arch/arm/common/mcpm_entry.c

   1 /*
   2  * arch/arm/common/mcpm_entry.c -- entry point for multi-cluster PM
   3  *
   4  * Created by:  Nicolas Pitre, March 2012
   5  * Copyright:   (C) 2012-2013  Linaro Limited
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/kernel.h>
  13 #include <linux/init.h>
  14 #include <linux/irqflags.h>
  15
  16 #include <asm/mcpm.h>
  17 #include <asm/cacheflush.h>
  18 #include <asm/idmap.h>
  19 #include <asm/cputype.h>
  20
  21 extern unsigned long mcpm_entry_vectors[MAX_NR_CLUSTERS][MAX_CPUS_PER_CLUSTER];
  22
  23 void mcpm_set_entry_vector(unsigned cpu, unsigned cluster, void *ptr)
  24 {
  25         unsigned long val = ptr ? virt_to_phys(ptr) : 0;
  26         mcpm_entry_vectors[cluster][cpu] = val;
  27         sync_cache_w(&mcpm_entry_vectors[cluster][cpu]);
  28 }
  29
  30 static const struct mcpm_platform_ops *platform_ops;
  31
  32 int __init mcpm_platform_register(const struct mcpm_platform_ops *ops)
  33 {
  34         if (platform_ops)
  35                 return -EBUSY;
  36         platform_ops = ops;
  37         return 0;
  38 }
  39
  40 int mcpm_cpu_power_up(unsigned int cpu, unsigned int cluster)
  41 {
  42         if (!platform_ops)
  43                 return -EUNATCH; /* try not to shadow power_up errors */
  44         might_sleep();
  45         return platform_ops->power_up(cpu, cluster);
  46 }
  47
  48 typedef void (*phys_reset_t)(unsigned long);
  49
  50 void mcpm_cpu_power_down(void)
  51 {
  52         phys_reset_t phys_reset;
  53
  54         if (WARN_ON_ONCE(!platform_ops || !platform_ops->power_down))
  55                 return;
  56         BUG_ON(!irqs_disabled());
  57
  58         /*
  59          * Do this before calling into the power_down method,
  60          * as it might not always be safe to do afterwards.
  61          */
  62         setup_mm_for_reboot();
  63
  64         platform_ops->power_down();
  65
  66         /*
  67          * It is possible for a power_up request to happen concurrently
  68          * with a power_down request for the same CPU. In this case the
  69          * power_down method might not be able to actually enter a
  70          * powered down state with the WFI instruction if the power_up
  71          * method has removed the required reset condition.  The
  72          * power_down method is then allowed to return. We must perform
  73          * a re-entry in the kernel as if the power_up method just had
  74          * deasserted reset on the CPU.
  75          *
  76          * To simplify race issues, the platform specific implementation
  77          * must accommodate for the possibility of unordered calls to
  78          * power_down and power_up with a usage count. Therefore, if a
  79          * call to power_up is issued for a CPU that is not down, then
  80          * the next call to power_down must not attempt a full shutdown
  81          * but only do the minimum (normally disabling L1 cache and CPU
  82          * coherency) and return just as if a concurrent power_up request
  83          * had happened as described above.
  84          */
  85
  86         phys_reset = (phys_reset_t)(unsigned long)virt_to_phys(cpu_reset);
  87         phys_reset(virt_to_phys(mcpm_entry_point));
  88
  89         /* should never get here */
  90         BUG();
  91 }
  92
  93 void mcpm_cpu_suspend(u64 expected_residency)
  94 {
  95         phys_reset_t phys_reset;
  96
  97         if (WARN_ON_ONCE(!platform_ops || !platform_ops->suspend))
  98                 return;
  99         BUG_ON(!irqs_disabled());
 100
 101         /* Very similar to mcpm_cpu_power_down() */
 102         setup_mm_for_reboot();
 103         platform_ops->suspend(expected_residency);
 104         phys_reset = (phys_reset_t)(unsigned long)virt_to_phys(cpu_reset);
 105         phys_reset(virt_to_phys(mcpm_entry_point));
 106         BUG();
 107 }
 108
 109 int mcpm_cpu_powered_up(void)
 110 {
 111         if (!platform_ops)
 112                 return -EUNATCH;
 113         if (platform_ops->powered_up)
 114                 platform_ops->powered_up();
 115         return 0;
 116 }
 117
 118 struct sync_struct mcpm_sync;
 119
 120 /*
 121  * __mcpm_cpu_going_down: Indicates that the cpu is being torn down.
 122  *    This must be called at the point of committing to teardown of a CPU.
 123  *    The CPU cache (SCTRL.C bit) is expected to still be active.
 124  */
 125 void __mcpm_cpu_going_down(unsigned int cpu, unsigned int cluster)
 126 {
 127         mcpm_sync.clusters[cluster].cpus[cpu].cpu = CPU_GOING_DOWN;
 128         sync_cache_w(&mcpm_sync.clusters[cluster].cpus[cpu].cpu);
 129 }
 130
 131 /*
 132  * __mcpm_cpu_down: Indicates that cpu teardown is complete and that the
 133  *    cluster can be torn down without disrupting this CPU.
 134  *    To avoid deadlocks, this must be called before a CPU is powered down.
 135  *    The CPU cache (SCTRL.C bit) is expected to be off.
 136  *    However L2 cache might or might not be active.
 137  */
 138 void __mcpm_cpu_down(unsigned int cpu, unsigned int cluster)
 139 {
 140         dmb();
 141         mcpm_sync.clusters[cluster].cpus[cpu].cpu = CPU_DOWN;
 142         sync_cache_w(&mcpm_sync.clusters[cluster].cpus[cpu].cpu);
 143         dsb_sev();
 144 }
 145
 146 /*
 147  * __mcpm_outbound_leave_critical: Leave the cluster teardown critical section.
 148  * @state: the final state of the cluster:
 149  *     CLUSTER_UP: no destructive teardown was done and the cluster has been
 150  *         restored to the previous state (CPU cache still active); or
 151  *     CLUSTER_DOWN: the cluster has been torn-down, ready for power-off
 152  *         (CPU cache disabled, L2 cache either enabled or disabled).
 153  */
 154 void __mcpm_outbound_leave_critical(unsigned int cluster, int state)
 155 {
 156         dmb();
 157         mcpm_sync.clusters[cluster].cluster = state;
 158         sync_cache_w(&mcpm_sync.clusters[cluster].cluster);
 159         dsb_sev();
 160 }
 161
 162 /*
 163  * __mcpm_outbound_enter_critical: Enter the cluster teardown critical section.
 164  * This function should be called by the last man, after local CPU teardown
 165  * is complete.  CPU cache expected to be active.
 166  *
 167  * Returns:
 168  *     false: the critical section was not entered because an inbound CPU was
 169  *         observed, or the cluster is already being set up;
 170  *     true: the critical section was entered: it is now safe to tear down the
 171  *         cluster.
 172  */
 173 bool __mcpm_outbound_enter_critical(unsigned int cpu, unsigned int cluster)
 174 {
 175         unsigned int i;
 176         struct mcpm_sync_struct *c = &mcpm_sync.clusters[cluster];
 177
 178         /* Warn inbound CPUs that the cluster is being torn down: */
 179         c->cluster = CLUSTER_GOING_DOWN;
 180         sync_cache_w(&c->cluster);
 181
 182         /* Back out if the inbound cluster is already in the critical region: */
 183         sync_cache_r(&c->inbound);
 184         if (c->inbound == INBOUND_COMING_UP)
 185                 goto abort;
 186
 187         /*
 188          * Wait for all CPUs to get out of the GOING_DOWN state, so that local
 189          * teardown is complete on each CPU before tearing down the cluster.
 190          *
 191          * If any CPU has been woken up again from the DOWN state, then we
 192          * shouldn't be taking the cluster down at all: abort in that case.
 193          */
 194         sync_cache_r(&c->cpus);
 195         for (i = 0; i < MAX_CPUS_PER_CLUSTER; i++) {
 196                 int cpustate;
 197
 198                 if (i == cpu)
 199                         continue;
 200
 201                 while (1) {
 202                         cpustate = c->cpus[i].cpu;
 203                         if (cpustate != CPU_GOING_DOWN)
 204                                 break;
 205
 206                         wfe();
 207                         sync_cache_r(&c->cpus[i].cpu);
 208                 }
 209
 210                 switch (cpustate) {
 211                 case CPU_DOWN:
 212                         continue;
 213
 214                 default:
 215                         goto abort;
 216                 }
 217         }
 218
 219         return true;
 220
 221 abort:
 222         __mcpm_outbound_leave_critical(cluster, CLUSTER_UP);
 223         return false;
 224 }
 225
 226 int __mcpm_cluster_state(unsigned int cluster)
 227 {
 228         sync_cache_r(&mcpm_sync.clusters[cluster].cluster);
 229         return mcpm_sync.clusters[cluster].cluster;
 230 }
 231
 232 extern unsigned long mcpm_power_up_setup_phys;
 233
 234 int __init mcpm_sync_init(
 235         void (*power_up_setup)(unsigned int affinity_level))
 236 {
 237         unsigned int i, j, mpidr, this_cluster;
 238
 239         BUILD_BUG_ON(MCPM_SYNC_CLUSTER_SIZE * MAX_NR_CLUSTERS != sizeof mcpm_sync);
 240         BUG_ON((unsigned long)&mcpm_sync & (__CACHE_WRITEBACK_GRANULE - 1));
 241
 242         /*
 243          * Set initial CPU and cluster states.
 244          * Only one cluster is assumed to be active at this point.
 245          */
 246         for (i = 0; i < MAX_NR_CLUSTERS; i++) {
 247                 mcpm_sync.clusters[i].cluster = CLUSTER_DOWN;
 248                 mcpm_sync.clusters[i].inbound = INBOUND_NOT_COMING_UP;
 249                 for (j = 0; j < MAX_CPUS_PER_CLUSTER; j++)
 250                         mcpm_sync.clusters[i].cpus[j].cpu = CPU_DOWN;
 251         }
 252         mpidr = read_cpuid_mpidr();
 253         this_cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
 254         for_each_online_cpu(i)
 255                 mcpm_sync.clusters[this_cluster].cpus[i].cpu = CPU_UP;
 256         mcpm_sync.clusters[this_cluster].cluster = CLUSTER_UP;
 257         sync_cache_w(&mcpm_sync);
 258
 259         if (power_up_setup) {
 260                 mcpm_power_up_setup_phys = virt_to_phys(power_up_setup);
 261                 sync_cache_w(&mcpm_power_up_setup_phys);
 262         }
 263
 264         return 0;
 265 }