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 */
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 */
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 */
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 */
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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