root/arch/arm/common/mcpm_entry.c

DEFINITIONS

1. __mcpm_cpu_going_down
2. __mcpm_cpu_down
3. __mcpm_outbound_leave_critical
4. __mcpm_outbound_enter_critical
5. __mcpm_cluster_state
6. mcpm_set_entry_vector
7. mcpm_set_early_poke
8. mcpm_platform_register
9. mcpm_is_available
10. mcpm_cluster_unused
11. mcpm_cpu_power_up
12. mcpm_cpu_power_down
13. mcpm_wait_for_cpu_powerdown
14. mcpm_cpu_suspend
15. mcpm_cpu_powered_up
16. nocache_trampoline
17. mcpm_loopback
18. mcpm_sync_init

   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/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 }