arch/arc/kernel/smp.c

   1 /*
   2  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * RajeshwarR: Dec 11, 2007
   9  *   -- Added support for Inter Processor Interrupts
  10  *
  11  * Vineetg: Nov 1st, 2007
  12  *    -- Initial Write (Borrowed heavily from ARM)
  13  */
  14
  15 #include <linux/spinlock.h>
  16 #include <linux/sched.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/profile.h>
  19 #include <linux/mm.h>
  20 #include <linux/cpu.h>
  21 #include <linux/irq.h>
  22 #include <linux/atomic.h>
  23 #include <linux/cpumask.h>
  24 #include <linux/reboot.h>
  25 #include <asm/processor.h>
  26 #include <asm/setup.h>
  27 #include <asm/mach_desc.h>
  28
  29 arch_spinlock_t smp_atomic_ops_lock = __ARCH_SPIN_LOCK_UNLOCKED;
  30 arch_spinlock_t smp_bitops_lock = __ARCH_SPIN_LOCK_UNLOCKED;
  31
  32 struct plat_smp_ops  plat_smp_ops;
  33
  34 /* XXX: per cpu ? Only needed once in early seconday boot */
  35 struct task_struct *secondary_idle_tsk;
  36
  37 /* Called from start_kernel */
  38 void __init smp_prepare_boot_cpu(void)
  39 {
  40 }
  41
  42 /*
  43  * Initialise the CPU possible map early - this describes the CPUs
  44  * which may be present or become present in the system.
  45  */
  46 void __init smp_init_cpus(void)
  47 {
  48         unsigned int i;
  49
  50         for (i = 0; i < NR_CPUS; i++)
  51                 set_cpu_possible(i, true);
  52 }
  53
  54 /* called from init ( ) =>  process 1 */
  55 void __init smp_prepare_cpus(unsigned int max_cpus)
  56 {
  57         int i;
  58
  59         /*
  60          * Initialise the present map, which describes the set of CPUs
  61          * actually populated at the present time.
  62          */
  63         for (i = 0; i < max_cpus; i++)
  64                 set_cpu_present(i, true);
  65 }
  66
  67 void __init smp_cpus_done(unsigned int max_cpus)
  68 {
  69
  70 }
  71
  72 /*
  73  * After power-up, a non Master CPU needs to wait for Master to kick start it
  74  *
  75  * The default implementation halts
  76  *
  77  * This relies on platform specific support allowing Master to directly set
  78  * this CPU's PC (to be @first_lines_of_secondary() and kick start it.
  79  *
  80  * In lack of such h/w assist, platforms can override this function
  81  *   - make this function busy-spin on a token, eventually set by Master
  82  *     (from arc_platform_smp_wakeup_cpu())
  83  *   - Once token is available, jump to @first_lines_of_secondary
  84  *     (using inline asm).
  85  *
  86  * Alert: can NOT use stack here as it has not been determined/setup for CPU.
  87  *        If it turns out to be elaborate, it's better to code it in assembly
  88  *
  89  */
  90 void __weak arc_platform_smp_wait_to_boot(int cpu)
  91 {
  92         /*
  93          * As a hack for debugging - since debugger will single-step over the
  94          * FLAG insn - wrap the halt itself it in a self loop
  95          */
  96         __asm__ __volatile__(
  97         "1:             \n"
  98         "       flag 1  \n"
  99         "       b 1b    \n");
 100 }
 101
 102 const char *arc_platform_smp_cpuinfo(void)
 103 {
 104         return plat_smp_ops.info ? : "";
 105 }
 106
 107 /*
 108  * The very first "C" code executed by secondary
 109  * Called from asm stub in head.S
 110  * "current"/R25 already setup by low level boot code
 111  */
 112 void start_kernel_secondary(void)
 113 {
 114         struct mm_struct *mm = &init_mm;
 115         unsigned int cpu = smp_processor_id();
 116
 117         /* MMU, Caches, Vector Table, Interrupts etc */
 118         setup_processor();
 119
 120         atomic_inc(&mm->mm_users);
 121         atomic_inc(&mm->mm_count);
 122         current->active_mm = mm;
 123         cpumask_set_cpu(cpu, mm_cpumask(mm));
 124
 125         notify_cpu_starting(cpu);
 126         set_cpu_online(cpu, true);
 127
 128         pr_info("## CPU%u LIVE ##: Executing Code...\n", cpu);
 129
 130         if (machine_desc->init_smp)
 131                 machine_desc->init_smp(cpu);
 132
 133         arc_local_timer_setup();
 134
 135         local_irq_enable();
 136         preempt_disable();
 137         cpu_startup_entry(CPUHP_ONLINE);
 138 }
 139
 140 /*
 141  * Called from kernel_init( ) -> smp_init( ) - for each CPU
 142  *
 143  * At this point, Secondary Processor  is "HALT"ed:
 144  *  -It booted, but was halted in head.S
 145  *  -It was configured to halt-on-reset
 146  *  So need to wake it up.
 147  *
 148  * Essential requirements being where to run from (PC) and stack (SP)
 149 */
 150 int __cpu_up(unsigned int cpu, struct task_struct *idle)
 151 {
 152         unsigned long wait_till;
 153
 154         secondary_idle_tsk = idle;
 155
 156         pr_info("Idle Task [%d] %p", cpu, idle);
 157         pr_info("Trying to bring up CPU%u ...\n", cpu);
 158
 159         if (plat_smp_ops.cpu_kick)
 160                 plat_smp_ops.cpu_kick(cpu,
 161                                 (unsigned long)first_lines_of_secondary);
 162
 163         /* wait for 1 sec after kicking the secondary */
 164         wait_till = jiffies + HZ;
 165         while (time_before(jiffies, wait_till)) {
 166                 if (cpu_online(cpu))
 167                         break;
 168         }
 169
 170         if (!cpu_online(cpu)) {
 171                 pr_info("Timeout: CPU%u FAILED to comeup !!!\n", cpu);
 172                 return -1;
 173         }
 174
 175         secondary_idle_tsk = NULL;
 176
 177         return 0;
 178 }
 179
 180 /*
 181  * not supported here
 182  */
 183 int __init setup_profiling_timer(unsigned int multiplier)
 184 {
 185         return -EINVAL;
 186 }
 187
 188 /*****************************************************************************/
 189 /*              Inter Processor Interrupt Handling                           */
 190 /*****************************************************************************/
 191
 192 enum ipi_msg_type {
 193         IPI_EMPTY = 0,
 194         IPI_RESCHEDULE = 1,
 195         IPI_CALL_FUNC,
 196         IPI_CPU_STOP,
 197 };
 198
 199 /*
 200  * In arches with IRQ for each msg type (above), receiver can use IRQ-id  to
 201  * figure out what msg was sent. For those which don't (ARC has dedicated IPI
 202  * IRQ), the msg-type needs to be conveyed via per-cpu data
 203  */
 204
 205 static DEFINE_PER_CPU(unsigned long, ipi_data);
 206
 207 static void ipi_send_msg_one(int cpu, enum ipi_msg_type msg)
 208 {
 209         unsigned long __percpu *ipi_data_ptr = per_cpu_ptr(&ipi_data, cpu);
 210         unsigned long old, new;
 211         unsigned long flags;
 212
 213         pr_debug("%d Sending msg [%d] to %d\n", smp_processor_id(), msg, cpu);
 214
 215         local_irq_save(flags);
 216
 217         /*
 218          * Atomically write new msg bit (in case others are writing too),
 219          * and read back old value
 220          */
 221         do {
 222                 new = old = *ipi_data_ptr;
 223                 new |= 1U << msg;
 224         } while (cmpxchg(ipi_data_ptr, old, new) != old);
 225
 226         /*
 227          * Call the platform specific IPI kick function, but avoid if possible:
 228          * Only do so if there's no pending msg from other concurrent sender(s).
 229          * Otherwise, recevier will see this msg as well when it takes the
 230          * IPI corresponding to that msg. This is true, even if it is already in
 231          * IPI handler, because !@old means it has not yet dequeued the msg(s)
 232          * so @new msg can be a free-loader
 233          */
 234         if (plat_smp_ops.ipi_send && !old)
 235                 plat_smp_ops.ipi_send(cpu);
 236
 237         local_irq_restore(flags);
 238 }
 239
 240 static void ipi_send_msg(const struct cpumask *callmap, enum ipi_msg_type msg)
 241 {
 242         unsigned int cpu;
 243
 244         for_each_cpu(cpu, callmap)
 245                 ipi_send_msg_one(cpu, msg);
 246 }
 247
 248 void smp_send_reschedule(int cpu)
 249 {
 250         ipi_send_msg_one(cpu, IPI_RESCHEDULE);
 251 }
 252
 253 void smp_send_stop(void)
 254 {
 255         struct cpumask targets;
 256         cpumask_copy(&targets, cpu_online_mask);
 257         cpumask_clear_cpu(smp_processor_id(), &targets);
 258         ipi_send_msg(&targets, IPI_CPU_STOP);
 259 }
 260
 261 void arch_send_call_function_single_ipi(int cpu)
 262 {
 263         ipi_send_msg_one(cpu, IPI_CALL_FUNC);
 264 }
 265
 266 void arch_send_call_function_ipi_mask(const struct cpumask *mask)
 267 {
 268         ipi_send_msg(mask, IPI_CALL_FUNC);
 269 }
 270
 271 /*
 272  * ipi_cpu_stop - handle IPI from smp_send_stop()
 273  */
 274 static void ipi_cpu_stop(void)
 275 {
 276         machine_halt();
 277 }
 278
 279 static inline void __do_IPI(unsigned long msg)
 280 {
 281         switch (msg) {
 282         case IPI_RESCHEDULE:
 283                 scheduler_ipi();
 284                 break;
 285
 286         case IPI_CALL_FUNC:
 287                 generic_smp_call_function_interrupt();
 288                 break;
 289
 290         case IPI_CPU_STOP:
 291                 ipi_cpu_stop();
 292                 break;
 293
 294         default:
 295                 pr_warn("IPI with unexpected msg %ld\n", msg);
 296         }
 297 }
 298
 299 /*
 300  * arch-common ISR to handle for inter-processor interrupts
 301  * Has hooks for platform specific IPI
 302  */
 303 irqreturn_t do_IPI(int irq, void *dev_id)
 304 {
 305         unsigned long pending;
 306
 307         pr_debug("IPI [%ld] received on cpu %d\n",
 308                  *this_cpu_ptr(&ipi_data), smp_processor_id());
 309
 310         if (plat_smp_ops.ipi_clear)
 311                 plat_smp_ops.ipi_clear(irq);
 312
 313         /*
 314          * "dequeue" the msg corresponding to this IPI (and possibly other
 315          * piggybacked msg from elided IPIs: see ipi_send_msg_one() above)
 316          */
 317         pending = xchg(this_cpu_ptr(&ipi_data), 0);
 318
 319         do {
 320                 unsigned long msg = __ffs(pending);
 321                 __do_IPI(msg);
 322                 pending &= ~(1U << msg);
 323         } while (pending);
 324
 325         return IRQ_HANDLED;
 326 }
 327
 328 /*
 329  * API called by platform code to hookup arch-common ISR to their IPI IRQ
 330  */
 331 static DEFINE_PER_CPU(int, ipi_dev);
 332
 333 int smp_ipi_irq_setup(int cpu, int irq)
 334 {
 335         int *dev = per_cpu_ptr(&ipi_dev, cpu);
 336
 337         arc_request_percpu_irq(irq, cpu, do_IPI, "IPI Interrupt", dev);
 338
 339         return 0;
 340 }