summaryrefslogtreecommitdiffstats
path: root/arch/powerpc/kernel/head_8xx.S
blob: de0978742221ae6eb0ddfb7e6a60120c7c48c4fa (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
/*
 *  arch/ppc/kernel/except_8xx.S
 *
 *  PowerPC version
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *  Rewritten by Cort Dougan (cort@cs.nmt.edu) for PReP
 *    Copyright (C) 1996 Cort Dougan <cort@cs.nmt.edu>
 *  Low-level exception handlers and MMU support
 *  rewritten by Paul Mackerras.
 *    Copyright (C) 1996 Paul Mackerras.
 *  MPC8xx modifications by Dan Malek
 *    Copyright (C) 1997 Dan Malek (dmalek@jlc.net).
 *
 *  This file contains low-level support and setup for PowerPC 8xx
 *  embedded processors, including trap and interrupt dispatch.
 *
 *  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.
 *
 */

#include <linux/config.h>
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/mmu.h>
#include <asm/cache.h>
#include <asm/pgtable.h>
#include <asm/cputable.h>
#include <asm/thread_info.h>
#include <asm/ppc_asm.h>
#include <asm/asm-offsets.h>

/* Macro to make the code more readable. */
#ifdef CONFIG_8xx_CPU6
#define DO_8xx_CPU6(val, reg)	\
	li	reg, val;	\
	stw	reg, 12(r0);	\
	lwz	reg, 12(r0);
#else
#define DO_8xx_CPU6(val, reg)
#endif
	.text
	.globl	_stext
_stext:
	.text
	.globl	_start
_start:

/* MPC8xx
 * This port was done on an MBX board with an 860.  Right now I only
 * support an ELF compressed (zImage) boot from EPPC-Bug because the
 * code there loads up some registers before calling us:
 *   r3: ptr to board info data
 *   r4: initrd_start or if no initrd then 0
 *   r5: initrd_end - unused if r4 is 0
 *   r6: Start of command line string
 *   r7: End of command line string
 *
 * I decided to use conditional compilation instead of checking PVR and
 * adding more processor specific branches around code I don't need.
 * Since this is an embedded processor, I also appreciate any memory
 * savings I can get.
 *
 * The MPC8xx does not have any BATs, but it supports large page sizes.
 * We first initialize the MMU to support 8M byte pages, then load one
 * entry into each of the instruction and data TLBs to map the first
 * 8M 1:1.  I also mapped an additional I/O space 1:1 so we can get to
 * the "internal" processor registers before MMU_init is called.
 *
 * The TLB code currently contains a major hack.  Since I use the condition
 * code register, I have to save and restore it.  I am out of registers, so
 * I just store it in memory location 0 (the TLB handlers are not reentrant).
 * To avoid making any decisions, I need to use the "segment" valid bit
 * in the first level table, but that would require many changes to the
 * Linux page directory/table functions that I don't want to do right now.
 *
 * I used to use SPRG2 for a temporary register in the TLB handler, but it
 * has since been put to other uses.  I now use a hack to save a register
 * and the CCR at memory location 0.....Someday I'll fix this.....
 *	-- Dan
 */
	.globl	__start
__start:
	mr	r31,r3			/* save parameters */
	mr	r30,r4
	mr	r29,r5
	mr	r28,r6
	mr	r27,r7

	/* We have to turn on the MMU right away so we get cache modes
	 * set correctly.
	 */
	bl	initial_mmu

/* We now have the lower 8 Meg mapped into TLB entries, and the caches
 * ready to work.
 */

turn_on_mmu:
	mfmsr	r0
	ori	r0,r0,MSR_DR|MSR_IR
	mtspr	SPRN_SRR1,r0
	lis	r0,start_here@h
	ori	r0,r0,start_here@l
	mtspr	SPRN_SRR0,r0
	SYNC
	rfi				/* enables MMU */

/*
 * Exception entry code.  This code runs with address translation
 * turned off, i.e. using physical addresses.
 * We assume sprg3 has the physical address of the current
 * task's thread_struct.
 */
#define EXCEPTION_PROLOG	\
	mtspr	SPRN_SPRG0,r10;	\
	mtspr	SPRN_SPRG1,r11;	\
	mfcr	r10;		\
	EXCEPTION_PROLOG_1;	\
	EXCEPTION_PROLOG_2

#define EXCEPTION_PROLOG_1	\
	mfspr	r11,SPRN_SRR1;		/* check whether user or kernel */ \
	andi.	r11,r11,MSR_PR;	\
	tophys(r11,r1);			/* use tophys(r1) if kernel */ \
	beq	1f;		\
	mfspr	r11,SPRN_SPRG3;	\
	lwz	r11,THREAD_INFO-THREAD(r11);	\
	addi	r11,r11,THREAD_SIZE;	\
	tophys(r11,r11);	\
1:	subi	r11,r11,INT_FRAME_SIZE	/* alloc exc. frame */


#define EXCEPTION_PROLOG_2	\
	CLR_TOP32(r11);		\
	stw	r10,_CCR(r11);		/* save registers */ \
	stw	r12,GPR12(r11);	\
	stw	r9,GPR9(r11);	\
	mfspr	r10,SPRN_SPRG0;	\
	stw	r10,GPR10(r11);	\
	mfspr	r12,SPRN_SPRG1;	\
	stw	r12,GPR11(r11);	\
	mflr	r10;		\
	stw	r10,_LINK(r11);	\
	mfspr	r12,SPRN_SRR0;	\
	mfspr	r9,SPRN_SRR1;	\
	stw	r1,GPR1(r11);	\
	stw	r1,0(r11);	\
	tovirt(r1,r11);			/* set new kernel sp */	\
	li	r10,MSR_KERNEL & ~(MSR_IR|MSR_DR); /* can take exceptions */ \
	MTMSRD(r10);			/* (except for mach check in rtas) */ \
	stw	r0,GPR0(r11);	\
	SAVE_4GPRS(3, r11);	\
	SAVE_2GPRS(7, r11)

/*
 * Note: code which follows this uses cr0.eq (set if from kernel),
 * r11, r12 (SRR0), and r9 (SRR1).
 *
 * Note2: once we have set r1 we are in a position to take exceptions
 * again, and we could thus set MSR:RI at that point.
 */

/*
 * Exception vectors.
 */
#define EXCEPTION(n, label, hdlr, xfer)		\
	. = n;					\
label:						\
	EXCEPTION_PROLOG;			\
	addi	r3,r1,STACK_FRAME_OVERHEAD;	\
	xfer(n, hdlr)

#define EXC_XFER_TEMPLATE(n, hdlr, trap, copyee, tfer, ret)	\
	li	r10,trap;					\
	stw	r10,TRAP(r11);					\
	li	r10,MSR_KERNEL;					\
	copyee(r10, r9);					\
	bl	tfer;						\
i##n:								\
	.long	hdlr;						\
	.long	ret

#define COPY_EE(d, s)		rlwimi d,s,0,16,16
#define NOCOPY(d, s)

#define EXC_XFER_STD(n, hdlr)		\
	EXC_XFER_TEMPLATE(n, hdlr, n, NOCOPY, transfer_to_handler_full,	\
			  ret_from_except_full)

#define EXC_XFER_LITE(n, hdlr)		\
	EXC_XFER_TEMPLATE(n, hdlr, n+1, NOCOPY, transfer_to_handler, \
			  ret_from_except)

#define EXC_XFER_EE(n, hdlr)		\
	EXC_XFER_TEMPLATE(n, hdlr, n, COPY_EE, transfer_to_handler_full, \
			  ret_from_except_full)

#define EXC_XFER_EE_LITE(n, hdlr)	\
	EXC_XFER_TEMPLATE(n, hdlr, n+1, COPY_EE, transfer_to_handler, \
			  ret_from_except)

/* System reset */
	EXCEPTION(0x100, Reset, unknown_exception, EXC_XFER_STD)

/* Machine check */
	. = 0x200
MachineCheck:
	EXCEPTION_PROLOG
	mfspr r4,SPRN_DAR
	stw r4,_DAR(r11)
	mfspr r5,SPRN_DSISR
	stw r5,_DSISR(r11)
	addi r3,r1,STACK_FRAME_OVERHEAD
	EXC_XFER_STD(0x200, machine_check_exception)

/* Data access exception.
 * This is "never generated" by the MPC8xx.  We jump to it for other
 * translation errors.
 */
	. = 0x300
DataAccess:
	EXCEPTION_PROLOG
	mfspr	r10,SPRN_DSISR
	stw	r10,_DSISR(r11)
	mr	r5,r10
	mfspr	r4,SPRN_DAR
	EXC_XFER_EE_LITE(0x300, handle_page_fault)

/* Instruction access exception.
 * This is "never generated" by the MPC8xx.  We jump to it for other
 * translation errors.
 */
	. = 0x400
InstructionAccess:
	EXCEPTION_PROLOG
	mr	r4,r12
	mr	r5,r9
	EXC_XFER_EE_LITE(0x400, handle_page_fault)

/* External interrupt */
	EXCEPTION(0x500, HardwareInterrupt, do_IRQ, EXC_XFER_LITE)

/* Alignment exception */
	. = 0x600
Alignment:
	EXCEPTION_PROLOG
	mfspr	r4,SPRN_DAR
	stw	r4,_DAR(r11)
	mfspr	r5,SPRN_DSISR
	stw	r5,_DSISR(r11)
	addi	r3,r1,STACK_FRAME_OVERHEAD
	EXC_XFER_EE(0x600, alignment_exception)

/* Program check exception */
	EXCEPTION(0x700, ProgramCheck, program_check_exception, EXC_XFER_STD)

/* No FPU on MPC8xx.  This exception is not supposed to happen.
*/
	EXCEPTION(0x800, FPUnavailable, unknown_exception, EXC_XFER_STD)

/* Decrementer */
	EXCEPTION(0x900, Decrementer, timer_interrupt, EXC_XFER_LITE)

	EXCEPTION(0xa00, Trap_0a, unknown_exception, EXC_XFER_EE)
	EXCEPTION(0xb00, Trap_0b, unknown_exception, EXC_XFER_EE)

/* System call */
	. = 0xc00
SystemCall:
	EXCEPTION_PROLOG
	EXC_XFER_EE_LITE(0xc00, DoSyscall)

/* Single step - not used on 601 */
	EXCEPTION(0xd00, SingleStep, single_step_exception, EXC_XFER_STD)
	EXCEPTION(0xe00, Trap_0e, unknown_exception, EXC_XFER_EE)
	EXCEPTION(0xf00, Trap_0f, unknown_exception, EXC_XFER_EE)

/* On the MPC8xx, this is a software emulation interrupt.  It occurs
 * for all unimplemented and illegal instructions.
 */
	EXCEPTION(0x1000, SoftEmu, SoftwareEmulation, EXC_XFER_STD)

	. = 0x1100
/*
 * For the MPC8xx, this is a software tablewalk to load the instruction
 * TLB.  It is modelled after the example in the Motorola manual.  The task
 * switch loads the M_TWB register with the pointer to the first level table.
 * If we discover there is no second level table (value is zero) or if there
 * is an invalid pte, we load that into the TLB, which causes another fault
 * into the TLB Error interrupt where we can handle such problems.
 * We have to use the MD_xxx registers for the tablewalk because the
 * equivalent MI_xxx registers only perform the attribute functions.
 */
InstructionTLBMiss:
#ifdef CONFIG_8xx_CPU6
	stw	r3, 8(r0)
#endif
	DO_8xx_CPU6(0x3f80, r3)
	mtspr	SPRN_M_TW, r10	/* Save a couple of working registers */
	mfcr	r10
	stw	r10, 0(r0)
	stw	r11, 4(r0)
	mfspr	r10, SPRN_SRR0	/* Get effective address of fault */
	DO_8xx_CPU6(0x3780, r3)
	mtspr	SPRN_MD_EPN, r10	/* Have to use MD_EPN for walk, MI_EPN can't */
	mfspr	r10, SPRN_M_TWB	/* Get level 1 table entry address */

	/* If we are faulting a kernel address, we have to use the
	 * kernel page tables.
	 */
	andi.	r11, r10, 0x0800	/* Address >= 0x80000000 */
	beq	3f
	lis	r11, swapper_pg_dir@h
	ori	r11, r11, swapper_pg_dir@l
	rlwimi	r10, r11, 0, 2, 19
3:
	lwz	r11, 0(r10)	/* Get the level 1 entry */
	rlwinm.	r10, r11,0,0,19	/* Extract page descriptor page address */
	beq	2f		/* If zero, don't try to find a pte */

	/* We have a pte table, so load the MI_TWC with the attributes
	 * for this "segment."
	 */
	ori	r11,r11,1		/* Set valid bit */
	DO_8xx_CPU6(0x2b80, r3)
	mtspr	SPRN_MI_TWC, r11	/* Set segment attributes */
	DO_8xx_CPU6(0x3b80, r3)
	mtspr	SPRN_MD_TWC, r11	/* Load pte table base address */
	mfspr	r11, SPRN_MD_TWC	/* ....and get the pte address */
	lwz	r10, 0(r11)	/* Get the pte */

	ori	r10, r10, _PAGE_ACCESSED
	stw	r10, 0(r11)

	/* The Linux PTE won't go exactly into the MMU TLB.
	 * Software indicator bits 21, 22 and 28 must be clear.
	 * Software indicator bits 24, 25, 26, and 27 must be
	 * set.  All other Linux PTE bits control the behavior
	 * of the MMU.
	 */
2:	li	r11, 0x00f0
	rlwimi	r10, r11, 0, 24, 28	/* Set 24-27, clear 28 */
	DO_8xx_CPU6(0x2d80, r3)
	mtspr	SPRN_MI_RPN, r10	/* Update TLB entry */

	mfspr	r10, SPRN_M_TW	/* Restore registers */
	lwz	r11, 0(r0)
	mtcr	r11
	lwz	r11, 4(r0)
#ifdef CONFIG_8xx_CPU6
	lwz	r3, 8(r0)
#endif
	rfi

	. = 0x1200
DataStoreTLBMiss:
#ifdef CONFIG_8xx_CPU6
	stw	r3, 8(r0)
#endif
	DO_8xx_CPU6(0x3f80, r3)
	mtspr	SPRN_M_TW, r10	/* Save a couple of working registers */
	mfcr	r10
	stw	r10, 0(r0)
	stw	r11, 4(r0)
	mfspr	r10, SPRN_M_TWB	/* Get level 1 table entry address */

	/* If we are faulting a kernel address, we have to use the
	 * kernel page tables.
	 */
	andi.	r11, r10, 0x0800
	beq	3f
	lis	r11, swapper_pg_dir@h
	ori	r11, r11, swapper_pg_dir@l
	rlwimi	r10, r11, 0, 2, 19
3:
	lwz	r11, 0(r10)	/* Get the level 1 entry */
	rlwinm.	r10, r11,0,0,19	/* Extract page descriptor page address */
	beq	2f		/* If zero, don't try to find a pte */

	/* We have a pte table, so load fetch the pte from the table.
	 */
	ori	r11, r11, 1	/* Set valid bit in physical L2 page */
	DO_8xx_CPU6(0x3b80, r3)
	mtspr	SPRN_MD_TWC, r11	/* Load pte table base address */
	mfspr	r10, SPRN_MD_TWC	/* ....and get the pte address */
	lwz	r10, 0(r10)	/* Get the pte */

	/* Insert the Guarded flag into the TWC from the Linux PTE.
	 * It is bit 27 of both the Linux PTE and the TWC (at least
	 * I got that right :-).  It will be better when we can put
	 * this into the Linux pgd/pmd and load it in the operation
	 * above.
	 */
	rlwimi	r11, r10, 0, 27, 27
	DO_8xx_CPU6(0x3b80, r3)
	mtspr	SPRN_MD_TWC, r11

	mfspr	r11, SPRN_MD_TWC	/* get the pte address again */
	ori	r10, r10, _PAGE_ACCESSED
	stw	r10, 0(r11)

	/* The Linux PTE won't go exactly into the MMU TLB.
	 * Software indicator bits 21, 22 and 28 must be clear.
	 * Software indicator bits 24, 25, 26, and 27 must be
	 * set.  All other Linux PTE bits control the behavior
	 * of the MMU.
	 */
2:	li	r11, 0x00f0
	rlwimi	r10, r11, 0, 24, 28	/* Set 24-27, clear 28 */
	DO_8xx_CPU6(0x3d80, r3)
	mtspr	SPRN_MD_RPN, r10	/* Update TLB entry */

	mfspr	r10, SPRN_M_TW	/* Restore registers */
	lwz	r11, 0(r0)
	mtcr	r11
	lwz	r11, 4(r0)
#ifdef CONFIG_8xx_CPU6
	lwz	r3, 8(r0)
#endif
	rfi

/* This is an instruction TLB error on the MPC8xx.  This could be due
 * to many reasons, such as executing guarded memory or illegal instruction
 * addresses.  There is nothing to do but handle a big time error fault.
 */
	. = 0x1300
InstructionTLBError:
	b	InstructionAccess

/* This is the data TLB error on the MPC8xx.  This could be due to
 * many reasons, including a dirty update to a pte.  We can catch that
 * one here, but anything else is an error.  First, we track down the
 * Linux pte.  If it is valid, write access is allowed, but the
 * page dirty bit is not set, we will set it and reload the TLB.  For
 * any other case, we bail out to a higher level function that can
 * handle it.
 */
	. = 0x1400
DataTLBError:
#ifdef CONFIG_8xx_CPU6
	stw	r3, 8(r0)
#endif
	DO_8xx_CPU6(0x3f80, r3)
	mtspr	SPRN_M_TW, r10	/* Save a couple of working registers */
	mfcr	r10
	stw	r10, 0(r0)
	stw	r11, 4(r0)

	/* First, make sure this was a store operation.
	*/
	mfspr	r10, SPRN_DSISR
	andis.	r11, r10, 0x0200	/* If set, indicates store op */
	beq	2f

	/* The EA of a data TLB miss is automatically stored in the MD_EPN
	 * register.  The EA of a data TLB error is automatically stored in
	 * the DAR, but not the MD_EPN register.  We must copy the 20 most
	 * significant bits of the EA from the DAR to MD_EPN before we
	 * start walking the page tables.  We also need to copy the CASID
	 * value from the M_CASID register.
	 * Addendum:  The EA of a data TLB error is _supposed_ to be stored
	 * in DAR, but it seems that this doesn't happen in some cases, such
	 * as when the error is due to a dcbi instruction to a page with a
	 * TLB that doesn't have the changed bit set.  In such cases, there
	 * does not appear to be any way  to recover the EA of the error
	 * since it is neither in DAR nor MD_EPN.  As a workaround, the
	 * _PAGE_HWWRITE bit is set for all kernel data pages when the PTEs
	 * are initialized in mapin_ram().  This will avoid the problem,
	 * assuming we only use the dcbi instruction on kernel addresses.
	 */
	mfspr	r10, SPRN_DAR
	rlwinm	r11, r10, 0, 0, 19
	ori	r11, r11, MD_EVALID
	mfspr	r10, SPRN_M_CASID
	rlwimi	r11, r10, 0, 28, 31
	DO_8xx_CPU6(0x3780, r3)
	mtspr	SPRN_MD_EPN, r11

	mfspr	r10, SPRN_M_TWB	/* Get level 1 table entry address */

	/* If we are faulting a kernel address, we have to use the
	 * kernel page tables.
	 */
	andi.	r11, r10, 0x0800
	beq	3f
	lis	r11, swapper_pg_dir@h
	ori	r11, r11, swapper_pg_dir@l
	rlwimi	r10, r11, 0, 2, 19
3:
	lwz	r11, 0(r10)	/* Get the level 1 entry */
	rlwinm.	r10, r11,0,0,19	/* Extract page descriptor page address */
	beq	2f		/* If zero, bail */

	/* We have a pte table, so fetch the pte from the table.
	 */
	ori	r11, r11, 1		/* Set valid bit in physical L2 page */
	DO_8xx_CPU6(0x3b80, r3)
	mtspr	SPRN_MD_TWC, r11		/* Load pte table base address */
	mfspr	r11, SPRN_MD_TWC		/* ....and get the pte address */
	lwz	r10, 0(r11)		/* Get the pte */

	andi.	r11, r10, _PAGE_RW	/* Is it writeable? */
	beq	2f			/* Bail out if not */

	/* Update 'changed', among others.
	*/
	ori	r10, r10, _PAGE_DIRTY|_PAGE_ACCESSED|_PAGE_HWWRITE
	mfspr	r11, SPRN_MD_TWC		/* Get pte address again */
	stw	r10, 0(r11)		/* and update pte in table */

	/* The Linux PTE won't go exactly into the MMU TLB.
	 * Software indicator bits 21, 22 and 28 must be clear.
	 * Software indicator bits 24, 25, 26, and 27 must be
	 * set.  All other Linux PTE bits control the behavior
	 * of the MMU.
	 */
	li	r11, 0x00f0
	rlwimi	r10, r11, 0, 24, 28	/* Set 24-27, clear 28 */
	DO_8xx_CPU6(0x3d80, r3)
	mtspr	SPRN_MD_RPN, r10	/* Update TLB entry */

	mfspr	r10, SPRN_M_TW	/* Restore registers */
	lwz	r11, 0(r0)
	mtcr	r11
	lwz	r11, 4(r0)
#ifdef CONFIG_8xx_CPU6
	lwz	r3, 8(r0)
#endif
	rfi
2:
	mfspr	r10, SPRN_M_TW	/* Restore registers */
	lwz	r11, 0(r0)
	mtcr	r11
	lwz	r11, 4(r0)
#ifdef CONFIG_8xx_CPU6
	lwz	r3, 8(r0)
#endif
	b	DataAccess

	EXCEPTION(0x1500, Trap_15, unknown_exception, EXC_XFER_EE)
	EXCEPTION(0x1600, Trap_16, unknown_exception, EXC_XFER_EE)
	EXCEPTION(0x1700, Trap_17, unknown_exception, EXC_XFER_EE)
	EXCEPTION(0x1800, Trap_18, unknown_exception, EXC_XFER_EE)
	EXCEPTION(0x1900, Trap_19, unknown_exception, EXC_XFER_EE)
	EXCEPTION(0x1a00, Trap_1a, unknown_exception, EXC_XFER_EE)
	EXCEPTION(0x1b00, Trap_1b, unknown_exception, EXC_XFER_EE)

/* On the MPC8xx, these next four traps are used for development
 * support of breakpoints and such.  Someday I will get around to
 * using them.
 */
	EXCEPTION(0x1c00, Trap_1c, unknown_exception, EXC_XFER_EE)
	EXCEPTION(0x1d00, Trap_1d, unknown_exception, EXC_XFER_EE)
	EXCEPTION(0x1e00, Trap_1e, unknown_exception, EXC_XFER_EE)
	EXCEPTION(0x1f00, Trap_1f, unknown_exception, EXC_XFER_EE)

	. = 0x2000

	.globl	giveup_fpu
giveup_fpu:
	blr

/*
 * This is where the main kernel code starts.
 */
start_here:
	/* ptr to current */
	lis	r2,init_task@h
	ori	r2,r2,init_task@l

	/* ptr to phys current thread */
	tophys(r4,r2)
	addi	r4,r4,THREAD	/* init task's THREAD */
	mtspr	SPRN_SPRG3,r4
	li	r3,0
	mtspr	SPRN_SPRG2,r3	/* 0 => r1 has kernel sp */

	/* stack */
	lis	r1,init_thread_union@ha
	addi	r1,r1,init_thread_union@l
	li	r0,0
	stwu	r0,THREAD_SIZE-STACK_FRAME_OVERHEAD(r1)

	bl	early_init	/* We have to do this with MMU on */

/*
 * Decide what sort of machine this is and initialize the MMU.
 */
	mr	r3,r31
	mr	r4,r30
	mr	r5,r29
	mr	r6,r28
	mr	r7,r27
	bl	machine_init
	bl	MMU_init

/*
 * Go back to running unmapped so we can load up new values
 * and change to using our exception vectors.
 * On the 8xx, all we have to do is invalidate the TLB to clear
 * the old 8M byte TLB mappings and load the page table base register.
 */
	/* The right way to do this would be to track it down through
	 * init's THREAD like the context switch code does, but this is
	 * easier......until someone changes init's static structures.
	 */
	lis	r6, swapper_pg_dir@h
	ori	r6, r6, swapper_pg_dir@l
	tophys(r6,r6)
#ifdef CONFIG_8xx_CPU6
	lis	r4, cpu6_errata_word@h
	ori	r4, r4, cpu6_errata_word@l
	li	r3, 0x3980
	stw	r3, 12(r4)
	lwz	r3, 12(r4)
#endif
	mtspr	SPRN_M_TWB, r6
	lis	r4,2f@h
	ori	r4,r4,2f@l
	tophys(r4,r4)
	li	r3,MSR_KERNEL & ~(MSR_IR|MSR_DR)
	mtspr	SPRN_SRR0,r4
	mtspr	SPRN_SRR1,r3
	rfi
/* Load up the kernel context */
2:
	SYNC			/* Force all PTE updates to finish */
	tlbia			/* Clear all TLB entries */
	sync			/* wait for tlbia/tlbie to finish */
	TLBSYNC			/* ... on all CPUs */

	/* set up the PTE pointers for the Abatron bdiGDB.
	*/
	tovirt(r6,r6)
	lis	r5, abatron_pteptrs@h
	ori	r5, r5, abatron_pteptrs@l
	stw	r5, 0xf0(r0)	/* Must match your Abatron config file */
	tophys(r5,r5)
	stw	r6, 0(r5)

/* Now turn on the MMU for real! */
	li	r4,MSR_KERNEL
	lis	r3,start_kernel@h
	ori	r3,r3,start_kernel@l
	mtspr	SPRN_SRR0,r3
	mtspr	SPRN_SRR1,r4
	rfi			/* enable MMU and jump to start_kernel */

/* Set up the initial MMU state so we can do the first level of
 * kernel initialization.  This maps the first 8 MBytes of memory 1:1
 * virtual to physical.  Also, set the cache mode since that is defined
 * by TLB entries and perform any additional mapping (like of the IMMR).
 * If configured to pin some TLBs, we pin the first 8 Mbytes of kernel,
 * 24 Mbytes of data, and the 8M IMMR space.  Anything not covered by
 * these mappings is mapped by page tables.
 */
initial_mmu:
	tlbia			/* Invalidate all TLB entries */
#ifdef CONFIG_PIN_TLB
	lis	r8, MI_RSV4I@h
	ori	r8, r8, 0x1c00
#else
	li	r8, 0
#endif
	mtspr	SPRN_MI_CTR, r8	/* Set instruction MMU control */

#ifdef CONFIG_PIN_TLB
	lis	r10, (MD_RSV4I | MD_RESETVAL)@h
	ori	r10, r10, 0x1c00
	mr	r8, r10
#else
	lis	r10, MD_RESETVAL@h
#endif
#ifndef CONFIG_8xx_COPYBACK
	oris	r10, r10, MD_WTDEF@h
#endif
	mtspr	SPRN_MD_CTR, r10	/* Set data TLB control */

	/* Now map the lower 8 Meg into the TLBs.  For this quick hack,
	 * we can load the instruction and data TLB registers with the
	 * same values.
	 */
	lis	r8, KERNELBASE@h	/* Create vaddr for TLB */
	ori	r8, r8, MI_EVALID	/* Mark it valid */
	mtspr	SPRN_MI_EPN, r8
	mtspr	SPRN_MD_EPN, r8
	li	r8, MI_PS8MEG		/* Set 8M byte page */
	ori	r8, r8, MI_SVALID	/* Make it valid */
	mtspr	SPRN_MI_TWC, r8
	mtspr	SPRN_MD_TWC, r8
	li	r8, MI_BOOTINIT		/* Create RPN for address 0 */
	mtspr	SPRN_MI_RPN, r8		/* Store TLB entry */
	mtspr	SPRN_MD_RPN, r8
	lis	r8, MI_Kp@h		/* Set the protection mode */
	mtspr	SPRN_MI_AP, r8
	mtspr	SPRN_MD_AP, r8

	/* Map another 8 MByte at the IMMR to get the processor
	 * internal registers (among other things).
	 */
#ifdef CONFIG_PIN_TLB
	addi	r10, r10, 0x0100
	mtspr	SPRN_MD_CTR, r10
#endif
	mfspr	r9, 638			/* Get current IMMR */
	andis.	r9, r9, 0xff80		/* Get 8Mbyte boundary */

	mr	r8, r9			/* Create vaddr for TLB */
	ori	r8, r8, MD_EVALID	/* Mark it valid */
	mtspr	SPRN_MD_EPN, r8
	li	r8, MD_PS8MEG		/* Set 8M byte page */
	ori	r8, r8, MD_SVALID	/* Make it valid */
	mtspr	SPRN_MD_TWC, r8
	mr	r8, r9			/* Create paddr for TLB */
	ori	r8, r8, MI_BOOTINIT|0x2 /* Inhibit cache -- Cort */
	mtspr	SPRN_MD_RPN, r8

#ifdef CONFIG_PIN_TLB
	/* Map two more 8M kernel data pages.
	*/
	addi	r10, r10, 0x0100
	mtspr	SPRN_MD_CTR, r10

	lis	r8, KERNELBASE@h	/* Create vaddr for TLB */
	addis	r8, r8, 0x0080		/* Add 8M */
	ori	r8, r8, MI_EVALID	/* Mark it valid */
	mtspr	SPRN_MD_EPN, r8
	li	r9, MI_PS8MEG		/* Set 8M byte page */
	ori	r9, r9, MI_SVALID	/* Make it valid */
	mtspr	SPRN_MD_TWC, r9
	li	r11, MI_BOOTINIT	/* Create RPN for address 0 */
	addis	r11, r11, 0x0080	/* Add 8M */
	mtspr	SPRN_MD_RPN, r8

	addis	r8, r8, 0x0080		/* Add 8M */
	mtspr	SPRN_MD_EPN, r8
	mtspr	SPRN_MD_TWC, r9
	addis	r11, r11, 0x0080	/* Add 8M */
	mtspr	SPRN_MD_RPN, r8
#endif

	/* Since the cache is enabled according to the information we
	 * just loaded into the TLB, invalidate and enable the caches here.
	 * We should probably check/set other modes....later.
	 */
	lis	r8, IDC_INVALL@h
	mtspr	SPRN_IC_CST, r8
	mtspr	SPRN_DC_CST, r8
	lis	r8, IDC_ENABLE@h
	mtspr	SPRN_IC_CST, r8
#ifdef CONFIG_8xx_COPYBACK
	mtspr	SPRN_DC_CST, r8
#else
	/* For a debug option, I left this here to easily enable
	 * the write through cache mode
	 */
	lis	r8, DC_SFWT@h
	mtspr	SPRN_DC_CST, r8
	lis	r8, IDC_ENABLE@h
	mtspr	SPRN_DC_CST, r8
#endif
	blr


/*
 * Set up to use a given MMU context.
 * r3 is context number, r4 is PGD pointer.
 *
 * We place the physical address of the new task page directory loaded
 * into the MMU base register, and set the ASID compare register with
 * the new "context."
 */
_GLOBAL(set_context)

#ifdef CONFIG_BDI_SWITCH
	/* Context switch the PTE pointer for the Abatron BDI2000.
	 * The PGDIR is passed as second argument.
	 */
	lis	r5, KERNELBASE@h
	lwz	r5, 0xf0(r5)
	stw	r4, 0x4(r5)
#endif

#ifdef CONFIG_8xx_CPU6
	lis	r6, cpu6_errata_word@h
	ori	r6, r6, cpu6_errata_word@l
	tophys	(r4, r4)
	li	r7, 0x3980
	stw	r7, 12(r6)
	lwz	r7, 12(r6)
        mtspr   SPRN_M_TWB, r4               /* Update MMU base address */
	li	r7, 0x3380
	stw	r7, 12(r6)
	lwz	r7, 12(r6)
        mtspr   SPRN_M_CASID, r3             /* Update context */
#else
        mtspr   SPRN_M_CASID,r3		/* Update context */
	tophys	(r4, r4)
	mtspr	SPRN_M_TWB, r4		/* and pgd */
#endif
	SYNC
	blr

#ifdef CONFIG_8xx_CPU6
/* It's here because it is unique to the 8xx.
 * It is important we get called with interrupts disabled.  I used to
 * do that, but it appears that all code that calls this already had
 * interrupt disabled.
 */
	.globl	set_dec_cpu6
set_dec_cpu6:
	lis	r7, cpu6_errata_word@h
	ori	r7, r7, cpu6_errata_word@l
	li	r4, 0x2c00
	stw	r4, 8(r7)
	lwz	r4, 8(r7)
        mtspr   22, r3		/* Update Decrementer */
	SYNC
	blr
#endif

/*
 * We put a few things here that have to be page-aligned.
 * This stuff goes at the beginning of the data segment,
 * which is page-aligned.
 */
	.data
	.globl	sdata
sdata:
	.globl	empty_zero_page
empty_zero_page:
	.space	4096

	.globl	swapper_pg_dir
swapper_pg_dir:
	.space	4096

/*
 * This space gets a copy of optional info passed to us by the bootstrap
 * Used to pass parameters into the kernel like root=/dev/sda1, etc.
 */
	.globl	cmd_line
cmd_line:
	.space	512

/* Room for two PTE table poiners, usually the kernel and current user
 * pointer to their respective root page table (pgdir).
 */
abatron_pteptrs:
	.space	8

#ifdef CONFIG_8xx_CPU6
	.globl	cpu6_errata_word
cpu6_errata_word:
	.space	16
#endif