summaryrefslogtreecommitdiffstats
path: root/drivers/scsi/atari_scsi.c
blob: a503dc50c4f805b81fb7e68beff664b7c7e8b908 (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
/*
 * atari_scsi.c -- Device dependent functions for the Atari generic SCSI port
 *
 * Copyright 1994 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
 *
 *   Loosely based on the work of Robert De Vries' team and added:
 *    - working real DMA
 *    - Falcon support (untested yet!)   ++bjoern fixed and now it works
 *    - lots of extensions and bug fixes.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file COPYING in the main directory of this archive
 * for more details.
 *
 */

/*
 * Notes for Falcon SCSI DMA
 *
 * The 5380 device is one of several that all share the DMA chip. Hence
 * "locking" and "unlocking" access to this chip is required.
 *
 * Two possible schemes for ST DMA acquisition by atari_scsi are:
 * 1) The lock is taken for each command separately (i.e. can_queue == 1).
 * 2) The lock is taken when the first command arrives and released
 * when the last command is finished (i.e. can_queue > 1).
 *
 * The first alternative limits SCSI bus utilization, since interleaving
 * commands is not possible. The second gives better performance but is
 * unfair to other drivers needing to use the ST DMA chip. In order to
 * allow the IDE and floppy drivers equal access to the ST DMA chip
 * the default is can_queue == 1.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/blkdev.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/nvram.h>
#include <linux/bitops.h>
#include <linux/wait.h>
#include <linux/platform_device.h>

#include <asm/setup.h>
#include <asm/atarihw.h>
#include <asm/atariints.h>
#include <asm/atari_stdma.h>
#include <asm/atari_stram.h>
#include <asm/io.h>

#include <scsi/scsi_host.h>

#define DMA_MIN_SIZE                    32

/* Definitions for the core NCR5380 driver. */

#define NCR5380_implementation_fields   /* none */

static u8 (*atari_scsi_reg_read)(unsigned int);
static void (*atari_scsi_reg_write)(unsigned int, u8);

#define NCR5380_read(reg)               atari_scsi_reg_read(reg)
#define NCR5380_write(reg, value)       atari_scsi_reg_write(reg, value)

#define NCR5380_queue_command           atari_scsi_queue_command
#define NCR5380_abort                   atari_scsi_abort
#define NCR5380_info                    atari_scsi_info

#define NCR5380_dma_xfer_len            atari_scsi_dma_xfer_len
#define NCR5380_dma_recv_setup          atari_scsi_dma_recv_setup
#define NCR5380_dma_send_setup          atari_scsi_dma_send_setup
#define NCR5380_dma_residual            atari_scsi_dma_residual

#define NCR5380_acquire_dma_irq(instance)      falcon_get_lock(instance)
#define NCR5380_release_dma_irq(instance)      falcon_release_lock()

#include "NCR5380.h"


#define	IS_A_TT()	ATARIHW_PRESENT(TT_SCSI)

#define	SCSI_DMA_WRITE_P(elt,val)				\
	do {							\
		unsigned long v = val;				\
		tt_scsi_dma.elt##_lo = v & 0xff;		\
		v >>= 8;					\
		tt_scsi_dma.elt##_lmd = v & 0xff;		\
		v >>= 8;					\
		tt_scsi_dma.elt##_hmd = v & 0xff;		\
		v >>= 8;					\
		tt_scsi_dma.elt##_hi = v & 0xff;		\
	} while(0)

#define	SCSI_DMA_READ_P(elt)					\
	(((((((unsigned long)tt_scsi_dma.elt##_hi << 8) |	\
	     (unsigned long)tt_scsi_dma.elt##_hmd) << 8) |	\
	   (unsigned long)tt_scsi_dma.elt##_lmd) << 8) |	\
	 (unsigned long)tt_scsi_dma.elt##_lo)


static inline void SCSI_DMA_SETADR(unsigned long adr)
{
	st_dma.dma_lo = (unsigned char)adr;
	MFPDELAY();
	adr >>= 8;
	st_dma.dma_md = (unsigned char)adr;
	MFPDELAY();
	adr >>= 8;
	st_dma.dma_hi = (unsigned char)adr;
	MFPDELAY();
}

static inline unsigned long SCSI_DMA_GETADR(void)
{
	unsigned long adr;
	adr = st_dma.dma_lo;
	MFPDELAY();
	adr |= (st_dma.dma_md & 0xff) << 8;
	MFPDELAY();
	adr |= (st_dma.dma_hi & 0xff) << 16;
	MFPDELAY();
	return adr;
}

static void atari_scsi_fetch_restbytes(void);

static unsigned long	atari_dma_residual, atari_dma_startaddr;
static short		atari_dma_active;
/* pointer to the dribble buffer */
static char		*atari_dma_buffer;
/* precalculated physical address of the dribble buffer */
static unsigned long	atari_dma_phys_buffer;
/* != 0 tells the Falcon int handler to copy data from the dribble buffer */
static char		*atari_dma_orig_addr;
/* size of the dribble buffer; 4k seems enough, since the Falcon cannot use
 * scatter-gather anyway, so most transfers are 1024 byte only. In the rare
 * cases where requests to physical contiguous buffers have been merged, this
 * request is <= 4k (one page). So I don't think we have to split transfers
 * just due to this buffer size...
 */
#define	STRAM_BUFFER_SIZE	(4096)
/* mask for address bits that can't be used with the ST-DMA */
static unsigned long	atari_dma_stram_mask;
#define STRAM_ADDR(a)	(((a) & atari_dma_stram_mask) == 0)

static int setup_can_queue = -1;
module_param(setup_can_queue, int, 0);
static int setup_cmd_per_lun = -1;
module_param(setup_cmd_per_lun, int, 0);
static int setup_sg_tablesize = -1;
module_param(setup_sg_tablesize, int, 0);
static int setup_hostid = -1;
module_param(setup_hostid, int, 0);
static int setup_toshiba_delay = -1;
module_param(setup_toshiba_delay, int, 0);


static int scsi_dma_is_ignored_buserr(unsigned char dma_stat)
{
	int i;
	unsigned long addr = SCSI_DMA_READ_P(dma_addr), end_addr;

	if (dma_stat & 0x01) {

		/* A bus error happens when DMA-ing from the last page of a
		 * physical memory chunk (DMA prefetch!), but that doesn't hurt.
		 * Check for this case:
		 */

		for (i = 0; i < m68k_num_memory; ++i) {
			end_addr = m68k_memory[i].addr + m68k_memory[i].size;
			if (end_addr <= addr && addr <= end_addr + 4)
				return 1;
		}
	}
	return 0;
}


static irqreturn_t scsi_tt_intr(int irq, void *dev)
{
	struct Scsi_Host *instance = dev;
	struct NCR5380_hostdata *hostdata = shost_priv(instance);
	int dma_stat;

	dma_stat = tt_scsi_dma.dma_ctrl;

	dsprintk(NDEBUG_INTR, instance, "NCR5380 interrupt, DMA status = %02x\n",
	         dma_stat & 0xff);

	/* Look if it was the DMA that has interrupted: First possibility
	 * is that a bus error occurred...
	 */
	if (dma_stat & 0x80) {
		if (!scsi_dma_is_ignored_buserr(dma_stat)) {
			printk(KERN_ERR "SCSI DMA caused bus error near 0x%08lx\n",
			       SCSI_DMA_READ_P(dma_addr));
			printk(KERN_CRIT "SCSI DMA bus error -- bad DMA programming!");
		}
	}

	/* If the DMA is active but not finished, we have the case
	 * that some other 5380 interrupt occurred within the DMA transfer.
	 * This means we have residual bytes, if the desired end address
	 * is not yet reached. Maybe we have to fetch some bytes from the
	 * rest data register, too. The residual must be calculated from
	 * the address pointer, not the counter register, because only the
	 * addr reg counts bytes not yet written and pending in the rest
	 * data reg!
	 */
	if ((dma_stat & 0x02) && !(dma_stat & 0x40)) {
		atari_dma_residual = hostdata->dma_len -
			(SCSI_DMA_READ_P(dma_addr) - atari_dma_startaddr);

		dprintk(NDEBUG_DMA, "SCSI DMA: There are %ld residual bytes.\n",
			   atari_dma_residual);

		if ((signed int)atari_dma_residual < 0)
			atari_dma_residual = 0;
		if ((dma_stat & 1) == 0) {
			/*
			 * After read operations, we maybe have to
			 * transport some rest bytes
			 */
			atari_scsi_fetch_restbytes();
		} else {
			/*
			 * There seems to be a nasty bug in some SCSI-DMA/NCR
			 * combinations: If a target disconnects while a write
			 * operation is going on, the address register of the
			 * DMA may be a few bytes farer than it actually read.
			 * This is probably due to DMA prefetching and a delay
			 * between DMA and NCR.  Experiments showed that the
			 * dma_addr is 9 bytes to high, but this could vary.
			 * The problem is, that the residual is thus calculated
			 * wrong and the next transfer will start behind where
			 * it should.  So we round up the residual to the next
			 * multiple of a sector size, if it isn't already a
			 * multiple and the originally expected transfer size
			 * was.  The latter condition is there to ensure that
			 * the correction is taken only for "real" data
			 * transfers and not for, e.g., the parameters of some
			 * other command.  These shouldn't disconnect anyway.
			 */
			if (atari_dma_residual & 0x1ff) {
				dprintk(NDEBUG_DMA, "SCSI DMA: DMA bug corrected, "
					   "difference %ld bytes\n",
					   512 - (atari_dma_residual & 0x1ff));
				atari_dma_residual = (atari_dma_residual + 511) & ~0x1ff;
			}
		}
		tt_scsi_dma.dma_ctrl = 0;
	}

	/* If the DMA is finished, fetch the rest bytes and turn it off */
	if (dma_stat & 0x40) {
		atari_dma_residual = 0;
		if ((dma_stat & 1) == 0)
			atari_scsi_fetch_restbytes();
		tt_scsi_dma.dma_ctrl = 0;
	}

	NCR5380_intr(irq, dev);

	return IRQ_HANDLED;
}


static irqreturn_t scsi_falcon_intr(int irq, void *dev)
{
	struct Scsi_Host *instance = dev;
	struct NCR5380_hostdata *hostdata = shost_priv(instance);
	int dma_stat;

	/* Turn off DMA and select sector counter register before
	 * accessing the status register (Atari recommendation!)
	 */
	st_dma.dma_mode_status = 0x90;
	dma_stat = st_dma.dma_mode_status;

	/* Bit 0 indicates some error in the DMA process... don't know
	 * what happened exactly (no further docu).
	 */
	if (!(dma_stat & 0x01)) {
		/* DMA error */
		printk(KERN_CRIT "SCSI DMA error near 0x%08lx!\n", SCSI_DMA_GETADR());
	}

	/* If the DMA was active, but now bit 1 is not clear, it is some
	 * other 5380 interrupt that finishes the DMA transfer. We have to
	 * calculate the number of residual bytes and give a warning if
	 * bytes are stuck in the ST-DMA fifo (there's no way to reach them!)
	 */
	if (atari_dma_active && (dma_stat & 0x02)) {
		unsigned long transferred;

		transferred = SCSI_DMA_GETADR() - atari_dma_startaddr;
		/* The ST-DMA address is incremented in 2-byte steps, but the
		 * data are written only in 16-byte chunks. If the number of
		 * transferred bytes is not divisible by 16, the remainder is
		 * lost somewhere in outer space.
		 */
		if (transferred & 15)
			printk(KERN_ERR "SCSI DMA error: %ld bytes lost in "
			       "ST-DMA fifo\n", transferred & 15);

		atari_dma_residual = hostdata->dma_len - transferred;
		dprintk(NDEBUG_DMA, "SCSI DMA: There are %ld residual bytes.\n",
			   atari_dma_residual);
	} else
		atari_dma_residual = 0;
	atari_dma_active = 0;

	if (atari_dma_orig_addr) {
		/* If the dribble buffer was used on a read operation, copy the DMA-ed
		 * data to the original destination address.
		 */
		memcpy(atari_dma_orig_addr, phys_to_virt(atari_dma_startaddr),
		       hostdata->dma_len - atari_dma_residual);
		atari_dma_orig_addr = NULL;
	}

	NCR5380_intr(irq, dev);

	return IRQ_HANDLED;
}


static void atari_scsi_fetch_restbytes(void)
{
	int nr;
	char *src, *dst;
	unsigned long phys_dst;

	/* fetch rest bytes in the DMA register */
	phys_dst = SCSI_DMA_READ_P(dma_addr);
	nr = phys_dst & 3;
	if (nr) {
		/* there are 'nr' bytes left for the last long address
		   before the DMA pointer */
		phys_dst ^= nr;
		dprintk(NDEBUG_DMA, "SCSI DMA: there are %d rest bytes for phys addr 0x%08lx",
			   nr, phys_dst);
		/* The content of the DMA pointer is a physical address!  */
		dst = phys_to_virt(phys_dst);
		dprintk(NDEBUG_DMA, " = virt addr %p\n", dst);
		for (src = (char *)&tt_scsi_dma.dma_restdata; nr != 0; --nr)
			*dst++ = *src++;
	}
}


/* This function releases the lock on the DMA chip if there is no
 * connected command and the disconnected queue is empty.
 */

static void falcon_release_lock(void)
{
	if (IS_A_TT())
		return;

	if (stdma_is_locked_by(scsi_falcon_intr))
		stdma_release();
}

/* This function manages the locking of the ST-DMA.
 * If the DMA isn't locked already for SCSI, it tries to lock it by
 * calling stdma_lock(). But if the DMA is locked by the SCSI code and
 * there are other drivers waiting for the chip, we do not issue the
 * command immediately but tell the SCSI mid-layer to defer.
 */

static int falcon_get_lock(struct Scsi_Host *instance)
{
	if (IS_A_TT())
		return 1;

	if (stdma_is_locked_by(scsi_falcon_intr) &&
	    instance->hostt->can_queue > 1)
		return 1;

	if (in_interrupt())
		return stdma_try_lock(scsi_falcon_intr, instance);

	stdma_lock(scsi_falcon_intr, instance);
	return 1;
}

#ifndef MODULE
static int __init atari_scsi_setup(char *str)
{
	/* Format of atascsi parameter is:
	 *   atascsi=<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
	 * Defaults depend on TT or Falcon, determined at run time.
	 * Negative values mean don't change.
	 */
	int ints[8];

	get_options(str, ARRAY_SIZE(ints), ints);

	if (ints[0] < 1) {
		printk("atari_scsi_setup: no arguments!\n");
		return 0;
	}
	if (ints[0] >= 1)
		setup_can_queue = ints[1];
	if (ints[0] >= 2)
		setup_cmd_per_lun = ints[2];
	if (ints[0] >= 3)
		setup_sg_tablesize = ints[3];
	if (ints[0] >= 4)
		setup_hostid = ints[4];
	/* ints[5] (use_tagged_queuing) is ignored */
	/* ints[6] (use_pdma) is ignored */
	if (ints[0] >= 7)
		setup_toshiba_delay = ints[7];

	return 1;
}

__setup("atascsi=", atari_scsi_setup);
#endif /* !MODULE */

static unsigned long atari_scsi_dma_setup(struct NCR5380_hostdata *hostdata,
					  void *data, unsigned long count,
					  int dir)
{
	unsigned long addr = virt_to_phys(data);

	dprintk(NDEBUG_DMA, "scsi%d: setting up dma, data = %p, phys = %lx, count = %ld, dir = %d\n",
	        hostdata->host->host_no, data, addr, count, dir);

	if (!IS_A_TT() && !STRAM_ADDR(addr)) {
		/* If we have a non-DMAable address on a Falcon, use the dribble
		 * buffer; 'orig_addr' != 0 in the read case tells the interrupt
		 * handler to copy data from the dribble buffer to the originally
		 * wanted address.
		 */
		if (dir)
			memcpy(atari_dma_buffer, data, count);
		else
			atari_dma_orig_addr = data;
		addr = atari_dma_phys_buffer;
	}

	atari_dma_startaddr = addr;	/* Needed for calculating residual later. */

	/* Cache cleanup stuff: On writes, push any dirty cache out before sending
	 * it to the peripheral. (Must be done before DMA setup, since at least
	 * the ST-DMA begins to fill internal buffers right after setup. For
	 * reads, invalidate any cache, may be altered after DMA without CPU
	 * knowledge.
	 *
	 * ++roman: For the Medusa, there's no need at all for that cache stuff,
	 * because the hardware does bus snooping (fine!).
	 */
	dma_cache_maintenance(addr, count, dir);

	if (IS_A_TT()) {
		tt_scsi_dma.dma_ctrl = dir;
		SCSI_DMA_WRITE_P(dma_addr, addr);
		SCSI_DMA_WRITE_P(dma_cnt, count);
		tt_scsi_dma.dma_ctrl = dir | 2;
	} else { /* ! IS_A_TT */

		/* set address */
		SCSI_DMA_SETADR(addr);

		/* toggle direction bit to clear FIFO and set DMA direction */
		dir <<= 8;
		st_dma.dma_mode_status = 0x90 | dir;
		st_dma.dma_mode_status = 0x90 | (dir ^ 0x100);
		st_dma.dma_mode_status = 0x90 | dir;
		udelay(40);
		/* On writes, round up the transfer length to the next multiple of 512
		 * (see also comment at atari_dma_xfer_len()). */
		st_dma.fdc_acces_seccount = (count + (dir ? 511 : 0)) >> 9;
		udelay(40);
		st_dma.dma_mode_status = 0x10 | dir;
		udelay(40);
		/* need not restore value of dir, only boolean value is tested */
		atari_dma_active = 1;
	}

	return count;
}

static inline int atari_scsi_dma_recv_setup(struct NCR5380_hostdata *hostdata,
                                            unsigned char *data, int count)
{
	return atari_scsi_dma_setup(hostdata, data, count, 0);
}

static inline int atari_scsi_dma_send_setup(struct NCR5380_hostdata *hostdata,
                                            unsigned char *data, int count)
{
	return atari_scsi_dma_setup(hostdata, data, count, 1);
}

static int atari_scsi_dma_residual(struct NCR5380_hostdata *hostdata)
{
	return atari_dma_residual;
}


#define	CMD_SURELY_BLOCK_MODE	0
#define	CMD_SURELY_BYTE_MODE	1
#define	CMD_MODE_UNKNOWN		2

static int falcon_classify_cmd(struct scsi_cmnd *cmd)
{
	unsigned char opcode = cmd->cmnd[0];

	if (opcode == READ_DEFECT_DATA || opcode == READ_LONG ||
	    opcode == READ_BUFFER)
		return CMD_SURELY_BYTE_MODE;
	else if (opcode == READ_6 || opcode == READ_10 ||
		 opcode == 0xa8 /* READ_12 */ || opcode == READ_REVERSE ||
		 opcode == RECOVER_BUFFERED_DATA) {
		/* In case of a sequential-access target (tape), special care is
		 * needed here: The transfer is block-mode only if the 'fixed' bit is
		 * set! */
		if (cmd->device->type == TYPE_TAPE && !(cmd->cmnd[1] & 1))
			return CMD_SURELY_BYTE_MODE;
		else
			return CMD_SURELY_BLOCK_MODE;
	} else
		return CMD_MODE_UNKNOWN;
}


/* This function calculates the number of bytes that can be transferred via
 * DMA. On the TT, this is arbitrary, but on the Falcon we have to use the
 * ST-DMA chip. There are only multiples of 512 bytes possible and max.
 * 255*512 bytes :-( This means also, that defining READ_OVERRUNS is not
 * possible on the Falcon, since that would require to program the DMA for
 * n*512 - atari_read_overrun bytes. But it seems that the Falcon doesn't have
 * the overrun problem, so this question is academic :-)
 */

static int atari_scsi_dma_xfer_len(struct NCR5380_hostdata *hostdata,
                                   struct scsi_cmnd *cmd)
{
	int wanted_len = cmd->SCp.this_residual;
	int possible_len, limit;

	if (wanted_len < DMA_MIN_SIZE)
		return 0;

	if (IS_A_TT())
		/* TT SCSI DMA can transfer arbitrary #bytes */
		return wanted_len;

	/* ST DMA chip is stupid -- only multiples of 512 bytes! (and max.
	 * 255*512 bytes, but this should be enough)
	 *
	 * ++roman: Aaargl! Another Falcon-SCSI problem... There are some commands
	 * that return a number of bytes which cannot be known beforehand. In this
	 * case, the given transfer length is an "allocation length". Now it
	 * can happen that this allocation length is a multiple of 512 bytes and
	 * the DMA is used. But if not n*512 bytes really arrive, some input data
	 * will be lost in the ST-DMA's FIFO :-( Thus, we have to distinguish
	 * between commands that do block transfers and those that do byte
	 * transfers. But this isn't easy... there are lots of vendor specific
	 * commands, and the user can issue any command via the
	 * SCSI_IOCTL_SEND_COMMAND.
	 *
	 * The solution: We classify SCSI commands in 1) surely block-mode cmd.s,
	 * 2) surely byte-mode cmd.s and 3) cmd.s with unknown mode. In case 1)
	 * and 3), the thing to do is obvious: allow any number of blocks via DMA
	 * or none. In case 2), we apply some heuristic: Byte mode is assumed if
	 * the transfer (allocation) length is < 1024, hoping that no cmd. not
	 * explicitly known as byte mode have such big allocation lengths...
	 * BTW, all the discussion above applies only to reads. DMA writes are
	 * unproblematic anyways, since the targets aborts the transfer after
	 * receiving a sufficient number of bytes.
	 *
	 * Another point: If the transfer is from/to an non-ST-RAM address, we
	 * use the dribble buffer and thus can do only STRAM_BUFFER_SIZE bytes.
	 */

	if (cmd->sc_data_direction == DMA_TO_DEVICE) {
		/* Write operation can always use the DMA, but the transfer size must
		 * be rounded up to the next multiple of 512 (atari_dma_setup() does
		 * this).
		 */
		possible_len = wanted_len;
	} else {
		/* Read operations: if the wanted transfer length is not a multiple of
		 * 512, we cannot use DMA, since the ST-DMA cannot split transfers
		 * (no interrupt on DMA finished!)
		 */
		if (wanted_len & 0x1ff)
			possible_len = 0;
		else {
			/* Now classify the command (see above) and decide whether it is
			 * allowed to do DMA at all */
			switch (falcon_classify_cmd(cmd)) {
			case CMD_SURELY_BLOCK_MODE:
				possible_len = wanted_len;
				break;
			case CMD_SURELY_BYTE_MODE:
				possible_len = 0; /* DMA prohibited */
				break;
			case CMD_MODE_UNKNOWN:
			default:
				/* For unknown commands assume block transfers if the transfer
				 * size/allocation length is >= 1024 */
				possible_len = (wanted_len < 1024) ? 0 : wanted_len;
				break;
			}
		}
	}

	/* Last step: apply the hard limit on DMA transfers */
	limit = (atari_dma_buffer && !STRAM_ADDR(virt_to_phys(cmd->SCp.ptr))) ?
		    STRAM_BUFFER_SIZE : 255*512;
	if (possible_len > limit)
		possible_len = limit;

	if (possible_len != wanted_len)
		dprintk(NDEBUG_DMA, "DMA transfer now %d bytes instead of %d\n",
		        possible_len, wanted_len);

	return possible_len;
}


/* NCR5380 register access functions
 *
 * There are separate functions for TT and Falcon, because the access
 * methods are quite different. The calling macros NCR5380_read and
 * NCR5380_write call these functions via function pointers.
 */

static u8 atari_scsi_tt_reg_read(unsigned int reg)
{
	return tt_scsi_regp[reg * 2];
}

static void atari_scsi_tt_reg_write(unsigned int reg, u8 value)
{
	tt_scsi_regp[reg * 2] = value;
}

static u8 atari_scsi_falcon_reg_read(unsigned int reg)
{
	unsigned long flags;
	u8 result;

	reg += 0x88;
	local_irq_save(flags);
	dma_wd.dma_mode_status = (u_short)reg;
	result = (u8)dma_wd.fdc_acces_seccount;
	local_irq_restore(flags);
	return result;
}

static void atari_scsi_falcon_reg_write(unsigned int reg, u8 value)
{
	unsigned long flags;

	reg += 0x88;
	local_irq_save(flags);
	dma_wd.dma_mode_status = (u_short)reg;
	dma_wd.fdc_acces_seccount = (u_short)value;
	local_irq_restore(flags);
}


#include "NCR5380.c"

static int atari_scsi_host_reset(struct scsi_cmnd *cmd)
{
	int rv;
	unsigned long flags;

	local_irq_save(flags);

	/* Abort a maybe active DMA transfer */
	if (IS_A_TT()) {
		tt_scsi_dma.dma_ctrl = 0;
	} else {
		if (stdma_is_locked_by(scsi_falcon_intr))
			st_dma.dma_mode_status = 0x90;
		atari_dma_active = 0;
		atari_dma_orig_addr = NULL;
	}

	rv = NCR5380_host_reset(cmd);

	/* The 5380 raises its IRQ line while _RST is active but the ST DMA
	 * "lock" has been released so this interrupt may end up handled by
	 * floppy or IDE driver (if one of them holds the lock). The NCR5380
	 * interrupt flag has been cleared already.
	 */

	local_irq_restore(flags);

	return rv;
}

#define DRV_MODULE_NAME         "atari_scsi"
#define PFX                     DRV_MODULE_NAME ": "

static struct scsi_host_template atari_scsi_template = {
	.module			= THIS_MODULE,
	.proc_name		= DRV_MODULE_NAME,
	.name			= "Atari native SCSI",
	.info			= atari_scsi_info,
	.queuecommand		= atari_scsi_queue_command,
	.eh_abort_handler	= atari_scsi_abort,
	.eh_host_reset_handler	= atari_scsi_host_reset,
	.this_id		= 7,
	.cmd_per_lun		= 2,
	.dma_boundary		= PAGE_SIZE - 1,
	.cmd_size		= NCR5380_CMD_SIZE,
};

static int __init atari_scsi_probe(struct platform_device *pdev)
{
	struct Scsi_Host *instance;
	int error;
	struct resource *irq;
	int host_flags = 0;

	irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
	if (!irq)
		return -ENODEV;

	if (ATARIHW_PRESENT(TT_SCSI)) {
		atari_scsi_reg_read  = atari_scsi_tt_reg_read;
		atari_scsi_reg_write = atari_scsi_tt_reg_write;
	} else {
		atari_scsi_reg_read  = atari_scsi_falcon_reg_read;
		atari_scsi_reg_write = atari_scsi_falcon_reg_write;
	}

	if (ATARIHW_PRESENT(TT_SCSI)) {
		atari_scsi_template.can_queue    = 16;
		atari_scsi_template.sg_tablesize = SG_ALL;
	} else {
		atari_scsi_template.can_queue    = 1;
		atari_scsi_template.sg_tablesize = SG_NONE;
	}

	if (setup_can_queue > 0)
		atari_scsi_template.can_queue = setup_can_queue;

	if (setup_cmd_per_lun > 0)
		atari_scsi_template.cmd_per_lun = setup_cmd_per_lun;

	/* Leave sg_tablesize at 0 on a Falcon! */
	if (ATARIHW_PRESENT(TT_SCSI) && setup_sg_tablesize >= 0)
		atari_scsi_template.sg_tablesize = setup_sg_tablesize;

	if (setup_hostid >= 0) {
		atari_scsi_template.this_id = setup_hostid & 7;
	} else {
		/* Test if a host id is set in the NVRam */
		if (ATARIHW_PRESENT(TT_CLK) && nvram_check_checksum()) {
			unsigned char b = nvram_read_byte(16);

			/* Arbitration enabled? (for TOS)
			 * If yes, use configured host ID
			 */
			if (b & 0x80)
				atari_scsi_template.this_id = b & 7;
		}
	}

	/* If running on a Falcon and if there's TT-Ram (i.e., more than one
	 * memory block, since there's always ST-Ram in a Falcon), then
	 * allocate a STRAM_BUFFER_SIZE byte dribble buffer for transfers
	 * from/to alternative Ram.
	 */
	if (ATARIHW_PRESENT(ST_SCSI) && !ATARIHW_PRESENT(EXTD_DMA) &&
	    m68k_realnum_memory > 1) {
		atari_dma_buffer = atari_stram_alloc(STRAM_BUFFER_SIZE, "SCSI");
		if (!atari_dma_buffer) {
			pr_err(PFX "can't allocate ST-RAM double buffer\n");
			return -ENOMEM;
		}
		atari_dma_phys_buffer = atari_stram_to_phys(atari_dma_buffer);
		atari_dma_orig_addr = NULL;
	}

	instance = scsi_host_alloc(&atari_scsi_template,
	                           sizeof(struct NCR5380_hostdata));
	if (!instance) {
		error = -ENOMEM;
		goto fail_alloc;
	}

	instance->irq = irq->start;

	host_flags |= IS_A_TT() ? 0 : FLAG_LATE_DMA_SETUP;
	host_flags |= setup_toshiba_delay > 0 ? FLAG_TOSHIBA_DELAY : 0;

	error = NCR5380_init(instance, host_flags);
	if (error)
		goto fail_init;

	if (IS_A_TT()) {
		error = request_irq(instance->irq, scsi_tt_intr, 0,
		                    "NCR5380", instance);
		if (error) {
			pr_err(PFX "request irq %d failed, aborting\n",
			       instance->irq);
			goto fail_irq;
		}
		tt_mfp.active_edge |= 0x80;	/* SCSI int on L->H */

		tt_scsi_dma.dma_ctrl = 0;
		atari_dma_residual = 0;

		/* While the read overruns (described by Drew Eckhardt in
		 * NCR5380.c) never happened on TTs, they do in fact on the
		 * Medusa (This was the cause why SCSI didn't work right for
		 * so long there.) Since handling the overruns slows down
		 * a bit, I turned the #ifdef's into a runtime condition.
		 *
		 * In principle it should be sufficient to do max. 1 byte with
		 * PIO, but there is another problem on the Medusa with the DMA
		 * rest data register. So read_overruns is currently set
		 * to 4 to avoid having transfers that aren't a multiple of 4.
		 * If the rest data bug is fixed, this can be lowered to 1.
		 */
		if (MACH_IS_MEDUSA) {
			struct NCR5380_hostdata *hostdata =
				shost_priv(instance);

			hostdata->read_overruns = 4;
		}
	} else {
		/* Nothing to do for the interrupt: the ST-DMA is initialized
		 * already.
		 */
		atari_dma_residual = 0;
		atari_dma_active = 0;
		atari_dma_stram_mask = (ATARIHW_PRESENT(EXTD_DMA) ? 0x00000000
					: 0xff000000);
	}

	NCR5380_maybe_reset_bus(instance);

	error = scsi_add_host(instance, NULL);
	if (error)
		goto fail_host;

	platform_set_drvdata(pdev, instance);

	scsi_scan_host(instance);
	return 0;

fail_host:
	if (IS_A_TT())
		free_irq(instance->irq, instance);
fail_irq:
	NCR5380_exit(instance);
fail_init:
	scsi_host_put(instance);
fail_alloc:
	if (atari_dma_buffer)
		atari_stram_free(atari_dma_buffer);
	return error;
}

static int __exit atari_scsi_remove(struct platform_device *pdev)
{
	struct Scsi_Host *instance = platform_get_drvdata(pdev);

	scsi_remove_host(instance);
	if (IS_A_TT())
		free_irq(instance->irq, instance);
	NCR5380_exit(instance);
	scsi_host_put(instance);
	if (atari_dma_buffer)
		atari_stram_free(atari_dma_buffer);
	return 0;
}

static struct platform_driver atari_scsi_driver = {
	.remove = __exit_p(atari_scsi_remove),
	.driver = {
		.name	= DRV_MODULE_NAME,
	},
};

module_platform_driver_probe(atari_scsi_driver, atari_scsi_probe);

MODULE_ALIAS("platform:" DRV_MODULE_NAME);
MODULE_LICENSE("GPL");