1 /*
2  * pseries CPU Hotplug infrastructure.
3  *
4  * Split out from arch/powerpc/platforms/pseries/setup.c
5  *  arch/powerpc/kernel/rtas.c, and arch/powerpc/platforms/pseries/smp.c
6  *
7  * Peter Bergner, IBM	March 2001.
8  * Copyright (C) 2001 IBM.
9  * Dave Engebretsen, Peter Bergner, and
10  * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
11  * Plus various changes from other IBM teams...
12  *
13  * Copyright (C) 2006 Michael Ellerman, IBM Corporation
14  *
15  *      This program is free software; you can redistribute it and/or
16  *      modify it under the terms of the GNU General Public License
17  *      as published by the Free Software Foundation; either version
18  *      2 of the License, or (at your option) any later version.
19  */
20 
21 #include <linux/kernel.h>
22 #include <linux/delay.h>
23 #include <linux/cpu.h>
24 #include <asm/system.h>
25 #include <asm/prom.h>
26 #include <asm/rtas.h>
27 #include <asm/firmware.h>
28 #include <asm/machdep.h>
29 #include <asm/vdso_datapage.h>
30 #include <asm/pSeries_reconfig.h>
31 #include "xics.h"
32 #include "plpar_wrappers.h"
33 #include "offline_states.h"
34 
35 /* This version can't take the spinlock, because it never returns */
36 static struct rtas_args rtas_stop_self_args = {
37 	.token = RTAS_UNKNOWN_SERVICE,
38 	.nargs = 0,
39 	.nret = 1,
40 	.rets = &rtas_stop_self_args.args[0],
41 };
42 
43 static DEFINE_PER_CPU(enum cpu_state_vals, preferred_offline_state) =
44 							CPU_STATE_OFFLINE;
45 static DEFINE_PER_CPU(enum cpu_state_vals, current_state) = CPU_STATE_OFFLINE;
46 
47 static enum cpu_state_vals default_offline_state = CPU_STATE_OFFLINE;
48 
49 static int cede_offline_enabled __read_mostly = 1;
50 
51 /*
52  * Enable/disable cede_offline when available.
53  */
54 static int __init setup_cede_offline(char *str)
55 {
56 	if (!strcmp(str, "off"))
57 		cede_offline_enabled = 0;
58 	else if (!strcmp(str, "on"))
59 		cede_offline_enabled = 1;
60 	else
61 		return 0;
62 	return 1;
63 }
64 
65 __setup("cede_offline=", setup_cede_offline);
66 
67 enum cpu_state_vals get_cpu_current_state(int cpu)
68 {
69 	return per_cpu(current_state, cpu);
70 }
71 
72 void set_cpu_current_state(int cpu, enum cpu_state_vals state)
73 {
74 	per_cpu(current_state, cpu) = state;
75 }
76 
77 enum cpu_state_vals get_preferred_offline_state(int cpu)
78 {
79 	return per_cpu(preferred_offline_state, cpu);
80 }
81 
82 void set_preferred_offline_state(int cpu, enum cpu_state_vals state)
83 {
84 	per_cpu(preferred_offline_state, cpu) = state;
85 }
86 
87 void set_default_offline_state(int cpu)
88 {
89 	per_cpu(preferred_offline_state, cpu) = default_offline_state;
90 }
91 
92 static void rtas_stop_self(void)
93 {
94 	struct rtas_args *args = &rtas_stop_self_args;
95 
96 	local_irq_disable();
97 
98 	BUG_ON(args->token == RTAS_UNKNOWN_SERVICE);
99 
100 	printk("cpu %u (hwid %u) Ready to die...\n",
101 	       smp_processor_id(), hard_smp_processor_id());
102 	enter_rtas(__pa(args));
103 
104 	panic("Alas, I survived.\n");
105 }
106 
107 static void pseries_mach_cpu_die(void)
108 {
109 	unsigned int cpu = smp_processor_id();
110 	unsigned int hwcpu = hard_smp_processor_id();
111 	u8 cede_latency_hint = 0;
112 
113 	local_irq_disable();
114 	idle_task_exit();
115 	xics_teardown_cpu();
116 
117 	if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
118 		set_cpu_current_state(cpu, CPU_STATE_INACTIVE);
119 		cede_latency_hint = 2;
120 
121 		get_lppaca()->idle = 1;
122 		if (!get_lppaca()->shared_proc)
123 			get_lppaca()->donate_dedicated_cpu = 1;
124 
125 		printk(KERN_INFO
126 			"cpu %u (hwid %u) ceding for offline with hint %d\n",
127 			cpu, hwcpu, cede_latency_hint);
128 		while (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
129 			extended_cede_processor(cede_latency_hint);
130 			printk(KERN_INFO "cpu %u (hwid %u) returned from cede.\n",
131 				cpu, hwcpu);
132 			printk(KERN_INFO
133 			"Decrementer value = %x Timebase value = %llx\n",
134 			get_dec(), get_tb());
135 		}
136 
137 		printk(KERN_INFO "cpu %u (hwid %u) got prodded to go online\n",
138 			cpu, hwcpu);
139 
140 		if (!get_lppaca()->shared_proc)
141 			get_lppaca()->donate_dedicated_cpu = 0;
142 		get_lppaca()->idle = 0;
143 	}
144 
145 	if (get_preferred_offline_state(cpu) == CPU_STATE_ONLINE) {
146 		unregister_slb_shadow(hwcpu, __pa(get_slb_shadow()));
147 
148 		/*
149 		 * NOTE: Calling start_secondary() here for now to
150 		 * start new context.
151 		 * However, need to do it cleanly by resetting the
152 		 * stack pointer.
153 		 */
154 		start_secondary();
155 
156 	} else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {
157 
158 		set_cpu_current_state(cpu, CPU_STATE_OFFLINE);
159 		unregister_slb_shadow(hard_smp_processor_id(),
160 					__pa(get_slb_shadow()));
161 		rtas_stop_self();
162 	}
163 
164 	/* Should never get here... */
165 	BUG();
166 	for(;;);
167 }
168 
169 static int qcss_tok;	/* query-cpu-stopped-state token */
170 
171 /* Get state of physical CPU.
172  * Return codes:
173  *	0	- The processor is in the RTAS stopped state
174  *	1	- stop-self is in progress
175  *	2	- The processor is not in the RTAS stopped state
176  *	-1	- Hardware Error
177  *	-2	- Hardware Busy, Try again later.
178  */
179 static int query_cpu_stopped(unsigned int pcpu)
180 {
181 	int cpu_status, status;
182 
183 	status = rtas_call(qcss_tok, 1, 2, &cpu_status, pcpu);
184 	if (status != 0) {
185 		printk(KERN_ERR
186 		       "RTAS query-cpu-stopped-state failed: %i\n", status);
187 		return status;
188 	}
189 
190 	return cpu_status;
191 }
192 
193 static int pseries_cpu_disable(void)
194 {
195 	int cpu = smp_processor_id();
196 
197 	set_cpu_online(cpu, false);
198 	vdso_data->processorCount--;
199 
200 	/*fix boot_cpuid here*/
201 	if (cpu == boot_cpuid)
202 		boot_cpuid = any_online_cpu(cpu_online_map);
203 
204 	/* FIXME: abstract this to not be platform specific later on */
205 	xics_migrate_irqs_away();
206 	return 0;
207 }
208 
209 /*
210  * pseries_cpu_die: Wait for the cpu to die.
211  * @cpu: logical processor id of the CPU whose death we're awaiting.
212  *
213  * This function is called from the context of the thread which is performing
214  * the cpu-offline. Here we wait for long enough to allow the cpu in question
215  * to self-destroy so that the cpu-offline thread can send the CPU_DEAD
216  * notifications.
217  *
218  * OTOH, pseries_mach_cpu_die() is called by the @cpu when it wants to
219  * self-destruct.
220  */
221 static void pseries_cpu_die(unsigned int cpu)
222 {
223 	int tries;
224 	int cpu_status = 1;
225 	unsigned int pcpu = get_hard_smp_processor_id(cpu);
226 
227 	if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
228 		cpu_status = 1;
229 		for (tries = 0; tries < 1000; tries++) {
230 			if (get_cpu_current_state(cpu) == CPU_STATE_INACTIVE) {
231 				cpu_status = 0;
232 				break;
233 			}
234 			cpu_relax();
235 		}
236 	} else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {
237 
238 		for (tries = 0; tries < 25; tries++) {
239 			cpu_status = query_cpu_stopped(pcpu);
240 			if (cpu_status == 0 || cpu_status == -1)
241 				break;
242 			cpu_relax();
243 		}
244 	}
245 
246 	if (cpu_status != 0) {
247 		printk("Querying DEAD? cpu %i (%i) shows %i\n",
248 		       cpu, pcpu, cpu_status);
249 	}
250 
251 	/* Isolation and deallocation are definatly done by
252 	 * drslot_chrp_cpu.  If they were not they would be
253 	 * done here.  Change isolate state to Isolate and
254 	 * change allocation-state to Unusable.
255 	 */
256 	paca[cpu].cpu_start = 0;
257 }
258 
259 /*
260  * Update cpu_present_map and paca(s) for a new cpu node.  The wrinkle
261  * here is that a cpu device node may represent up to two logical cpus
262  * in the SMT case.  We must honor the assumption in other code that
263  * the logical ids for sibling SMT threads x and y are adjacent, such
264  * that x^1 == y and y^1 == x.
265  */
266 static int pseries_add_processor(struct device_node *np)
267 {
268 	unsigned int cpu;
269 	cpumask_t candidate_map, tmp = CPU_MASK_NONE;
270 	int err = -ENOSPC, len, nthreads, i;
271 	const u32 *intserv;
272 
273 	intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
274 	if (!intserv)
275 		return 0;
276 
277 	nthreads = len / sizeof(u32);
278 	for (i = 0; i < nthreads; i++)
279 		cpu_set(i, tmp);
280 
281 	cpu_maps_update_begin();
282 
283 	BUG_ON(!cpus_subset(cpu_present_map, cpu_possible_map));
284 
285 	/* Get a bitmap of unoccupied slots. */
286 	cpus_xor(candidate_map, cpu_possible_map, cpu_present_map);
287 	if (cpus_empty(candidate_map)) {
288 		/* If we get here, it most likely means that NR_CPUS is
289 		 * less than the partition's max processors setting.
290 		 */
291 		printk(KERN_ERR "Cannot add cpu %s; this system configuration"
292 		       " supports %d logical cpus.\n", np->full_name,
293 		       cpus_weight(cpu_possible_map));
294 		goto out_unlock;
295 	}
296 
297 	while (!cpus_empty(tmp))
298 		if (cpus_subset(tmp, candidate_map))
299 			/* Found a range where we can insert the new cpu(s) */
300 			break;
301 		else
302 			cpus_shift_left(tmp, tmp, nthreads);
303 
304 	if (cpus_empty(tmp)) {
305 		printk(KERN_ERR "Unable to find space in cpu_present_map for"
306 		       " processor %s with %d thread(s)\n", np->name,
307 		       nthreads);
308 		goto out_unlock;
309 	}
310 
311 	for_each_cpu_mask(cpu, tmp) {
312 		BUG_ON(cpu_isset(cpu, cpu_present_map));
313 		set_cpu_present(cpu, true);
314 		set_hard_smp_processor_id(cpu, *intserv++);
315 	}
316 	err = 0;
317 out_unlock:
318 	cpu_maps_update_done();
319 	return err;
320 }
321 
322 /*
323  * Update the present map for a cpu node which is going away, and set
324  * the hard id in the paca(s) to -1 to be consistent with boot time
325  * convention for non-present cpus.
326  */
327 static void pseries_remove_processor(struct device_node *np)
328 {
329 	unsigned int cpu;
330 	int len, nthreads, i;
331 	const u32 *intserv;
332 
333 	intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
334 	if (!intserv)
335 		return;
336 
337 	nthreads = len / sizeof(u32);
338 
339 	cpu_maps_update_begin();
340 	for (i = 0; i < nthreads; i++) {
341 		for_each_present_cpu(cpu) {
342 			if (get_hard_smp_processor_id(cpu) != intserv[i])
343 				continue;
344 			BUG_ON(cpu_online(cpu));
345 			set_cpu_present(cpu, false);
346 			set_hard_smp_processor_id(cpu, -1);
347 			break;
348 		}
349 		if (cpu == NR_CPUS)
350 			printk(KERN_WARNING "Could not find cpu to remove "
351 			       "with physical id 0x%x\n", intserv[i]);
352 	}
353 	cpu_maps_update_done();
354 }
355 
356 static int pseries_smp_notifier(struct notifier_block *nb,
357 				unsigned long action, void *node)
358 {
359 	int err = NOTIFY_OK;
360 
361 	switch (action) {
362 	case PSERIES_RECONFIG_ADD:
363 		if (pseries_add_processor(node))
364 			err = NOTIFY_BAD;
365 		break;
366 	case PSERIES_RECONFIG_REMOVE:
367 		pseries_remove_processor(node);
368 		break;
369 	default:
370 		err = NOTIFY_DONE;
371 		break;
372 	}
373 	return err;
374 }
375 
376 static struct notifier_block pseries_smp_nb = {
377 	.notifier_call = pseries_smp_notifier,
378 };
379 
380 #define MAX_CEDE_LATENCY_LEVELS		4
381 #define	CEDE_LATENCY_PARAM_LENGTH	10
382 #define CEDE_LATENCY_PARAM_MAX_LENGTH	\
383 	(MAX_CEDE_LATENCY_LEVELS * CEDE_LATENCY_PARAM_LENGTH * sizeof(char))
384 #define CEDE_LATENCY_TOKEN		45
385 
386 static char cede_parameters[CEDE_LATENCY_PARAM_MAX_LENGTH];
387 
388 static int parse_cede_parameters(void)
389 {
390 	int call_status;
391 
392 	memset(cede_parameters, 0, CEDE_LATENCY_PARAM_MAX_LENGTH);
393 	call_status = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
394 				NULL,
395 				CEDE_LATENCY_TOKEN,
396 				__pa(cede_parameters),
397 				CEDE_LATENCY_PARAM_MAX_LENGTH);
398 
399 	if (call_status != 0)
400 		printk(KERN_INFO "CEDE_LATENCY: \
401 			%s %s Error calling get-system-parameter(0x%x)\n",
402 			__FILE__, __func__, call_status);
403 	else
404 		printk(KERN_INFO "CEDE_LATENCY: \
405 			get-system-parameter successful.\n");
406 
407 	return call_status;
408 }
409 
410 static int __init pseries_cpu_hotplug_init(void)
411 {
412 	struct device_node *np;
413 	const char *typep;
414 	int cpu;
415 
416 	for_each_node_by_name(np, "interrupt-controller") {
417 		typep = of_get_property(np, "compatible", NULL);
418 		if (strstr(typep, "open-pic")) {
419 			of_node_put(np);
420 
421 			printk(KERN_INFO "CPU Hotplug not supported on "
422 				"systems using MPIC\n");
423 			return 0;
424 		}
425 	}
426 
427 	rtas_stop_self_args.token = rtas_token("stop-self");
428 	qcss_tok = rtas_token("query-cpu-stopped-state");
429 
430 	if (rtas_stop_self_args.token == RTAS_UNKNOWN_SERVICE ||
431 			qcss_tok == RTAS_UNKNOWN_SERVICE) {
432 		printk(KERN_INFO "CPU Hotplug not supported by firmware "
433 				"- disabling.\n");
434 		return 0;
435 	}
436 
437 	ppc_md.cpu_die = pseries_mach_cpu_die;
438 	smp_ops->cpu_disable = pseries_cpu_disable;
439 	smp_ops->cpu_die = pseries_cpu_die;
440 
441 	/* Processors can be added/removed only on LPAR */
442 	if (firmware_has_feature(FW_FEATURE_LPAR)) {
443 		pSeries_reconfig_notifier_register(&pseries_smp_nb);
444 		cpu_maps_update_begin();
445 		if (cede_offline_enabled && parse_cede_parameters() == 0) {
446 			default_offline_state = CPU_STATE_INACTIVE;
447 			for_each_online_cpu(cpu)
448 				set_default_offline_state(cpu);
449 		}
450 		cpu_maps_update_done();
451 	}
452 
453 	return 0;
454 }
455 arch_initcall(pseries_cpu_hotplug_init);
456