summaryrefslogtreecommitdiffstats
path: root/arch/arm/vfp/vfpmodule.c
blob: f6e4d56eda007faeb26639fc54a2014b8fae1b58 (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
/*
 *  linux/arch/arm/vfp/vfpmodule.c
 *
 *  Copyright (C) 2004 ARM Limited.
 *  Written by Deep Blue Solutions Limited.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/types.h>
#include <linux/cpu.h>
#include <linux/cpu_pm.h>
#include <linux/hardirq.h>
#include <linux/kernel.h>
#include <linux/notifier.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/init.h>
#include <linux/uaccess.h>
#include <linux/user.h>
#include <linux/export.h>

#include <asm/cp15.h>
#include <asm/cputype.h>
#include <asm/system_info.h>
#include <asm/thread_notify.h>
#include <asm/vfp.h>

#include "vfpinstr.h"
#include "vfp.h"

/*
 * Our undef handlers (in entry.S)
 */
void vfp_testing_entry(void);
void vfp_support_entry(void);
void vfp_null_entry(void);

void (*vfp_vector)(void) = vfp_null_entry;

/*
 * Dual-use variable.
 * Used in startup: set to non-zero if VFP checks fail
 * After startup, holds VFP architecture
 */
unsigned int VFP_arch;

/*
 * The pointer to the vfpstate structure of the thread which currently
 * owns the context held in the VFP hardware, or NULL if the hardware
 * context is invalid.
 *
 * For UP, this is sufficient to tell which thread owns the VFP context.
 * However, for SMP, we also need to check the CPU number stored in the
 * saved state too to catch migrations.
 */
union vfp_state *vfp_current_hw_state[NR_CPUS];

/*
 * Is 'thread's most up to date state stored in this CPUs hardware?
 * Must be called from non-preemptible context.
 */
static bool vfp_state_in_hw(unsigned int cpu, struct thread_info *thread)
{
#ifdef CONFIG_SMP
	if (thread->vfpstate.hard.cpu != cpu)
		return false;
#endif
	return vfp_current_hw_state[cpu] == &thread->vfpstate;
}

/*
 * Force a reload of the VFP context from the thread structure.  We do
 * this by ensuring that access to the VFP hardware is disabled, and
 * clear vfp_current_hw_state.  Must be called from non-preemptible context.
 */
static void vfp_force_reload(unsigned int cpu, struct thread_info *thread)
{
	if (vfp_state_in_hw(cpu, thread)) {
		fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
		vfp_current_hw_state[cpu] = NULL;
	}
#ifdef CONFIG_SMP
	thread->vfpstate.hard.cpu = NR_CPUS;
#endif
}

/*
 * Per-thread VFP initialization.
 */
static void vfp_thread_flush(struct thread_info *thread)
{
	union vfp_state *vfp = &thread->vfpstate;
	unsigned int cpu;

	/*
	 * Disable VFP to ensure we initialize it first.  We must ensure
	 * that the modification of vfp_current_hw_state[] and hardware
	 * disable are done for the same CPU and without preemption.
	 *
	 * Do this first to ensure that preemption won't overwrite our
	 * state saving should access to the VFP be enabled at this point.
	 */
	cpu = get_cpu();
	if (vfp_current_hw_state[cpu] == vfp)
		vfp_current_hw_state[cpu] = NULL;
	fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
	put_cpu();

	memset(vfp, 0, sizeof(union vfp_state));

	vfp->hard.fpexc = FPEXC_EN;
	vfp->hard.fpscr = FPSCR_ROUND_NEAREST;
#ifdef CONFIG_SMP
	vfp->hard.cpu = NR_CPUS;
#endif
}

static void vfp_thread_exit(struct thread_info *thread)
{
	/* release case: Per-thread VFP cleanup. */
	union vfp_state *vfp = &thread->vfpstate;
	unsigned int cpu = get_cpu();

	if (vfp_current_hw_state[cpu] == vfp)
		vfp_current_hw_state[cpu] = NULL;
	put_cpu();
}

static void vfp_thread_copy(struct thread_info *thread)
{
	struct thread_info *parent = current_thread_info();

	vfp_sync_hwstate(parent);
	thread->vfpstate = parent->vfpstate;
#ifdef CONFIG_SMP
	thread->vfpstate.hard.cpu = NR_CPUS;
#endif
}

/*
 * When this function is called with the following 'cmd's, the following
 * is true while this function is being run:
 *  THREAD_NOFTIFY_SWTICH:
 *   - the previously running thread will not be scheduled onto another CPU.
 *   - the next thread to be run (v) will not be running on another CPU.
 *   - thread->cpu is the local CPU number
 *   - not preemptible as we're called in the middle of a thread switch
 *  THREAD_NOTIFY_FLUSH:
 *   - the thread (v) will be running on the local CPU, so
 *	v === current_thread_info()
 *   - thread->cpu is the local CPU number at the time it is accessed,
 *	but may change at any time.
 *   - we could be preempted if tree preempt rcu is enabled, so
 *	it is unsafe to use thread->cpu.
 *  THREAD_NOTIFY_EXIT
 *   - the thread (v) will be running on the local CPU, so
 *	v === current_thread_info()
 *   - thread->cpu is the local CPU number at the time it is accessed,
 *	but may change at any time.
 *   - we could be preempted if tree preempt rcu is enabled, so
 *	it is unsafe to use thread->cpu.
 */
static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
{
	struct thread_info *thread = v;
	u32 fpexc;
#ifdef CONFIG_SMP
	unsigned int cpu;
#endif

	switch (cmd) {
	case THREAD_NOTIFY_SWITCH:
		fpexc = fmrx(FPEXC);

#ifdef CONFIG_SMP
		cpu = thread->cpu;

		/*
		 * On SMP, if VFP is enabled, save the old state in
		 * case the thread migrates to a different CPU. The
		 * restoring is done lazily.
		 */
		if ((fpexc & FPEXC_EN) && vfp_current_hw_state[cpu])
			vfp_save_state(vfp_current_hw_state[cpu], fpexc);
#endif

		/*
		 * Always disable VFP so we can lazily save/restore the
		 * old state.
		 */
		fmxr(FPEXC, fpexc & ~FPEXC_EN);
		break;

	case THREAD_NOTIFY_FLUSH:
		vfp_thread_flush(thread);
		break;

	case THREAD_NOTIFY_EXIT:
		vfp_thread_exit(thread);
		break;

	case THREAD_NOTIFY_COPY:
		vfp_thread_copy(thread);
		break;
	}

	return NOTIFY_DONE;
}

static struct notifier_block vfp_notifier_block = {
	.notifier_call	= vfp_notifier,
};

/*
 * Raise a SIGFPE for the current process.
 * sicode describes the signal being raised.
 */
static void vfp_raise_sigfpe(unsigned int sicode, struct pt_regs *regs)
{
	siginfo_t info;

	memset(&info, 0, sizeof(info));

	info.si_signo = SIGFPE;
	info.si_code = sicode;
	info.si_addr = (void __user *)(instruction_pointer(regs) - 4);

	/*
	 * This is the same as NWFPE, because it's not clear what
	 * this is used for
	 */
	current->thread.error_code = 0;
	current->thread.trap_no = 6;

	send_sig_info(SIGFPE, &info, current);
}

static void vfp_panic(char *reason, u32 inst)
{
	int i;

	pr_err("VFP: Error: %s\n", reason);
	pr_err("VFP: EXC 0x%08x SCR 0x%08x INST 0x%08x\n",
		fmrx(FPEXC), fmrx(FPSCR), inst);
	for (i = 0; i < 32; i += 2)
		pr_err("VFP: s%2u: 0x%08x s%2u: 0x%08x\n",
		       i, vfp_get_float(i), i+1, vfp_get_float(i+1));
}

/*
 * Process bitmask of exception conditions.
 */
static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_regs *regs)
{
	int si_code = 0;

	pr_debug("VFP: raising exceptions %08x\n", exceptions);

	if (exceptions == VFP_EXCEPTION_ERROR) {
		vfp_panic("unhandled bounce", inst);
		vfp_raise_sigfpe(0, regs);
		return;
	}

	/*
	 * If any of the status flags are set, update the FPSCR.
	 * Comparison instructions always return at least one of
	 * these flags set.
	 */
	if (exceptions & (FPSCR_N|FPSCR_Z|FPSCR_C|FPSCR_V))
		fpscr &= ~(FPSCR_N|FPSCR_Z|FPSCR_C|FPSCR_V);

	fpscr |= exceptions;

	fmxr(FPSCR, fpscr);

#define RAISE(stat,en,sig)				\
	if (exceptions & stat && fpscr & en)		\
		si_code = sig;

	/*
	 * These are arranged in priority order, least to highest.
	 */
	RAISE(FPSCR_DZC, FPSCR_DZE, FPE_FLTDIV);
	RAISE(FPSCR_IXC, FPSCR_IXE, FPE_FLTRES);
	RAISE(FPSCR_UFC, FPSCR_UFE, FPE_FLTUND);
	RAISE(FPSCR_OFC, FPSCR_OFE, FPE_FLTOVF);
	RAISE(FPSCR_IOC, FPSCR_IOE, FPE_FLTINV);

	if (si_code)
		vfp_raise_sigfpe(si_code, regs);
}

/*
 * Emulate a VFP instruction.
 */
static u32 vfp_emulate_instruction(u32 inst, u32 fpscr, struct pt_regs *regs)
{
	u32 exceptions = VFP_EXCEPTION_ERROR;

	pr_debug("VFP: emulate: INST=0x%08x SCR=0x%08x\n", inst, fpscr);

	if (INST_CPRTDO(inst)) {
		if (!INST_CPRT(inst)) {
			/*
			 * CPDO
			 */
			if (vfp_single(inst)) {
				exceptions = vfp_single_cpdo(inst, fpscr);
			} else {
				exceptions = vfp_double_cpdo(inst, fpscr);
			}
		} else {
			/*
			 * A CPRT instruction can not appear in FPINST2, nor
			 * can it cause an exception.  Therefore, we do not
			 * have to emulate it.
			 */
		}
	} else {
		/*
		 * A CPDT instruction can not appear in FPINST2, nor can
		 * it cause an exception.  Therefore, we do not have to
		 * emulate it.
		 */
	}
	return exceptions & ~VFP_NAN_FLAG;
}

/*
 * Package up a bounce condition.
 */
void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs)
{
	u32 fpscr, orig_fpscr, fpsid, exceptions;

	pr_debug("VFP: bounce: trigger %08x fpexc %08x\n", trigger, fpexc);

	/*
	 * At this point, FPEXC can have the following configuration:
	 *
	 *  EX DEX IXE
	 *  0   1   x   - synchronous exception
	 *  1   x   0   - asynchronous exception
	 *  1   x   1   - sychronous on VFP subarch 1 and asynchronous on later
	 *  0   0   1   - synchronous on VFP9 (non-standard subarch 1
	 *                implementation), undefined otherwise
	 *
	 * Clear various bits and enable access to the VFP so we can
	 * handle the bounce.
	 */
	fmxr(FPEXC, fpexc & ~(FPEXC_EX|FPEXC_DEX|FPEXC_FP2V|FPEXC_VV|FPEXC_TRAP_MASK));

	fpsid = fmrx(FPSID);
	orig_fpscr = fpscr = fmrx(FPSCR);

	/*
	 * Check for the special VFP subarch 1 and FPSCR.IXE bit case
	 */
	if ((fpsid & FPSID_ARCH_MASK) == (1 << FPSID_ARCH_BIT)
	    && (fpscr & FPSCR_IXE)) {
		/*
		 * Synchronous exception, emulate the trigger instruction
		 */
		goto emulate;
	}

	if (fpexc & FPEXC_EX) {
#ifndef CONFIG_CPU_FEROCEON
		/*
		 * Asynchronous exception. The instruction is read from FPINST
		 * and the interrupted instruction has to be restarted.
		 */
		trigger = fmrx(FPINST);
		regs->ARM_pc -= 4;
#endif
	} else if (!(fpexc & FPEXC_DEX)) {
		/*
		 * Illegal combination of bits. It can be caused by an
		 * unallocated VFP instruction but with FPSCR.IXE set and not
		 * on VFP subarch 1.
		 */
		 vfp_raise_exceptions(VFP_EXCEPTION_ERROR, trigger, fpscr, regs);
		goto exit;
	}

	/*
	 * Modify fpscr to indicate the number of iterations remaining.
	 * If FPEXC.EX is 0, FPEXC.DEX is 1 and the FPEXC.VV bit indicates
	 * whether FPEXC.VECITR or FPSCR.LEN is used.
	 */
	if (fpexc & (FPEXC_EX | FPEXC_VV)) {
		u32 len;

		len = fpexc + (1 << FPEXC_LENGTH_BIT);

		fpscr &= ~FPSCR_LENGTH_MASK;
		fpscr |= (len & FPEXC_LENGTH_MASK) << (FPSCR_LENGTH_BIT - FPEXC_LENGTH_BIT);
	}

	/*
	 * Handle the first FP instruction.  We used to take note of the
	 * FPEXC bounce reason, but this appears to be unreliable.
	 * Emulate the bounced instruction instead.
	 */
	exceptions = vfp_emulate_instruction(trigger, fpscr, regs);
	if (exceptions)
		vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);

	/*
	 * If there isn't a second FP instruction, exit now. Note that
	 * the FPEXC.FP2V bit is valid only if FPEXC.EX is 1.
	 */
	if ((fpexc & (FPEXC_EX | FPEXC_FP2V)) != (FPEXC_EX | FPEXC_FP2V))
		goto exit;

	/*
	 * The barrier() here prevents fpinst2 being read
	 * before the condition above.
	 */
	barrier();
	trigger = fmrx(FPINST2);

 emulate:
	exceptions = vfp_emulate_instruction(trigger, orig_fpscr, regs);
	if (exceptions)
		vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);
 exit:
	preempt_enable();
}

static void vfp_enable(void *unused)
{
	u32 access;

	BUG_ON(preemptible());
	access = get_copro_access();

	/*
	 * Enable full access to VFP (cp10 and cp11)
	 */
	set_copro_access(access | CPACC_FULL(10) | CPACC_FULL(11));
}

#ifdef CONFIG_CPU_PM
static int vfp_pm_suspend(void)
{
	struct thread_info *ti = current_thread_info();
	u32 fpexc = fmrx(FPEXC);

	/* if vfp is on, then save state for resumption */
	if (fpexc & FPEXC_EN) {
		pr_debug("%s: saving vfp state\n", __func__);
		vfp_save_state(&ti->vfpstate, fpexc);

		/* disable, just in case */
		fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
	} else if (vfp_current_hw_state[ti->cpu]) {
#ifndef CONFIG_SMP
		fmxr(FPEXC, fpexc | FPEXC_EN);
		vfp_save_state(vfp_current_hw_state[ti->cpu], fpexc);
		fmxr(FPEXC, fpexc);
#endif
	}

	/* clear any information we had about last context state */
	vfp_current_hw_state[ti->cpu] = NULL;

	return 0;
}

static void vfp_pm_resume(void)
{
	/* ensure we have access to the vfp */
	vfp_enable(NULL);

	/* and disable it to ensure the next usage restores the state */
	fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
}

static int vfp_cpu_pm_notifier(struct notifier_block *self, unsigned long cmd,
	void *v)
{
	switch (cmd) {
	case CPU_PM_ENTER:
		vfp_pm_suspend();
		break;
	case CPU_PM_ENTER_FAILED:
	case CPU_PM_EXIT:
		vfp_pm_resume();
		break;
	}
	return NOTIFY_OK;
}

static struct notifier_block vfp_cpu_pm_notifier_block = {
	.notifier_call = vfp_cpu_pm_notifier,
};

static void vfp_pm_init(void)
{
	cpu_pm_register_notifier(&vfp_cpu_pm_notifier_block);
}

#else
static inline void vfp_pm_init(void) { }
#endif /* CONFIG_CPU_PM */

/*
 * Ensure that the VFP state stored in 'thread->vfpstate' is up to date
 * with the hardware state.
 */
void vfp_sync_hwstate(struct thread_info *thread)
{
	unsigned int cpu = get_cpu();

	if (vfp_state_in_hw(cpu, thread)) {
		u32 fpexc = fmrx(FPEXC);

		/*
		 * Save the last VFP state on this CPU.
		 */
		fmxr(FPEXC, fpexc | FPEXC_EN);
		vfp_save_state(&thread->vfpstate, fpexc | FPEXC_EN);
		fmxr(FPEXC, fpexc);
	}

	put_cpu();
}

/* Ensure that the thread reloads the hardware VFP state on the next use. */
void vfp_flush_hwstate(struct thread_info *thread)
{
	unsigned int cpu = get_cpu();

	vfp_force_reload(cpu, thread);

	put_cpu();
}

/*
 * Save the current VFP state into the provided structures and prepare
 * for entry into a new function (signal handler).
 */
int vfp_preserve_user_clear_hwstate(struct user_vfp __user *ufp,
				    struct user_vfp_exc __user *ufp_exc)
{
	struct thread_info *thread = current_thread_info();
	struct vfp_hard_struct *hwstate = &thread->vfpstate.hard;
	int err = 0;

	/* Ensure that the saved hwstate is up-to-date. */
	vfp_sync_hwstate(thread);

	/*
	 * Copy the floating point registers. There can be unused
	 * registers see asm/hwcap.h for details.
	 */
	err |= __copy_to_user(&ufp->fpregs, &hwstate->fpregs,
			      sizeof(hwstate->fpregs));
	/*
	 * Copy the status and control register.
	 */
	__put_user_error(hwstate->fpscr, &ufp->fpscr, err);

	/*
	 * Copy the exception registers.
	 */
	__put_user_error(hwstate->fpexc, &ufp_exc->fpexc, err);
	__put_user_error(hwstate->fpinst, &ufp_exc->fpinst, err);
	__put_user_error(hwstate->fpinst2, &ufp_exc->fpinst2, err);

	if (err)
		return -EFAULT;

	/* Ensure that VFP is disabled. */
	vfp_flush_hwstate(thread);

	/*
	 * As per the PCS, clear the length and stride bits for function
	 * entry.
	 */
	hwstate->fpscr &= ~(FPSCR_LENGTH_MASK | FPSCR_STRIDE_MASK);
	return 0;
}

/* Sanitise and restore the current VFP state from the provided structures. */
int vfp_restore_user_hwstate(struct user_vfp __user *ufp,
			     struct user_vfp_exc __user *ufp_exc)
{
	struct thread_info *thread = current_thread_info();
	struct vfp_hard_struct *hwstate = &thread->vfpstate.hard;
	unsigned long fpexc;
	int err = 0;

	/* Disable VFP to avoid corrupting the new thread state. */
	vfp_flush_hwstate(thread);

	/*
	 * Copy the floating point registers. There can be unused
	 * registers see asm/hwcap.h for details.
	 */
	err |= __copy_from_user(&hwstate->fpregs, &ufp->fpregs,
				sizeof(hwstate->fpregs));
	/*
	 * Copy the status and control register.
	 */
	__get_user_error(hwstate->fpscr, &ufp->fpscr, err);

	/*
	 * Sanitise and restore the exception registers.
	 */
	__get_user_error(fpexc, &ufp_exc->fpexc, err);

	/* Ensure the VFP is enabled. */
	fpexc |= FPEXC_EN;

	/* Ensure FPINST2 is invalid and the exception flag is cleared. */
	fpexc &= ~(FPEXC_EX | FPEXC_FP2V);
	hwstate->fpexc = fpexc;

	__get_user_error(hwstate->fpinst, &ufp_exc->fpinst, err);
	__get_user_error(hwstate->fpinst2, &ufp_exc->fpinst2, err);

	return err ? -EFAULT : 0;
}

/*
 * VFP hardware can lose all context when a CPU goes offline.
 * As we will be running in SMP mode with CPU hotplug, we will save the
 * hardware state at every thread switch.  We clear our held state when
 * a CPU has been killed, indicating that the VFP hardware doesn't contain
 * a threads VFP state.  When a CPU starts up, we re-enable access to the
 * VFP hardware.
 *
 * Both CPU_DYING and CPU_STARTING are called on the CPU which
 * is being offlined/onlined.
 */
static int vfp_hotplug(struct notifier_block *b, unsigned long action,
	void *hcpu)
{
	if (action == CPU_DYING || action == CPU_DYING_FROZEN)
		vfp_current_hw_state[(long)hcpu] = NULL;
	else if (action == CPU_STARTING || action == CPU_STARTING_FROZEN)
		vfp_enable(NULL);
	return NOTIFY_OK;
}

void vfp_kmode_exception(void)
{
	/*
	 * If we reach this point, a floating point exception has been raised
	 * while running in kernel mode. If the NEON/VFP unit was enabled at the
	 * time, it means a VFP instruction has been issued that requires
	 * software assistance to complete, something which is not currently
	 * supported in kernel mode.
	 * If the NEON/VFP unit was disabled, and the location pointed to below
	 * is properly preceded by a call to kernel_neon_begin(), something has
	 * caused the task to be scheduled out and back in again. In this case,
	 * rebuilding and running with CONFIG_DEBUG_ATOMIC_SLEEP enabled should
	 * be helpful in localizing the problem.
	 */
	if (fmrx(FPEXC) & FPEXC_EN)
		pr_crit("BUG: unsupported FP instruction in kernel mode\n");
	else
		pr_crit("BUG: FP instruction issued in kernel mode with FP unit disabled\n");
}

#ifdef CONFIG_KERNEL_MODE_NEON

/*
 * Kernel-side NEON support functions
 */
void kernel_neon_begin(void)
{
	struct thread_info *thread = current_thread_info();
	unsigned int cpu;
	u32 fpexc;

	/*
	 * Kernel mode NEON is only allowed outside of interrupt context
	 * with preemption disabled. This will make sure that the kernel
	 * mode NEON register contents never need to be preserved.
	 */
	BUG_ON(in_interrupt());
	cpu = get_cpu();

	fpexc = fmrx(FPEXC) | FPEXC_EN;
	fmxr(FPEXC, fpexc);

	/*
	 * Save the userland NEON/VFP state. Under UP,
	 * the owner could be a task other than 'current'
	 */
	if (vfp_state_in_hw(cpu, thread))
		vfp_save_state(&thread->vfpstate, fpexc);
#ifndef CONFIG_SMP
	else if (vfp_current_hw_state[cpu] != NULL)
		vfp_save_state(vfp_current_hw_state[cpu], fpexc);
#endif
	vfp_current_hw_state[cpu] = NULL;
}
EXPORT_SYMBOL(kernel_neon_begin);

void kernel_neon_end(void)
{
	/* Disable the NEON/VFP unit. */
	fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
	put_cpu();
}
EXPORT_SYMBOL(kernel_neon_end);

#endif /* CONFIG_KERNEL_MODE_NEON */

/*
 * VFP support code initialisation.
 */
static int __init vfp_init(void)
{
	unsigned int vfpsid;
	unsigned int cpu_arch = cpu_architecture();

	if (cpu_arch >= CPU_ARCH_ARMv6)
		on_each_cpu(vfp_enable, NULL, 1);

	/*
	 * First check that there is a VFP that we can use.
	 * The handler is already setup to just log calls, so
	 * we just need to read the VFPSID register.
	 */
	vfp_vector = vfp_testing_entry;
	barrier();
	vfpsid = fmrx(FPSID);
	barrier();
	vfp_vector = vfp_null_entry;

	pr_info("VFP support v0.3: ");
	if (VFP_arch) {
		pr_cont("not present\n");
		return 0;
	/* Extract the architecture on CPUID scheme */
	} else if ((read_cpuid_id() & 0x000f0000) == 0x000f0000) {
		VFP_arch = vfpsid & FPSID_CPUID_ARCH_MASK;
		VFP_arch >>= FPSID_ARCH_BIT;
		/*
		 * Check for the presence of the Advanced SIMD
		 * load/store instructions, integer and single
		 * precision floating point operations. Only check
		 * for NEON if the hardware has the MVFR registers.
		 */
		if (IS_ENABLED(CONFIG_NEON) &&
		   (fmrx(MVFR1) & 0x000fff00) == 0x00011100)
			elf_hwcap |= HWCAP_NEON;

		if (IS_ENABLED(CONFIG_VFPv3)) {
			u32 mvfr0 = fmrx(MVFR0);
			if (((mvfr0 & MVFR0_DP_MASK) >> MVFR0_DP_BIT) == 0x2 ||
			    ((mvfr0 & MVFR0_SP_MASK) >> MVFR0_SP_BIT) == 0x2) {
				elf_hwcap |= HWCAP_VFPv3;
				/*
				 * Check for VFPv3 D16 and VFPv4 D16.  CPUs in
				 * this configuration only have 16 x 64bit
				 * registers.
				 */
				if ((mvfr0 & MVFR0_A_SIMD_MASK) == 1)
					/* also v4-D16 */
					elf_hwcap |= HWCAP_VFPv3D16;
				else
					elf_hwcap |= HWCAP_VFPD32;
			}

			if ((fmrx(MVFR1) & 0xf0000000) == 0x10000000)
				elf_hwcap |= HWCAP_VFPv4;
		}
	/* Extract the architecture version on pre-cpuid scheme */
	} else {
		if (vfpsid & FPSID_NODOUBLE) {
			pr_cont("no double precision support\n");
			return 0;
		}

		VFP_arch = (vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT;
	}

	hotcpu_notifier(vfp_hotplug, 0);

	vfp_vector = vfp_support_entry;

	thread_register_notifier(&vfp_notifier_block);
	vfp_pm_init();

	/*
	 * We detected VFP, and the support code is
	 * in place; report VFP support to userspace.
	 */
	elf_hwcap |= HWCAP_VFP;

	pr_cont("implementor %02x architecture %d part %02x variant %x rev %x\n",
		(vfpsid & FPSID_IMPLEMENTER_MASK) >> FPSID_IMPLEMENTER_BIT,
		VFP_arch,
		(vfpsid & FPSID_PART_MASK) >> FPSID_PART_BIT,
		(vfpsid & FPSID_VARIANT_MASK) >> FPSID_VARIANT_BIT,
		(vfpsid & FPSID_REV_MASK) >> FPSID_REV_BIT);

	return 0;
}

core_initcall(vfp_init);
OpenPOWER on IntegriCloud