summaryrefslogtreecommitdiffstats
path: root/cpu/nios/traps.S
blob: bc4d3f66dae70fa7473f6ca9f248a0b1af48a88c (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
/*
 * (C) Copyright 2003, Psyent Corporation <www.psyent.com>
 * Scott McNutt <smcnutt@psyent.com>
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */

#include <config.h>

/*************************************************************************
 * Register window underflow
 *
 * The register window underflow exception occurs whenever the lowest
 * valid register window is in use (CWP=LO_LIMIT) and a save instruction
 * is issued. The save moves CWP below LO_LIMIT, %sp is set as normal,
 * then the exception is generated prior to executing the instruction
 * after the save.
 ************************************************************************/
	.text
	.global _cwp_lolimit
	.align	4

_cwp_lolimit:

	/* Sixteen words are always allocated by the compiler in every
	 * procedure's stack frame, always starting at %sp, for saving
	 * 'in' and 'local' registers on a window overflow.
	 *
	 * Save the 'global' and 'in' regs on stack. They are restored
	 * at cwp = HI_LIMIT. The 'local' regs aren't in-use at this point.
	 */
	sts	[%sp,0], %g0		/* Save 'global' regs*/
	sts	[%sp,1], %g1
	sts	[%sp,2], %g2
	sts	[%sp,3], %g3
	sts	[%sp,4], %g4
	sts	[%sp,5], %g5
	sts	[%sp,6], %g6
	sts	[%sp,7], %g7

	sts	[%sp,8], %i0		/* Save 'in' regs */
	sts	[%sp,9], %i1
	sts	[%sp,10], %i2
	sts	[%sp,11], %i3
	sts	[%sp,12], %i4
	sts	[%sp,13], %i5
	sts	[%sp,14], %i6
	sts	[%sp,15], %i7

	/* Save current %sp and return address in a global so they are
	 * available at cwp = HI_LIMIT ... where the 'global'/'in' regs
	 * are restored. NOTE: %sp changes with cwp.
	 */
	mov	%g7, %o7
	mov	%g6, %sp

	/* Get LO_LIMIT/HI_LIMIT to know where to start & stop. Note: in
	 * the underflow exception, cwp is __NOT__ guaranteed to be zero.
	 * If the OCI debug module is enabled the reset value for LO_LIMIT
	 * is 2, not 1 -- so cwp can be 1 or 0.
	 */
	pfx	2			/* WVALID */
	rdctl	%g1
	mov	%g2, %g1
	pfx	0
	and	%g1, 0x1f		/* g1 <- LO_LIMIT */
	lsri	%g2, 5
	pfx	0
	and	%g2,0x1f		/* g2 <- HI_LIMIT */

	/* Set istatus so cwp = HI_LIMIT after tret
	 */
	movi	%g5, 0x1f
	lsli	%g5, 4
	not	%g5			/* mask to clr cwp */
	pfx	1			/* istatus */
	rdctl	%g0
	and	%g0, %g5		/* clear cwp field */

	mov	%g4, %g2
	lsli	%g4, 4
	or	%g0, %g4		/* cwp = HI_LIMIT */
	pfx	1
	wrctl	%g0			/* update istatus */

	/* Now move up the register file, saving as we go. When loop
	 * is first entered, %g1 is at LO_LIMIT.
	 */
0:
	restore				/* cwp++ */
	sts	[%sp,0], %l0		/* Save "local" regs*/
	sts	[%sp,1], %l1
	sts	[%sp,2], %l2
	sts	[%sp,3], %l3
	sts	[%sp,4], %l4
	sts	[%sp,5], %l5
	sts	[%sp,6], %l6
	sts	[%sp,7], %l7

	sts	[%sp,8], %i0		/* Save 'in' regs */
	sts	[%sp,9], %i1
	sts	[%sp,10], %i2
	sts	[%sp,11], %i3
	sts	[%sp,12], %i4
	sts	[%sp,13], %i5
	sts	[%sp,14], %i6
	sts	[%sp,15], %i7

	cmp	%g1, %g2		/* cwp == HI_LIMIT ? */
	skps	cc_ne			/* if so, we're done */
	br	1f
	nop				/* delay slot */

	inc	%g1			/* g1 <- cwp++ */
	br	0b
	nop				/* delay slot */

	/* At this point cwp = HI_LIMIT, so the global/in regs that were
	 * in place when the underflow occurred must be restored using
	 * the original stack pointer (saved in g6).
	 */
1:
	mov	%o7, %g7		/* restore return addr */
	mov	%sp, %g6		/* Restore original sp */

	lds	%g0, [%sp,0]		/* Restore 'global' regs*/
	lds	%g1, [%sp,1]
	lds	%g2, [%sp,2]
	lds	%g3, [%sp,3]
	lds	%g4, [%sp,4]
	lds	%g5, [%sp,5]
	lds	%g6, [%sp,6]
	lds	%g7, [%sp,7]

	lds	%i0, [%sp,8]		/* Restore 'in' regs*/
	lds	%i1, [%sp,9]
	lds	%i2, [%sp,10]
	lds	%i3, [%sp,11]
	lds	%i4, [%sp,12]
	lds	%i5, [%sp,13]
	lds	%i6, [%sp,14]
	lds	%i7, [%sp,15]

	tret	%o7			/* All done */

/*************************************************************************
 * Register window overflow
 *
 * The register window overflow exception occurs whenever the highest
 * valid register window is in use (cwp = HI_LIMIT) and a restore
 * instruction is issued. Control is transferred to the overflow handler
 * before the instruction following restore is executed.
 *
 * When a register window overflow exception is taken, the exception
 * handler sees cwp at HI_LIMIT.
 ************************************************************************/
	.text
	.global _cwp_hilimit
	.align	4

_cwp_hilimit:

	/* Save 'global'/'in' regs on the stack -- will restore when cwp
	 * is at LO_LIMIT. Locals don't need saving as they are going away.
	 */
	sts	[%sp,0], %g0		/* Save "global" regs*/
	sts	[%sp,1], %g1
	sts	[%sp,2], %g2
	sts	[%sp,3], %g3
	sts	[%sp,4], %g4
	sts	[%sp,5], %g5
	sts	[%sp,6], %g6
	sts	[%sp,7], %g7

	sts	[%sp,8], %i0		/* Save 'in' regs */
	sts	[%sp,9], %i1
	sts	[%sp,10], %i2
	sts	[%sp,11], %i3
	sts	[%sp,12], %i4
	sts	[%sp,13], %i5
	sts	[%sp,14], %i6
	sts	[%sp,15], %i7

	/* The current %sp must be available in global to restore regs
	 * saved on stack. Need return addr as well ;-)
	 */
	mov	%g7, %o7
	mov	%g6, %sp

	/* Get HI_LIMIT & LO_LIMIT
	 */
	pfx	2			/* WVALID */
	rdctl	%g1
	mov	%g2, %g1
	pfx	0
	and	%g1, 0x1f		/* g1 <- LO_LIMIT */
	lsri	%g2, 5
	pfx	0
	and	%g2,0x1f		/* g2 <- HI_LIMIT */

	/* Set istatus so cwp = LO_LIMIT after tret
	 */
	movi	%g5, 0x1f
	lsli	%g5, 4
	not	%g5			/* mask to clr cwp */
	pfx	1			/* istatus */
	rdctl	%g0
	and	%g0, %g5		/* clear cwp field */

	mov	%g4, %g1		/* g4 <- LO_LIMIT */
	lsli	%g4, 4
	or	%g0, %g4		/* cwp = LO_LIMIT */
	pfx	1
	wrctl	%g0			/* update istatus */

	/* Move to cwp = LO_LIMIT-1 and restore 'in' regs.
	 */
	subi	%g4,(1 << 4)		/* g4 <- LO_LIMIT - 1 */
	rdctl	%g0
	and	%g0, %g5		/* clear cwp field */
	or	%g0, %g4		/* cwp = LO_LIMIT - 1 */
	wrctl	%g0			/* update status */
	nop

	mov	%sp, %g6		/* Restore sp */
	lds	%i0, [%sp,8]		/* Restore 'in' regs */
	lds	%i1, [%sp,9]
	lds	%i2, [%sp,10]
	lds	%i3, [%sp,11]
	lds	%i4, [%sp,12]
	lds	%i5, [%sp,13]
	lds	%i6, [%sp,14]		/* sp in next window */
	lds	%i7, [%sp,15]

	/* Starting at LO_LIMIT-1, move up the register file, restoring
	 * along the way.
	 */
0:
	restore				/* cwp++ */
	lds	%l0, [%sp,0]		/* Restore 'local' regs*/
	lds	%l1, [%sp,1]
	lds	%l2, [%sp,2]
	lds	%l3, [%sp,3]
	lds	%l4, [%sp,4]
	lds	%l5, [%sp,5]
	lds	%l6, [%sp,6]
	lds	%l7, [%sp,7]

	lds	%i0, [%sp,8]		/* Restore 'in' regs */
	lds	%i1, [%sp,9]
	lds	%i2, [%sp,10]
	lds	%i3, [%sp,11]
	lds	%i4, [%sp,12]
	lds	%i5, [%sp,13]
	lds	%i6, [%sp,14]		/* sp in next window */
	lds	%i7, [%sp,15]

	cmp	%g1, %g2		/* cwp == HI_LIMIT ? */
	skps	cc_ne			/* if so, we're done */
	br	1f
	nop				/* delay slot */

	inc	%g1			/* cwp++ */
	br	0b
	nop				/* delay slot */

	/* All windows have been updated at this point, but the globals
	 * still need to be restored. Go to cwp = LO_LIMIT-1 to get
	 * some registers to use.
	 */
1:
	rdctl	%g0
	and	%g0, %g5		/* clear cwp field */
	or	%g0, %g4		/* cwp = LO_LIMIT - 1 */
	wrctl	%g0			/* update status */
	nop

	/* Now there are some registers available to use in restoring
	 * the globals.
	 */
	mov	%sp, %g6
	mov	%o7, %g7

	lds	%g0, [%sp,0]		/* Restore "global" regs*/
	lds	%g1, [%sp,1]
	lds	%g2, [%sp,2]
	lds	%g3, [%sp,3]
	lds	%g4, [%sp,4]
	lds	%g5, [%sp,5]
	lds	%g6, [%sp,6]
	lds	%g7, [%sp,7]

	/* The tret moves istatus -> status. istatus was already set for
	 * cwp = LO_LIMIT.
	 */

	tret	%o7			/* done */

/*************************************************************************
 * Default exception handler
 *
 * The default handler passes control to external_interrupt(). So trap
 * or hardware interrupt hanlders can be installed using the familiar
 * irq_install_handler().
 *
 * Here, the stack is fixed-up and cwp is incremented prior to calling
 * external_interrupt(). This lets the underflow and overflow handlers
 * operate normally during the exception.
 ************************************************************************/
	.text
	.global _def_xhandler
	.align	4

_def_xhandler:

	/* Allocate some stack space: 16 words at %sp to accomodate
	 * a reg window underflow, 8 words to save interrupted task's
	 * 'out' regs (which are now the 'in' regs), 8 words to preserve
	 * the 'global' regs and 3 words to save the return address,
	 * status and istatus. istatus must be saved in the event an
	 * underflow occurs in a dispatched handler. status is saved so
	 * a handler can access it on stack.
	 */
	pfx	%hi((16+16+3) * 4)
	subi	%fp, %lo((16+16+3) * 4)
	mov	%sp, %fp

	/* Save the 'global' regs and the interrupted task's 'out' regs
	 * (our 'in' regs) along with the return addr, status & istatus.
	 * First 16 words are for underflow exception.
	 */
	rdctl	%l0			/* status */
	pfx	1			/* istatus */
	rdctl	%l1

	sts	[%sp,16+0], %g0		/* Save 'global' regs*/
	sts	[%sp,16+1], %g1
	sts	[%sp,16+2], %g2
	sts	[%sp,16+3], %g3
	sts	[%sp,16+4], %g4
	sts	[%sp,16+5], %g5
	sts	[%sp,16+6], %g6
	sts	[%sp,16+7], %g7

	sts	[%sp,16+8], %i0		/* Save 'in' regs */
	sts	[%sp,16+9], %i1
	sts	[%sp,16+10], %i2
	sts	[%sp,16+11], %i3
	sts	[%sp,16+12], %i4
	sts	[%sp,16+13], %i5
	sts	[%sp,16+14], %i6
	sts	[%sp,16+15], %i7

	sts	[%sp,16+16], %l0	/* status */
	sts	[%sp,16+17], %l1	/* istatus */
	sts	[%sp,16+18], %o7	/* return addr */

	/* Move to cwp+1 ... this guarantees cwp is at or above LO_LIMIT.
	 * Need to set IPRI=3 and IE=1 to enable underflow exceptions.
	 * NOTE: only the 'out' regs have been saved ... can't touch
	 * the 'in' or 'local' here.
	 */
	restore				/* cwp++ */
	rdctl	%o0			/* o0 <- status */

	pfx	%hi(0x7e00)
	movi	%o1, %lo(0x7e00)
	not	%o1
	and	%o0, %o1		/* clear IPRI */

	pfx	%hi(0x8600)
	movi	%o1, %lo(0x8600)
	or	%o0, %o1		/* IPRI=3, IE=1 */

	wrctl	%o0			/* o0 -> status */
	nop

	/* It's ok to call a C routine now since cwp >= LO_LIMIT,
	 * interrupt task's registers are/will be preserved, and
	 * underflow exceptions can be handled.
	 */
	pfx	%hi(external_interrupt@h)
	movi	%o1, %lo(external_interrupt@h)
	pfx	%xhi(external_interrupt@h)
	movhi	%o1, %xlo(external_interrupt@h)
	bgen	%o0, 4+2		/* 16 * 4 */
	add	%o0, %sp		/* Ptr to regs */
	call	%o1
	nop

	/* Move back to the exception register window, restore the 'out'
	 * registers, then return from exception.
	 */
	rdctl	%o0			/* o0 <- status */
	subi	%o0, 16
	wrctl	%o0			/* cwp-- */
	nop

	mov	%sp, %fp
	lds	%g0, [%sp,16+0]		/* Restore 'global' regs*/
	lds	%g1, [%sp,16+1]
	lds	%g2, [%sp,16+2]
	lds	%g3, [%sp,16+3]
	lds	%g4, [%sp,16+4]
	lds	%g5, [%sp,16+5]
	lds	%g6, [%sp,16+6]
	lds	%g7, [%sp,16+7]

	lds	%i0, [%sp,16+8]		/* Restore 'in' regs*/
	lds	%i1, [%sp,16+9]
	lds	%i2, [%sp,16+10]
	lds	%i3, [%sp,16+11]
	lds	%i4, [%sp,16+12]
	lds	%i5, [%sp,16+13]
	lds	%i6, [%sp,16+14]
	lds	%i7, [%sp,16+15]

	lds	%l0, [%sp,16+16]	/* status */
	lds	%l1, [%sp,16+17]	/* istatus */
	lds	%o7, [%sp,16+18]	/* return addr */

	pfx	1
	wrctl	%l1			/* restore istatus */

	pfx	%hi((16+16+3) * 4)
	addi	%sp, %lo((16+16+3) * 4)
	mov	%fp, %sp

	tret	%o7			/* Done */


/*************************************************************************
 * Timebase Timer Interrupt -- This has identical structure to above,
 * but calls timer_interrupt().  Doing it this way keeps things similar
 * to other architectures (e.g. ppc).
 ************************************************************************/
	.text
	.global _timebase_int
	.align	4

_timebase_int:

	/* Allocate  stack space.
	 */
	pfx	%hi((16+16+3) * 4)
	subi	%fp, %lo((16+16+3) * 4)
	mov	%sp, %fp

	/* Save the 'global' regs & 'out' regs (our 'in' regs)
	 */
	rdctl	%l0			/* status */
	pfx	1			/* istatus */
	rdctl	%l1

	sts	[%sp,16+0], %g0		/* Save 'global' regs*/
	sts	[%sp,16+1], %g1
	sts	[%sp,16+2], %g2
	sts	[%sp,16+3], %g3
	sts	[%sp,16+4], %g4
	sts	[%sp,16+5], %g5
	sts	[%sp,16+6], %g6
	sts	[%sp,16+7], %g7

	sts	[%sp,16+8], %i0		/* Save 'in' regs */
	sts	[%sp,16+9], %i1
	sts	[%sp,16+10], %i2
	sts	[%sp,16+11], %i3
	sts	[%sp,16+12], %i4
	sts	[%sp,16+13], %i5
	sts	[%sp,16+14], %i6
	sts	[%sp,16+15], %i7

	sts	[%sp,16+16], %l0	/* status */
	sts	[%sp,16+17], %l1	/* istatus */
	sts	[%sp,16+18], %o7	/* return addr */

	/* Move to cwp+1.
	 */
	restore				/* cwp++ */
	rdctl	%o0			/* o0 <- status */

	pfx	%hi(0x7e00)
	movi	%o1, %lo(0x7e00)
	not	%o1
	and	%o0, %o1		/* clear IPRI */

	pfx	%hi(0x8600)
	movi	%o1, %lo(0x8600)
	or	%o0, %o1		/* IPRI=3, IE=1 */

	wrctl	%o0			/* o0 -> status */
	nop

	/* Call timer_interrupt()
	 */
	pfx	%hi(timer_interrupt@h)
	movi	%o1, %lo(timer_interrupt@h)
	pfx	%xhi(timer_interrupt@h)
	movhi	%o1, %xlo(timer_interrupt@h)
	bgen	%o0, 4+2		/* 16 * 4 */
	add	%o0, %sp		/* Ptr to regs */
	call	%o1
	nop

	/* Move back to the exception register window, restore the 'out'
	 * registers, then return from exception.
	 */
	rdctl	%o0			/* o0 <- status */
	subi	%o0, 16
	wrctl	%o0			/* cwp-- */
	nop

	mov	%sp, %fp
	lds	%g0, [%sp,16+0]		/* Restore 'global' regs*/
	lds	%g1, [%sp,16+1]
	lds	%g2, [%sp,16+2]
	lds	%g3, [%sp,16+3]
	lds	%g4, [%sp,16+4]
	lds	%g5, [%sp,16+5]
	lds	%g6, [%sp,16+6]
	lds	%g7, [%sp,16+7]

	lds	%i0, [%sp,16+8]		/* Restore 'in' regs*/
	lds	%i1, [%sp,16+9]
	lds	%i2, [%sp,16+10]
	lds	%i3, [%sp,16+11]
	lds	%i4, [%sp,16+12]
	lds	%i5, [%sp,16+13]
	lds	%i6, [%sp,16+14]
	lds	%i7, [%sp,16+15]

	lds	%l0, [%sp,16+16]	/* status */
	lds	%l1, [%sp,16+17]	/* istatus */
	lds	%o7, [%sp,16+18]	/* return addr */

	pfx	1
	wrctl	%l1			/* restore istatus */

	pfx	%hi((16+16+3) * 4)
	addi	%sp, %lo((16+16+3) * 4)
	mov	%fp, %sp

	tret	%o7			/* Done */

/*************************************************************************
 * GDB stubs
 ************************************************************************/
	.text
	.global _brkpt_hw_int, _brkpt_sw_int
	.align	4

_brkpt_hw_int:
	movi	%l1, 9
	pfx	3
	wrctl	%l1
	pfx	4
	wrctl	%l1

_brkpt_sw_int:
	movi	%l1, 9
	pfx	3
	wrctl	%l1
	pfx	4
	wrctl	%l1

	tret	%o7