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/interrupt.h>
23 #include <linux/delay.h>
24 #include <linux/sched.h>	/* for idle_task_exit */
25 #include <linux/cpu.h>
26 #include <linux/of.h>
27 #include <asm/prom.h>
28 #include <asm/rtas.h>
29 #include <asm/firmware.h>
30 #include <asm/machdep.h>
31 #include <asm/vdso_datapage.h>
32 #include <asm/xics.h>
33 #include <asm/plpar_wrappers.h>
34 
35 #include "offline_states.h"
36 
37 /* This version can't take the spinlock, because it never returns */
38 static int rtas_stop_self_token = RTAS_UNKNOWN_SERVICE;
39 
40 static DEFINE_PER_CPU(enum cpu_state_vals, preferred_offline_state) =
41 							CPU_STATE_OFFLINE;
42 static DEFINE_PER_CPU(enum cpu_state_vals, current_state) = CPU_STATE_OFFLINE;
43 
44 static enum cpu_state_vals default_offline_state = CPU_STATE_OFFLINE;
45 
46 static int cede_offline_enabled __read_mostly = 1;
47 
48 /*
49  * Enable/disable cede_offline when available.
50  */
51 static int __init setup_cede_offline(char *str)
52 {
53 	if (!strcmp(str, "off"))
54 		cede_offline_enabled = 0;
55 	else if (!strcmp(str, "on"))
56 		cede_offline_enabled = 1;
57 	else
58 		return 0;
59 	return 1;
60 }
61 
62 __setup("cede_offline=", setup_cede_offline);
63 
64 enum cpu_state_vals get_cpu_current_state(int cpu)
65 {
66 	return per_cpu(current_state, cpu);
67 }
68 
69 void set_cpu_current_state(int cpu, enum cpu_state_vals state)
70 {
71 	per_cpu(current_state, cpu) = state;
72 }
73 
74 enum cpu_state_vals get_preferred_offline_state(int cpu)
75 {
76 	return per_cpu(preferred_offline_state, cpu);
77 }
78 
79 void set_preferred_offline_state(int cpu, enum cpu_state_vals state)
80 {
81 	per_cpu(preferred_offline_state, cpu) = state;
82 }
83 
84 void set_default_offline_state(int cpu)
85 {
86 	per_cpu(preferred_offline_state, cpu) = default_offline_state;
87 }
88 
89 static void rtas_stop_self(void)
90 {
91 	static struct rtas_args args = {
92 		.nargs = 0,
93 		.nret = cpu_to_be32(1),
94 		.rets = &args.args[0],
95 	};
96 
97 	args.token = cpu_to_be32(rtas_stop_self_token);
98 
99 	local_irq_disable();
100 
101 	BUG_ON(rtas_stop_self_token == RTAS_UNKNOWN_SERVICE);
102 
103 	printk("cpu %u (hwid %u) Ready to die...\n",
104 	       smp_processor_id(), hard_smp_processor_id());
105 	enter_rtas(__pa(&args));
106 
107 	panic("Alas, I survived.\n");
108 }
109 
110 static void pseries_mach_cpu_die(void)
111 {
112 	unsigned int cpu = smp_processor_id();
113 	unsigned int hwcpu = hard_smp_processor_id();
114 	u8 cede_latency_hint = 0;
115 
116 	local_irq_disable();
117 	idle_task_exit();
118 	xics_teardown_cpu();
119 
120 	if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
121 		set_cpu_current_state(cpu, CPU_STATE_INACTIVE);
122 		if (ppc_md.suspend_disable_cpu)
123 			ppc_md.suspend_disable_cpu();
124 
125 		cede_latency_hint = 2;
126 
127 		get_lppaca()->idle = 1;
128 		if (!lppaca_shared_proc(get_lppaca()))
129 			get_lppaca()->donate_dedicated_cpu = 1;
130 
131 		while (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
132 			while (!prep_irq_for_idle()) {
133 				local_irq_enable();
134 				local_irq_disable();
135 			}
136 
137 			extended_cede_processor(cede_latency_hint);
138 		}
139 
140 		local_irq_disable();
141 
142 		if (!lppaca_shared_proc(get_lppaca()))
143 			get_lppaca()->donate_dedicated_cpu = 0;
144 		get_lppaca()->idle = 0;
145 
146 		if (get_preferred_offline_state(cpu) == CPU_STATE_ONLINE) {
147 			unregister_slb_shadow(hwcpu);
148 
149 			hard_irq_disable();
150 			/*
151 			 * Call to start_secondary_resume() will not return.
152 			 * Kernel stack will be reset and start_secondary()
153 			 * will be called to continue the online operation.
154 			 */
155 			start_secondary_resume();
156 		}
157 	}
158 
159 	/* Requested state is CPU_STATE_OFFLINE at this point */
160 	WARN_ON(get_preferred_offline_state(cpu) != CPU_STATE_OFFLINE);
161 
162 	set_cpu_current_state(cpu, CPU_STATE_OFFLINE);
163 	unregister_slb_shadow(hwcpu);
164 	rtas_stop_self();
165 
166 	/* Should never get here... */
167 	BUG();
168 	for(;;);
169 }
170 
171 static int pseries_cpu_disable(void)
172 {
173 	int cpu = smp_processor_id();
174 
175 	set_cpu_online(cpu, false);
176 	vdso_data->processorCount--;
177 
178 	/*fix boot_cpuid here*/
179 	if (cpu == boot_cpuid)
180 		boot_cpuid = cpumask_any(cpu_online_mask);
181 
182 	/* FIXME: abstract this to not be platform specific later on */
183 	xics_migrate_irqs_away();
184 	return 0;
185 }
186 
187 /*
188  * pseries_cpu_die: Wait for the cpu to die.
189  * @cpu: logical processor id of the CPU whose death we're awaiting.
190  *
191  * This function is called from the context of the thread which is performing
192  * the cpu-offline. Here we wait for long enough to allow the cpu in question
193  * to self-destroy so that the cpu-offline thread can send the CPU_DEAD
194  * notifications.
195  *
196  * OTOH, pseries_mach_cpu_die() is called by the @cpu when it wants to
197  * self-destruct.
198  */
199 static void pseries_cpu_die(unsigned int cpu)
200 {
201 	int tries;
202 	int cpu_status = 1;
203 	unsigned int pcpu = get_hard_smp_processor_id(cpu);
204 
205 	if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
206 		cpu_status = 1;
207 		for (tries = 0; tries < 5000; tries++) {
208 			if (get_cpu_current_state(cpu) == CPU_STATE_INACTIVE) {
209 				cpu_status = 0;
210 				break;
211 			}
212 			msleep(1);
213 		}
214 	} else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {
215 
216 		for (tries = 0; tries < 25; tries++) {
217 			cpu_status = smp_query_cpu_stopped(pcpu);
218 			if (cpu_status == QCSS_STOPPED ||
219 			    cpu_status == QCSS_HARDWARE_ERROR)
220 				break;
221 			cpu_relax();
222 		}
223 	}
224 
225 	if (cpu_status != 0) {
226 		printk("Querying DEAD? cpu %i (%i) shows %i\n",
227 		       cpu, pcpu, cpu_status);
228 	}
229 
230 	/* Isolation and deallocation are definitely done by
231 	 * drslot_chrp_cpu.  If they were not they would be
232 	 * done here.  Change isolate state to Isolate and
233 	 * change allocation-state to Unusable.
234 	 */
235 	paca[cpu].cpu_start = 0;
236 }
237 
238 /*
239  * Update cpu_present_mask and paca(s) for a new cpu node.  The wrinkle
240  * here is that a cpu device node may represent up to two logical cpus
241  * in the SMT case.  We must honor the assumption in other code that
242  * the logical ids for sibling SMT threads x and y are adjacent, such
243  * that x^1 == y and y^1 == x.
244  */
245 static int pseries_add_processor(struct device_node *np)
246 {
247 	unsigned int cpu;
248 	cpumask_var_t candidate_mask, tmp;
249 	int err = -ENOSPC, len, nthreads, i;
250 	const __be32 *intserv;
251 
252 	intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
253 	if (!intserv)
254 		return 0;
255 
256 	zalloc_cpumask_var(&candidate_mask, GFP_KERNEL);
257 	zalloc_cpumask_var(&tmp, GFP_KERNEL);
258 
259 	nthreads = len / sizeof(u32);
260 	for (i = 0; i < nthreads; i++)
261 		cpumask_set_cpu(i, tmp);
262 
263 	cpu_maps_update_begin();
264 
265 	BUG_ON(!cpumask_subset(cpu_present_mask, cpu_possible_mask));
266 
267 	/* Get a bitmap of unoccupied slots. */
268 	cpumask_xor(candidate_mask, cpu_possible_mask, cpu_present_mask);
269 	if (cpumask_empty(candidate_mask)) {
270 		/* If we get here, it most likely means that NR_CPUS is
271 		 * less than the partition's max processors setting.
272 		 */
273 		printk(KERN_ERR "Cannot add cpu %s; this system configuration"
274 		       " supports %d logical cpus.\n", np->full_name,
275 		       cpumask_weight(cpu_possible_mask));
276 		goto out_unlock;
277 	}
278 
279 	while (!cpumask_empty(tmp))
280 		if (cpumask_subset(tmp, candidate_mask))
281 			/* Found a range where we can insert the new cpu(s) */
282 			break;
283 		else
284 			cpumask_shift_left(tmp, tmp, nthreads);
285 
286 	if (cpumask_empty(tmp)) {
287 		printk(KERN_ERR "Unable to find space in cpu_present_mask for"
288 		       " processor %s with %d thread(s)\n", np->name,
289 		       nthreads);
290 		goto out_unlock;
291 	}
292 
293 	for_each_cpu(cpu, tmp) {
294 		BUG_ON(cpu_present(cpu));
295 		set_cpu_present(cpu, true);
296 		set_hard_smp_processor_id(cpu, be32_to_cpu(*intserv++));
297 	}
298 	err = 0;
299 out_unlock:
300 	cpu_maps_update_done();
301 	free_cpumask_var(candidate_mask);
302 	free_cpumask_var(tmp);
303 	return err;
304 }
305 
306 /*
307  * Update the present map for a cpu node which is going away, and set
308  * the hard id in the paca(s) to -1 to be consistent with boot time
309  * convention for non-present cpus.
310  */
311 static void pseries_remove_processor(struct device_node *np)
312 {
313 	unsigned int cpu;
314 	int len, nthreads, i;
315 	const __be32 *intserv;
316 	u32 thread;
317 
318 	intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
319 	if (!intserv)
320 		return;
321 
322 	nthreads = len / sizeof(u32);
323 
324 	cpu_maps_update_begin();
325 	for (i = 0; i < nthreads; i++) {
326 		thread = be32_to_cpu(intserv[i]);
327 		for_each_present_cpu(cpu) {
328 			if (get_hard_smp_processor_id(cpu) != thread)
329 				continue;
330 			BUG_ON(cpu_online(cpu));
331 			set_cpu_present(cpu, false);
332 			set_hard_smp_processor_id(cpu, -1);
333 			break;
334 		}
335 		if (cpu >= nr_cpu_ids)
336 			printk(KERN_WARNING "Could not find cpu to remove "
337 			       "with physical id 0x%x\n", thread);
338 	}
339 	cpu_maps_update_done();
340 }
341 
342 static int pseries_smp_notifier(struct notifier_block *nb,
343 				unsigned long action, void *data)
344 {
345 	struct of_reconfig_data *rd = data;
346 	int err = 0;
347 
348 	switch (action) {
349 	case OF_RECONFIG_ATTACH_NODE:
350 		err = pseries_add_processor(rd->dn);
351 		break;
352 	case OF_RECONFIG_DETACH_NODE:
353 		pseries_remove_processor(rd->dn);
354 		break;
355 	}
356 	return notifier_from_errno(err);
357 }
358 
359 static struct notifier_block pseries_smp_nb = {
360 	.notifier_call = pseries_smp_notifier,
361 };
362 
363 #define MAX_CEDE_LATENCY_LEVELS		4
364 #define	CEDE_LATENCY_PARAM_LENGTH	10
365 #define CEDE_LATENCY_PARAM_MAX_LENGTH	\
366 	(MAX_CEDE_LATENCY_LEVELS * CEDE_LATENCY_PARAM_LENGTH * sizeof(char))
367 #define CEDE_LATENCY_TOKEN		45
368 
369 static char cede_parameters[CEDE_LATENCY_PARAM_MAX_LENGTH];
370 
371 static int parse_cede_parameters(void)
372 {
373 	memset(cede_parameters, 0, CEDE_LATENCY_PARAM_MAX_LENGTH);
374 	return rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
375 			 NULL,
376 			 CEDE_LATENCY_TOKEN,
377 			 __pa(cede_parameters),
378 			 CEDE_LATENCY_PARAM_MAX_LENGTH);
379 }
380 
381 static int __init pseries_cpu_hotplug_init(void)
382 {
383 	struct device_node *np;
384 	const char *typep;
385 	int cpu;
386 	int qcss_tok;
387 
388 	for_each_node_by_name(np, "interrupt-controller") {
389 		typep = of_get_property(np, "compatible", NULL);
390 		if (strstr(typep, "open-pic")) {
391 			of_node_put(np);
392 
393 			printk(KERN_INFO "CPU Hotplug not supported on "
394 				"systems using MPIC\n");
395 			return 0;
396 		}
397 	}
398 
399 	rtas_stop_self_token = rtas_token("stop-self");
400 	qcss_tok = rtas_token("query-cpu-stopped-state");
401 
402 	if (rtas_stop_self_token == RTAS_UNKNOWN_SERVICE ||
403 			qcss_tok == RTAS_UNKNOWN_SERVICE) {
404 		printk(KERN_INFO "CPU Hotplug not supported by firmware "
405 				"- disabling.\n");
406 		return 0;
407 	}
408 
409 	ppc_md.cpu_die = pseries_mach_cpu_die;
410 	smp_ops->cpu_disable = pseries_cpu_disable;
411 	smp_ops->cpu_die = pseries_cpu_die;
412 
413 	/* Processors can be added/removed only on LPAR */
414 	if (firmware_has_feature(FW_FEATURE_LPAR)) {
415 		of_reconfig_notifier_register(&pseries_smp_nb);
416 		cpu_maps_update_begin();
417 		if (cede_offline_enabled && parse_cede_parameters() == 0) {
418 			default_offline_state = CPU_STATE_INACTIVE;
419 			for_each_online_cpu(cpu)
420 				set_default_offline_state(cpu);
421 		}
422 		cpu_maps_update_done();
423 	}
424 
425 	return 0;
426 }
427 machine_arch_initcall(pseries, pseries_cpu_hotplug_init);
428