summaryrefslogtreecommitdiffstats
path: root/c/src/lib/libbsp/m68k/mvme167/console/console.c
blob: 11b546ed0a01a0d303e83d4f6fb1b9cfb38aebc0 (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
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
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
/*
 *  console.c
 *
 *  This file contains the MVME167 termios console package. Only asynchronous
 *  I/O is supported.
 *
 *  /dev/tty0 is channel 0, Serial Port 1/Console on the MVME712M.
 *  /dev/tty1 is channel 1, Serial Port 2/TTY01 on the MVME712M.
 *  /dev/tty2 is channel 2, Serial Port 3 on the MVME712M.
 *  /dev/tty3 is channel 3, Serial Port 4 on the MVME712M.
 *
 *  Normal I/O uses DMA for output, interrupts for input. /dev/console is
 *  fixed to be /dev/tty01, Serial Port 2. Very limited support is provided
 *  for polled I/O. Polled I/O is intended only for running the RTEMS test
 *  suites. In all cases, Serial Port 1/Console is allocated to 167Bug and
 *  is the dedicated debugger port. We configure GDB to use 167Bug for
 *  debugging. When debugging with GDB or 167Bug, do not open /dev/tty00.
 *
 *  Modern I/O chips often contain a number of I/O devices that can operate
 *  almost independently of each other. Typically, in RTEMS, all devices in
 *  an I/O chip are handled by a single device driver, but that need not be
 *  always the case. Each device driver must supply six entry points in the
 *  Device Driver Table: a device initialization function, as well as an open,
 *  close, read, write and a control function. RTEMS assigns a device major
 *  number to each device driver. This major device number is the index of the
 *  device driver entries in the Device Driver Table, and it used to identify
 *  a particular device driver. To distinguish multiple I/O sub-devices within
 *  an I/O chip, RTEMS supports device minor numbers. When a I/O device is
 *  initialized, the major number is supplied to the initialization function.
 *  That function must register each sub-device with a separate name and minor
 *  number (as well as the supplied major number). When an application opens a
 *  device by name, the corresponding major and minor numbers are returned to
 *  the caller to be used in subsequent I/O operations (although these details
 *  are typically hidden within the library functions).
 *
 *  Such a scheme recognizes that the initialization of the individual
 *  sub-devices is generally not completely independent. For example, the
 *  four serial ports of the CD2401 can be configured almost independently
 *  from each other. One port could be configured to operate in asynchronous
 *  mode with interrupt-driven I/O, while another port could be configured to
 *  operate in HDLC mode with DMA I/O. However, a device reset command will
 *  reset all four channels, and the width of DMA transfers and the number of
 *  retries following bus errors selected applies to all four channels.
 *  Consequently, when initializing one channel, one must be careful not to
 *  destroy the configuration of other channels that are already configured.
 *
 *  One problem with the RTEMS I/O initialization model is that no information
 *  other than a device major number is passed to the initialization function.
 *  Consequently, the sub-devices must be initialized with some pre-determined
 *  configuration. To change the configuration of a sub-device, it is
 *  necessary to either rewrite the initialization function, or to make a
 *  series of rtems_io_control() calls after initialization. The first
 *  approach is not very elegant. The second approach is acceptable if an
 *  application is simply changing baud rates, parity or other such
 *  asynchronous parameters (as supplied by the termios package). But what if
 *  an application requires one channel to run in HDLC or Bisync mode and
 *  another in async mode? With a single driver per I/O chip approach, the
 *  device driver must support multiple protocols. This is feasible, but it
 *  often means that an application that only does asynchronous I/O now links
 *  in code for other unused protocols, thus wasting precious ROM space.
 *  Worse, it requires that the sub-devices be initialized in some
 *  configuration, and that configuration then changed through a series of
 *  device driver control calls. There is no standard API in RTEMS to switch
 *  a serial line to some synchronous protocol.
 *
 *  A better approach is to treat each channel as a separate device, each with
 *  its own device device driver. The application then supplies its own device
 *  driver table with only the required protocols (drivers) on each line. The
 *  problem with this approach is that the device drivers are not really
 *  independent, given that the I/O sub-devices within a common chip are not
 *  independent themselves. Consequently, the related device drivers must
 *  share some information. In RTEMS, there is no standard location in which
 *  to share information.
 *
 *  This driver handles all four channels, i.e. it distinguishes the
 *  sub-devices using minor device numbers. Only asynchronous I/O is
 *  supported. The console is currently fixed to be channel 1 on the CD2401,
 *  which corresponds to the TTY01 port (Serial Port 2) on the MVME712M
 *  Transition Module.
 *
 *  The CD2401 does either interrupt-driven or DMA I/O; it does not support
 *  polling. In interrupt-driven or DMA I/O modes, interrupts from the CD2401
 *  are routed to the MC68040, and the processor generates an interrupt
 *  acknowledge cycle directly to the CD2401 to obtain an interrupt vector.
 *  The PCCchip2 supports a pseudo-polling mode in which interrupts from the
 *  CD2401 are not routed to the MC68040, but can be detected by the processor
 *  by reading the appropriate CD2401 registers. In this mode, interrupt
 *  acknowledge cycles must be generated to the CD2401 by reading the
 *  appropriate PCCchip2 registers.
 *
 *  Interrupts from the four channels cannot be routed independently; either
 *  all channels are used in the pseudo-polling mode, or all channels are used
 *  in interrupt-driven/DMA mode. There is no advantage in using the speudo-
 *  polling mode. Consenquently, this driver performs DMA input and output.
 *  Output is performed directly from the termios raw output buffer, while
 *  input is accumulated into a separate buffer.
 *
 *  THIS MODULE IS NOT RE-ENTRANT! Simultaneous access to a device from
 *  multiple tasks is likely to cause significant problems! Concurrency
 *  control is implemented in the termios package.
 *
 *  THE INTERRUPT LEVEL IS SET TO 1 FOR ALL CHANNELS.
 *  If the CD2401 is to be used for high speed synchronous serial I/O, the
 *  interrupt priority might need to be increased.
 *
 *  ALL INTERRUPT HANDLERS ARE SHARED.
 *  When adding extra device drivers, either rewrite the interrupt handlers
 *  to demultiplex the interrupts, or install separate vectors. Common vectors
 *  are currently used to catch spurious interrupts. We could already have
 *  installed separate vectors for each channel and used the spurious
 *  interrupt handler defined in some other BSPs, but handling spurious
 *  interrupts from the CD2401 in this device driver allows us to record more
 *  information on the source of the interrupts. Furthermore, we have observed
 *  the occasional spurious interrupt from channel 0. We definitely do not
 *  to call a debugger for those.
 *
 *  All page references are to the MVME166/MVME167/MVME187 Single Board
 *  Computer Programmer's Reference Guide (MVME187PG/D2) with the April
 *  1993 supplements/addenda (MVME187PG/D2A1).
 *
 *  Copyright (c) 1998, National Research Council of Canada
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.com/license/LICENSE.
 */

#define M167_INIT

#include <stdarg.h>
#include <stdio.h>
#include <termios.h>
#include <rtems/termiostypes.h>
#include <bsp.h>                /* Must be before libio.h */
#include <rtems/libio.h>

/* Utility functions */
void cd2401_udelay( unsigned long delay );
void cd2401_chan_cmd( uint8_t         channel, uint8_t         cmd, uint8_t         wait );
uint16_t         cd2401_bitrate_divisor( uint32_t         clkrate, uint32_t        * bitrate );
void cd2401_initialize( void );
void cd2401_interrupts_initialize( bool enable );

/* ISRs */
rtems_isr cd2401_modem_isr( rtems_vector_number vector );
rtems_isr cd2401_re_isr( rtems_vector_number vector );
rtems_isr cd2401_rx_isr( rtems_vector_number vector );
rtems_isr cd2401_tx_isr( rtems_vector_number vector );

/* Termios callbacks */
int cd2401_firstOpen( int major, int minor, void *arg );
int cd2401_lastClose( int major, int minor, void *arg );
int cd2401_setAttributes( int minor, const struct termios *t );
int cd2401_startRemoteTx( int minor );
int cd2401_stopRemoteTx( int minor );
ssize_t cd2401_write( int minor, const char *buf, size_t len );
int cd2401_drainOutput( int minor );
int _167Bug_pollRead( int minor );
ssize_t _167Bug_pollWrite( int minor, const char *buf, size_t len );

/* Printk function */
static void _BSP_output_char( char c );
BSP_output_char_function_type BSP_output_char = _BSP_output_char;

/* '\r' character in memory. This used to live on
 * the stack but storing the '\r' character is
 * optimized away by gcc-4.3.2 (since it seems to
 * be unused [only referenced from inline assembly
 * code in _167Bug_pollWrite()]).
 * Hence we make it a global constant.
 */
static const char cr_char = '\r';

/* Channel info */
/* static */ volatile struct {
  void *tty;                    /* Really a struct rtems_termios_tty * */
  int len;                      /* Record nb of chars being TX'ed */
  const char *buf;              /* Record where DMA is coming from */
  uint32_t         spur_cnt;    /* Nb of spurious ints so far */
  uint32_t         spur_dev;    /* Indo on last spurious int */
  uint32_t         buserr_addr; /* Faulting address */
  uint32_t         buserr_type; /* Reason of bus error during DMA */
  uint8_t          own_buf_A;   /* If true, buffer A belongs to the driver */
  uint8_t          own_buf_B;   /* If true, buffer B belongs to the driver */
  uint8_t          txEmpty;     /* If true, the output FIFO should be empty */
} CD2401_Channel_Info[4];

/*
 *  The number of channels already opened. If zero, enable the interrupts. The
 *  initial value must be 0. If initialized explicitly, the variable ends up
 *  in the .data section. Its value is not re-initialized on system restart.
 *  Furthermore, because the variable is changed, the .data section would not
 *  be ROMable. We thus leave the variable uninitialized, which causes it to
 *  be allocated in the .bss section, and rely on RTEMS to zero the .bss
 *  section on every startup.
 */
uint8_t         Init_count;

/* Record previous handlers */
rtems_isr_entry Prev_re_isr;        /* Previous rx exception isr */
rtems_isr_entry Prev_rx_isr;        /* Previous rx isr */
rtems_isr_entry Prev_tx_isr;        /* Previous tx isr */
rtems_isr_entry Prev_modem_isr;     /* Previous modem/timer isr */

/* Define the following symbol to trace the calls to this driver */
/* #define CD2401_RECORD_DEBUG_INFO */
#include "console-recording.h"

/*
 *  Utility functions.
 */

/*
 *  Assumes that clock ticks 1 million times per second.
 *
 *  MAXIMUM DELAY IS ABOUT 20 ms
 *
 *  Input parameters:
 *    delay: Number of microseconds to delay.
 *
 *  Output parameters: NONE
 *
 *  Return values: NONE
 */
 void cd2401_udelay
(
  unsigned long delay
)
{
  unsigned long i = 20000;  /* In case clock is off */
  rtems_interval ticks_per_second, start_ticks, end_ticks, current_ticks;

  ticks_per_second = rtems_clock_get_ticks_per_second();
  start_ticks = rtems_clock_get_ticks_since_boot();
  end_ticks = start_ticks + delay;

  do {
    current_ticks = rtems_clock_get_ticks_since_boot();
  } while ( --i && (current_ticks <= end_ticks) );

  CD2401_RECORD_DELAY_INFO(( start_ticks, end_ticks, current_ticks, i ));
}

/*
 *  cd2401_chan_cmd
 *
 *  Sends a CCR command to the specified channel. Waits for any unfinished
 *  previous command to complete, then sends the specified command. Optionally
 *  wait for the current command to finish before returning.
 *
 *  Input parameters:
 *    channel - CD2401 channel number
 *    cmd  - command byte
 *    wait - if non-zero, wait for specified command to complete before
 *          returning.
 *
 *  Output parameters: NONE
 *
 *  Return values: NONE
 */
void cd2401_chan_cmd(
  uint8_t         channel,
  uint8_t         cmd,
  uint8_t         wait
)
{
  if ( channel < 4 ) {
    cd2401->car = channel;      /* Select channel */

    while ( cd2401->ccr != 0 ); /* Wait for completion of previous command */
    cd2401->ccr = cmd;          /* Send command */
    if ( wait )
      while( cd2401->ccr != 0 );/* Wait for completion */
  }
  else {
    /* This may not be the best error message */
    rtems_fatal_error_occurred( RTEMS_INVALID_NUMBER );
  }
}

/*
 *  cd2401_bitrate_divisor
 *
 *  Compute the divisor and clock source to use to obtain the desired bitrate.
 *
 *  Input parameters:
 *    clkrate - system clock rate (CLK input frequency)
 *    bitrate - the desired bitrate
 *
 *  Output parameters:
 *    bitrate - The actual bitrate achievable, to the nearest bps.
 *
 *  Return values:
 *    Returns divisor in lower byte and clock source in upper byte for the
 *    specified bitrate.
 */
uint16_t         cd2401_bitrate_divisor(
  uint32_t         clkrate,
  uint32_t        * bitrate
)
{
  uint32_t         divisor;
  uint16_t         clksource;

  divisor = *bitrate << 3;          /* temporary; multiply by 8 for CLK/8 */
  divisor = (clkrate + (divisor>>1)) / divisor; /* divisor for clk0 (CLK/8) */

  /* Use highest speed clock source for best precision - try clk0 to clk4 */
  for( clksource = 0; clksource < 0x0400 && divisor > 0x100; clksource += 0x0100 )
      divisor >>= 2;
  divisor--;                        /* adjustment, see specs */
  if( divisor < 1 )
    divisor = 1;
  else if( divisor > 0xFF )
    divisor = 0xFF;
  *bitrate = clkrate / (1 << ((clksource >> 7)+3)) / (divisor+1);
  return( clksource | divisor );
}

/*
 *  cd2401_initialize
 *
 *  Initializes the CD2401 device. Individual channels on the chip are left in
 *  their default reset state, and should be subsequently configured.
 *
 *  Input parameters: NONE
 *
 *  Output parameters:  NONE
 *
 *  Return values: NONE
 */
void cd2401_initialize( void )
{
  int i;

  for ( i = 3; i >= 0; i-- ) {
    CD2401_Channel_Info[i].tty = NULL;
    CD2401_Channel_Info[i].len = 0;
    CD2401_Channel_Info[i].buf = NULL;
    CD2401_Channel_Info[i].spur_cnt = 0;
    CD2401_Channel_Info[i].spur_dev = 0;
    CD2401_Channel_Info[i].buserr_type = 0;
    CD2401_Channel_Info[i].buserr_addr = 0;
    CD2401_Channel_Info[i].own_buf_A = TRUE;
    CD2401_Channel_Info[i].own_buf_B = TRUE;
    CD2401_Channel_Info[i].txEmpty = TRUE;
  }

 /*
  *  Normally, do a device reset here. If we do it, we will most likely clober
  *  the port settings for 167Bug on channel 0. So we just shut up all the
  *  ports by disabling their interrupts.
  */
#if 0
  cd2401->gfrcr = 0;            /* So we can detect that device init is done */
  cd2401_chan_cmd( 0x10, 0);    /* Reset all */
  while(cd2401->gfrcr == 0);    /* Wait for reset all */
#endif

  /*
   *  The CL-CD2400/2401 manual (part no 542400-003) states on page 87 that
   *  the LICR "contains the number of the interrupting channel being served.
   *  The channel number is always that of the current acknowledged interrupt."
   *  THE USER MUST PROGRAM CHANNEL NUMBER IN LICR! It is not set automatically
   *  by the hardware, as suggested by the manual.
   *
   *  The updated manual (part no 542400-007) has the story straight. The
   *  CD2401 automatically initializes the LICR to contain the channel number
   *  in bits 2 and 3. However, these bits are not preserved when the user
   *  defined bits are written.
   *
   *  The same vector number is used for all four channels. Different vector
   *  numbers could be programmed for each channel, thus avoiding the need to
   *  demultiplex the interrupts in the ISR.
   */
  for ( i = 0; i < 4; i++ ) {
    cd2401->car = i;            /* Select channel */
    cd2401->livr = 0x5C;        /* Motorola suggested value p. 3-15 */
    cd2401->licr = i << 2;      /* Don't rely on reset value */
    cd2401->ier = 0;            /* Disable all interrupts */
  }

  /*
   *  The content of the CD2401 xpilr registers must match the A7-A0 addresses
   *  generated by the PCCchip2 during interrupt acknowledge cycles in order
   *  for the CD2401 to recognize the IACK cycle and clear its interrupt
   *  request.
   */
  cd2401->mpilr = 0x01;         /* Match pccchip2->modem_piack p. 3-27 */
  cd2401->tpilr = 0x02;         /* Match pccchip2->tx_piack p. 3-28 */
  cd2401->rpilr = 0x03;         /* Match pccchip2->rx_piack p. 3-29 */

  /* Global CD2401 registers */
  cd2401->dmr = 0;              /* 16-bit DMA transfers when possible */
  cd2401->bercnt = 0;           /* Do not retry DMA upon bus errors */

  /*
   *  Setup timer prescaler period, which clocks timers 1 and 2 (or rx timeout
   *  and tx delay). The prescaler is clocked by the system clock) / 2048. The
   *  register must be in the range 0x0A..0xFF, ie. a rescaler period range of
   *  about 1ms..26ms for a nominal system clock rate  of 20MHz.
   */
  cd2401->tpr  = 0x0A;          /* Same value as 167Bug */
}

/*
 *  cd2401_interrupts_initialize
 *
 *  This routine enables or disables the CD2401 interrupts to the MC68040.
 *  Interrupts cannot be enabled/disabled on a per-channel basis.
 *
 *  Input parameters:
 *    enable - if true, enable the interrupts, else disable them.
 *
 *  Output parameters:  NONE
 *
 *  Return values: NONE
 *
 *  THE FIRST CD2401 CHANNEL OPENED SHOULD ENABLE INTERRUPTS.
 *  THE LAST CD2401 CHANNEL CLOSED SHOULD DISABLE INTERRUPTS.
 */
void cd2401_interrupts_initialize(
  bool enable
)
{
  if ( enable ) {
   /*
    *  Enable interrupts from the CD2401 in the PCCchip2.
    *  During DMA transfers, the MC68040 supplies dirty data during read cycles
    *  from the CD2401 and leaves the data dirty in its data cache if there is
    *  a cache hit. The MC68040 updates the data cache during write cycles from
    *  the CD2401 if there is a cache hit.
    */
    pccchip2->SCC_error = 0x01;
    pccchip2->SCC_modem_int_ctl = 0x10 | CD2401_INT_LEVEL;
    pccchip2->SCC_tx_int_ctl = 0x10 | CD2401_INT_LEVEL;
    pccchip2->SCC_rx_int_ctl = 0x50 | CD2401_INT_LEVEL;

    pccchip2->gen_control |= 0x02;      /* Enable pccchip2 interrupts */
  }
  else {
    /* Disable interrupts */
    pccchip2->SCC_modem_int_ctl &= 0xEF;
    pccchip2->SCC_tx_int_ctl &= 0xEF;
    pccchip2->SCC_rx_int_ctl &= 0xEF;
  }
}

/* ISRs */

/*
 *  cd2401_modem_isr
 *
 *  Modem/timer interrupt (group 1) from CD2401. These are not used, and not
 *  expected. Record as spurious and clear.
 *
 *  Input parameters:
 *    vector - vector number
 *
 *  Output parameters: NONE
 *
 *  Return values: NONE
 */
rtems_isr cd2401_modem_isr(
  rtems_vector_number vector
)
{
  uint8_t         ch;

  /* Get interrupting channel ID */
  ch = cd2401->licr >> 2;

  /* Record interrupt info for debugging */
  CD2401_Channel_Info[ch].spur_dev =
      (vector << 24) | (cd2401->stk << 16) | (cd2401->mir << 8) | cd2401->misr;
  CD2401_Channel_Info[ch].spur_cnt++;

  cd2401->meoir = 0;            /* EOI */
  CD2401_RECORD_MODEM_ISR_SPURIOUS_INFO(( ch,
                                          CD2401_Channel_Info[ch].spur_dev,
                                          CD2401_Channel_Info[ch].spur_cnt ));
}

/*
 *  cd2401_re_isr
 *
 *  RX exception interrupt (group 3, receiver exception) from CD2401. These are
 *  not used, and not expected. Record as spurious and clear.
 *
 *  FIX THIS ISR TO DETECT BREAK CONDITIONS AND RAISE SIGINT
 *
 *  Input parameters:
 *    vector - vector number
 *
 *  Output parameters: NONE
 *
 *  Return values: NONE
 */
rtems_isr cd2401_re_isr(
  rtems_vector_number vector
)
{
  uint8_t         ch;

  /* Get interrupting channel ID */
  ch = cd2401->licr >> 2;

  /* Record interrupt info for debugging */
  CD2401_Channel_Info[ch].spur_dev =
      (vector << 24) | (cd2401->stk << 16) | (cd2401->rir << 8) | cd2401->u5.b.risrl;
  CD2401_Channel_Info[ch].spur_cnt++;

  if ( cd2401->u5.b.risrl & 0x80 )  /* Timeout interrupt? */
    cd2401->ier &= 0xDF;            /* Disable rx timeout interrupt */
  cd2401->reoir = 0x08;             /* EOI; exception char not read */
  CD2401_RECORD_RE_ISR_SPURIOUS_INFO(( ch,
                                       CD2401_Channel_Info[ch].spur_dev,
                                       CD2401_Channel_Info[ch].spur_cnt ));
}

/*
 *  cd2401_rx_isr
 *
 *  RX interrupt (group 3, receiver data) from CD2401.
 *
 *  Input parameters:
 *     vector - vector number
 *
 *  Output parameters: NONE
 *
 *  Return values: NONE
 */
rtems_isr cd2401_rx_isr(
  rtems_vector_number vector
)
{
  char c;
  uint8_t         ch, status, nchars, i, total;
  char buffer[256];

  status = cd2401->u5.b.risrl;
  ch = cd2401->licr >> 2;

  /* Has this channel been initialized or is it a condition we ignore? */
  if ( CD2401_Channel_Info[ch].tty && !status ) {
    /* Normal Rx Int, read chars, enqueue them, and issue EOI */
    total = nchars = cd2401->rfoc;  /* Nb of chars to retrieve from rx FIFO */
    i = 0;
    while ( nchars-- > 0 ) {
      c = (char)cd2401->dr;         /* Next char in rx FIFO */
      rtems_termios_enqueue_raw_characters( CD2401_Channel_Info[ch].tty ,&c, 1 );
      buffer[i++] = c;
    }
    cd2401->reoir = 0;              /* EOI */
    CD2401_RECORD_RX_ISR_INFO(( ch, total, buffer ));
  } else {
    /* No, record as spurious interrupt */
    CD2401_Channel_Info[ch].spur_dev =
        (vector << 24) | (cd2401->stk << 16) | (cd2401->rir << 8) | cd2401->u5.b.risrl;
    CD2401_Channel_Info[ch].spur_cnt++;
    cd2401->reoir = 0x04;           /* EOI - character not read */
    CD2401_RECORD_RX_ISR_SPURIOUS_INFO(( ch, status,
                                         CD2401_Channel_Info[ch].spur_dev,
                                         CD2401_Channel_Info[ch].spur_cnt ));
  }
}

/*
 *  cd2401_tx_isr
 *
 *  TX interrupt (group 2) from CD2401.
 *
 *  Input parameters:
 *    vector - vector number
 *
 *  Output parameters: NONE
 *
 *  Return values: NONE
 */
rtems_isr cd2401_tx_isr(
  rtems_vector_number vector
)
{
  uint8_t         ch, status, buserr, initial_ier, final_ier;

  status = cd2401->tisr;
  ch = cd2401->licr >> 2;
  initial_ier = cd2401->ier;

  /* Has this channel been initialized? */
  if ( !CD2401_Channel_Info[ch].tty ) {
    /* No, record as spurious interrupt */
    CD2401_Channel_Info[ch].spur_dev =
        (vector << 24) | (cd2401->stk << 16) | (cd2401->tir << 8) | cd2401->tisr;
    CD2401_Channel_Info[ch].spur_cnt++;
    final_ier = cd2401->ier &= 0xFC;/* Shut up, whoever you are */
    cd2401->teoir = 0x88;           /* EOI - Terminate buffer and no transfer */
    CD2401_RECORD_TX_ISR_SPURIOUS_INFO(( ch, status, initial_ier, final_ier,
                                         CD2401_Channel_Info[ch].spur_dev,
                                         CD2401_Channel_Info[ch].spur_cnt ));
    return;
  }

  if ( status & 0x80 ) {
    /*
     *  Bus error occurred during DMA transfer. For now, just record.
     *  Get reason for DMA bus error and clear the report for the next
     *  occurrence
     */
    buserr = pccchip2->SCC_error;
    pccchip2->SCC_error = 0x01;
    CD2401_Channel_Info[ch].buserr_type =
         (vector << 24) | (buserr << 16) | (cd2401->tir << 8) | cd2401->tisr;
    CD2401_Channel_Info[ch].buserr_addr =
        (((uint32_t)cd2401->tcbadru) << 16) | cd2401->tcbadrl;

    cd2401->teoir = 0x80;           /* EOI - terminate bad buffer */
    CD2401_RECORD_TX_ISR_BUSERR_INFO(( ch, status, initial_ier, buserr,
                                       CD2401_Channel_Info[ch].buserr_type,
                                       CD2401_Channel_Info[ch].buserr_addr ));
    return;
  }

  if ( status & 0x20 ) {
    /* DMA done -- Turn off TxD int, turn on TxMpty */
    final_ier = cd2401->ier = (cd2401->ier & 0xFE) | 0x02;
    if( status & 0x08 ) {
      /* Transmit buffer B was released */
      CD2401_Channel_Info[ch].own_buf_B = TRUE;
    }
    else {
      /* Transmit buffer A was released */
      CD2401_Channel_Info[ch].own_buf_A = TRUE;
    }
    CD2401_RECORD_TX_ISR_INFO(( ch, status, initial_ier, final_ier,
                                CD2401_Channel_Info[ch].txEmpty ));

    /* This call can result in a call to cd2401_write() */
    rtems_termios_dequeue_characters (
        CD2401_Channel_Info[ch].tty,
        CD2401_Channel_Info[ch].len );
    cd2401->teoir = 0x08;           /* EOI - no data transfered */
  }
  else if ( status & 0x02 ) {
    /* TxEmpty */
    CD2401_Channel_Info[ch].txEmpty = TRUE;
    final_ier = cd2401->ier &= 0xFD;/* Shut up the interrupts */
    cd2401->teoir = 0x08;           /* EOI - no data transfered */
    CD2401_RECORD_TX_ISR_INFO(( ch, status, initial_ier, final_ier,
                                CD2401_Channel_Info[ch].txEmpty ));
  }
  else {
    /* Why did we get a Tx interrupt? */
    CD2401_Channel_Info[ch].spur_dev =
        (vector << 24) | (cd2401->stk << 16) | (cd2401->tir << 8) | cd2401->tisr;
    CD2401_Channel_Info[ch].spur_cnt++;
    cd2401->teoir = 0x08;           /* EOI - no data transfered */
    CD2401_RECORD_TX_ISR_SPURIOUS_INFO(( ch, status, initial_ier, 0xFF,
                                         CD2401_Channel_Info[ch].spur_dev,
                                         CD2401_Channel_Info[ch].spur_cnt ));
  }
}

/*
 *  termios callbacks
 */

/*
 *  cd2401_firstOpen
 *
 *  This is the first time that this minor device (channel) is opened.
 *  Complete the asynchronous initialization.
 *
 *  Input parameters:
 *    major - device major number
 *    minor - channel number
 *    arg - pointer to a struct rtems_libio_open_close_args_t
 *
 *  Output parameters: NONE
 *
 *  Return value: IGNORED
 */
int cd2401_firstOpen(
  int major,
  int minor,
  void *arg
)
{
  rtems_libio_open_close_args_t *args = arg;
  rtems_libio_ioctl_args_t newarg;
  struct termios termios;
  rtems_status_code sc;
  rtems_interrupt_level level;

  rtems_interrupt_disable (level);

  /*
   * Set up the line with the specified parameters. The difficulty is that
   * the line parameters are stored in the struct termios field of a
   * struct rtems_termios_tty that is not defined in a public header file.
   * Therefore, we do not have direct access to the termios passed in with
   * arg. So we make a rtems_termios_ioctl() call to get a pointer to the
   * termios structure.
   *
   * THIS KLUDGE MAY BREAK IN THE FUTURE!
   *
   * We could have made a tcgetattr() call if we had our fd.
   */
  newarg.iop = args->iop;
  newarg.command = RTEMS_IO_GET_ATTRIBUTES;
  newarg.buffer = &termios;
  sc = rtems_termios_ioctl (&newarg);
  if (sc != RTEMS_SUCCESSFUL)
    rtems_fatal_error_occurred (sc);

  /*
   *  Turn off hardware flow control. It is a pain with 3-wire cables.
   *  The rtems_termios_ioctl() call below results in a call to
   *  cd2401_setAttributes to initialize the line. The caller will "wait"
   *  on the ttyMutex that it already owns; this is safe in RTEMS.
   */
  termios.c_cflag |= CLOCAL;    /* Ignore modem status lines */
  newarg.command = RTEMS_IO_SET_ATTRIBUTES;
  sc = rtems_termios_ioctl (&newarg);
  if (sc != RTEMS_SUCCESSFUL)
    rtems_fatal_error_occurred (sc);

  /* Mark that the channel as initialized */
  CD2401_Channel_Info[minor].tty = args->iop->data1;

  /* If the first of the four channels to open, set up the interrupts */
  if ( !Init_count++ ) {
    /* Install the interrupt handlers */
    Prev_re_isr    = (rtems_isr_entry) set_vector( cd2401_re_isr,    0x5C, 1 );
    Prev_modem_isr = (rtems_isr_entry) set_vector( cd2401_modem_isr, 0x5D, 1 );
    Prev_tx_isr    = (rtems_isr_entry) set_vector( cd2401_tx_isr,    0x5E, 1 );
    Prev_rx_isr    = (rtems_isr_entry) set_vector( cd2401_rx_isr,    0x5F, 1 );

    cd2401_interrupts_initialize( TRUE );
  }

  CD2401_RECORD_FIRST_OPEN_INFO(( minor, Init_count ));

  rtems_interrupt_enable (level);

  /* Return something */
  return RTEMS_SUCCESSFUL;
}

/*
 * cd2401_lastClose
 *
 *  There are no more opened file descriptors to this device. Close it down.
 *
 *  Input parameters:
 *    major - device major number
 *    minor - channel number
 *    arg - pointer to a struct rtems_libio_open_close_args_t
 */
int cd2401_lastClose(
  int major,
  int minor,
  void *arg
)
{
  rtems_interrupt_level level;

  rtems_interrupt_disable (level);

  /* Mark that the channel is no longer is use */
  CD2401_Channel_Info[minor].tty = NULL;

  /* If the last of the four channels to close, disable the interrupts */
  if ( !--Init_count ) {
    cd2401_interrupts_initialize( FALSE );

    /* De-install the interrupt handlers */
    set_vector( Prev_re_isr,    0x5C, 1 );
    set_vector( Prev_modem_isr, 0x5D, 1 );
    set_vector( Prev_tx_isr,    0x5E, 1 );
    set_vector( Prev_rx_isr,    0x5F, 1 );
  }

  CD2401_RECORD_LAST_CLOSE_INFO(( minor, Init_count ));

  rtems_interrupt_enable (level);

  /* return something */
  return RTEMS_SUCCESSFUL;
}

/*
 *  cd2401_setAttributes
 *
 *  Set up the selected channel of the CD2401 chip for doing asynchronous
 *  I/O with DMA.
 *
 *  The chip must already have been initialized by cd2401_initialize().
 *
 *  This code was written for clarity. The code space it occupies could be
 *  reduced. The code could also be compiled with aggressive optimization
 *  turned on.
 *
 *  Input parameters:
 *    minor - the selected channel
 *    t - the termios parameters
 *
 *  Output parameters: NONE
 *
 *  Return value: IGNORED
 */
int cd2401_setAttributes(
  int minor,
  const struct termios *t
)
{
  uint8_t         csize, cstopb, parodd, parenb, ignpar, inpck;
  uint8_t         hw_flow_ctl, sw_flow_ctl, extra_flow_ctl;
  uint8_t         icrnl, igncr, inlcr, brkint, ignbrk, parmrk, istrip;
  uint8_t         need_reinitialization = FALSE;
  uint8_t         read_enabled;
  uint16_t         tx_period, rx_period;
  uint32_t         out_baud, in_baud;
  rtems_interrupt_level level;

  /* Determine what the line parameters should be */

  /* baud rates */
  out_baud = rtems_termios_baud_to_number(t->c_cflag & CBAUD);
  in_baud  = rtems_termios_baud_to_number(t->c_cflag & CBAUD);

  /* Number of bits per char */
  csize = 0x07; /* to avoid a warning */
  switch ( t->c_cflag & CSIZE ) {
    case CS5:     csize = 0x04;       break;
    case CS6:     csize = 0x05;       break;
    case CS7:     csize = 0x06;       break;
    case CS8:     csize = 0x07;       break;
  }

  /* Parity */
  if ( t->c_cflag & PARODD )
    parodd = 0x80;              /* Odd parity */
  else
    parodd = 0;

  if ( t->c_cflag & PARENB )
    parenb = 0x40;              /* Parity enabled on Tx and Rx */
  else
    parenb = 0x00;              /* No parity on Tx and Rx */

  /* CD2401 IGNPAR and INPCK bits are inverted wrt POSIX standard? */
  if ( t->c_iflag & INPCK )
    ignpar = 0;                 /* Check parity on input */
  else
    ignpar = 0x10;              /* Do not check parity on input */
  if ( t->c_iflag & IGNPAR ) {
    inpck = 0x03;               /* Discard error character */
    parmrk = 0;
  } else {
    if ( t->c_iflag & PARMRK ) {
      inpck = 0x01;             /* Translate to 0xFF 0x00 <char> */
      parmrk = 0x04;
    } else {
      inpck = 0x01;             /* Translate to 0x00 */
      parmrk = 0;
    }
  }

  /* Stop bits */
  if ( t->c_cflag & CSTOPB )
    cstopb = 0x04;              /* Two stop bits */
  else
    cstopb = 0x02;              /* One stop bit */

  /* Modem flow control */
  if ( t->c_cflag & CLOCAL )
    hw_flow_ctl = 0x04;         /* Always assert RTS before Tx */
  else
    hw_flow_ctl = 0x07;         /* Always assert RTS before Tx,
                                   wait for CTS and DSR */

  /* XON/XOFF Tx flow control */
  if ( t->c_iflag & IXON ) {
    sw_flow_ctl = 0x40;         /* Tx in-band flow ctl enabled, wait for XON */
    extra_flow_ctl = 0x30;      /* Eat XON/XOFF, XON/XOFF in SCHR1, SCHR2 */
  }
  else {
    sw_flow_ctl = 0;            /* Tx in-band flow ctl disabled */
    extra_flow_ctl = 0;         /* Pass on XON/XOFF */
  }

  /* CL/LF translation */
  if ( t->c_iflag & ICRNL )
    icrnl = 0x40;               /* Map CR to NL on input */
  else
    icrnl = 0;                  /* Pass on CR */
  if ( t->c_iflag & INLCR )
    inlcr = 0x20;               /* Map NL to CR on input */
  else
    inlcr = 0;                  /* Pass on NL */
  if ( t->c_iflag & IGNCR )
    igncr = 0x80;               /* CR discarded on input */
  else
    igncr = 0;

  /* Break handling */
  if ( t->c_iflag & IGNBRK ) {
    ignbrk = 0x10;              /* Ignore break on input */
    brkint = 0x08;
  } else {
    if ( t->c_iflag & BRKINT ) {
      ignbrk = 0;               /* Generate SIGINT (interrupt ) */
      brkint = 0;
    } else {
      ignbrk = 0;               /* Convert to 0x00 */
      brkint = 0x08;
    }
  }

  /* Stripping */
  if ( t->c_iflag & ISTRIP )
    istrip = 0x80;              /* Strip to 7 bits */
  else
    istrip = 0;                 /* Leave as 8 bits */

  rx_period = cd2401_bitrate_divisor( 20000000Ul, &in_baud );
  tx_period = cd2401_bitrate_divisor( 20000000Ul, &out_baud );

  /*
   *  If this is the first time that the line characteristics are set up, then
   *  the device must be re-initialized.
   *  Also check if we need to change anything. It is preferable to not touch
   *  the device if nothing changes. As soon as we touch it, it tends to
   *  glitch. If anything changes, we reprogram all registers. This is
   *  harmless.
   */
  if ( ( CD2401_Channel_Info[minor].tty == 0 ) ||
       ( cd2401->cor1 != (parodd | parenb | ignpar | csize) ) ||
       ( cd2401->cor2 != (sw_flow_ctl | hw_flow_ctl) ) ||
       ( cd2401->cor3 != (extra_flow_ctl | cstopb) )  ||
       ( cd2401->cor6 != (igncr | icrnl | inlcr | ignbrk | brkint | parmrk | inpck) ) ||
       ( cd2401->cor7 != istrip ) ||
       ( cd2401->u1.async.schr1 != t->c_cc[VSTART] ) ||
       ( cd2401->u1.async.schr2 != t->c_cc[VSTOP] ) ||
       ( cd2401->rbpr != (unsigned char)rx_period ) ||
       ( cd2401->rcor != (unsigned char)(rx_period >> 8) ) ||
       ( cd2401->tbpr != (unsigned char)tx_period ) ||
       ( cd2401->tcor != ( (tx_period >> 3) & 0xE0 ) ) )
    need_reinitialization = TRUE;

  /* Write to the ports */
  rtems_interrupt_disable (level);

  cd2401->car = minor;          /* Select channel */
  read_enabled = cd2401->csr & 0x80 ? TRUE : FALSE;

  if ( (t->c_cflag & CREAD ? TRUE : FALSE ) != read_enabled ) {
    /* Read enable status is changing */
    need_reinitialization = TRUE;
  }

  if ( need_reinitialization ) {
    /*
     *  Could not find a way to test whether the CD2401 was done transmitting.
     *  The TxEmpty interrupt does not seem to indicate that the FIFO is empty
     *  in DMA mode. So, just wait a while for output to drain. May not be
     *  enough, but it will have to do (should be long enough for 1 char at
     *  9600 bsp)...
     */
    cd2401_udelay( 2000L );

    /* Clear channel */
    cd2401_chan_cmd (minor, 0x40, 1);

    cd2401->car = minor;    /* Select channel */
    cd2401->cmr = 0x42;     /* Interrupt Rx, DMA Tx, async mode */
    cd2401->cor1 = parodd | parenb | ignpar | csize;
    cd2401->cor2 = sw_flow_ctl | hw_flow_ctl;
    cd2401->cor3 = extra_flow_ctl | cstopb;
    cd2401->cor4 = 0x0A;    /* No DSR/DCD/CTS detect; FIFO threshold of 10 */
    cd2401->cor5 = 0x0A;    /* No DSR/DCD/CTS detect; DTR threshold of 10 */
    cd2401->cor6 = igncr | icrnl | inlcr | ignbrk | brkint | parmrk | inpck;
    cd2401->cor7 = istrip;  /* No LNext; ignore XON/XOFF if frame error; no tx translations */
    /* Special char 1: XON character */
    cd2401->u1.async.schr1 = t->c_cc[VSTART];
    /* special char 2: XOFF character */
    cd2401->u1.async.schr2 = t->c_cc[VSTOP];

    /*
     *  Special chars 3 and 4, char range, LNext, RFAR[1..4] and CRC
     *  are unused, left as is.
     */

    /* Set baudrates for receiver and transmitter */
    cd2401->rbpr = (unsigned char)rx_period;
    cd2401->rcor = (unsigned char)(rx_period >> 8); /* no DPLL */
    cd2401->tbpr = (unsigned char)tx_period;
    cd2401->tcor = (tx_period >> 3) & 0xE0; /* no x1 ext clk, no loopback */

    /* Timeout for 4 chars at 9600, 8 bits per char, 1 stop bit */
    cd2401->u2.w.rtpr  = 0x04;  /* NEED TO LOOK AT THIS LINE! */

    if ( t->c_cflag & CREAD ) {
      /* Re-initialize channel, enable rx and tx */
      cd2401_chan_cmd (minor, 0x2A, 1);
      /* Enable rx data ints */
      cd2401->ier = 0x08;
    } else {
      /* Re-initialize channel, enable tx, disable rx */
      cd2401_chan_cmd (minor, 0x29, 1);
    }
  }

  CD2401_RECORD_SET_ATTRIBUTES_INFO(( minor, need_reinitialization, csize,
                                      cstopb, parodd, parenb, ignpar, inpck,
                                      hw_flow_ctl, sw_flow_ctl, extra_flow_ctl,
                                      icrnl, igncr, inlcr, brkint, ignbrk,
                                      parmrk, istrip, tx_period, rx_period,
                                      out_baud, in_baud ));

  rtems_interrupt_enable (level);

  /*
   *  Looks like the CD2401 needs time to settle after initialization. Give it
   *  10 ms. I don't really believe it, but if output resumes to quickly after
   *  this call, the first few characters are not right.
   */
  if ( need_reinitialization )
    cd2401_udelay( 10000L );

  /* Return something */
  return RTEMS_SUCCESSFUL;
}

/*
 *  cd2401_startRemoreTx
 *
 *  Defined as a callback, but it would appear that it is never called. The
 *  POSIX standard states that when the tcflow() function is called with the
 *  TCION action, the system wall transmit a START character. Presumably,
 *  tcflow() is called internally when IXOFF is set in the termios c_iflag
 *  field when the input buffer can accomodate enough characters. It should
 *  probably be called from fillBufferQueue(). Clearly, the function is also
 *  explicitly callable by user code. The action is clearly to send the START
 *  character, regardless of whether START/STOP flow control is in effect.
 *
 *  Input parameters:
 *    minor - selected channel
 *
 *  Output parameters: NONE
 *
 *  Return value: IGNORED
 *
 *  PROPER START CHARACTER MUST BE PROGRAMMED IN SCHR1.
 */
int cd2401_startRemoteTx(
  int minor
)
{
  rtems_interrupt_level level;

  rtems_interrupt_disable (level);

  cd2401->car = minor;              /* Select channel */
  cd2401->stcr = 0x01;              /* Send SCHR1 ahead of chars in FIFO */

  CD2401_RECORD_START_REMOTE_TX_INFO(( minor ));

  rtems_interrupt_enable (level);

  /* Return something */
  return RTEMS_SUCCESSFUL;
}

/*
 *  cd2401_stopRemoteTx
 *
 *  Defined as a callback, but it would appear that it is never called. The
 *  POSIX standard states that when the tcflow() function is called with the
 *  TCIOFF function, the system wall transmit a STOP character. Presumably,
 *  tcflow() is called internally when IXOFF is set in the termios c_iflag
 *  field as the input buffer is about to overflow. It should probably be
 *  called from rtems_termios_enqueue_raw_characters(). Clearly, the function
 *  is also explicitly callable by user code. The action is clearly to send
 *  the STOP character, regardless of whether START/STOP flow control is in
 *  effect.
 *
 *  Input parameters:
 *    minor - selected channel
 *
 *  Output parameters: NONE
 *
 *  Return value: IGNORED
 *
 *  PROPER STOP CHARACTER MUST BE PROGRAMMED IN SCHR2.
 */
int cd2401_stopRemoteTx(
  int minor
)
{
  rtems_interrupt_level level;

  rtems_interrupt_disable (level);

  cd2401->car = minor;              /* Select channel */
  cd2401->stcr = 0x02;              /* Send SCHR2 ahead of chars in FIFO */

  CD2401_RECORD_STOP_REMOTE_TX_INFO(( minor ));

  rtems_interrupt_enable (level);

  /* Return something */
  return RTEMS_SUCCESSFUL;
}

/*
 *  cd2401_write
 *
 *  Initiate DMA output. Termios guarantees that the buffer does not wrap
 *  around, so we can do DMA strait from the supplied buffer.
 *
 *  Input parameters:
 *    minor - selected channel
 *    buf - output buffer
 *    len - number of chars to output
 *
 *  Output parameters:  NONE
 *
 *  Return value: IGNORED
 *
 *  MUST BE EXECUTED WITH THE CD2401 INTERRUPTS DISABLED!
 *  The processor is placed at interrupt level CD2401_INT_LEVEL explicitly in
 *  console_write(). The processor is necessarily at interrupt level 1 in
 *  cd2401_tx_isr().
 */
ssize_t cd2401_write(
  int minor,
  const char *buf,
  size_t len
)
{
  cd2401->car = minor;              /* Select channel */

  if ( (cd2401->dmabsts & 0x08) == 0 ) {
    /* Next buffer is A. Wait for it to be ours. */
    while ( cd2401->atbsts & 0x01 );

    CD2401_Channel_Info[minor].own_buf_A = FALSE;
    CD2401_Channel_Info[minor].len = len;
    CD2401_Channel_Info[minor].buf = buf;
    cd2401->atbadru = (uint16_t)( ( (uint32_t) buf ) >> 16 );
    cd2401->atbadrl = (uint16_t)( (uint32_t) buf );
    cd2401->atbcnt = len;
    CD2401_RECORD_WRITE_INFO(( len, buf, 'A' ));
    cd2401->atbsts = 0x03;          /* CD2401 owns buffer, int when empty */
  }
  else {
    /* Next buffer is B. Wait for it to be ours. */
    while ( cd2401->btbsts & 0x01 );

    CD2401_Channel_Info[minor].own_buf_B = FALSE;
    CD2401_Channel_Info[minor].len = len;
    CD2401_Channel_Info[minor].buf = buf;
    cd2401->btbadru = (uint16_t)( ( (uint32_t) buf ) >> 16 );
    cd2401->btbadrl = (uint16_t)( (uint32_t) buf );
    cd2401->btbcnt = len;
    CD2401_RECORD_WRITE_INFO(( len, buf, 'B' ));
    cd2401->btbsts = 0x03;          /* CD2401 owns buffer, int when empty */
  }
  /* Nuts -- Need TxD ints */
  CD2401_Channel_Info[minor].txEmpty = FALSE;
  cd2401->ier |= 0x01;

  /* Return something */
  return len;
}

#if 0
/*
 *  cd2401_drainOutput
 *
 *  Wait for the txEmpty indication on the specified channel.
 *
 *  Input parameters:
 *    minor - selected channel
 *
 *  Output parameters:  NONE
 *
 *  Return value: IGNORED
 *
 *  MUST NOT BE EXECUTED WITH THE CD2401 INTERRUPTS DISABLED!
 *  The txEmpty flag is set by the tx ISR.
 *
 *  DOES NOT WORK! DO NOT ENABLE THIS CODE. THE CD2401 DOES NOT COOPERATE!
 *  The code is here to document that the output FIFO is NOT empty when
 *  the CD2401 reports that the Tx buffer is empty.
 */
int cd2401_drainOutput(
  int minor
)
{
  CD2401_RECORD_DRAIN_OUTPUT_INFO(( CD2401_Channel_Info[minor].txEmpty,
                                    CD2401_Channel_Info[minor].own_buf_A,
                                    CD2401_Channel_Info[minor].own_buf_B ));

  while( ! (CD2401_Channel_Info[minor].txEmpty &&
            CD2401_Channel_Info[minor].own_buf_A &&
            CD2401_Channel_Info[minor].own_buf_B) );

  /* Return something */
  return RTEMS_SUCCESSFUL;
}
#endif

/*
 * _167Bug_pollRead
 *
 *  Read a character from the 167Bug console, and return it. Return -1
 *  if there is no character in the input FIFO.
 *
 *  Input parameters:
 *    minor - selected channel
 *
 *  Output parameters:  NONE
 *
 *  Return value: char returned as positive signed int
 *                -1 if no character is present in the input FIFO.
 *
 *  CANNOT BE COMBINED WITH INTERRUPT DRIVEN I/O!
 */
int _167Bug_pollRead(
  int minor
)
{
  int char_not_available;
  unsigned char c;
  rtems_interrupt_level previous_level;

  /*
   *  Redirection of .INSTAT does not work: 167-Bug crashes.
   *  Switch the input stream to the specified port.
   *  Make sure this is atomic code.
   */
  rtems_interrupt_disable( previous_level );

  asm volatile( "movew  %1, -(%%sp)\n\t"/* Channel */
                "trap   #15\n\t"        /* Trap to 167Bug */
                ".short 0x61\n\t"       /* Code for .REDIR_I */
                "trap   #15\n\t"        /* Trap to 167Bug */
		".short 0x01\n\t"       /* Code for .INSTAT */
                "move   %%cc, %0\n\t"   /* Get condition codes */
                "andil  #4, %0"         /* Keep the Zero bit */
    : "=d" (char_not_available) : "d" (minor): "%%cc" );

  if (char_not_available) {
    rtems_interrupt_enable( previous_level );
    return -1;
  }

  /* Read the char and return it */
  asm volatile( "subq.l #2,%%a7\n\t"    /* Space for result */
                "trap   #15\n\t"        /* Trap to 167 Bug */
                ".short 0x00\n\t"       /* Code for .INCHR */
                "moveb  (%%a7)+, %0"    /* Pop char into c */
    : "=d" (c) : );

  rtems_interrupt_enable( previous_level );

  return (int)c;
}

/*
 * _167Bug_pollWrite
 *
 *  Output buffer through 167Bug. Returns only once every character has been
 *  sent (polled output).
 *
 *  Input parameters:
 *    minor - selected channel
 *    buf - output buffer
 *    len - number of chars to output
 *
 *  Output parameters:  NONE
 *
 *  Return value: IGNORED
 *
 *  CANNOT BE COMBINED WITH INTERRUPT DRIVEN I/O!
 */
ssize_t _167Bug_pollWrite(
  int minor,
  const char *buf,
  size_t len
)
{
  const char *endbuf = buf + len;

  asm volatile( "pea    (%0)\n\t"            /* endbuf */
                "pea    (%1)\n\t"            /* buf */
                "movew  #0x21, -(%%sp)\n\t"  /* Code for .OUTSTR */
                "movew  %2, -(%%sp)\n\t"     /* Channel */
                "trap   #15\n\t"             /* Trap to 167Bug */
                ".short 0x60"                /* Code for .REDIR */
    :: "a" (endbuf), "a" (buf), "d" (minor) );

  /* Return something */
  return len;
}

/*
 *  do_poll_read
 *
 *  Input characters through 167Bug. Returns has soon as a character has been
 *  received. Otherwise, if we wait for the number of requested characters, we
 *  could be here forever!
 *
 *  CR is converted to LF on input. The terminal should not send a CR/LF pair
 *  when the return or enter key is pressed.
 *
 *  Input parameters:
 *    major - ignored. Should be the major number for this driver.
 *    minor - selected channel.
 *    arg->buffer - where to put the received characters.
 *    arg->count  - number of characters to receive before returning--Ignored.
 *
 *  Output parameters:
 *    arg->bytes_moved - the number of characters read. Always 1.
 *
 *  Return value: RTEMS_SUCCESSFUL
 *
 *  CANNOT BE COMBINED WITH INTERRUPT DRIVEN I/O!
 */
rtems_status_code do_poll_read(
  rtems_device_major_number major,
  rtems_device_minor_number minor,
  void                    * arg
)
{
  rtems_libio_rw_args_t *rw_args = arg;
  int c;

  while( (c = _167Bug_pollRead (minor)) == -1 );
  rw_args->buffer[0] = (uint8_t)c;
  if( rw_args->buffer[0] == '\r' )
      rw_args->buffer[0] = '\n';
  rw_args->bytes_moved = 1;
  return RTEMS_SUCCESSFUL;
}

/*
 *  do_poll_write
 *
 *  Output characters through 167Bug. Returns only once every character has
 *  been sent.
 *
 *  CR is transmitted AFTER a LF on output.
 *
 *  Input parameters:
 *    major - ignored. Should be the major number for this driver.
 *    minor - selected channel
 *    arg->buffer - where to get the characters to transmit.
 *    arg->count  - the number of characters to transmit before returning.
 *
 *  Output parameters:
 *    arg->bytes_moved - the number of characters read
 *
 *  Return value: RTEMS_SUCCESSFUL
 *
 *  CANNOT BE COMBINED WITH INTERRUPT DRIVEN I/O!
 */
rtems_status_code do_poll_write(
  rtems_device_major_number major,
  rtems_device_minor_number minor,
  void                    * arg
)
{
  rtems_libio_rw_args_t *rw_args = arg;
  uint32_t   i;

  for( i = 0; i < rw_args->count; i++ ) {
    _167Bug_pollWrite(minor, &(rw_args->buffer[i]), 1);
    if ( rw_args->buffer[i] == '\n' )
      _167Bug_pollWrite(minor, &cr_char, 1);
  }
  rw_args->bytes_moved = i;
  return RTEMS_SUCCESSFUL;
}

/*
 *  _BSP_output_char
 *
 *  printk() function prototyped in bspIo.h. Does not use termios.
 */
void _BSP_output_char(char c)
{
  rtems_device_minor_number printk_minor;

  /*
   *  Can't rely on console_initialize having been called before this function
   *  is used.
   */
  if ( NVRAM_CONFIGURE )
    /* J1-4 is on, use NVRAM info for configuration */
    printk_minor = (nvram->console_printk_port & 0x30) >> 4;
  else
    printk_minor = PRINTK_MINOR;

  _167Bug_pollWrite(printk_minor, &c, 1);
  if ( c == '\n' )
      _167Bug_pollWrite(printk_minor, &cr_char, 1);
}

/*
 ***************
 * BOILERPLATE *
 ***************
 *
 *  All these functions are prototyped in rtems/c/src/lib/include/console.h.
 */

/*
 * Initialize and register the device
 */
rtems_device_driver console_initialize(
  rtems_device_major_number  major,
  rtems_device_minor_number  minor,
  void                      *arg
)
{
  rtems_status_code status;
  rtems_device_minor_number console_minor;

  /*
   * Set up TERMIOS if needed
   */
  if ( NVRAM_CONFIGURE ) {
    /* J1-4 is on, use NVRAM info for configuration */
    console_minor = nvram->console_printk_port & 0x03;

    if ( nvram->console_mode & 0x01 )
      /* termios */
      rtems_termios_initialize ();
  }
  else {
    console_minor = CONSOLE_MINOR;
#if CD2401_USE_TERMIOS == 1
    rtems_termios_initialize ();
#endif
  }

  /*
   * Do device-specific initialization
   * Does not affect 167-Bug.
   */
  cd2401_initialize ();

  /*
   * Register the devices
   */
  status = rtems_io_register_name ("/dev/tty0", major, 0);
  if (status != RTEMS_SUCCESSFUL)
    rtems_fatal_error_occurred (status);

  status = rtems_io_register_name ("/dev/tty1", major, 1);
  if (status != RTEMS_SUCCESSFUL)
    rtems_fatal_error_occurred (status);

  status = rtems_io_register_name ("/dev/console", major, console_minor);
  if (status != RTEMS_SUCCESSFUL)
    rtems_fatal_error_occurred (status);

  status = rtems_io_register_name ("/dev/tty2", major, 2);
  if (status != RTEMS_SUCCESSFUL)
    rtems_fatal_error_occurred (status);

  status = rtems_io_register_name ("/dev/tty3", major, 3);
  if (status != RTEMS_SUCCESSFUL)
    rtems_fatal_error_occurred (status);

  return RTEMS_SUCCESSFUL;
}

/*
 * Open the device
 */
rtems_device_driver console_open(
  rtems_device_major_number major,
  rtems_device_minor_number minor,
  void                    * arg
)
{
  static const rtems_termios_callbacks pollCallbacks = {
    NULL,                       /* firstOpen */
    NULL,                       /* lastClose */
    _167Bug_pollRead,           /* pollRead */
    _167Bug_pollWrite,          /* write */
    NULL,                       /* setAttributes */
    NULL,                       /* stopRemoteTx */
    NULL,                       /* startRemoteTx */
    0                           /* outputUsesInterrupts */
  };

  static const rtems_termios_callbacks intrCallbacks = {
    cd2401_firstOpen,           /* firstOpen */
    cd2401_lastClose,           /* lastClose */
    NULL,                       /* pollRead */
    cd2401_write,               /* write */
    cd2401_setAttributes,       /* setAttributes */
    cd2401_stopRemoteTx,        /* stopRemoteTx */
    cd2401_startRemoteTx,       /* startRemoteTx */
    1                           /* outputUsesInterrupts */
  };

  if ( NVRAM_CONFIGURE )
    /* J1-4 is on, use NVRAM info for configuration */
    if ( nvram->console_mode & 0x01 )
      /* termios */
      if ( nvram->console_mode & 0x02 )
        /* interrupt-driven I/O */
        return rtems_termios_open (major, minor, arg, &intrCallbacks);
	    else
        /* polled I/O */
        return rtems_termios_open (major, minor, arg, &pollCallbacks);
	  else
	    /* no termios -- default to polled I/O */
	    return RTEMS_SUCCESSFUL;
#if CD2401_USE_TERMIOS == 1
#if CD2401_IO_MODE != 1
  else
    /* termios & polled I/O*/
    return rtems_termios_open (major, minor, arg, &pollCallbacks);
#else
  else
    /* termios & interrupt-driven I/O*/
    return rtems_termios_open (major, minor, arg, &intrCallbacks);
#endif
#else
  else
    /* no termios -- default to polled I/O */
    return RTEMS_SUCCESSFUL;
#endif
}

/*
 * Close the device
 */
rtems_device_driver console_close(
  rtems_device_major_number major,
  rtems_device_minor_number minor,
  void                    * arg
)
{
  if ( NVRAM_CONFIGURE ) {
    /* J1-4 is on, use NVRAM info for configuration */
    if ( nvram->console_mode & 0x01 )
      /* termios */
      return rtems_termios_close (arg);
    else
      /* no termios */
      return RTEMS_SUCCESSFUL;
  }
#if CD2401_USE_TERMIOS == 1
  else
    /* termios */
    return rtems_termios_close (arg);
#else
  else
    /* no termios */
    return RTEMS_SUCCESSFUL;
#endif
}

/*
 * Read from the device
 */
rtems_device_driver console_read(
  rtems_device_major_number major,
  rtems_device_minor_number minor,
  void                    * arg
)
{
  if ( NVRAM_CONFIGURE ) {
    /* J1-4 is on, use NVRAM info for configuration */
    if ( nvram->console_mode & 0x01 )
      /* termios */
      return rtems_termios_read (arg);
    else
      /* no termios -- default to polled */
      return do_poll_read (major, minor, arg);
  }
#if CD2401_USE_TERMIOS == 1
  else
    /* termios */
    return rtems_termios_read (arg);
#else
  else
    /* no termios -- default to polled */
    return do_poll_read (major, minor, arg);
#endif
}

/*
 * Write to the device
 */
rtems_device_driver console_write(
  rtems_device_major_number major,
  rtems_device_minor_number minor,
  void                    * arg
)
{
  if ( NVRAM_CONFIGURE ) {
    /* J1-4 is on, use NVRAM info for configuration */
    if ( nvram->console_mode & 0x01 )
      /* termios */
      return rtems_termios_write (arg);
    else
      /* no termios -- default to polled */
      return do_poll_write (major, minor, arg);
  }
#if CD2401_USE_TERMIOS == 1
  else
    /* termios */
    return rtems_termios_write (arg);
#else
  else
    /* no termios -- default to polled */
    return do_poll_write (major, minor, arg);
#endif
}

/*
 * Handle ioctl request.
 */
rtems_device_driver console_control(
  rtems_device_major_number major,
  rtems_device_minor_number minor,
  void                    * arg
)
{
  if ( NVRAM_CONFIGURE ) {
    /* J1-4 is on, use NVRAM info for configuration */
    if ( nvram->console_mode & 0x01 )
      /* termios */
      return rtems_termios_ioctl (arg);
    else
      /* no termios -- default to polled */
      return RTEMS_SUCCESSFUL;
  }
#if CD2401_USE_TERMIOS == 1
  else
    /* termios */
    return rtems_termios_ioctl (arg);
#else
  else
    /* no termios -- default to polled */
    return RTEMS_SUCCESSFUL;
#endif
}