xref: /openbmc/linux/arch/arm/common/mcpm_entry.c (revision e318b36e)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * arch/arm/common/mcpm_entry.c -- entry point for multi-cluster PM
4  *
5  * Created by:  Nicolas Pitre, March 2012
6  * Copyright:   (C) 2012-2013  Linaro Limited
7  */
8 
9 #include <linux/export.h>
10 #include <linux/kernel.h>
11 #include <linux/init.h>
12 #include <linux/irqflags.h>
13 #include <linux/cpu_pm.h>
14 
15 #include <asm/mcpm.h>
16 #include <asm/cacheflush.h>
17 #include <asm/idmap.h>
18 #include <asm/cputype.h>
19 #include <asm/suspend.h>
20 
21 /*
22  * The public API for this code is documented in arch/arm/include/asm/mcpm.h.
23  * For a comprehensive description of the main algorithm used here, please
24  * see Documentation/arch/arm/cluster-pm-race-avoidance.rst.
25  */
26 
27 struct sync_struct mcpm_sync;
28 
29 /*
30  * __mcpm_cpu_going_down: Indicates that the cpu is being torn down.
31  *    This must be called at the point of committing to teardown of a CPU.
32  *    The CPU cache (SCTRL.C bit) is expected to still be active.
33  */
__mcpm_cpu_going_down(unsigned int cpu,unsigned int cluster)34 static void __mcpm_cpu_going_down(unsigned int cpu, unsigned int cluster)
35 {
36 	mcpm_sync.clusters[cluster].cpus[cpu].cpu = CPU_GOING_DOWN;
37 	sync_cache_w(&mcpm_sync.clusters[cluster].cpus[cpu].cpu);
38 }
39 
40 /*
41  * __mcpm_cpu_down: Indicates that cpu teardown is complete and that the
42  *    cluster can be torn down without disrupting this CPU.
43  *    To avoid deadlocks, this must be called before a CPU is powered down.
44  *    The CPU cache (SCTRL.C bit) is expected to be off.
45  *    However L2 cache might or might not be active.
46  */
__mcpm_cpu_down(unsigned int cpu,unsigned int cluster)47 static void __mcpm_cpu_down(unsigned int cpu, unsigned int cluster)
48 {
49 	dmb();
50 	mcpm_sync.clusters[cluster].cpus[cpu].cpu = CPU_DOWN;
51 	sync_cache_w(&mcpm_sync.clusters[cluster].cpus[cpu].cpu);
52 	sev();
53 }
54 
55 /*
56  * __mcpm_outbound_leave_critical: Leave the cluster teardown critical section.
57  * @state: the final state of the cluster:
58  *     CLUSTER_UP: no destructive teardown was done and the cluster has been
59  *         restored to the previous state (CPU cache still active); or
60  *     CLUSTER_DOWN: the cluster has been torn-down, ready for power-off
61  *         (CPU cache disabled, L2 cache either enabled or disabled).
62  */
__mcpm_outbound_leave_critical(unsigned int cluster,int state)63 static void __mcpm_outbound_leave_critical(unsigned int cluster, int state)
64 {
65 	dmb();
66 	mcpm_sync.clusters[cluster].cluster = state;
67 	sync_cache_w(&mcpm_sync.clusters[cluster].cluster);
68 	sev();
69 }
70 
71 /*
72  * __mcpm_outbound_enter_critical: Enter the cluster teardown critical section.
73  * This function should be called by the last man, after local CPU teardown
74  * is complete.  CPU cache expected to be active.
75  *
76  * Returns:
77  *     false: the critical section was not entered because an inbound CPU was
78  *         observed, or the cluster is already being set up;
79  *     true: the critical section was entered: it is now safe to tear down the
80  *         cluster.
81  */
__mcpm_outbound_enter_critical(unsigned int cpu,unsigned int cluster)82 static bool __mcpm_outbound_enter_critical(unsigned int cpu, unsigned int cluster)
83 {
84 	unsigned int i;
85 	struct mcpm_sync_struct *c = &mcpm_sync.clusters[cluster];
86 
87 	/* Warn inbound CPUs that the cluster is being torn down: */
88 	c->cluster = CLUSTER_GOING_DOWN;
89 	sync_cache_w(&c->cluster);
90 
91 	/* Back out if the inbound cluster is already in the critical region: */
92 	sync_cache_r(&c->inbound);
93 	if (c->inbound == INBOUND_COMING_UP)
94 		goto abort;
95 
96 	/*
97 	 * Wait for all CPUs to get out of the GOING_DOWN state, so that local
98 	 * teardown is complete on each CPU before tearing down the cluster.
99 	 *
100 	 * If any CPU has been woken up again from the DOWN state, then we
101 	 * shouldn't be taking the cluster down at all: abort in that case.
102 	 */
103 	sync_cache_r(&c->cpus);
104 	for (i = 0; i < MAX_CPUS_PER_CLUSTER; i++) {
105 		int cpustate;
106 
107 		if (i == cpu)
108 			continue;
109 
110 		while (1) {
111 			cpustate = c->cpus[i].cpu;
112 			if (cpustate != CPU_GOING_DOWN)
113 				break;
114 
115 			wfe();
116 			sync_cache_r(&c->cpus[i].cpu);
117 		}
118 
119 		switch (cpustate) {
120 		case CPU_DOWN:
121 			continue;
122 
123 		default:
124 			goto abort;
125 		}
126 	}
127 
128 	return true;
129 
130 abort:
131 	__mcpm_outbound_leave_critical(cluster, CLUSTER_UP);
132 	return false;
133 }
134 
__mcpm_cluster_state(unsigned int cluster)135 static int __mcpm_cluster_state(unsigned int cluster)
136 {
137 	sync_cache_r(&mcpm_sync.clusters[cluster].cluster);
138 	return mcpm_sync.clusters[cluster].cluster;
139 }
140 
141 extern unsigned long mcpm_entry_vectors[MAX_NR_CLUSTERS][MAX_CPUS_PER_CLUSTER];
142 
mcpm_set_entry_vector(unsigned cpu,unsigned cluster,void * ptr)143 void mcpm_set_entry_vector(unsigned cpu, unsigned cluster, void *ptr)
144 {
145 	unsigned long val = ptr ? __pa_symbol(ptr) : 0;
146 	mcpm_entry_vectors[cluster][cpu] = val;
147 	sync_cache_w(&mcpm_entry_vectors[cluster][cpu]);
148 }
149 
150 extern unsigned long mcpm_entry_early_pokes[MAX_NR_CLUSTERS][MAX_CPUS_PER_CLUSTER][2];
151 
mcpm_set_early_poke(unsigned cpu,unsigned cluster,unsigned long poke_phys_addr,unsigned long poke_val)152 void mcpm_set_early_poke(unsigned cpu, unsigned cluster,
153 			 unsigned long poke_phys_addr, unsigned long poke_val)
154 {
155 	unsigned long *poke = &mcpm_entry_early_pokes[cluster][cpu][0];
156 	poke[0] = poke_phys_addr;
157 	poke[1] = poke_val;
158 	__sync_cache_range_w(poke, 2 * sizeof(*poke));
159 }
160 
161 static const struct mcpm_platform_ops *platform_ops;
162 
mcpm_platform_register(const struct mcpm_platform_ops * ops)163 int __init mcpm_platform_register(const struct mcpm_platform_ops *ops)
164 {
165 	if (platform_ops)
166 		return -EBUSY;
167 	platform_ops = ops;
168 	return 0;
169 }
170 
mcpm_is_available(void)171 bool mcpm_is_available(void)
172 {
173 	return (platform_ops) ? true : false;
174 }
175 EXPORT_SYMBOL_GPL(mcpm_is_available);
176 
177 /*
178  * We can't use regular spinlocks. In the switcher case, it is possible
179  * for an outbound CPU to call power_down() after its inbound counterpart
180  * is already live using the same logical CPU number which trips lockdep
181  * debugging.
182  */
183 static arch_spinlock_t mcpm_lock = __ARCH_SPIN_LOCK_UNLOCKED;
184 
185 static int mcpm_cpu_use_count[MAX_NR_CLUSTERS][MAX_CPUS_PER_CLUSTER];
186 
mcpm_cluster_unused(unsigned int cluster)187 static inline bool mcpm_cluster_unused(unsigned int cluster)
188 {
189 	int i, cnt;
190 	for (i = 0, cnt = 0; i < MAX_CPUS_PER_CLUSTER; i++)
191 		cnt |= mcpm_cpu_use_count[cluster][i];
192 	return !cnt;
193 }
194 
mcpm_cpu_power_up(unsigned int cpu,unsigned int cluster)195 int mcpm_cpu_power_up(unsigned int cpu, unsigned int cluster)
196 {
197 	bool cpu_is_down, cluster_is_down;
198 	int ret = 0;
199 
200 	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
201 	if (!platform_ops)
202 		return -EUNATCH; /* try not to shadow power_up errors */
203 	might_sleep();
204 
205 	/*
206 	 * Since this is called with IRQs enabled, and no arch_spin_lock_irq
207 	 * variant exists, we need to disable IRQs manually here.
208 	 */
209 	local_irq_disable();
210 	arch_spin_lock(&mcpm_lock);
211 
212 	cpu_is_down = !mcpm_cpu_use_count[cluster][cpu];
213 	cluster_is_down = mcpm_cluster_unused(cluster);
214 
215 	mcpm_cpu_use_count[cluster][cpu]++;
216 	/*
217 	 * The only possible values are:
218 	 * 0 = CPU down
219 	 * 1 = CPU (still) up
220 	 * 2 = CPU requested to be up before it had a chance
221 	 *     to actually make itself down.
222 	 * Any other value is a bug.
223 	 */
224 	BUG_ON(mcpm_cpu_use_count[cluster][cpu] != 1 &&
225 	       mcpm_cpu_use_count[cluster][cpu] != 2);
226 
227 	if (cluster_is_down)
228 		ret = platform_ops->cluster_powerup(cluster);
229 	if (cpu_is_down && !ret)
230 		ret = platform_ops->cpu_powerup(cpu, cluster);
231 
232 	arch_spin_unlock(&mcpm_lock);
233 	local_irq_enable();
234 	return ret;
235 }
236 
237 typedef typeof(cpu_reset) phys_reset_t;
238 
mcpm_cpu_power_down(void)239 void mcpm_cpu_power_down(void)
240 {
241 	unsigned int mpidr, cpu, cluster;
242 	bool cpu_going_down, last_man;
243 	phys_reset_t phys_reset;
244 
245 	mpidr = read_cpuid_mpidr();
246 	cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
247 	cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
248 	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
249 	if (WARN_ON_ONCE(!platform_ops))
250 	       return;
251 	BUG_ON(!irqs_disabled());
252 
253 	setup_mm_for_reboot();
254 
255 	__mcpm_cpu_going_down(cpu, cluster);
256 	arch_spin_lock(&mcpm_lock);
257 	BUG_ON(__mcpm_cluster_state(cluster) != CLUSTER_UP);
258 
259 	mcpm_cpu_use_count[cluster][cpu]--;
260 	BUG_ON(mcpm_cpu_use_count[cluster][cpu] != 0 &&
261 	       mcpm_cpu_use_count[cluster][cpu] != 1);
262 	cpu_going_down = !mcpm_cpu_use_count[cluster][cpu];
263 	last_man = mcpm_cluster_unused(cluster);
264 
265 	if (last_man && __mcpm_outbound_enter_critical(cpu, cluster)) {
266 		platform_ops->cpu_powerdown_prepare(cpu, cluster);
267 		platform_ops->cluster_powerdown_prepare(cluster);
268 		arch_spin_unlock(&mcpm_lock);
269 		platform_ops->cluster_cache_disable();
270 		__mcpm_outbound_leave_critical(cluster, CLUSTER_DOWN);
271 	} else {
272 		if (cpu_going_down)
273 			platform_ops->cpu_powerdown_prepare(cpu, cluster);
274 		arch_spin_unlock(&mcpm_lock);
275 		/*
276 		 * If cpu_going_down is false here, that means a power_up
277 		 * request raced ahead of us.  Even if we do not want to
278 		 * shut this CPU down, the caller still expects execution
279 		 * to return through the system resume entry path, like
280 		 * when the WFI is aborted due to a new IRQ or the like..
281 		 * So let's continue with cache cleaning in all cases.
282 		 */
283 		platform_ops->cpu_cache_disable();
284 	}
285 
286 	__mcpm_cpu_down(cpu, cluster);
287 
288 	/* Now we are prepared for power-down, do it: */
289 	if (cpu_going_down)
290 		wfi();
291 
292 	/*
293 	 * It is possible for a power_up request to happen concurrently
294 	 * with a power_down request for the same CPU. In this case the
295 	 * CPU might not be able to actually enter a powered down state
296 	 * with the WFI instruction if the power_up request has removed
297 	 * the required reset condition.  We must perform a re-entry in
298 	 * the kernel as if the power_up method just had deasserted reset
299 	 * on the CPU.
300 	 */
301 	phys_reset = (phys_reset_t)(unsigned long)__pa_symbol(cpu_reset);
302 	phys_reset(__pa_symbol(mcpm_entry_point), false);
303 
304 	/* should never get here */
305 	BUG();
306 }
307 
mcpm_wait_for_cpu_powerdown(unsigned int cpu,unsigned int cluster)308 int mcpm_wait_for_cpu_powerdown(unsigned int cpu, unsigned int cluster)
309 {
310 	int ret;
311 
312 	if (WARN_ON_ONCE(!platform_ops || !platform_ops->wait_for_powerdown))
313 		return -EUNATCH;
314 
315 	ret = platform_ops->wait_for_powerdown(cpu, cluster);
316 	if (ret)
317 		pr_warn("%s: cpu %u, cluster %u failed to power down (%d)\n",
318 			__func__, cpu, cluster, ret);
319 
320 	return ret;
321 }
322 
mcpm_cpu_suspend(void)323 void mcpm_cpu_suspend(void)
324 {
325 	if (WARN_ON_ONCE(!platform_ops))
326 		return;
327 
328 	/* Some platforms might have to enable special resume modes, etc. */
329 	if (platform_ops->cpu_suspend_prepare) {
330 		unsigned int mpidr = read_cpuid_mpidr();
331 		unsigned int cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
332 		unsigned int cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
333 		arch_spin_lock(&mcpm_lock);
334 		platform_ops->cpu_suspend_prepare(cpu, cluster);
335 		arch_spin_unlock(&mcpm_lock);
336 	}
337 	mcpm_cpu_power_down();
338 }
339 
mcpm_cpu_powered_up(void)340 int mcpm_cpu_powered_up(void)
341 {
342 	unsigned int mpidr, cpu, cluster;
343 	bool cpu_was_down, first_man;
344 	unsigned long flags;
345 
346 	if (!platform_ops)
347 		return -EUNATCH;
348 
349 	mpidr = read_cpuid_mpidr();
350 	cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
351 	cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
352 	local_irq_save(flags);
353 	arch_spin_lock(&mcpm_lock);
354 
355 	cpu_was_down = !mcpm_cpu_use_count[cluster][cpu];
356 	first_man = mcpm_cluster_unused(cluster);
357 
358 	if (first_man && platform_ops->cluster_is_up)
359 		platform_ops->cluster_is_up(cluster);
360 	if (cpu_was_down)
361 		mcpm_cpu_use_count[cluster][cpu] = 1;
362 	if (platform_ops->cpu_is_up)
363 		platform_ops->cpu_is_up(cpu, cluster);
364 
365 	arch_spin_unlock(&mcpm_lock);
366 	local_irq_restore(flags);
367 
368 	return 0;
369 }
370 
371 #ifdef CONFIG_ARM_CPU_SUSPEND
372 
nocache_trampoline(unsigned long _arg)373 static int __init nocache_trampoline(unsigned long _arg)
374 {
375 	void (*cache_disable)(void) = (void *)_arg;
376 	unsigned int mpidr = read_cpuid_mpidr();
377 	unsigned int cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
378 	unsigned int cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
379 	phys_reset_t phys_reset;
380 
381 	mcpm_set_entry_vector(cpu, cluster, cpu_resume_no_hyp);
382 	setup_mm_for_reboot();
383 
384 	__mcpm_cpu_going_down(cpu, cluster);
385 	BUG_ON(!__mcpm_outbound_enter_critical(cpu, cluster));
386 	cache_disable();
387 	__mcpm_outbound_leave_critical(cluster, CLUSTER_DOWN);
388 	__mcpm_cpu_down(cpu, cluster);
389 
390 	phys_reset = (phys_reset_t)(unsigned long)__pa_symbol(cpu_reset);
391 	phys_reset(__pa_symbol(mcpm_entry_point), false);
392 	BUG();
393 }
394 
mcpm_loopback(void (* cache_disable)(void))395 int __init mcpm_loopback(void (*cache_disable)(void))
396 {
397 	int ret;
398 
399 	/*
400 	 * We're going to soft-restart the current CPU through the
401 	 * low-level MCPM code by leveraging the suspend/resume
402 	 * infrastructure. Let's play it safe by using cpu_pm_enter()
403 	 * in case the CPU init code path resets the VFP or similar.
404 	 */
405 	local_irq_disable();
406 	local_fiq_disable();
407 	ret = cpu_pm_enter();
408 	if (!ret) {
409 		ret = cpu_suspend((unsigned long)cache_disable, nocache_trampoline);
410 		cpu_pm_exit();
411 	}
412 	local_fiq_enable();
413 	local_irq_enable();
414 	if (ret)
415 		pr_err("%s returned %d\n", __func__, ret);
416 	return ret;
417 }
418 
419 #endif
420 
421 extern unsigned long mcpm_power_up_setup_phys;
422 
mcpm_sync_init(void (* power_up_setup)(unsigned int affinity_level))423 int __init mcpm_sync_init(
424 	void (*power_up_setup)(unsigned int affinity_level))
425 {
426 	unsigned int i, j, mpidr, this_cluster;
427 
428 	BUILD_BUG_ON(MCPM_SYNC_CLUSTER_SIZE * MAX_NR_CLUSTERS != sizeof mcpm_sync);
429 	BUG_ON((unsigned long)&mcpm_sync & (__CACHE_WRITEBACK_GRANULE - 1));
430 
431 	/*
432 	 * Set initial CPU and cluster states.
433 	 * Only one cluster is assumed to be active at this point.
434 	 */
435 	for (i = 0; i < MAX_NR_CLUSTERS; i++) {
436 		mcpm_sync.clusters[i].cluster = CLUSTER_DOWN;
437 		mcpm_sync.clusters[i].inbound = INBOUND_NOT_COMING_UP;
438 		for (j = 0; j < MAX_CPUS_PER_CLUSTER; j++)
439 			mcpm_sync.clusters[i].cpus[j].cpu = CPU_DOWN;
440 	}
441 	mpidr = read_cpuid_mpidr();
442 	this_cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
443 	for_each_online_cpu(i) {
444 		mcpm_cpu_use_count[this_cluster][i] = 1;
445 		mcpm_sync.clusters[this_cluster].cpus[i].cpu = CPU_UP;
446 	}
447 	mcpm_sync.clusters[this_cluster].cluster = CLUSTER_UP;
448 	sync_cache_w(&mcpm_sync);
449 
450 	if (power_up_setup) {
451 		mcpm_power_up_setup_phys = __pa_symbol(power_up_setup);
452 		sync_cache_w(&mcpm_power_up_setup_phys);
453 	}
454 
455 	return 0;
456 }
457