1 /*
2 * linux/arch/arm/vfp/vfpmodule.c
3 *
4 * Copyright (C) 2004 ARM Limited.
5 * Written by Deep Blue Solutions Limited.
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 */
11 #include <linux/types.h>
12 #include <linux/cpu.h>
13 #include <linux/cpu_pm.h>
14 #include <linux/kernel.h>
15 #include <linux/notifier.h>
16 #include <linux/signal.h>
17 #include <linux/sched.h>
18 #include <linux/smp.h>
19 #include <linux/init.h>
20
21 #include <asm/cputype.h>
22 #include <asm/thread_notify.h>
23 #include <asm/vfp.h>
24
25 #include "vfpinstr.h"
26 #include "vfp.h"
27
28 /*
29 * Our undef handlers (in entry.S)
30 */
31 void vfp_testing_entry(void);
32 void vfp_support_entry(void);
33 void vfp_null_entry(void);
34
35 void (*vfp_vector)(void) = vfp_null_entry;
36
37 /*
38 * Dual-use variable.
39 * Used in startup: set to non-zero if VFP checks fail
40 * After startup, holds VFP architecture
41 */
42 unsigned int VFP_arch;
43
44 /*
45 * The pointer to the vfpstate structure of the thread which currently
46 * owns the context held in the VFP hardware, or NULL if the hardware
47 * context is invalid.
48 *
49 * For UP, this is sufficient to tell which thread owns the VFP context.
50 * However, for SMP, we also need to check the CPU number stored in the
51 * saved state too to catch migrations.
52 */
53 union vfp_state *vfp_current_hw_state[NR_CPUS];
54
55 /*
56 * Is 'thread's most up to date state stored in this CPUs hardware?
57 * Must be called from non-preemptible context.
58 */
vfp_state_in_hw(unsigned int cpu,struct thread_info * thread)59 static bool vfp_state_in_hw(unsigned int cpu, struct thread_info *thread)
60 {
61 #ifdef CONFIG_SMP
62 if (thread->vfpstate.hard.cpu != cpu)
63 return false;
64 #endif
65 return vfp_current_hw_state[cpu] == &thread->vfpstate;
66 }
67
68 /*
69 * Force a reload of the VFP context from the thread structure. We do
70 * this by ensuring that access to the VFP hardware is disabled, and
71 * clear vfp_current_hw_state. Must be called from non-preemptible context.
72 */
vfp_force_reload(unsigned int cpu,struct thread_info * thread)73 static void vfp_force_reload(unsigned int cpu, struct thread_info *thread)
74 {
75 if (vfp_state_in_hw(cpu, thread)) {
76 fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
77 vfp_current_hw_state[cpu] = NULL;
78 }
79 #ifdef CONFIG_SMP
80 thread->vfpstate.hard.cpu = NR_CPUS;
81 #endif
82 }
83
84 /*
85 * Per-thread VFP initialization.
86 */
vfp_thread_flush(struct thread_info * thread)87 static void vfp_thread_flush(struct thread_info *thread)
88 {
89 union vfp_state *vfp = &thread->vfpstate;
90 unsigned int cpu;
91
92 /*
93 * Disable VFP to ensure we initialize it first. We must ensure
94 * that the modification of vfp_current_hw_state[] and hardware
95 * disable are done for the same CPU and without preemption.
96 *
97 * Do this first to ensure that preemption won't overwrite our
98 * state saving should access to the VFP be enabled at this point.
99 */
100 cpu = get_cpu();
101 if (vfp_current_hw_state[cpu] == vfp)
102 vfp_current_hw_state[cpu] = NULL;
103 fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
104 put_cpu();
105
106 memset(vfp, 0, sizeof(union vfp_state));
107
108 vfp->hard.fpexc = FPEXC_EN;
109 vfp->hard.fpscr = FPSCR_ROUND_NEAREST;
110 #ifdef CONFIG_SMP
111 vfp->hard.cpu = NR_CPUS;
112 #endif
113 }
114
vfp_thread_exit(struct thread_info * thread)115 static void vfp_thread_exit(struct thread_info *thread)
116 {
117 /* release case: Per-thread VFP cleanup. */
118 union vfp_state *vfp = &thread->vfpstate;
119 unsigned int cpu = get_cpu();
120
121 if (vfp_current_hw_state[cpu] == vfp)
122 vfp_current_hw_state[cpu] = NULL;
123 put_cpu();
124 }
125
vfp_thread_copy(struct thread_info * thread)126 static void vfp_thread_copy(struct thread_info *thread)
127 {
128 struct thread_info *parent = current_thread_info();
129
130 vfp_sync_hwstate(parent);
131 thread->vfpstate = parent->vfpstate;
132 #ifdef CONFIG_SMP
133 thread->vfpstate.hard.cpu = NR_CPUS;
134 #endif
135 }
136
137 /*
138 * When this function is called with the following 'cmd's, the following
139 * is true while this function is being run:
140 * THREAD_NOFTIFY_SWTICH:
141 * - the previously running thread will not be scheduled onto another CPU.
142 * - the next thread to be run (v) will not be running on another CPU.
143 * - thread->cpu is the local CPU number
144 * - not preemptible as we're called in the middle of a thread switch
145 * THREAD_NOTIFY_FLUSH:
146 * - the thread (v) will be running on the local CPU, so
147 * v === current_thread_info()
148 * - thread->cpu is the local CPU number at the time it is accessed,
149 * but may change at any time.
150 * - we could be preempted if tree preempt rcu is enabled, so
151 * it is unsafe to use thread->cpu.
152 * THREAD_NOTIFY_EXIT
153 * - the thread (v) will be running on the local CPU, so
154 * v === current_thread_info()
155 * - thread->cpu is the local CPU number at the time it is accessed,
156 * but may change at any time.
157 * - we could be preempted if tree preempt rcu is enabled, so
158 * it is unsafe to use thread->cpu.
159 */
vfp_notifier(struct notifier_block * self,unsigned long cmd,void * v)160 static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
161 {
162 struct thread_info *thread = v;
163 u32 fpexc;
164 #ifdef CONFIG_SMP
165 unsigned int cpu;
166 #endif
167
168 switch (cmd) {
169 case THREAD_NOTIFY_SWITCH:
170 fpexc = fmrx(FPEXC);
171
172 #ifdef CONFIG_SMP
173 cpu = thread->cpu;
174
175 /*
176 * On SMP, if VFP is enabled, save the old state in
177 * case the thread migrates to a different CPU. The
178 * restoring is done lazily.
179 */
180 if ((fpexc & FPEXC_EN) && vfp_current_hw_state[cpu])
181 vfp_save_state(vfp_current_hw_state[cpu], fpexc);
182 #endif
183
184 /*
185 * Always disable VFP so we can lazily save/restore the
186 * old state.
187 */
188 fmxr(FPEXC, fpexc & ~FPEXC_EN);
189 break;
190
191 case THREAD_NOTIFY_FLUSH:
192 vfp_thread_flush(thread);
193 break;
194
195 case THREAD_NOTIFY_EXIT:
196 vfp_thread_exit(thread);
197 break;
198
199 case THREAD_NOTIFY_COPY:
200 vfp_thread_copy(thread);
201 break;
202 }
203
204 return NOTIFY_DONE;
205 }
206
207 static struct notifier_block vfp_notifier_block = {
208 .notifier_call = vfp_notifier,
209 };
210
211 /*
212 * Raise a SIGFPE for the current process.
213 * sicode describes the signal being raised.
214 */
vfp_raise_sigfpe(unsigned int sicode,struct pt_regs * regs)215 static void vfp_raise_sigfpe(unsigned int sicode, struct pt_regs *regs)
216 {
217 siginfo_t info;
218
219 memset(&info, 0, sizeof(info));
220
221 info.si_signo = SIGFPE;
222 info.si_code = sicode;
223 info.si_addr = (void __user *)(instruction_pointer(regs) - 4);
224
225 /*
226 * This is the same as NWFPE, because it's not clear what
227 * this is used for
228 */
229 current->thread.error_code = 0;
230 current->thread.trap_no = 6;
231
232 send_sig_info(SIGFPE, &info, current);
233 }
234
vfp_panic(char * reason,u32 inst)235 static void vfp_panic(char *reason, u32 inst)
236 {
237 int i;
238
239 printk(KERN_ERR "VFP: Error: %s\n", reason);
240 printk(KERN_ERR "VFP: EXC 0x%08x SCR 0x%08x INST 0x%08x\n",
241 fmrx(FPEXC), fmrx(FPSCR), inst);
242 for (i = 0; i < 32; i += 2)
243 printk(KERN_ERR "VFP: s%2u: 0x%08x s%2u: 0x%08x\n",
244 i, vfp_get_float(i), i+1, vfp_get_float(i+1));
245 }
246
247 /*
248 * Process bitmask of exception conditions.
249 */
vfp_raise_exceptions(u32 exceptions,u32 inst,u32 fpscr,struct pt_regs * regs)250 static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_regs *regs)
251 {
252 int si_code = 0;
253
254 pr_debug("VFP: raising exceptions %08x\n", exceptions);
255
256 if (exceptions == VFP_EXCEPTION_ERROR) {
257 vfp_panic("unhandled bounce", inst);
258 vfp_raise_sigfpe(0, regs);
259 return;
260 }
261
262 /*
263 * If any of the status flags are set, update the FPSCR.
264 * Comparison instructions always return at least one of
265 * these flags set.
266 */
267 if (exceptions & (FPSCR_N|FPSCR_Z|FPSCR_C|FPSCR_V))
268 fpscr &= ~(FPSCR_N|FPSCR_Z|FPSCR_C|FPSCR_V);
269
270 fpscr |= exceptions;
271
272 fmxr(FPSCR, fpscr);
273
274 #define RAISE(stat,en,sig) \
275 if (exceptions & stat && fpscr & en) \
276 si_code = sig;
277
278 /*
279 * These are arranged in priority order, least to highest.
280 */
281 RAISE(FPSCR_DZC, FPSCR_DZE, FPE_FLTDIV);
282 RAISE(FPSCR_IXC, FPSCR_IXE, FPE_FLTRES);
283 RAISE(FPSCR_UFC, FPSCR_UFE, FPE_FLTUND);
284 RAISE(FPSCR_OFC, FPSCR_OFE, FPE_FLTOVF);
285 RAISE(FPSCR_IOC, FPSCR_IOE, FPE_FLTINV);
286
287 if (si_code)
288 vfp_raise_sigfpe(si_code, regs);
289 }
290
291 /*
292 * Emulate a VFP instruction.
293 */
vfp_emulate_instruction(u32 inst,u32 fpscr,struct pt_regs * regs)294 static u32 vfp_emulate_instruction(u32 inst, u32 fpscr, struct pt_regs *regs)
295 {
296 u32 exceptions = VFP_EXCEPTION_ERROR;
297
298 pr_debug("VFP: emulate: INST=0x%08x SCR=0x%08x\n", inst, fpscr);
299
300 if (INST_CPRTDO(inst)) {
301 if (!INST_CPRT(inst)) {
302 /*
303 * CPDO
304 */
305 if (vfp_single(inst)) {
306 exceptions = vfp_single_cpdo(inst, fpscr);
307 } else {
308 exceptions = vfp_double_cpdo(inst, fpscr);
309 }
310 } else {
311 /*
312 * A CPRT instruction can not appear in FPINST2, nor
313 * can it cause an exception. Therefore, we do not
314 * have to emulate it.
315 */
316 }
317 } else {
318 /*
319 * A CPDT instruction can not appear in FPINST2, nor can
320 * it cause an exception. Therefore, we do not have to
321 * emulate it.
322 */
323 }
324 return exceptions & ~VFP_NAN_FLAG;
325 }
326
327 /*
328 * Package up a bounce condition.
329 */
VFP_bounce(u32 trigger,u32 fpexc,struct pt_regs * regs)330 void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs)
331 {
332 u32 fpscr, orig_fpscr, fpsid, exceptions;
333
334 pr_debug("VFP: bounce: trigger %08x fpexc %08x\n", trigger, fpexc);
335
336 /*
337 * At this point, FPEXC can have the following configuration:
338 *
339 * EX DEX IXE
340 * 0 1 x - synchronous exception
341 * 1 x 0 - asynchronous exception
342 * 1 x 1 - sychronous on VFP subarch 1 and asynchronous on later
343 * 0 0 1 - synchronous on VFP9 (non-standard subarch 1
344 * implementation), undefined otherwise
345 *
346 * Clear various bits and enable access to the VFP so we can
347 * handle the bounce.
348 */
349 fmxr(FPEXC, fpexc & ~(FPEXC_EX|FPEXC_DEX|FPEXC_FP2V|FPEXC_VV|FPEXC_TRAP_MASK));
350
351 fpsid = fmrx(FPSID);
352 orig_fpscr = fpscr = fmrx(FPSCR);
353
354 /*
355 * Check for the special VFP subarch 1 and FPSCR.IXE bit case
356 */
357 if ((fpsid & FPSID_ARCH_MASK) == (1 << FPSID_ARCH_BIT)
358 && (fpscr & FPSCR_IXE)) {
359 /*
360 * Synchronous exception, emulate the trigger instruction
361 */
362 goto emulate;
363 }
364
365 if (fpexc & FPEXC_EX) {
366 #ifndef CONFIG_CPU_FEROCEON
367 /*
368 * Asynchronous exception. The instruction is read from FPINST
369 * and the interrupted instruction has to be restarted.
370 */
371 trigger = fmrx(FPINST);
372 regs->ARM_pc -= 4;
373 #endif
374 } else if (!(fpexc & FPEXC_DEX)) {
375 /*
376 * Illegal combination of bits. It can be caused by an
377 * unallocated VFP instruction but with FPSCR.IXE set and not
378 * on VFP subarch 1.
379 */
380 vfp_raise_exceptions(VFP_EXCEPTION_ERROR, trigger, fpscr, regs);
381 goto exit;
382 }
383
384 /*
385 * Modify fpscr to indicate the number of iterations remaining.
386 * If FPEXC.EX is 0, FPEXC.DEX is 1 and the FPEXC.VV bit indicates
387 * whether FPEXC.VECITR or FPSCR.LEN is used.
388 */
389 if (fpexc & (FPEXC_EX | FPEXC_VV)) {
390 u32 len;
391
392 len = fpexc + (1 << FPEXC_LENGTH_BIT);
393
394 fpscr &= ~FPSCR_LENGTH_MASK;
395 fpscr |= (len & FPEXC_LENGTH_MASK) << (FPSCR_LENGTH_BIT - FPEXC_LENGTH_BIT);
396 }
397
398 /*
399 * Handle the first FP instruction. We used to take note of the
400 * FPEXC bounce reason, but this appears to be unreliable.
401 * Emulate the bounced instruction instead.
402 */
403 exceptions = vfp_emulate_instruction(trigger, fpscr, regs);
404 if (exceptions)
405 vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);
406
407 /*
408 * If there isn't a second FP instruction, exit now. Note that
409 * the FPEXC.FP2V bit is valid only if FPEXC.EX is 1.
410 */
411 if (fpexc ^ (FPEXC_EX | FPEXC_FP2V))
412 goto exit;
413
414 /*
415 * The barrier() here prevents fpinst2 being read
416 * before the condition above.
417 */
418 barrier();
419 trigger = fmrx(FPINST2);
420
421 emulate:
422 exceptions = vfp_emulate_instruction(trigger, orig_fpscr, regs);
423 if (exceptions)
424 vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);
425 exit:
426 preempt_enable();
427 }
428
vfp_enable(void * unused)429 static void vfp_enable(void *unused)
430 {
431 u32 access = get_copro_access();
432
433 /*
434 * Enable full access to VFP (cp10 and cp11)
435 */
436 set_copro_access(access | CPACC_FULL(10) | CPACC_FULL(11));
437 }
438
439 #ifdef CONFIG_CPU_PM
vfp_pm_suspend(void)440 static int vfp_pm_suspend(void)
441 {
442 struct thread_info *ti = current_thread_info();
443 u32 fpexc = fmrx(FPEXC);
444
445 /* if vfp is on, then save state for resumption */
446 if (fpexc & FPEXC_EN) {
447 printk(KERN_DEBUG "%s: saving vfp state\n", __func__);
448 vfp_save_state(&ti->vfpstate, fpexc);
449
450 /* disable, just in case */
451 fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
452 }
453
454 /* clear any information we had about last context state */
455 memset(vfp_current_hw_state, 0, sizeof(vfp_current_hw_state));
456
457 return 0;
458 }
459
vfp_pm_resume(void)460 static void vfp_pm_resume(void)
461 {
462 /* ensure we have access to the vfp */
463 vfp_enable(NULL);
464
465 /* and disable it to ensure the next usage restores the state */
466 fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
467 }
468
vfp_cpu_pm_notifier(struct notifier_block * self,unsigned long cmd,void * v)469 static int vfp_cpu_pm_notifier(struct notifier_block *self, unsigned long cmd,
470 void *v)
471 {
472 switch (cmd) {
473 case CPU_PM_ENTER:
474 vfp_pm_suspend();
475 break;
476 case CPU_PM_ENTER_FAILED:
477 case CPU_PM_EXIT:
478 vfp_pm_resume();
479 break;
480 }
481 return NOTIFY_OK;
482 }
483
484 static struct notifier_block vfp_cpu_pm_notifier_block = {
485 .notifier_call = vfp_cpu_pm_notifier,
486 };
487
vfp_pm_init(void)488 static void vfp_pm_init(void)
489 {
490 cpu_pm_register_notifier(&vfp_cpu_pm_notifier_block);
491 }
492
493 #else
vfp_pm_init(void)494 static inline void vfp_pm_init(void) { }
495 #endif /* CONFIG_CPU_PM */
496
497 /*
498 * Ensure that the VFP state stored in 'thread->vfpstate' is up to date
499 * with the hardware state.
500 */
vfp_sync_hwstate(struct thread_info * thread)501 void vfp_sync_hwstate(struct thread_info *thread)
502 {
503 unsigned int cpu = get_cpu();
504
505 if (vfp_state_in_hw(cpu, thread)) {
506 u32 fpexc = fmrx(FPEXC);
507
508 /*
509 * Save the last VFP state on this CPU.
510 */
511 fmxr(FPEXC, fpexc | FPEXC_EN);
512 vfp_save_state(&thread->vfpstate, fpexc | FPEXC_EN);
513 fmxr(FPEXC, fpexc);
514 }
515
516 put_cpu();
517 }
518
519 /* Ensure that the thread reloads the hardware VFP state on the next use. */
vfp_flush_hwstate(struct thread_info * thread)520 void vfp_flush_hwstate(struct thread_info *thread)
521 {
522 unsigned int cpu = get_cpu();
523
524 vfp_force_reload(cpu, thread);
525
526 put_cpu();
527 }
528
529 /*
530 * VFP hardware can lose all context when a CPU goes offline.
531 * As we will be running in SMP mode with CPU hotplug, we will save the
532 * hardware state at every thread switch. We clear our held state when
533 * a CPU has been killed, indicating that the VFP hardware doesn't contain
534 * a threads VFP state. When a CPU starts up, we re-enable access to the
535 * VFP hardware.
536 *
537 * Both CPU_DYING and CPU_STARTING are called on the CPU which
538 * is being offlined/onlined.
539 */
vfp_hotplug(struct notifier_block * b,unsigned long action,void * hcpu)540 static int vfp_hotplug(struct notifier_block *b, unsigned long action,
541 void *hcpu)
542 {
543 if (action == CPU_DYING || action == CPU_DYING_FROZEN) {
544 vfp_force_reload((long)hcpu, current_thread_info());
545 } else if (action == CPU_STARTING || action == CPU_STARTING_FROZEN)
546 vfp_enable(NULL);
547 return NOTIFY_OK;
548 }
549
550 /*
551 * VFP support code initialisation.
552 */
vfp_init(void)553 static int __init vfp_init(void)
554 {
555 unsigned int vfpsid;
556 unsigned int cpu_arch = cpu_architecture();
557
558 if (cpu_arch >= CPU_ARCH_ARMv6)
559 vfp_enable(NULL);
560
561 /*
562 * First check that there is a VFP that we can use.
563 * The handler is already setup to just log calls, so
564 * we just need to read the VFPSID register.
565 */
566 vfp_vector = vfp_testing_entry;
567 barrier();
568 vfpsid = fmrx(FPSID);
569 barrier();
570 vfp_vector = vfp_null_entry;
571
572 printk(KERN_INFO "VFP support v0.3: ");
573 if (VFP_arch)
574 printk("not present\n");
575 else if (vfpsid & FPSID_NODOUBLE) {
576 printk("no double precision support\n");
577 } else {
578 hotcpu_notifier(vfp_hotplug, 0);
579
580 smp_call_function(vfp_enable, NULL, 1);
581
582 VFP_arch = (vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT; /* Extract the architecture version */
583 printk("implementor %02x architecture %d part %02x variant %x rev %x\n",
584 (vfpsid & FPSID_IMPLEMENTER_MASK) >> FPSID_IMPLEMENTER_BIT,
585 (vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT,
586 (vfpsid & FPSID_PART_MASK) >> FPSID_PART_BIT,
587 (vfpsid & FPSID_VARIANT_MASK) >> FPSID_VARIANT_BIT,
588 (vfpsid & FPSID_REV_MASK) >> FPSID_REV_BIT);
589
590 vfp_vector = vfp_support_entry;
591
592 thread_register_notifier(&vfp_notifier_block);
593 vfp_pm_init();
594
595 /*
596 * We detected VFP, and the support code is
597 * in place; report VFP support to userspace.
598 */
599 elf_hwcap |= HWCAP_VFP;
600 #ifdef CONFIG_VFPv3
601 if (VFP_arch >= 2) {
602 elf_hwcap |= HWCAP_VFPv3;
603
604 /*
605 * Check for VFPv3 D16. CPUs in this configuration
606 * only have 16 x 64bit registers.
607 */
608 if (((fmrx(MVFR0) & MVFR0_A_SIMD_MASK)) == 1)
609 elf_hwcap |= HWCAP_VFPv3D16;
610 }
611 #endif
612 /*
613 * Check for the presence of the Advanced SIMD
614 * load/store instructions, integer and single
615 * precision floating point operations. Only check
616 * for NEON if the hardware has the MVFR registers.
617 */
618 if ((read_cpuid_id() & 0x000f0000) == 0x000f0000) {
619 #ifdef CONFIG_NEON
620 if ((fmrx(MVFR1) & 0x000fff00) == 0x00011100)
621 elf_hwcap |= HWCAP_NEON;
622 #endif
623 if ((fmrx(MVFR1) & 0xf0000000) == 0x10000000)
624 elf_hwcap |= HWCAP_VFPv4;
625 }
626 }
627 return 0;
628 }
629
630 late_initcall(vfp_init);
631