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