arch/tile/kernel/smpboot.c

   1 /*
   2  * Copyright 2010 Tilera Corporation. All Rights Reserved.
   3  *
   4  *   This program is free software; you can redistribute it and/or
   5  *   modify it under the terms of the GNU General Public License
   6  *   as published by the Free Software Foundation, version 2.
   7  *
   8  *   This program is distributed in the hope that it will be useful, but
   9  *   WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  11  *   NON INFRINGEMENT.  See the GNU General Public License for
  12  *   more details.
  13  */
  14
  15 #include <linux/module.h>
  16 #include <linux/init.h>
  17 #include <linux/kernel.h>
  18 #include <linux/mm.h>
  19 #include <linux/sched.h>
  20 #include <linux/kernel_stat.h>
  21 #include <linux/bootmem.h>
  22 #include <linux/notifier.h>
  23 #include <linux/cpu.h>
  24 #include <linux/percpu.h>
  25 #include <linux/delay.h>
  26 #include <linux/err.h>
  27 #include <linux/irq.h>
  28 #include <asm/mmu_context.h>
  29 #include <asm/tlbflush.h>
  30 #include <asm/sections.h>
  31
  32 /* State of each CPU. */
  33 static DEFINE_PER_CPU(int, cpu_state) = { 0 };
  34
  35 /* The messaging code jumps to this pointer during boot-up */
  36 unsigned long start_cpu_function_addr;
  37
  38 /* Called very early during startup to mark boot cpu as online */
  39 void __init smp_prepare_boot_cpu(void)
  40 {
  41         int cpu = smp_processor_id();
  42         set_cpu_online(cpu, 1);
  43         set_cpu_present(cpu, 1);
  44         __this_cpu_write(cpu_state, CPU_ONLINE);
  45
  46         init_messaging();
  47 }
  48
  49 static void start_secondary(void);
  50
  51 /*
  52  * Called at the top of init() to launch all the other CPUs.
  53  * They run free to complete their initialization and then wait
  54  * until they get an IPI from the boot cpu to come online.
  55  */
  56 void __init smp_prepare_cpus(unsigned int max_cpus)
  57 {
  58         long rc;
  59         int cpu, cpu_count;
  60         int boot_cpu = smp_processor_id();
  61
  62         current_thread_info()->cpu = boot_cpu;
  63
  64         /*
  65          * Pin this task to the boot CPU while we bring up the others,
  66          * just to make sure we don't uselessly migrate as they come up.
  67          */
  68         rc = sched_setaffinity(current->pid, cpumask_of(boot_cpu));
  69         if (rc != 0)
  70                 pr_err("Couldn't set init affinity to boot cpu (%ld)\n", rc);
  71
  72         /* Print information about disabled and dataplane cpus. */
  73         print_disabled_cpus();
  74
  75         /*
  76          * Tell the messaging subsystem how to respond to the
  77          * startup message.  We use a level of indirection to avoid
  78          * confusing the linker with the fact that the messaging
  79          * subsystem is calling __init code.
  80          */
  81         start_cpu_function_addr = (unsigned long) &online_secondary;
  82
  83         /* Set up thread context for all new processors. */
  84         cpu_count = 1;
  85         for (cpu = 0; cpu < NR_CPUS; ++cpu)     {
  86                 struct task_struct *idle;
  87
  88                 if (cpu == boot_cpu)
  89                         continue;
  90
  91                 if (!cpu_possible(cpu)) {
  92                         /*
  93                          * Make this processor do nothing on boot.
  94                          * Note that we don't give the boot_pc function
  95                          * a stack, so it has to be assembly code.
  96                          */
  97                         per_cpu(boot_sp, cpu) = 0;
  98                         per_cpu(boot_pc, cpu) = (unsigned long) smp_nap;
  99                         continue;
 100                 }
 101
 102                 /* Create a new idle thread to run start_secondary() */
 103                 idle = fork_idle(cpu);
 104                 if (IS_ERR(idle))
 105                         panic("failed fork for CPU %d", cpu);
 106                 idle->thread.pc = (unsigned long) start_secondary;
 107
 108                 /* Make this thread the boot thread for this processor */
 109                 per_cpu(boot_sp, cpu) = task_ksp0(idle);
 110                 per_cpu(boot_pc, cpu) = idle->thread.pc;
 111
 112                 ++cpu_count;
 113         }
 114         BUG_ON(cpu_count > (max_cpus ? max_cpus : 1));
 115
 116         /* Fire up the other tiles, if any */
 117         init_cpu_present(cpu_possible_mask);
 118         if (cpumask_weight(cpu_present_mask) > 1) {
 119                 mb();  /* make sure all data is visible to new processors */
 120                 hv_start_all_tiles();
 121         }
 122 }
 123
 124 static __initdata struct cpumask init_affinity;
 125
 126 static __init int reset_init_affinity(void)
 127 {
 128         long rc = sched_setaffinity(current->pid, &init_affinity);
 129         if (rc != 0)
 130                 pr_warn("couldn't reset init affinity (%ld)\n", rc);
 131         return 0;
 132 }
 133 late_initcall(reset_init_affinity);
 134
 135 static struct cpumask cpu_started;
 136
 137 /*
 138  * Activate a secondary processor.  Very minimal; don't add anything
 139  * to this path without knowing what you're doing, since SMP booting
 140  * is pretty fragile.
 141  */
 142 static void start_secondary(void)
 143 {
 144         int cpuid;
 145
 146         preempt_disable();
 147
 148         cpuid = smp_processor_id();
 149
 150         /* Set our thread pointer appropriately. */
 151         set_my_cpu_offset(__per_cpu_offset[cpuid]);
 152
 153         /*
 154          * In large machines even this will slow us down, since we
 155          * will be contending for for the printk spinlock.
 156          */
 157         /* printk(KERN_DEBUG "Initializing CPU#%d\n", cpuid); */
 158
 159         /* Initialize the current asid for our first page table. */
 160         __this_cpu_write(current_asid, min_asid);
 161
 162         /* Set up this thread as another owner of the init_mm */
 163         atomic_inc(&init_mm.mm_count);
 164         current->active_mm = &init_mm;
 165         if (current->mm)
 166                 BUG();
 167         enter_lazy_tlb(&init_mm, current);
 168
 169         /* Allow hypervisor messages to be received */
 170         init_messaging();
 171         local_irq_enable();
 172
 173         /* Indicate that we're ready to come up. */
 174         /* Must not do this before we're ready to receive messages */
 175         if (cpumask_test_and_set_cpu(cpuid, &cpu_started)) {
 176                 pr_warn("CPU#%d already started!\n", cpuid);
 177                 for (;;)
 178                         local_irq_enable();
 179         }
 180
 181         smp_nap();
 182 }
 183
 184 /*
 185  * Bring a secondary processor online.
 186  */
 187 void online_secondary(void)
 188 {
 189         /*
 190          * low-memory mappings have been cleared, flush them from
 191          * the local TLBs too.
 192          */
 193         local_flush_tlb();
 194
 195         BUG_ON(in_interrupt());
 196
 197         /* This must be done before setting cpu_online_mask */
 198         wmb();
 199
 200         notify_cpu_starting(smp_processor_id());
 201
 202         set_cpu_online(smp_processor_id(), 1);
 203         __this_cpu_write(cpu_state, CPU_ONLINE);
 204
 205         /* Set up tile-specific state for this cpu. */
 206         setup_cpu(0);
 207
 208         /* Set up tile-timer clock-event device on this cpu */
 209         setup_tile_timer();
 210
 211         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 212 }
 213
 214 int __cpu_up(unsigned int cpu, struct task_struct *tidle)
 215 {
 216         /* Wait 5s total for all CPUs for them to come online */
 217         static int timeout;
 218         for (; !cpumask_test_cpu(cpu, &cpu_started); timeout++) {
 219                 if (timeout >= 50000) {
 220                         pr_info("skipping unresponsive cpu%d\n", cpu);
 221                         local_irq_enable();
 222                         return -EIO;
 223                 }
 224                 udelay(100);
 225         }
 226
 227         local_irq_enable();
 228         per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
 229
 230         /* Unleash the CPU! */
 231         send_IPI_single(cpu, MSG_TAG_START_CPU);
 232         while (!cpumask_test_cpu(cpu, cpu_online_mask))
 233                 cpu_relax();
 234         return 0;
 235 }
 236
 237 static void panic_start_cpu(void)
 238 {
 239         panic("Received a MSG_START_CPU IPI after boot finished.");
 240 }
 241
 242 void __init smp_cpus_done(unsigned int max_cpus)
 243 {
 244         int cpu, next, rc;
 245
 246         /* Reset the response to a (now illegal) MSG_START_CPU IPI. */
 247         start_cpu_function_addr = (unsigned long) &panic_start_cpu;
 248
 249         cpumask_copy(&init_affinity, cpu_online_mask);
 250
 251         /*
 252          * Pin ourselves to a single cpu in the initial affinity set
 253          * so that kernel mappings for the rootfs are not in the dataplane,
 254          * if set, and to avoid unnecessary migrating during bringup.
 255          * Use the last cpu just in case the whole chip has been
 256          * isolated from the scheduler, to keep init away from likely
 257          * more useful user code.  This also ensures that work scheduled
 258          * via schedule_delayed_work() in the init routines will land
 259          * on this cpu.
 260          */
 261         for (cpu = cpumask_first(&init_affinity);
 262              (next = cpumask_next(cpu, &init_affinity)) < nr_cpu_ids;
 263              cpu = next)
 264                 ;
 265         rc = sched_setaffinity(current->pid, cpumask_of(cpu));
 266         if (rc != 0)
 267                 pr_err("Couldn't set init affinity to cpu %d (%d)\n", cpu, rc);
 268 }