summaryrefslogtreecommitdiff
path: root/drivers/scsi/ppa.c
blob: 0ae800c5b7396aa5944eb36bf8bbb4ae5f1f632c (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
/* ppa.c   --  low level driver for the IOMEGA PPA3 
 * parallel port SCSI host adapter.
 * 
 * (The PPA3 is the embedded controller in the ZIP drive.)
 * 
 * (c) 1995,1996 Grant R. Guenther, grant@torque.net,
 * under the terms of the GNU General Public License.
 * 
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/blkdev.h>
#include <linux/parport.h>
#include <linux/workqueue.h>
#include <linux/delay.h>
#include <linux/jiffies.h>
#include <asm/io.h>

#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_host.h>


static void ppa_reset_pulse(unsigned int base);

typedef struct {
	struct pardevice *dev;	/* Parport device entry         */
	int base;		/* Actual port address          */
	int mode;		/* Transfer mode                */
	struct scsi_cmnd *cur_cmd;	/* Current queued command       */
	struct delayed_work ppa_tq;	/* Polling interrupt stuff       */
	unsigned long jstart;	/* Jiffies at start             */
	unsigned long recon_tmo;	/* How many usecs to wait for reconnection (6th bit) */
	unsigned int failed:1;	/* Failure flag                 */
	unsigned wanted:1;	/* Parport sharing busy flag    */
	unsigned int dev_no;	/* Device number		*/
	wait_queue_head_t *waiting;
	struct Scsi_Host *host;
	struct list_head list;
} ppa_struct;

#include  "ppa.h"

static inline ppa_struct *ppa_dev(struct Scsi_Host *host)
{
	return *(ppa_struct **)&host->hostdata;
}

static DEFINE_SPINLOCK(arbitration_lock);

static void got_it(ppa_struct *dev)
{
	dev->base = dev->dev->port->base;
	if (dev->cur_cmd)
		dev->cur_cmd->SCp.phase = 1;
	else
		wake_up(dev->waiting);
}

static void ppa_wakeup(void *ref)
{
	ppa_struct *dev = (ppa_struct *) ref;
	unsigned long flags;

	spin_lock_irqsave(&arbitration_lock, flags);
	if (dev->wanted) {
		parport_claim(dev->dev);
		got_it(dev);
		dev->wanted = 0;
	}
	spin_unlock_irqrestore(&arbitration_lock, flags);
	return;
}

static int ppa_pb_claim(ppa_struct *dev)
{
	unsigned long flags;
	int res = 1;
	spin_lock_irqsave(&arbitration_lock, flags);
	if (parport_claim(dev->dev) == 0) {
		got_it(dev);
		res = 0;
	}
	dev->wanted = res;
	spin_unlock_irqrestore(&arbitration_lock, flags);
	return res;
}

static void ppa_pb_dismiss(ppa_struct *dev)
{
	unsigned long flags;
	int wanted;
	spin_lock_irqsave(&arbitration_lock, flags);
	wanted = dev->wanted;
	dev->wanted = 0;
	spin_unlock_irqrestore(&arbitration_lock, flags);
	if (!wanted)
		parport_release(dev->dev);
}

static inline void ppa_pb_release(ppa_struct *dev)
{
	parport_release(dev->dev);
}

/*
 * Start of Chipset kludges
 */

/* This is to give the ppa driver a way to modify the timings (and other
 * parameters) by writing to the /proc/scsi/ppa/0 file.
 * Very simple method really... (To simple, no error checking :( )
 * Reason: Kernel hackers HATE having to unload and reload modules for
 * testing...
 * Also gives a method to use a script to obtain optimum timings (TODO)
 */

static inline int ppa_write_info(struct Scsi_Host *host, char *buffer, int length)
{
	ppa_struct *dev = ppa_dev(host);
	unsigned long x;

	if ((length > 5) && (strncmp(buffer, "mode=", 5) == 0)) {
		x = simple_strtoul(buffer + 5, NULL, 0);
		dev->mode = x;
		return length;
	}
	if ((length > 10) && (strncmp(buffer, "recon_tmo=", 10) == 0)) {
		x = simple_strtoul(buffer + 10, NULL, 0);
		dev->recon_tmo = x;
		printk(KERN_INFO "ppa: recon_tmo set to %ld\n", x);
		return length;
	}
	printk(KERN_WARNING "ppa /proc: invalid variable\n");
	return -EINVAL;
}

static int ppa_show_info(struct seq_file *m, struct Scsi_Host *host)
{
	ppa_struct *dev = ppa_dev(host);

	seq_printf(m, "Version : %s\n", PPA_VERSION);
	seq_printf(m, "Parport : %s\n", dev->dev->port->name);
	seq_printf(m, "Mode    : %s\n", PPA_MODE_STRING[dev->mode]);
#if PPA_DEBUG > 0
	seq_printf(m, "recon_tmo : %lu\n", dev->recon_tmo);
#endif
	return 0;
}

static int device_check(ppa_struct *dev);

#if PPA_DEBUG > 0
#define ppa_fail(x,y) printk("ppa: ppa_fail(%i) from %s at line %d\n",\
	   y, __func__, __LINE__); ppa_fail_func(x,y);
static inline void ppa_fail_func(ppa_struct *dev, int error_code)
#else
static inline void ppa_fail(ppa_struct *dev, int error_code)
#endif
{
	/* If we fail a device then we trash status / message bytes */
	if (dev->cur_cmd) {
		dev->cur_cmd->result = error_code << 16;
		dev->failed = 1;
	}
}

/*
 * Wait for the high bit to be set.
 * 
 * In principle, this could be tied to an interrupt, but the adapter
 * doesn't appear to be designed to support interrupts.  We spin on
 * the 0x80 ready bit. 
 */
static unsigned char ppa_wait(ppa_struct *dev)
{
	int k;
	unsigned short ppb = dev->base;
	unsigned char r;

	k = PPA_SPIN_TMO;
	/* Wait for bit 6 and 7 - PJC */
	for (r = r_str(ppb); ((r & 0xc0) != 0xc0) && (k); k--) {
		udelay(1);
		r = r_str(ppb);
	}

	/*
	 * return some status information.
	 * Semantics: 0xc0 = ZIP wants more data
	 *            0xd0 = ZIP wants to send more data
	 *            0xe0 = ZIP is expecting SCSI command data
	 *            0xf0 = end of transfer, ZIP is sending status
	 */
	if (k)
		return (r & 0xf0);

	/* Counter expired - Time out occurred */
	ppa_fail(dev, DID_TIME_OUT);
	printk(KERN_WARNING "ppa timeout in ppa_wait\n");
	return 0;		/* command timed out */
}

/*
 * Clear EPP Timeout Bit 
 */
static inline void epp_reset(unsigned short ppb)
{
	int i;

	i = r_str(ppb);
	w_str(ppb, i);
	w_str(ppb, i & 0xfe);
}

/* 
 * Wait for empty ECP fifo (if we are in ECP fifo mode only)
 */
static inline void ecp_sync(ppa_struct *dev)
{
	int i, ppb_hi = dev->dev->port->base_hi;

	if (ppb_hi == 0)
		return;

	if ((r_ecr(ppb_hi) & 0xe0) == 0x60) {	/* mode 011 == ECP fifo mode */
		for (i = 0; i < 100; i++) {
			if (r_ecr(ppb_hi) & 0x01)
				return;
			udelay(5);
		}
		printk(KERN_WARNING "ppa: ECP sync failed as data still present in FIFO.\n");
	}
}

static int ppa_byte_out(unsigned short base, const char *buffer, int len)
{
	int i;

	for (i = len; i; i--) {
		w_dtr(base, *buffer++);
		w_ctr(base, 0xe);
		w_ctr(base, 0xc);
	}
	return 1;		/* All went well - we hope! */
}

static int ppa_byte_in(unsigned short base, char *buffer, int len)
{
	int i;

	for (i = len; i; i--) {
		*buffer++ = r_dtr(base);
		w_ctr(base, 0x27);
		w_ctr(base, 0x25);
	}
	return 1;		/* All went well - we hope! */
}

static int ppa_nibble_in(unsigned short base, char *buffer, int len)
{
	for (; len; len--) {
		unsigned char h;

		w_ctr(base, 0x4);
		h = r_str(base) & 0xf0;
		w_ctr(base, 0x6);
		*buffer++ = h | ((r_str(base) & 0xf0) >> 4);
	}
	return 1;		/* All went well - we hope! */
}

static int ppa_out(ppa_struct *dev, char *buffer, int len)
{
	int r;
	unsigned short ppb = dev->base;

	r = ppa_wait(dev);

	if ((r & 0x50) != 0x40) {
		ppa_fail(dev, DID_ERROR);
		return 0;
	}
	switch (dev->mode) {
	case PPA_NIBBLE:
	case PPA_PS2:
		/* 8 bit output, with a loop */
		r = ppa_byte_out(ppb, buffer, len);
		break;

	case PPA_EPP_32:
	case PPA_EPP_16:
	case PPA_EPP_8:
		epp_reset(ppb);
		w_ctr(ppb, 0x4);
#ifdef CONFIG_SCSI_IZIP_EPP16
		if (!(((long) buffer | len) & 0x01))
			outsw(ppb + 4, buffer, len >> 1);
#else
		if (!(((long) buffer | len) & 0x03))
			outsl(ppb + 4, buffer, len >> 2);
#endif
		else
			outsb(ppb + 4, buffer, len);
		w_ctr(ppb, 0xc);
		r = !(r_str(ppb) & 0x01);
		w_ctr(ppb, 0xc);
		ecp_sync(dev);
		break;

	default:
		printk(KERN_ERR "PPA: bug in ppa_out()\n");
		r = 0;
	}
	return r;
}

static int ppa_in(ppa_struct *dev, char *buffer, int len)
{
	int r;
	unsigned short ppb = dev->base;

	r = ppa_wait(dev);

	if ((r & 0x50) != 0x50) {
		ppa_fail(dev, DID_ERROR);
		return 0;
	}
	switch (dev->mode) {
	case PPA_NIBBLE:
		/* 4 bit input, with a loop */
		r = ppa_nibble_in(ppb, buffer, len);
		w_ctr(ppb, 0xc);
		break;

	case PPA_PS2:
		/* 8 bit input, with a loop */
		w_ctr(ppb, 0x25);
		r = ppa_byte_in(ppb, buffer, len);
		w_ctr(ppb, 0x4);
		w_ctr(ppb, 0xc);
		break;

	case PPA_EPP_32:
	case PPA_EPP_16:
	case PPA_EPP_8:
		epp_reset(ppb);
		w_ctr(ppb, 0x24);
#ifdef CONFIG_SCSI_IZIP_EPP16
		if (!(((long) buffer | len) & 0x01))
			insw(ppb + 4, buffer, len >> 1);
#else
		if (!(((long) buffer | len) & 0x03))
			insl(ppb + 4, buffer, len >> 2);
#endif
		else
			insb(ppb + 4, buffer, len);
		w_ctr(ppb, 0x2c);
		r = !(r_str(ppb) & 0x01);
		w_ctr(ppb, 0x2c);
		ecp_sync(dev);
		break;

	default:
		printk(KERN_ERR "PPA: bug in ppa_ins()\n");
		r = 0;
		break;
	}
	return r;
}

/* end of ppa_io.h */
static inline void ppa_d_pulse(unsigned short ppb, unsigned char b)
{
	w_dtr(ppb, b);
	w_ctr(ppb, 0xc);
	w_ctr(ppb, 0xe);
	w_ctr(ppb, 0xc);
	w_ctr(ppb, 0x4);
	w_ctr(ppb, 0xc);
}

static void ppa_disconnect(ppa_struct *dev)
{
	unsigned short ppb = dev->base;

	ppa_d_pulse(ppb, 0);
	ppa_d_pulse(ppb, 0x3c);
	ppa_d_pulse(ppb, 0x20);
	ppa_d_pulse(ppb, 0xf);
}

static inline void ppa_c_pulse(unsigned short ppb, unsigned char b)
{
	w_dtr(ppb, b);
	w_ctr(ppb, 0x4);
	w_ctr(ppb, 0x6);
	w_ctr(ppb, 0x4);
	w_ctr(ppb, 0xc);
}

static inline void ppa_connect(ppa_struct *dev, int flag)
{
	unsigned short ppb = dev->base;

	ppa_c_pulse(ppb, 0);
	ppa_c_pulse(ppb, 0x3c);
	ppa_c_pulse(ppb, 0x20);
	if ((flag == CONNECT_EPP_MAYBE) && IN_EPP_MODE(dev->mode))
		ppa_c_pulse(ppb, 0xcf);
	else
		ppa_c_pulse(ppb, 0x8f);
}

static int ppa_select(ppa_struct *dev, int target)
{
	int k;
	unsigned short ppb = dev->base;

	/*
	 * Bit 6 (0x40) is the device selected bit.
	 * First we must wait till the current device goes off line...
	 */
	k = PPA_SELECT_TMO;
	do {
		k--;
		udelay(1);
	} while ((r_str(ppb) & 0x40) && (k));
	if (!k)
		return 0;

	w_dtr(ppb, (1 << target));
	w_ctr(ppb, 0xe);
	w_ctr(ppb, 0xc);
	w_dtr(ppb, 0x80);	/* This is NOT the initator */
	w_ctr(ppb, 0x8);

	k = PPA_SELECT_TMO;
	do {
		k--;
		udelay(1);
	}
	while (!(r_str(ppb) & 0x40) && (k));
	if (!k)
		return 0;

	return 1;
}

/* 
 * This is based on a trace of what the Iomega DOS 'guest' driver does.
 * I've tried several different kinds of parallel ports with guest and
 * coded this to react in the same ways that it does.
 * 
 * The return value from this function is just a hint about where the
 * handshaking failed.
 * 
 */
static int ppa_init(ppa_struct *dev)
{
	int retv;
	unsigned short ppb = dev->base;

	ppa_disconnect(dev);
	ppa_connect(dev, CONNECT_NORMAL);

	retv = 2;		/* Failed */

	w_ctr(ppb, 0xe);
	if ((r_str(ppb) & 0x08) == 0x08)
		retv--;

	w_ctr(ppb, 0xc);
	if ((r_str(ppb) & 0x08) == 0x00)
		retv--;

	if (!retv)
		ppa_reset_pulse(ppb);
	udelay(1000);		/* Allow devices to settle down */
	ppa_disconnect(dev);
	udelay(1000);		/* Another delay to allow devices to settle */

	if (retv)
		return -EIO;

	return device_check(dev);
}

static inline int ppa_send_command(struct scsi_cmnd *cmd)
{
	ppa_struct *dev = ppa_dev(cmd->device->host);
	int k;

	w_ctr(dev->base, 0x0c);

	for (k = 0; k < cmd->cmd_len; k++)
		if (!ppa_out(dev, &cmd->cmnd[k], 1))
			return 0;
	return 1;
}

/*
 * The bulk flag enables some optimisations in the data transfer loops,
 * it should be true for any command that transfers data in integral
 * numbers of sectors.
 * 
 * The driver appears to remain stable if we speed up the parallel port
 * i/o in this function, but not elsewhere.
 */
static int ppa_completion(struct scsi_cmnd *cmd)
{
	/* Return codes:
	 * -1     Error
	 *  0     Told to schedule
	 *  1     Finished data transfer
	 */
	ppa_struct *dev = ppa_dev(cmd->device->host);
	unsigned short ppb = dev->base;
	unsigned long start_jiffies = jiffies;

	unsigned char r, v;
	int fast, bulk, status;

	v = cmd->cmnd[0];
	bulk = ((v == READ_6) ||
		(v == READ_10) || (v == WRITE_6) || (v == WRITE_10));

	/*
	 * We only get here if the drive is ready to comunicate,
	 * hence no need for a full ppa_wait.
	 */
	r = (r_str(ppb) & 0xf0);

	while (r != (unsigned char) 0xf0) {
		/*
		 * If we have been running for more than a full timer tick
		 * then take a rest.
		 */
		if (time_after(jiffies, start_jiffies + 1))
			return 0;

		if ((cmd->SCp.this_residual <= 0)) {
			ppa_fail(dev, DID_ERROR);
			return -1;	/* ERROR_RETURN */
		}

		/* On some hardware we have SCSI disconnected (6th bit low)
		 * for about 100usecs. It is too expensive to wait a 
		 * tick on every loop so we busy wait for no more than
		 * 500usecs to give the drive a chance first. We do not 
		 * change things for "normal" hardware since generally 
		 * the 6th bit is always high.
		 * This makes the CPU load higher on some hardware 
		 * but otherwise we can not get more than 50K/secs 
		 * on this problem hardware.
		 */
		if ((r & 0xc0) != 0xc0) {
			/* Wait for reconnection should be no more than 
			 * jiffy/2 = 5ms = 5000 loops
			 */
			unsigned long k = dev->recon_tmo;
			for (; k && ((r = (r_str(ppb) & 0xf0)) & 0xc0) != 0xc0;
			     k--)
				udelay(1);

			if (!k)
				return 0;
		}

		/* determine if we should use burst I/O */
		fast = (bulk && (cmd->SCp.this_residual >= PPA_BURST_SIZE))
		    ? PPA_BURST_SIZE : 1;

		if (r == (unsigned char) 0xc0)
			status = ppa_out(dev, cmd->SCp.ptr, fast);
		else
			status = ppa_in(dev, cmd->SCp.ptr, fast);

		cmd->SCp.ptr += fast;
		cmd->SCp.this_residual -= fast;

		if (!status) {
			ppa_fail(dev, DID_BUS_BUSY);
			return -1;	/* ERROR_RETURN */
		}
		if (cmd->SCp.buffer && !cmd->SCp.this_residual) {
			/* if scatter/gather, advance to the next segment */
			if (cmd->SCp.buffers_residual--) {
				cmd->SCp.buffer = sg_next(cmd->SCp.buffer);
				cmd->SCp.this_residual =
				    cmd->SCp.buffer->length;
				cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
			}
		}
		/* Now check to see if the drive is ready to comunicate */
		r = (r_str(ppb) & 0xf0);
		/* If not, drop back down to the scheduler and wait a timer tick */
		if (!(r & 0x80))
			return 0;
	}
	return 1;		/* FINISH_RETURN */
}

/*
 * Since the PPA itself doesn't generate interrupts, we use
 * the scheduler's task queue to generate a stream of call-backs and
 * complete the request when the drive is ready.
 */
static void ppa_interrupt(struct work_struct *work)
{
	ppa_struct *dev = container_of(work, ppa_struct, ppa_tq.work);
	struct scsi_cmnd *cmd = dev->cur_cmd;

	if (!cmd) {
		printk(KERN_ERR "PPA: bug in ppa_interrupt\n");
		return;
	}
	if (ppa_engine(dev, cmd)) {
		schedule_delayed_work(&dev->ppa_tq, 1);
		return;
	}
	/* Command must of completed hence it is safe to let go... */
#if PPA_DEBUG > 0
	switch ((cmd->result >> 16) & 0xff) {
	case DID_OK:
		break;
	case DID_NO_CONNECT:
		printk(KERN_DEBUG "ppa: no device at SCSI ID %i\n", cmd->device->target);
		break;
	case DID_BUS_BUSY:
		printk(KERN_DEBUG "ppa: BUS BUSY - EPP timeout detected\n");
		break;
	case DID_TIME_OUT:
		printk(KERN_DEBUG "ppa: unknown timeout\n");
		break;
	case DID_ABORT:
		printk(KERN_DEBUG "ppa: told to abort\n");
		break;
	case DID_PARITY:
		printk(KERN_DEBUG "ppa: parity error (???)\n");
		break;
	case DID_ERROR:
		printk(KERN_DEBUG "ppa: internal driver error\n");
		break;
	case DID_RESET:
		printk(KERN_DEBUG "ppa: told to reset device\n");
		break;
	case DID_BAD_INTR:
		printk(KERN_WARNING "ppa: bad interrupt (???)\n");
		break;
	default:
		printk(KERN_WARNING "ppa: bad return code (%02x)\n",
		       (cmd->result >> 16) & 0xff);
	}
#endif

	if (cmd->SCp.phase > 1)
		ppa_disconnect(dev);

	ppa_pb_dismiss(dev);

	dev->cur_cmd = NULL;

	cmd->scsi_done(cmd);
}

static int ppa_engine(ppa_struct *dev, struct scsi_cmnd *cmd)
{
	unsigned short ppb = dev->base;
	unsigned char l = 0, h = 0;
	int retv;

	/* First check for any errors that may of occurred
	 * Here we check for internal errors
	 */
	if (dev->failed)
		return 0;

	switch (cmd->SCp.phase) {
	case 0:		/* Phase 0 - Waiting for parport */
		if (time_after(jiffies, dev->jstart + HZ)) {
			/*
			 * We waited more than a second
			 * for parport to call us
			 */
			ppa_fail(dev, DID_BUS_BUSY);
			return 0;
		}
		return 1;	/* wait until ppa_wakeup claims parport */
	case 1:		/* Phase 1 - Connected */
		{		/* Perform a sanity check for cable unplugged */
			int retv = 2;	/* Failed */

			ppa_connect(dev, CONNECT_EPP_MAYBE);

			w_ctr(ppb, 0xe);
			if ((r_str(ppb) & 0x08) == 0x08)
				retv--;

			w_ctr(ppb, 0xc);
			if ((r_str(ppb) & 0x08) == 0x00)
				retv--;

			if (retv) {
				if (time_after(jiffies, dev->jstart + (1 * HZ))) {
					printk(KERN_ERR "ppa: Parallel port cable is unplugged.\n");
					ppa_fail(dev, DID_BUS_BUSY);
					return 0;
				} else {
					ppa_disconnect(dev);
					return 1;	/* Try again in a jiffy */
				}
			}
			cmd->SCp.phase++;
		}
		/* fall through */

	case 2:		/* Phase 2 - We are now talking to the scsi bus */
		if (!ppa_select(dev, scmd_id(cmd))) {
			ppa_fail(dev, DID_NO_CONNECT);
			return 0;
		}
		cmd->SCp.phase++;
		/* fall through */

	case 3:		/* Phase 3 - Ready to accept a command */
		w_ctr(ppb, 0x0c);
		if (!(r_str(ppb) & 0x80))
			return 1;

		if (!ppa_send_command(cmd))
			return 0;
		cmd->SCp.phase++;
		/* fall through */

	case 4:		/* Phase 4 - Setup scatter/gather buffers */
		if (scsi_bufflen(cmd)) {
			cmd->SCp.buffer = scsi_sglist(cmd);
			cmd->SCp.this_residual = cmd->SCp.buffer->length;
			cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
		} else {
			cmd->SCp.buffer = NULL;
			cmd->SCp.this_residual = 0;
			cmd->SCp.ptr = NULL;
		}
		cmd->SCp.buffers_residual = scsi_sg_count(cmd) - 1;
		cmd->SCp.phase++;
		/* fall through */

	case 5:		/* Phase 5 - Data transfer stage */
		w_ctr(ppb, 0x0c);
		if (!(r_str(ppb) & 0x80))
			return 1;

		retv = ppa_completion(cmd);
		if (retv == -1)
			return 0;
		if (retv == 0)
			return 1;
		cmd->SCp.phase++;
		/* fall through */

	case 6:		/* Phase 6 - Read status/message */
		cmd->result = DID_OK << 16;
		/* Check for data overrun */
		if (ppa_wait(dev) != (unsigned char) 0xf0) {
			ppa_fail(dev, DID_ERROR);
			return 0;
		}
		if (ppa_in(dev, &l, 1)) {	/* read status byte */
			/* Check for optional message byte */
			if (ppa_wait(dev) == (unsigned char) 0xf0)
				ppa_in(dev, &h, 1);
			cmd->result =
			    (DID_OK << 16) + (h << 8) + (l & STATUS_MASK);
		}
		return 0;	/* Finished */

	default:
		printk(KERN_ERR "ppa: Invalid scsi phase\n");
	}
	return 0;
}

static int ppa_queuecommand_lck(struct scsi_cmnd *cmd,
		void (*done) (struct scsi_cmnd *))
{
	ppa_struct *dev = ppa_dev(cmd->device->host);

	if (dev->cur_cmd) {
		printk(KERN_ERR "PPA: bug in ppa_queuecommand\n");
		return 0;
	}
	dev->failed = 0;
	dev->jstart = jiffies;
	dev->cur_cmd = cmd;
	cmd->scsi_done = done;
	cmd->result = DID_ERROR << 16;	/* default return code */
	cmd->SCp.phase = 0;	/* bus free */

	schedule_delayed_work(&dev->ppa_tq, 0);

	ppa_pb_claim(dev);

	return 0;
}

static DEF_SCSI_QCMD(ppa_queuecommand)

/*
 * Apparently the disk->capacity attribute is off by 1 sector 
 * for all disk drives.  We add the one here, but it should really
 * be done in sd.c.  Even if it gets fixed there, this will still
 * work.
 */
static int ppa_biosparam(struct scsi_device *sdev, struct block_device *dev,
	      sector_t capacity, int ip[])
{
	ip[0] = 0x40;
	ip[1] = 0x20;
	ip[2] = ((unsigned long) capacity + 1) / (ip[0] * ip[1]);
	if (ip[2] > 1024) {
		ip[0] = 0xff;
		ip[1] = 0x3f;
		ip[2] = ((unsigned long) capacity + 1) / (ip[0] * ip[1]);
		if (ip[2] > 1023)
			ip[2] = 1023;
	}
	return 0;
}

static int ppa_abort(struct scsi_cmnd *cmd)
{
	ppa_struct *dev = ppa_dev(cmd->device->host);
	/*
	 * There is no method for aborting commands since Iomega
	 * have tied the SCSI_MESSAGE line high in the interface
	 */

	switch (cmd->SCp.phase) {
	case 0:		/* Do not have access to parport */
	case 1:		/* Have not connected to interface */
		dev->cur_cmd = NULL;	/* Forget the problem */
		return SUCCESS;
	default:		/* SCSI command sent, can not abort */
		return FAILED;
	}
}

static void ppa_reset_pulse(unsigned int base)
{
	w_dtr(base, 0x40);
	w_ctr(base, 0x8);
	udelay(30);
	w_ctr(base, 0xc);
}

static int ppa_reset(struct scsi_cmnd *cmd)
{
	ppa_struct *dev = ppa_dev(cmd->device->host);

	if (cmd->SCp.phase)
		ppa_disconnect(dev);
	dev->cur_cmd = NULL;	/* Forget the problem */

	ppa_connect(dev, CONNECT_NORMAL);
	ppa_reset_pulse(dev->base);
	mdelay(1);		/* device settle delay */
	ppa_disconnect(dev);
	mdelay(1);		/* device settle delay */
	return SUCCESS;
}

static int device_check(ppa_struct *dev)
{
	/* This routine looks for a device and then attempts to use EPP
	   to send a command. If all goes as planned then EPP is available. */

	static u8 cmd[6] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
	int loop, old_mode, status, k, ppb = dev->base;
	unsigned char l;

	old_mode = dev->mode;
	for (loop = 0; loop < 8; loop++) {
		/* Attempt to use EPP for Test Unit Ready */
		if ((ppb & 0x0007) == 0x0000)
			dev->mode = PPA_EPP_32;

second_pass:
		ppa_connect(dev, CONNECT_EPP_MAYBE);
		/* Select SCSI device */
		if (!ppa_select(dev, loop)) {
			ppa_disconnect(dev);
			continue;
		}
		printk(KERN_INFO "ppa: Found device at ID %i, Attempting to use %s\n",
		       loop, PPA_MODE_STRING[dev->mode]);

		/* Send SCSI command */
		status = 1;
		w_ctr(ppb, 0x0c);
		for (l = 0; (l < 6) && (status); l++)
			status = ppa_out(dev, cmd, 1);

		if (!status) {
			ppa_disconnect(dev);
			ppa_connect(dev, CONNECT_EPP_MAYBE);
			w_dtr(ppb, 0x40);
			w_ctr(ppb, 0x08);
			udelay(30);
			w_ctr(ppb, 0x0c);
			udelay(1000);
			ppa_disconnect(dev);
			udelay(1000);
			if (dev->mode == PPA_EPP_32) {
				dev->mode = old_mode;
				goto second_pass;
			}
			return -EIO;
		}
		w_ctr(ppb, 0x0c);
		k = 1000000;	/* 1 Second */
		do {
			l = r_str(ppb);
			k--;
			udelay(1);
		} while (!(l & 0x80) && (k));

		l &= 0xf0;

		if (l != 0xf0) {
			ppa_disconnect(dev);
			ppa_connect(dev, CONNECT_EPP_MAYBE);
			ppa_reset_pulse(ppb);
			udelay(1000);
			ppa_disconnect(dev);
			udelay(1000);
			if (dev->mode == PPA_EPP_32) {
				dev->mode = old_mode;
				goto second_pass;
			}
			return -EIO;
		}
		ppa_disconnect(dev);
		printk(KERN_INFO "ppa: Communication established with ID %i using %s\n",
		       loop, PPA_MODE_STRING[dev->mode]);
		ppa_connect(dev, CONNECT_EPP_MAYBE);
		ppa_reset_pulse(ppb);
		udelay(1000);
		ppa_disconnect(dev);
		udelay(1000);
		return 0;
	}
	return -ENODEV;
}

static int ppa_adjust_queue(struct scsi_device *device)
{
	blk_queue_bounce_limit(device->request_queue, BLK_BOUNCE_HIGH);
	return 0;
}

static struct scsi_host_template ppa_template = {
	.module			= THIS_MODULE,
	.proc_name		= "ppa",
	.show_info		= ppa_show_info,
	.write_info		= ppa_write_info,
	.name			= "Iomega VPI0 (ppa) interface",
	.queuecommand		= ppa_queuecommand,
	.eh_abort_handler	= ppa_abort,
	.eh_host_reset_handler	= ppa_reset,
	.bios_param		= ppa_biosparam,
	.this_id		= -1,
	.sg_tablesize		= SG_ALL,
	.can_queue		= 1,
	.slave_alloc		= ppa_adjust_queue,
};

/***************************************************************************
 *                   Parallel port probing routines                        *
 ***************************************************************************/

static LIST_HEAD(ppa_hosts);

/*
 * Finds the first available device number that can be alloted to the
 * new ppa device and returns the address of the previous node so that
 * we can add to the tail and have a list in the ascending order.
 */

static inline ppa_struct *find_parent(void)
{
	ppa_struct *dev, *par = NULL;
	unsigned int cnt = 0;

	if (list_empty(&ppa_hosts))
		return NULL;

	list_for_each_entry(dev, &ppa_hosts, list) {
		if (dev->dev_no != cnt)
			return par;
		cnt++;
		par = dev;
	}

	return par;
}

static int __ppa_attach(struct parport *pb)
{
	struct Scsi_Host *host;
	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(waiting);
	DEFINE_WAIT(wait);
	ppa_struct *dev, *temp;
	int ports;
	int modes, ppb, ppb_hi;
	int err = -ENOMEM;
	struct pardev_cb ppa_cb;

	dev = kzalloc(sizeof(ppa_struct), GFP_KERNEL);
	if (!dev)
		return -ENOMEM;
	dev->base = -1;
	dev->mode = PPA_AUTODETECT;
	dev->recon_tmo = PPA_RECON_TMO;
	init_waitqueue_head(&waiting);
	temp = find_parent();
	if (temp)
		dev->dev_no = temp->dev_no + 1;

	memset(&ppa_cb, 0, sizeof(ppa_cb));
	ppa_cb.private = dev;
	ppa_cb.wakeup = ppa_wakeup;

	dev->dev = parport_register_dev_model(pb, "ppa", &ppa_cb, dev->dev_no);

	if (!dev->dev)
		goto out;

	/* Claim the bus so it remembers what we do to the control
	 * registers. [ CTR and ECP ]
	 */
	err = -EBUSY;
	dev->waiting = &waiting;
	prepare_to_wait(&waiting, &wait, TASK_UNINTERRUPTIBLE);
	if (ppa_pb_claim(dev))
		schedule_timeout(3 * HZ);
	if (dev->wanted) {
		printk(KERN_ERR "ppa%d: failed to claim parport because "
				"a pardevice is owning the port for too long "
				"time!\n", pb->number);
		ppa_pb_dismiss(dev);
		dev->waiting = NULL;
		finish_wait(&waiting, &wait);
		goto out1;
	}
	dev->waiting = NULL;
	finish_wait(&waiting, &wait);
	ppb = dev->base = dev->dev->port->base;
	ppb_hi = dev->dev->port->base_hi;
	w_ctr(ppb, 0x0c);
	modes = dev->dev->port->modes;

	/* Mode detection works up the chain of speed
	 * This avoids a nasty if-then-else-if-... tree
	 */
	dev->mode = PPA_NIBBLE;

	if (modes & PARPORT_MODE_TRISTATE)
		dev->mode = PPA_PS2;

	if (modes & PARPORT_MODE_ECP) {
		w_ecr(ppb_hi, 0x20);
		dev->mode = PPA_PS2;
	}
	if ((modes & PARPORT_MODE_EPP) && (modes & PARPORT_MODE_ECP))
		w_ecr(ppb_hi, 0x80);

	/* Done configuration */

	err = ppa_init(dev);
	ppa_pb_release(dev);

	if (err)
		goto out1;

	/* now the glue ... */
	if (dev->mode == PPA_NIBBLE || dev->mode == PPA_PS2)
		ports = 3;
	else
		ports = 8;

	INIT_DELAYED_WORK(&dev->ppa_tq, ppa_interrupt);

	err = -ENOMEM;
	host = scsi_host_alloc(&ppa_template, sizeof(ppa_struct *));
	if (!host)
		goto out1;
	host->io_port = pb->base;
	host->n_io_port = ports;
	host->dma_channel = -1;
	host->unique_id = pb->number;
	*(ppa_struct **)&host->hostdata = dev;
	dev->host = host;
	list_add_tail(&dev->list, &ppa_hosts);
	err = scsi_add_host(host, NULL);
	if (err)
		goto out2;
	scsi_scan_host(host);
	return 0;
out2:
	list_del_init(&dev->list);
	scsi_host_put(host);
out1:
	parport_unregister_device(dev->dev);
out:
	kfree(dev);
	return err;
}

static void ppa_attach(struct parport *pb)
{
	__ppa_attach(pb);
}

static void ppa_detach(struct parport *pb)
{
	ppa_struct *dev;
	list_for_each_entry(dev, &ppa_hosts, list) {
		if (dev->dev->port == pb) {
			list_del_init(&dev->list);
			scsi_remove_host(dev->host);
			scsi_host_put(dev->host);
			parport_unregister_device(dev->dev);
			kfree(dev);
			break;
		}
	}
}

static struct parport_driver ppa_driver = {
	.name		= "ppa",
	.match_port	= ppa_attach,
	.detach		= ppa_detach,
	.devmodel	= true,
};

static int __init ppa_driver_init(void)
{
	printk(KERN_INFO "ppa: Version %s\n", PPA_VERSION);
	return parport_register_driver(&ppa_driver);
}

static void __exit ppa_driver_exit(void)
{
	parport_unregister_driver(&ppa_driver);
}

module_init(ppa_driver_init);
module_exit(ppa_driver_exit);
MODULE_LICENSE("GPL");