocked
 *
 * See above notes about why we can't use multi-BD RX queues except in
 * rare cases (mass storage class), and can never use the hardware "rndis"
 * mode (since it's not a "true" RNDIS mode) with complete safety..
 *
 * It's ESSENTIAL that callers specify "onepacket" mode unless they kick in
 * code to recover from corrupted datastreams after each short transfer.
 */
static void
cppi_next_rx_segment(struct musb *musb, struct cppi_channel *rx, int onepacket)
{
	unsigned		maxpacket = rx->maxpacket;
	dma_addr_t		addr = rx->buf_dma + rx->offset;
	size_t			length = rx->buf_len - rx->offset;
	struct cppi_descriptor	*bd, *tail;
	unsigned		n_bds;
	unsigned		i;
	void __iomem		*tibase = musb->ctrl_base;
	int			is_rndis = 0;
	struct cppi_rx_stateram	__iomem *rx_ram = rx->state_ram;

	if (onepacket) {
		/* almost every USB driver, host or peripheral side */
		n_bds = 1;

		/* maybe apply the heuristic above */
		if (cppi_rx_rndis
				&& is_peripheral_active(musb)
				&& length > maxpacket
				&& (length & ~0xffff) == 0
				&& (length & 0x0fff) != 0
				&& (length & (maxpacket - 1)) == 0) {
			maxpacket = length;
			is_rndis = 1;
		}
	} else {
		/* virtually nothing except mass storage class */
		if (length > 0xffff) {
			n_bds = 0xffff / maxpacket;
			length = n_bds * maxpacket;
		} else {
			n_bds = length / maxpacket;
			if (length % maxpacket)
				n_bds++;
		}
		if (n_bds == 1)
			onepacket = 1;
		else
			n_bds = min(n_bds, (unsigned) NUM_RXCHAN_BD);
	}

	/* In host mode, autorequest logic can generate some IN tokens; it's
	 * tricky since we can't leave REQPKT set in RXCSR after the transfer
	 * finishes. So:  multipacket transfers involve two or more segments.
	 * And always at least two IRQs ... RNDIS mode is not an option.
	 */
	if (is_host_active(musb))
		n_bds = cppi_autoreq_update(rx, tibase, onepacket, n_bds);

	cppi_rndis_update(rx, 1, musb->ctrl_base, is_rndis);

	length = min(n_bds * maxpacket, length);

	DBG(4, "RX DMA%d seg, maxp %d %s bds %d (cnt %d) "
			"dma 0x%x len %u %u/%u\n",
			rx->index, maxpacket,
			onepacket
				? (is_rndis ? "rndis" : "onepacket")
				: "multipacket",
			n_bds,
			musb_readl(tibase,
				DAVINCI_RXCPPI_BUFCNT0_REG + (rx->index * 4))
					& 0xffff,
			addr, length, rx->channel.actual_len, rx->buf_len);

	/* only queue one segment at a time, since the hardware prevents
	 * correct queue shutdown after unexpected short packets
	 */
	bd = cppi_bd_alloc(rx);
	rx->head = bd;

	/* Build BDs for all packets in this segment */
	for (i = 0, tail = NULL; bd && i < n_bds; i++, tail = bd) {
		u32	bd_len;

		if (i) {
			bd = cppi_bd_alloc(rx);
			if (!bd)
				break;
			tail->next = bd;
			tail->hw_next = bd->dma;
		}
		bd->hw_next = 0;

		/* all but the last packet will be maxpacket size */
		if (maxpacket < length)
			bd_len = maxpacket;
		else
			bd_len = length;

		bd->hw_bufp = addr;
		addr += bd_len;
		rx->offset += bd_len;

		bd->hw_off_len = (0 /*offset*/ << 16) + bd_len;
		bd->buflen = bd_len;

		bd->hw_options = CPPI_OWN_SET | (i == 0 ? length : 0);
		length -= bd_len;
	}

	/* we always expect at least one reusable BD! */
	if (!tail) {
		WARNING("rx dma%d -- no BDs? need %d\n", rx->index, n_bds);
		return;
	} else if (i < n_bds)
		WARNING("rx dma%d -- only %d of %d BDs\n", rx->index, i, n_bds);

	tail->next = NULL;
	tail->hw_next = 0;

	bd = rx->head;
	rx->tail = tail;

	/* short reads and other faults should terminate this entire
	 * dma segment.  we want one "dma packet" per dma segment, not
	 * one per USB packet, terminating the whole queue at once...
	 * NOTE that current hardware seems to ignore SOP and EOP.
	 */
	bd->hw_options |= CPPI_SOP_SET;
	tail->hw_options |= CPPI_EOP_SET;

#ifdef CONFIG_USB_MUSB_DEBUG
	if (_dbg_level(5)) {
		struct cppi_descriptor	*d;

		for (d = rx->head; d; d = d->next)
			cppi_dump_rxbd("S", d);
	}
#endif

	/* in case the preceding transfer left some state... */
	tail = rx->last_processed;
	if (tail) {
		tail->next = bd;
		tail->hw_next = bd->dma;
	}

	core_rxirq_enable(tibase, rx->index + 1);

	/* BDs live in DMA-coherent memory, but writes might be pending */
	cpu_drain_writebuffer();

	/* REVISIT specs say to write this AFTER the BUFCNT register
	 * below ... but that loses badly.
	 */
	musb_writel(&rx_ram->rx_head, 0, bd->dma);

	/* bufferCount must be at least 3, and zeroes on completion
	 * unless it underflows below zero, or stops at two, or keeps
	 * growing ... grr.
	 */
	i = musb_readl(tibase,
			DAVINCI_RXCPPI_BUFCNT0_REG + (rx->index * 4))
			& 0xffff;

	if (!i)
		musb_writel(tibase,
			DAVINCI_RXCPPI_BUFCNT0_REG + (rx->index * 4),
			n_bds + 2);
	else if (n_bds > (i - 3))
		musb_writel(tibase,
			DAVINCI_RXCPPI_BUFCNT0_REG + (rx->index * 4),
			n_bds - (i - 3));

	i = musb_readl(tibase,
			DAVINCI_RXCPPI_BUFCNT0_REG + (rx->index * 4))
			& 0xffff;
	if (i < (2 + n_bds)) {
		DBG(2, "bufcnt%d underrun - %d (for %d)\n",
					rx->index, i, n_bds);
		musb_writel(tibase,
			DAVINCI_RXCPPI_BUFCNT0_REG + (rx->index * 4),
			n_bds + 2);
	}

	cppi_dump_rx(4, rx, "/S");
}

/**
 * cppi_channel_program - program channel for data transfer
 * @ch: the channel
 * @maxpacket: max packet size
 * @mode: For RX, 1 unless the usb protocol driver promised to treat
 *	all short reads as errors and kick in high level fault recovery.
 *	For TX, ignored because of RNDIS mode races/glitches.
 * @dma_addr: dma address of buffer
 * @len: length of buffer
 * Context: controller irqlocked
 */
static int cppi_channel_program(struct dma_channel *ch,
		u16 maxpacket, u8 mode,
		dma_addr_t dma_addr, u32 len)
{
	struct cppi_channel	*cppi_ch;
	struct cppi		*controller;
	struct musb		*musb;

	cppi_ch = container_of(ch, struct cppi_channel, channel);
	controller = cppi_ch->controller;
	musb = controller->musb;

	switch (ch->status) {
	case MUSB_DMA_STATUS_BUS_ABORT:
	case MUSB_DMA_STATUS_CORE_ABORT:
		/* fault irq handler should have handled cleanup */
		WARNING("%cX DMA%d not cleaned up after abort!\n",
				cppi_ch->transmit ? 'T' : 'R',
				cppi_ch->index);
		/* WARN_ON(1); */
		break;
	case MUSB_DMA_STATUS_BUSY:
		WARNING("program active channel?  %cX DMA%d\n",
				cppi_ch->transmit ? 'T' : 'R',
				cppi_ch->index);
		/* WARN_ON(1); */
		break;
	case MUSB_DMA_STATUS_UNKNOWN:
		DBG(1, "%cX DMA%d not allocated!\n",
				cppi_ch->transmit ? 'T' : 'R',
				cppi_ch->index);
		/* FALLTHROUGH */
	case MUSB_DMA_STATUS_FREE:
		break;
	}

	ch->status = MUSB_DMA_STATUS_BUSY;

	/* set transfer parameters, then queue up its first segment */
	cppi_ch->buf_dma = dma_addr;
	cppi_ch->offset = 0;
	cppi_ch->maxpacket = maxpacket;
	cppi_ch->buf_len = len;
	cppi_ch->channel.actual_len = 0;

	/* TX channel? or RX? */
	if (cppi_ch->transmit)
		cppi_next_tx_segment(musb, cppi_ch);
	else
		cppi_next_rx_segment(musb, cppi_ch, mode);

	return true;
}

static bool cppi_rx_scan(struct cppi *cppi, unsigned ch)
{
	struct cppi_channel		*rx = &cppi->rx[ch];
	struct cppi_rx_stateram __iomem	*state = rx->state_ram;
	struct cppi_descriptor		*bd;
	struct cppi_descriptor		*last = rx->last_processed;
	bool				completed = false;
	bool				acked = false;
	int				i;
	dma_addr_t			safe2ack;
	void __iomem			*regs = rx->hw_ep->regs;

	cppi_dump_rx(6, rx, "/K");

	bd = last ? last->next : rx->head;
	if (!bd)
		return false;

	/* run through all completed BDs */
	for (i = 0, safe2ack = musb_readl(&state->rx_complete, 0);
			(safe2ack || completed) && bd && i < NUM_RXCHAN_BD;
			i++, bd = bd->next) {
		u16	len;

		/* catch latest BD writes from CPPI */
		rmb();
		if (!completed && (bd->hw_options & CPPI_OWN_SET))
			break;

		DBG(5, "C/RXBD %08x: nxt %08x buf %08x "
			"off.len %08x opt.len %08x (%d)\n",
			bd->dma, bd->hw_next, bd->hw_bufp,
			bd->hw_off_len, bd->hw_options,
			rx->channel.actual_len);

		/* actual packet received length */
		if ((bd->hw_options & CPPI_SOP_SET) && !completed)
			len = bd->hw_off_len & CPPI_RECV_PKTLEN_MASK;
		else
			len = 0;

		if (bd->hw_options & CPPI_EOQ_MASK)
			completed = true;

		if (!completed && len < bd->buflen) {
			/* NOTE:  when we get a short packet, RXCSR_H_REQPKT
			 * must have been cleared, and no more DMA packets may
			 * active be in the queue... TI docs didn't say, but
			 * CPPI ignores those BDs even though OWN is still set.
			 */
			completed = true;
			DBG(3, "rx short %d/%d (%d)\n",
					len, bd->buflen,
					rx->channel.actual_len);
		}

		/* If we got here, we expect to ack at least one BD; meanwhile
		 * CPPI may completing other BDs while we scan this list...
		 *
		 * RACE: we can notice OWN cleared before CPPI raises the
		 * matching irq by writing that BD as the completion pointer.
		 * In such cases, stop scanning and wait for the irq, avoiding
		 * lost acks and states where BD ownership is unclear.
		 */
		if (bd->dma == safe2ack) {
			musb_writel(&state->rx_complete, 0, safe2ack);
			safe2ack = musb_readl(&state->rx_complete, 0);
			acked = true;
			if (bd->dma == safe2ack)
				safe2ack = 0;
		}

		rx->channel.actual_len += len;

		cppi_bd_free(rx, last);
		last = bd;

		/* stop scanning on end-of-segment */
		if (bd->hw_next == 0)
			completed = true;
	}
	rx->last_processed = last;

	/* dma abort, lost ack, or ... */
	if (!acked && last) {
		int	csr;

		if (safe2ack == 0 || safe2ack == rx->last_processed->dma)
			musb_writel(&state->rx_complete, 0, safe2ack);
		if (safe2ack == 0) {
			cppi_bd_free(rx, last);
			rx->last_processed = NULL;

			/* if we land here on the host side, H_REQPKT will
			 * be clear and we need to restart the queue...
			 */
			WARN_ON(rx->head);
		}
		musb_ep_select(cppi->mregs, rx->index + 1);
		csr = musb_readw(regs, MUSB_RXCSR);
		if (csr & MUSB_RXCSR_DMAENAB) {
			DBG(4, "list%d %p/%p, last %08x%s, csr %04x\n",
				rx->index,
				rx->head, rx->tail,
				rx->last_processed
					? rx->last_processed->dma
					: 0,
				completed ? ", completed" : "",
				csr);
			cppi_dump_rxq(4, "/what?", rx);
		}
	}
	if (!completed) {
		int	csr;

		rx->head = bd;

		/* REVISIT seems like "autoreq all but EOP" doesn't...
		 * setting it here "should" be racey, but seems to work
		 */
		csr = musb_readw(rx->hw_ep->regs, MUSB_RXCSR);
		if (is_host_active(cppi->musb)
				&& bd
				&& !(csr & MUSB_RXCSR_H_REQPKT)) {
			csr |= MUSB_RXCSR_H_REQPKT;
			musb_writew(regs, MUSB_RXCSR,
					MUSB_RXCSR_H_WZC_BITS | csr);
			csr = musb_readw(rx->hw_ep->regs, MUSB_RXCSR);
		}
	} else {
		rx->head = NULL;
		rx->tail = NULL;
	}

	cppi_dump_rx(6, rx, completed ? "/completed" : "/cleaned");
	return completed;
}

irqreturn_t cppi_interrupt(int irq, void *dev_id)
{
	struct musb		*musb = dev_id;
	struct cppi		*cppi;
	void __iomem		*tibase;
	struct musb_hw_ep	*hw_ep = NULL;
	u32			rx, tx;
	int			i, index;

	cppi = container_of(musb->dma_controller, struct cppi, controller);

	tibase = musb->ctrl_base;

	tx = musb_readl(tibase, DAVINCI_TXCPPI_MASKED_REG);
	rx = musb_readl(tibase, DAVINCI_RXCPPI_MASKED_REG);

	if (!tx && !rx)
		return IRQ_NONE;

	DBG(4, "CPPI IRQ Tx%x Rx%x\n", tx, rx);

	/* process TX channels */
	for (index = 0; tx; tx = tx >> 1, index++) {
		struct cppi_channel		*tx_ch;
		struct cppi_tx_stateram __iomem	*tx_ram;
		bool				completed = false;
		struct cppi_descriptor		*bd;

		if (!(tx & 1))
			continue;

		tx_ch = cppi->tx + index;
		tx_ram = tx_ch->state_ram;

		/* FIXME  need a cppi_tx_scan() routine, which
		 * can also be called from abort code
		 */

		cppi_dump_tx(5, tx_ch, "/E");

		bd = tx_ch->head;

		if (NULL == bd) {
			DBG(1, "null BD\n");
			continue;
		}

		/* run through all completed BDs */
		for (i = 0; !completed && bd && i < NUM_TXCHAN_BD;
				i++, bd = bd->next) {
			u16	len;

			/* catch latest BD writes from CPPI */
			rmb();
			if (bd->hw_options & CPPI_OWN_SET)
				break;

			DBG(5, "C/TXBD %p n %x b %x off %x opt %x\n",
					bd, bd->hw_next, bd->hw_bufp,
					bd->hw_off_len, bd->hw_options);

			len = bd->hw_off_len & CPPI_BUFFER_LEN_MASK;
			tx_ch->channel.actual_len += len;

			tx_ch->last_processed = bd;

			/* write completion register to acknowledge
			 * processing of completed BDs, and possibly
			 * release the IRQ; EOQ might not be set ...
			 *
			 * REVISIT use the same ack strategy as rx
			 *
			 * REVISIT have observed bit 18 set; huh??
			 */
			/* if ((bd->hw_options & CPPI_EOQ_MASK)) */
				musb_writel(&tx_ram->tx_complete, 0, bd->dma);

			/* stop scanning on end-of-segment */
			if (bd->hw_next == 0)
				completed = true;
		}

		/* on end of segment, maybe go to next one */
		if (completed) {
			/* cppi_dump_tx(4, tx_ch, "/complete"); */

			/* transfer more, or report completion */
			if (tx_ch->offset >= tx_ch->buf_len) {
				tx_ch->head = NULL;
				tx_ch->tail = NULL;
				tx_ch->channel.status = MUSB_DMA_STATUS_FREE;

				hw_ep = tx_ch->hw_ep;

				musb_dma_completion(musb, index + 1, 1);

			} else {
				/* Bigger transfer than we could fit in
				 * that first batch of descriptors...
				 */
				cppi_next_tx_segment(musb, tx_ch);
			}
		} else
			tx_ch->head = bd;
	}

	/* Start processing the RX block */
	for (index = 0; rx; rx = rx >> 1, index++) {

		if (rx & 1) {
			struct cppi_channel		*rx_ch;

			rx_ch = cppi->rx + index;

			/* let incomplete dma segments finish */
			if (!cppi_rx_scan(cppi, index))
				continue;

			/* start another dma segment if needed */
			if (rx_ch->channel.actual_len != rx_ch->buf_len
					&& rx_ch->channel.actual_len
						== rx_ch->offset) {
				cppi_next_rx_segment(musb, rx_ch, 1);
				continue;
			}

			/* all segments completed! */
			rx_ch->channel.status = MUSB_DMA_STATUS_FREE;

			hw_ep = rx_ch->hw_ep;

			core_rxirq_disable(tibase, index + 1);
			musb_dma_completion(musb, index + 1, 0);
		}
	}

	/* write to CPPI EOI register to re-enable interrupts */
	musb_writel(tibase, DAVINCI_CPPI_EOI_REG, 0);

	return IRQ_HANDLED;
}

/* Instantiate a software object representing a DMA controller. */
struct dma_controller *__init
dma_controller_create(struct musb *musb, void __iomem *mregs)
{
	struct cppi		*controller;
	struct device		*dev = musb->controller;
	struct platform_device	*pdev = to_platform_device(dev);
	int			irq = platform_get_irq(pdev, 1);

	controller = kzalloc(sizeof *controller, GFP_KERNEL);
	if (!controller)
		return NULL;

	controller->mregs = mregs;
	controller->tibase = mregs - DAVINCI_BASE_OFFSET;

	controller->musb = musb;
	controller->controller.start = cppi_controller_start;
	controller->controller.stop = cppi_controller_stop;
	controller->controller.channel_alloc = cppi_channel_allocate;
	controller->controller.channel_release = cppi_channel_release;
	controller->controller.channel_program = cppi_channel_program;
	controller->controller.channel_abort = cppi_channel_abort;

	/* NOTE: allocating from on-chip SRAM would give the least
	 * contention for memory access, if that ever matters here.
	 */

	/* setup BufferPool */
	controller->pool = dma_pool_create("cppi",
			controller->musb->controller,
			sizeof(struct cppi_descriptor),
			CPPI_DESCRIPTOR_ALIGN, 0);
	if (!controller->pool) {
		kfree(controller);
		return NULL;
	}

	if (irq > 0) {
		if (request_irq(irq, cppi_interrupt, 0, "cppi-dma", musb)) {
			dev_err(dev, "request_irq %d failed!\n", irq);
			dma_controller_destroy(&controller->controller);
			return NULL;
		}
		controller->irq = irq;
	}

	return &controller->controller;
}

/*
 *  Destroy a previously-instantiated DMA controller.
 */
void dma_controller_destroy(struct dma_controller *c)
{
	struct cppi	*cppi;

	cppi = container_of(c, struct cppi, controller);

	if (cppi->irq)
		free_irq(cppi->irq, cppi->musb);

	/* assert:  caller stopped the controller first */
	dma_pool_destroy(cppi->pool);

	kfree(cppi);
}

/*
 * Context: controller irqlocked, endpoint selected
 */
static int cppi_channel_abort(struct dma_channel *channel)
{
	struct cppi_channel	*cppi_ch;
	struct cppi		*controller;
	void __iomem		*mbase;
	void __iomem		*tibase;
	void __iomem		*regs;
	u32			value;
	struct cppi_descriptor	*queue;

	cppi_ch = container_of(channel, struct cppi_channel, channel);

	controller = cppi_ch->controller;

	switch (channel->status) {
	case MUSB_DMA_STATUS_BUS_ABORT:
	case MUSB_DMA_STATUS_CORE_ABORT:
		/* from RX or TX fault irq handler */
	case MUSB_DMA_STATUS_BUSY:
		/* the hardware needs shutting down */
		regs = cppi_ch->hw_ep->regs;
		break;
	case MUSB_DMA_STATUS_UNKNOWN:
	case MUSB_DMA_STATUS_FREE:
		return 0;
	default:
		return -EINVAL;
	}

	if (!cppi_ch->transmit && cppi_ch->head)
		cppi_dump_rxq(3, "/abort", cppi_ch);

	mbase = controller->mregs;
	tibase = controller->tibase;

	queue = cppi_ch->head;
	cppi_ch->head = NULL;
	cppi_ch->tail = NULL;

	/* REVISIT should rely on caller having done this,
	 * and caller should rely on us not changing it.
	 * peripheral code is safe ... check host too.
	 */
	musb_ep_select(mbase, cppi_ch->index + 1);

	if (cppi_ch->transmit) {
		struct cppi_tx_stateram __iomem *tx_ram;
		int			enabled;

		/* mask interrupts raised to signal teardown complete.  */
		enabled = musb_readl(tibase, DAVINCI_TXCPPI_INTENAB_REG)
				& (1 << cppi_ch->index);
		if (enabled)
			musb_writel(tibase, DAVINCI_TXCPPI_INTCLR_REG,
					(1 << cppi_ch->index));

		/* REVISIT put timeouts on these controller handshakes */

		cppi_dump_tx(6, cppi_ch, " (teardown)");

		/* teardown DMA engine then usb core */
		do {
			value = musb_readl(tibase, DAVINCI_TXCPPI_TEAR_REG);
		} while (!(value & CPPI_TEAR_READY));
		musb_writel(tibase, DAVINCI_TXCPPI_TEAR_REG, cppi_ch->index);

		tx_ram = cppi_ch->state_ram;
		do {
			value = musb_readl(&tx_ram->tx_complete, 0);
		} while (0xFFFFFFFC != value);
		musb_writel(&tx_ram->tx_complete, 0, 0xFFFFFFFC);

		/* FIXME clean up the transfer state ... here?
		 * the completion routine should get called with
		 * an appropriate status code.
		 */

		value = musb_readw(regs, MUSB_TXCSR);
		value &= ~MUSB_TXCSR_DMAENAB;
		value |= MUSB_TXCSR_FLUSHFIFO;
		musb_writew(regs, MUSB_TXCSR, value);
		musb_writew(regs, MUSB_TXCSR, value);

		/* While we scrub the TX state RAM, ensure that we clean
		 * up any interrupt that's currently asserted:
		 * 1. Write to completion Ptr value 0x1(bit 0 set)
		 *    (write back mode)
		 * 2. Write to completion Ptr value 0x0(bit 0 cleared)
		 *    (compare mode)
		 * Value written is compared(for bits 31:2) and when
		 * equal, interrupt is deasserted.
		 */
		cppi_reset_tx(tx_ram, 1);
		musb_writel(&tx_ram->tx_complete, 0, 0);

		/* re-enable interrupt */
		if (enabled)
			musb_writel(tibase, DAVINCI_TXCPPI_INTENAB_REG,
					(1 << cppi_ch->index));

		cppi_dump_tx(5, cppi_ch, " (done teardown)");

		/* REVISIT tx side _should_ clean up the same way
		 * as the RX side ... this does no cleanup at all!
		 */

	} else /* RX */ {
		u16			csr;

		/* NOTE: docs don't guarantee any of this works ...  we
		 * expect that if the usb core stops telling the cppi core
		 * to pull more data from it, then it'll be safe to flush
		 * current RX DMA state iff any pending fifo transfer is done.
		 */

		core_rxirq_disable(tibase, cppi_ch->index + 1);

		/* for host, ensure ReqPkt is never set again */
		if (is_host_active(cppi_ch->controller->musb)) {
			value = musb_readl(tibase, DAVINCI_AUTOREQ_REG);
			value &= ~((0x3) << (cppi_ch->index * 2));
			musb_writel(tibase, DAVINCI_AUTOREQ_REG, value);
		}

		csr = musb_readw(regs, MUSB_RXCSR);

		/* for host, clear (just) ReqPkt at end of current packet(s) */
		if (is_host_active(cppi_ch->controller->musb)) {
			csr |= MUSB_RXCSR_H_WZC_BITS;
			csr &= ~MUSB_RXCSR_H_REQPKT;
		} else
			csr |= MUSB_RXCSR_P_WZC_BITS;

		/* clear dma enable */
		csr &= ~(MUSB_RXCSR_DMAENAB);
		musb_writew(regs, MUSB_RXCSR, csr);
		csr = musb_readw(regs, MUSB_RXCSR);

		/* Quiesce: wait for current dma to finish (if not cleanup).
		 * We can't use bit zero of stateram->rx_sop, since that
		 * refers to an entire "DMA packet" not just emptying the
		 * current fifo.  Most segments need multiple usb packets.
		 */
		if (channel->status == MUSB_DMA_STATUS_BUSY)
			udelay(50);

		/* scan the current list, reporting any data that was
		 * transferred and acking any IRQ
		 */
		cppi_rx_scan(controller, cppi_ch->index);

		/* clobber the existing state once it's idle
		 *
		 * NOTE:  arguably, we should also wait for all the other
		 * RX channels to quiesce (how??) and then temporarily
		 * disable RXCPPI_CTRL_REG ... but it seems that we can
		 * rely on the controller restarting from state ram, with
		 * only RXCPPI_BUFCNT state being bogus.  BUFCNT will
		 * correct itself after the next DMA transfer though.
		 *
		 * REVISIT does using rndis mode change that?
		 */
		cppi_reset_rx(cppi_ch->state_ram);

		/* next DMA request _should_ load cppi head ptr */

		/* ... we don't "free" that list, only mutate it in place.  */
		cppi_dump_rx(5, cppi_ch, " (done abort)");

		/* clean up previously pending bds */
		cppi_bd_free(cppi_ch, cppi_ch->last_processed);
		cppi_ch->last_processed = NULL;

		while (queue) {
			struct cppi_descriptor	*tmp = queue->next;

			cppi_bd_free(cppi_ch, queue);
			queue = tmp;
		}
	}

	channel->status = MUSB_DMA_STATUS_FREE;
	cppi_ch->buf_dma = 0;
	cppi_ch->offset = 0;
	cppi_ch->buf_len = 0;
	cppi_ch->maxpacket = 0;
	return 0;
}

/* TBD Queries:
 *
 * Power Management ... probably turn off cppi during suspend, restart;
 * check state ram?  Clocking is presumably shared with usb core.
 */