xref: /openbmc/linux/arch/powerpc/kernel/sysfs.c (revision f42b3800)
1 #include <linux/sysdev.h>
2 #include <linux/cpu.h>
3 #include <linux/smp.h>
4 #include <linux/percpu.h>
5 #include <linux/init.h>
6 #include <linux/sched.h>
7 #include <linux/module.h>
8 #include <linux/nodemask.h>
9 #include <linux/cpumask.h>
10 #include <linux/notifier.h>
11 
12 #include <asm/current.h>
13 #include <asm/processor.h>
14 #include <asm/cputable.h>
15 #include <asm/firmware.h>
16 #include <asm/hvcall.h>
17 #include <asm/prom.h>
18 #include <asm/paca.h>
19 #include <asm/lppaca.h>
20 #include <asm/machdep.h>
21 #include <asm/smp.h>
22 
23 static DEFINE_PER_CPU(struct cpu, cpu_devices);
24 
25 /* SMT stuff */
26 
27 #ifdef CONFIG_PPC_MULTIPLATFORM
28 /* Time in microseconds we delay before sleeping in the idle loop */
29 DEFINE_PER_CPU(unsigned long, smt_snooze_delay) = { 100 };
30 
31 static ssize_t store_smt_snooze_delay(struct sys_device *dev, const char *buf,
32 				      size_t count)
33 {
34 	struct cpu *cpu = container_of(dev, struct cpu, sysdev);
35 	ssize_t ret;
36 	unsigned long snooze;
37 
38 	ret = sscanf(buf, "%lu", &snooze);
39 	if (ret != 1)
40 		return -EINVAL;
41 
42 	per_cpu(smt_snooze_delay, cpu->sysdev.id) = snooze;
43 
44 	return count;
45 }
46 
47 static ssize_t show_smt_snooze_delay(struct sys_device *dev, char *buf)
48 {
49 	struct cpu *cpu = container_of(dev, struct cpu, sysdev);
50 
51 	return sprintf(buf, "%lu\n", per_cpu(smt_snooze_delay, cpu->sysdev.id));
52 }
53 
54 static SYSDEV_ATTR(smt_snooze_delay, 0644, show_smt_snooze_delay,
55 		   store_smt_snooze_delay);
56 
57 /* Only parse OF options if the matching cmdline option was not specified */
58 static int smt_snooze_cmdline;
59 
60 static int __init smt_setup(void)
61 {
62 	struct device_node *options;
63 	const unsigned int *val;
64 	unsigned int cpu;
65 
66 	if (!cpu_has_feature(CPU_FTR_SMT))
67 		return -ENODEV;
68 
69 	options = of_find_node_by_path("/options");
70 	if (!options)
71 		return -ENODEV;
72 
73 	val = of_get_property(options, "ibm,smt-snooze-delay", NULL);
74 	if (!smt_snooze_cmdline && val) {
75 		for_each_possible_cpu(cpu)
76 			per_cpu(smt_snooze_delay, cpu) = *val;
77 	}
78 
79 	of_node_put(options);
80 	return 0;
81 }
82 __initcall(smt_setup);
83 
84 static int __init setup_smt_snooze_delay(char *str)
85 {
86 	unsigned int cpu;
87 	int snooze;
88 
89 	if (!cpu_has_feature(CPU_FTR_SMT))
90 		return 1;
91 
92 	smt_snooze_cmdline = 1;
93 
94 	if (get_option(&str, &snooze)) {
95 		for_each_possible_cpu(cpu)
96 			per_cpu(smt_snooze_delay, cpu) = snooze;
97 	}
98 
99 	return 1;
100 }
101 __setup("smt-snooze-delay=", setup_smt_snooze_delay);
102 
103 #endif /* CONFIG_PPC_MULTIPLATFORM */
104 
105 /*
106  * Enabling PMCs will slow partition context switch times so we only do
107  * it the first time we write to the PMCs.
108  */
109 
110 static DEFINE_PER_CPU(char, pmcs_enabled);
111 
112 void ppc64_enable_pmcs(void)
113 {
114 	/* Only need to enable them once */
115 	if (__get_cpu_var(pmcs_enabled))
116 		return;
117 
118 	__get_cpu_var(pmcs_enabled) = 1;
119 
120 	if (ppc_md.enable_pmcs)
121 		ppc_md.enable_pmcs();
122 }
123 EXPORT_SYMBOL(ppc64_enable_pmcs);
124 
125 /* XXX convert to rusty's on_one_cpu */
126 static unsigned long run_on_cpu(unsigned long cpu,
127 			        unsigned long (*func)(unsigned long),
128 				unsigned long arg)
129 {
130 	cpumask_t old_affinity = current->cpus_allowed;
131 	unsigned long ret;
132 
133 	/* should return -EINVAL to userspace */
134 	if (set_cpus_allowed(current, cpumask_of_cpu(cpu)))
135 		return 0;
136 
137 	ret = func(arg);
138 
139 	set_cpus_allowed(current, old_affinity);
140 
141 	return ret;
142 }
143 
144 #define SYSFS_PMCSETUP(NAME, ADDRESS) \
145 static unsigned long read_##NAME(unsigned long junk) \
146 { \
147 	return mfspr(ADDRESS); \
148 } \
149 static unsigned long write_##NAME(unsigned long val) \
150 { \
151 	ppc64_enable_pmcs(); \
152 	mtspr(ADDRESS, val); \
153 	return 0; \
154 } \
155 static ssize_t show_##NAME(struct sys_device *dev, char *buf) \
156 { \
157 	struct cpu *cpu = container_of(dev, struct cpu, sysdev); \
158 	unsigned long val = run_on_cpu(cpu->sysdev.id, read_##NAME, 0); \
159 	return sprintf(buf, "%lx\n", val); \
160 } \
161 static ssize_t __used \
162 	store_##NAME(struct sys_device *dev, const char *buf, size_t count) \
163 { \
164 	struct cpu *cpu = container_of(dev, struct cpu, sysdev); \
165 	unsigned long val; \
166 	int ret = sscanf(buf, "%lx", &val); \
167 	if (ret != 1) \
168 		return -EINVAL; \
169 	run_on_cpu(cpu->sysdev.id, write_##NAME, val); \
170 	return count; \
171 }
172 
173 
174 /* Let's define all possible registers, we'll only hook up the ones
175  * that are implemented on the current processor
176  */
177 
178 SYSFS_PMCSETUP(mmcr0, SPRN_MMCR0);
179 SYSFS_PMCSETUP(mmcr1, SPRN_MMCR1);
180 SYSFS_PMCSETUP(mmcra, SPRN_MMCRA);
181 SYSFS_PMCSETUP(pmc1, SPRN_PMC1);
182 SYSFS_PMCSETUP(pmc2, SPRN_PMC2);
183 SYSFS_PMCSETUP(pmc3, SPRN_PMC3);
184 SYSFS_PMCSETUP(pmc4, SPRN_PMC4);
185 SYSFS_PMCSETUP(pmc5, SPRN_PMC5);
186 SYSFS_PMCSETUP(pmc6, SPRN_PMC6);
187 SYSFS_PMCSETUP(pmc7, SPRN_PMC7);
188 SYSFS_PMCSETUP(pmc8, SPRN_PMC8);
189 SYSFS_PMCSETUP(purr, SPRN_PURR);
190 SYSFS_PMCSETUP(spurr, SPRN_SPURR);
191 SYSFS_PMCSETUP(dscr, SPRN_DSCR);
192 
193 SYSFS_PMCSETUP(pa6t_pmc0, SPRN_PA6T_PMC0);
194 SYSFS_PMCSETUP(pa6t_pmc1, SPRN_PA6T_PMC1);
195 SYSFS_PMCSETUP(pa6t_pmc2, SPRN_PA6T_PMC2);
196 SYSFS_PMCSETUP(pa6t_pmc3, SPRN_PA6T_PMC3);
197 SYSFS_PMCSETUP(pa6t_pmc4, SPRN_PA6T_PMC4);
198 SYSFS_PMCSETUP(pa6t_pmc5, SPRN_PA6T_PMC5);
199 
200 #ifdef CONFIG_DEBUG_KERNEL
201 SYSFS_PMCSETUP(hid0, SPRN_HID0);
202 SYSFS_PMCSETUP(hid1, SPRN_HID1);
203 SYSFS_PMCSETUP(hid4, SPRN_HID4);
204 SYSFS_PMCSETUP(hid5, SPRN_HID5);
205 SYSFS_PMCSETUP(ima0, SPRN_PA6T_IMA0);
206 SYSFS_PMCSETUP(ima1, SPRN_PA6T_IMA1);
207 SYSFS_PMCSETUP(ima2, SPRN_PA6T_IMA2);
208 SYSFS_PMCSETUP(ima3, SPRN_PA6T_IMA3);
209 SYSFS_PMCSETUP(ima4, SPRN_PA6T_IMA4);
210 SYSFS_PMCSETUP(ima5, SPRN_PA6T_IMA5);
211 SYSFS_PMCSETUP(ima6, SPRN_PA6T_IMA6);
212 SYSFS_PMCSETUP(ima7, SPRN_PA6T_IMA7);
213 SYSFS_PMCSETUP(ima8, SPRN_PA6T_IMA8);
214 SYSFS_PMCSETUP(ima9, SPRN_PA6T_IMA9);
215 SYSFS_PMCSETUP(imaat, SPRN_PA6T_IMAAT);
216 SYSFS_PMCSETUP(btcr, SPRN_PA6T_BTCR);
217 SYSFS_PMCSETUP(pccr, SPRN_PA6T_PCCR);
218 SYSFS_PMCSETUP(rpccr, SPRN_PA6T_RPCCR);
219 SYSFS_PMCSETUP(der, SPRN_PA6T_DER);
220 SYSFS_PMCSETUP(mer, SPRN_PA6T_MER);
221 SYSFS_PMCSETUP(ber, SPRN_PA6T_BER);
222 SYSFS_PMCSETUP(ier, SPRN_PA6T_IER);
223 SYSFS_PMCSETUP(sier, SPRN_PA6T_SIER);
224 SYSFS_PMCSETUP(siar, SPRN_PA6T_SIAR);
225 SYSFS_PMCSETUP(tsr0, SPRN_PA6T_TSR0);
226 SYSFS_PMCSETUP(tsr1, SPRN_PA6T_TSR1);
227 SYSFS_PMCSETUP(tsr2, SPRN_PA6T_TSR2);
228 SYSFS_PMCSETUP(tsr3, SPRN_PA6T_TSR3);
229 #endif /* CONFIG_DEBUG_KERNEL */
230 
231 static SYSDEV_ATTR(mmcra, 0600, show_mmcra, store_mmcra);
232 static SYSDEV_ATTR(spurr, 0600, show_spurr, NULL);
233 static SYSDEV_ATTR(dscr, 0600, show_dscr, store_dscr);
234 static SYSDEV_ATTR(purr, 0600, show_purr, store_purr);
235 
236 static struct sysdev_attribute ibm_common_attrs[] = {
237 	_SYSDEV_ATTR(mmcr0, 0600, show_mmcr0, store_mmcr0),
238 	_SYSDEV_ATTR(mmcr1, 0600, show_mmcr1, store_mmcr1),
239 };
240 
241 static struct sysdev_attribute ibm_pmc_attrs[] = {
242 	_SYSDEV_ATTR(pmc1, 0600, show_pmc1, store_pmc1),
243 	_SYSDEV_ATTR(pmc2, 0600, show_pmc2, store_pmc2),
244 	_SYSDEV_ATTR(pmc3, 0600, show_pmc3, store_pmc3),
245 	_SYSDEV_ATTR(pmc4, 0600, show_pmc4, store_pmc4),
246 	_SYSDEV_ATTR(pmc5, 0600, show_pmc5, store_pmc5),
247 	_SYSDEV_ATTR(pmc6, 0600, show_pmc6, store_pmc6),
248 	_SYSDEV_ATTR(pmc7, 0600, show_pmc7, store_pmc7),
249 	_SYSDEV_ATTR(pmc8, 0600, show_pmc8, store_pmc8),
250 };
251 
252 static struct sysdev_attribute pa6t_attrs[] = {
253 	_SYSDEV_ATTR(mmcr0, 0600, show_mmcr0, store_mmcr0),
254 	_SYSDEV_ATTR(mmcr1, 0600, show_mmcr1, store_mmcr1),
255 	_SYSDEV_ATTR(pmc0, 0600, show_pa6t_pmc0, store_pa6t_pmc0),
256 	_SYSDEV_ATTR(pmc1, 0600, show_pa6t_pmc1, store_pa6t_pmc1),
257 	_SYSDEV_ATTR(pmc2, 0600, show_pa6t_pmc2, store_pa6t_pmc2),
258 	_SYSDEV_ATTR(pmc3, 0600, show_pa6t_pmc3, store_pa6t_pmc3),
259 	_SYSDEV_ATTR(pmc4, 0600, show_pa6t_pmc4, store_pa6t_pmc4),
260 	_SYSDEV_ATTR(pmc5, 0600, show_pa6t_pmc5, store_pa6t_pmc5),
261 #ifdef CONFIG_DEBUG_KERNEL
262 	_SYSDEV_ATTR(hid0, 0600, show_hid0, store_hid0),
263 	_SYSDEV_ATTR(hid1, 0600, show_hid1, store_hid1),
264 	_SYSDEV_ATTR(hid4, 0600, show_hid4, store_hid4),
265 	_SYSDEV_ATTR(hid5, 0600, show_hid5, store_hid5),
266 	_SYSDEV_ATTR(ima0, 0600, show_ima0, store_ima0),
267 	_SYSDEV_ATTR(ima1, 0600, show_ima1, store_ima1),
268 	_SYSDEV_ATTR(ima2, 0600, show_ima2, store_ima2),
269 	_SYSDEV_ATTR(ima3, 0600, show_ima3, store_ima3),
270 	_SYSDEV_ATTR(ima4, 0600, show_ima4, store_ima4),
271 	_SYSDEV_ATTR(ima5, 0600, show_ima5, store_ima5),
272 	_SYSDEV_ATTR(ima6, 0600, show_ima6, store_ima6),
273 	_SYSDEV_ATTR(ima7, 0600, show_ima7, store_ima7),
274 	_SYSDEV_ATTR(ima8, 0600, show_ima8, store_ima8),
275 	_SYSDEV_ATTR(ima9, 0600, show_ima9, store_ima9),
276 	_SYSDEV_ATTR(imaat, 0600, show_imaat, store_imaat),
277 	_SYSDEV_ATTR(btcr, 0600, show_btcr, store_btcr),
278 	_SYSDEV_ATTR(pccr, 0600, show_pccr, store_pccr),
279 	_SYSDEV_ATTR(rpccr, 0600, show_rpccr, store_rpccr),
280 	_SYSDEV_ATTR(der, 0600, show_der, store_der),
281 	_SYSDEV_ATTR(mer, 0600, show_mer, store_mer),
282 	_SYSDEV_ATTR(ber, 0600, show_ber, store_ber),
283 	_SYSDEV_ATTR(ier, 0600, show_ier, store_ier),
284 	_SYSDEV_ATTR(sier, 0600, show_sier, store_sier),
285 	_SYSDEV_ATTR(siar, 0600, show_siar, store_siar),
286 	_SYSDEV_ATTR(tsr0, 0600, show_tsr0, store_tsr0),
287 	_SYSDEV_ATTR(tsr1, 0600, show_tsr1, store_tsr1),
288 	_SYSDEV_ATTR(tsr2, 0600, show_tsr2, store_tsr2),
289 	_SYSDEV_ATTR(tsr3, 0600, show_tsr3, store_tsr3),
290 #endif /* CONFIG_DEBUG_KERNEL */
291 };
292 
293 
294 static void register_cpu_online(unsigned int cpu)
295 {
296 	struct cpu *c = &per_cpu(cpu_devices, cpu);
297 	struct sys_device *s = &c->sysdev;
298 	struct sysdev_attribute *attrs, *pmc_attrs;
299 	int i, nattrs;
300 
301 	if (!firmware_has_feature(FW_FEATURE_ISERIES) &&
302 			cpu_has_feature(CPU_FTR_SMT))
303 		sysdev_create_file(s, &attr_smt_snooze_delay);
304 
305 	/* PMC stuff */
306 	switch (cur_cpu_spec->pmc_type) {
307 	case PPC_PMC_IBM:
308 		attrs = ibm_common_attrs;
309 		nattrs = sizeof(ibm_common_attrs) / sizeof(struct sysdev_attribute);
310 		pmc_attrs = ibm_pmc_attrs;
311 		break;
312 	case PPC_PMC_PA6T:
313 		/* PA Semi starts counting at PMC0 */
314 		attrs = pa6t_attrs;
315 		nattrs = sizeof(pa6t_attrs) / sizeof(struct sysdev_attribute);
316 		pmc_attrs = NULL;
317 		break;
318 	default:
319 		attrs = NULL;
320 		nattrs = 0;
321 		pmc_attrs = NULL;
322 	}
323 
324 	for (i = 0; i < nattrs; i++)
325 		sysdev_create_file(s, &attrs[i]);
326 
327 	if (pmc_attrs)
328 		for (i = 0; i < cur_cpu_spec->num_pmcs; i++)
329 			sysdev_create_file(s, &pmc_attrs[i]);
330 
331 	if (cpu_has_feature(CPU_FTR_MMCRA))
332 		sysdev_create_file(s, &attr_mmcra);
333 
334 	if (cpu_has_feature(CPU_FTR_PURR))
335 		sysdev_create_file(s, &attr_purr);
336 
337 	if (cpu_has_feature(CPU_FTR_SPURR))
338 		sysdev_create_file(s, &attr_spurr);
339 
340 	if (cpu_has_feature(CPU_FTR_DSCR))
341 		sysdev_create_file(s, &attr_dscr);
342 }
343 
344 #ifdef CONFIG_HOTPLUG_CPU
345 static void unregister_cpu_online(unsigned int cpu)
346 {
347 	struct cpu *c = &per_cpu(cpu_devices, cpu);
348 	struct sys_device *s = &c->sysdev;
349 	struct sysdev_attribute *attrs, *pmc_attrs;
350 	int i, nattrs;
351 
352 	BUG_ON(!c->hotpluggable);
353 
354 	if (!firmware_has_feature(FW_FEATURE_ISERIES) &&
355 			cpu_has_feature(CPU_FTR_SMT))
356 		sysdev_remove_file(s, &attr_smt_snooze_delay);
357 
358 	/* PMC stuff */
359 	switch (cur_cpu_spec->pmc_type) {
360 	case PPC_PMC_IBM:
361 		attrs = ibm_common_attrs;
362 		nattrs = sizeof(ibm_common_attrs) / sizeof(struct sysdev_attribute);
363 		pmc_attrs = ibm_pmc_attrs;
364 		break;
365 	case PPC_PMC_PA6T:
366 		/* PA Semi starts counting at PMC0 */
367 		attrs = pa6t_attrs;
368 		nattrs = sizeof(pa6t_attrs) / sizeof(struct sysdev_attribute);
369 		pmc_attrs = NULL;
370 		break;
371 	default:
372 		attrs = NULL;
373 		nattrs = 0;
374 		pmc_attrs = NULL;
375 	}
376 
377 	for (i = 0; i < nattrs; i++)
378 		sysdev_remove_file(s, &attrs[i]);
379 
380 	if (pmc_attrs)
381 		for (i = 0; i < cur_cpu_spec->num_pmcs; i++)
382 			sysdev_remove_file(s, &pmc_attrs[i]);
383 
384 	if (cpu_has_feature(CPU_FTR_MMCRA))
385 		sysdev_remove_file(s, &attr_mmcra);
386 
387 	if (cpu_has_feature(CPU_FTR_PURR))
388 		sysdev_remove_file(s, &attr_purr);
389 
390 	if (cpu_has_feature(CPU_FTR_SPURR))
391 		sysdev_remove_file(s, &attr_spurr);
392 
393 	if (cpu_has_feature(CPU_FTR_DSCR))
394 		sysdev_remove_file(s, &attr_dscr);
395 }
396 #endif /* CONFIG_HOTPLUG_CPU */
397 
398 static int __cpuinit sysfs_cpu_notify(struct notifier_block *self,
399 				      unsigned long action, void *hcpu)
400 {
401 	unsigned int cpu = (unsigned int)(long)hcpu;
402 
403 	switch (action) {
404 	case CPU_ONLINE:
405 	case CPU_ONLINE_FROZEN:
406 		register_cpu_online(cpu);
407 		break;
408 #ifdef CONFIG_HOTPLUG_CPU
409 	case CPU_DEAD:
410 	case CPU_DEAD_FROZEN:
411 		unregister_cpu_online(cpu);
412 		break;
413 #endif
414 	}
415 	return NOTIFY_OK;
416 }
417 
418 static struct notifier_block __cpuinitdata sysfs_cpu_nb = {
419 	.notifier_call	= sysfs_cpu_notify,
420 };
421 
422 static DEFINE_MUTEX(cpu_mutex);
423 
424 int cpu_add_sysdev_attr(struct sysdev_attribute *attr)
425 {
426 	int cpu;
427 
428 	mutex_lock(&cpu_mutex);
429 
430 	for_each_possible_cpu(cpu) {
431 		sysdev_create_file(get_cpu_sysdev(cpu), attr);
432 	}
433 
434 	mutex_unlock(&cpu_mutex);
435 	return 0;
436 }
437 EXPORT_SYMBOL_GPL(cpu_add_sysdev_attr);
438 
439 int cpu_add_sysdev_attr_group(struct attribute_group *attrs)
440 {
441 	int cpu;
442 	struct sys_device *sysdev;
443 	int ret;
444 
445 	mutex_lock(&cpu_mutex);
446 
447 	for_each_possible_cpu(cpu) {
448 		sysdev = get_cpu_sysdev(cpu);
449 		ret = sysfs_create_group(&sysdev->kobj, attrs);
450 		WARN_ON(ret != 0);
451 	}
452 
453 	mutex_unlock(&cpu_mutex);
454 	return 0;
455 }
456 EXPORT_SYMBOL_GPL(cpu_add_sysdev_attr_group);
457 
458 
459 void cpu_remove_sysdev_attr(struct sysdev_attribute *attr)
460 {
461 	int cpu;
462 
463 	mutex_lock(&cpu_mutex);
464 
465 	for_each_possible_cpu(cpu) {
466 		sysdev_remove_file(get_cpu_sysdev(cpu), attr);
467 	}
468 
469 	mutex_unlock(&cpu_mutex);
470 }
471 EXPORT_SYMBOL_GPL(cpu_remove_sysdev_attr);
472 
473 void cpu_remove_sysdev_attr_group(struct attribute_group *attrs)
474 {
475 	int cpu;
476 	struct sys_device *sysdev;
477 
478 	mutex_lock(&cpu_mutex);
479 
480 	for_each_possible_cpu(cpu) {
481 		sysdev = get_cpu_sysdev(cpu);
482 		sysfs_remove_group(&sysdev->kobj, attrs);
483 	}
484 
485 	mutex_unlock(&cpu_mutex);
486 }
487 EXPORT_SYMBOL_GPL(cpu_remove_sysdev_attr_group);
488 
489 
490 /* NUMA stuff */
491 
492 #ifdef CONFIG_NUMA
493 static void register_nodes(void)
494 {
495 	int i;
496 
497 	for (i = 0; i < MAX_NUMNODES; i++)
498 		register_one_node(i);
499 }
500 
501 int sysfs_add_device_to_node(struct sys_device *dev, int nid)
502 {
503 	struct node *node = &node_devices[nid];
504 	return sysfs_create_link(&node->sysdev.kobj, &dev->kobj,
505 			kobject_name(&dev->kobj));
506 }
507 EXPORT_SYMBOL_GPL(sysfs_add_device_to_node);
508 
509 void sysfs_remove_device_from_node(struct sys_device *dev, int nid)
510 {
511 	struct node *node = &node_devices[nid];
512 	sysfs_remove_link(&node->sysdev.kobj, kobject_name(&dev->kobj));
513 }
514 EXPORT_SYMBOL_GPL(sysfs_remove_device_from_node);
515 
516 #else
517 static void register_nodes(void)
518 {
519 	return;
520 }
521 
522 #endif
523 
524 /* Only valid if CPU is present. */
525 static ssize_t show_physical_id(struct sys_device *dev, char *buf)
526 {
527 	struct cpu *cpu = container_of(dev, struct cpu, sysdev);
528 
529 	return sprintf(buf, "%d\n", get_hard_smp_processor_id(cpu->sysdev.id));
530 }
531 static SYSDEV_ATTR(physical_id, 0444, show_physical_id, NULL);
532 
533 static int __init topology_init(void)
534 {
535 	int cpu;
536 
537 	register_nodes();
538 	register_cpu_notifier(&sysfs_cpu_nb);
539 
540 	for_each_possible_cpu(cpu) {
541 		struct cpu *c = &per_cpu(cpu_devices, cpu);
542 
543 		/*
544 		 * For now, we just see if the system supports making
545 		 * the RTAS calls for CPU hotplug.  But, there may be a
546 		 * more comprehensive way to do this for an individual
547 		 * CPU.  For instance, the boot cpu might never be valid
548 		 * for hotplugging.
549 		 */
550 		if (ppc_md.cpu_die)
551 			c->hotpluggable = 1;
552 
553 		if (cpu_online(cpu) || c->hotpluggable) {
554 			register_cpu(c, cpu);
555 
556 			sysdev_create_file(&c->sysdev, &attr_physical_id);
557 		}
558 
559 		if (cpu_online(cpu))
560 			register_cpu_online(cpu);
561 	}
562 
563 	return 0;
564 }
565 subsys_initcall(topology_init);
566