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hotplug.c

/*
 *  linux/arch/arm/mach-realview/hotplug.c
 *
 *  Copyright (C) 2002 ARM Ltd.
 *  All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/smp.h>
#include <linux/completion.h>

extern volatile int pen_release;

static DECLARE_COMPLETION(cpu_killed);

static inline void cpu_enter_lowpower(void)
{
      unsigned int v;

      asm volatile(     "mcr  p15, 0, %1, c7, c14, 0\n"
      "     mcr   p15, 0, %1, c7, c5, 0\n"
      "     mcr   p15, 0, %1, c7, c10, 4\n"
      /*
       * Turn off coherency
       */
      "     mrc   p15, 0, %0, c1, c0, 1\n"
      "     bic   %0, %0, #0x20\n"
      "     mcr   p15, 0, %0, c1, c0, 1\n"
      "     mrc   p15, 0, %0, c1, c0, 0\n"
      "     bic   %0, %0, #0x04\n"
      "     mcr   p15, 0, %0, c1, c0, 0\n"
        : "=&r" (v)
        : "r" (0)
        : "cc");
}

static inline void cpu_leave_lowpower(void)
{
      unsigned int v;

      asm volatile(     "mrc  p15, 0, %0, c1, c0, 0\n"
      "     orr   %0, %0, #0x04\n"
      "     mcr   p15, 0, %0, c1, c0, 0\n"
      "     mrc   p15, 0, %0, c1, c0, 1\n"
      "     orr   %0, %0, #0x20\n"
      "     mcr   p15, 0, %0, c1, c0, 1\n"
        : "=&r" (v)
        :
        : "cc");
}

static inline void platform_do_lowpower(unsigned int cpu)
{
      /*
       * there is no power-control hardware on this platform, so all
       * we can do is put the core into WFI; this is safe as the calling
       * code will have already disabled interrupts
       */
      for (;;) {
            /*
             * here's the WFI
             */
            asm(".word  0xe320f003\n"
                :
                :
                : "memory", "cc");

            if (pen_release == cpu) {
                  /*
                   * OK, proper wakeup, we're done
                   */
                  break;
            }

            /*
             * getting here, means that we have come out of WFI without
             * having been woken up - this shouldn't happen
             *
             * The trouble is, letting people know about this is not really
             * possible, since we are currently running incoherently, and
             * therefore cannot safely call printk() or anything else
             */
#ifdef DEBUG
            printk("CPU%u: spurious wakeup call\n", cpu);
#endif
      }
}

int platform_cpu_kill(unsigned int cpu)
{
      return wait_for_completion_timeout(&cpu_killed, 5000);
}

/*
 * platform-specific code to shutdown a CPU
 *
 * Called with IRQs disabled
 */
void platform_cpu_die(unsigned int cpu)
{
#ifdef DEBUG
      unsigned int this_cpu = hard_smp_processor_id();

      if (cpu != this_cpu) {
            printk(KERN_CRIT "Eek! platform_cpu_die running on %u, should be %u\n",
                     this_cpu, cpu);
            BUG();
      }
#endif

      printk(KERN_NOTICE "CPU%u: shutdown\n", cpu);
      complete(&cpu_killed);

      /*
       * we're ready for shutdown now, so do it
       */
      cpu_enter_lowpower();
      platform_do_lowpower(cpu);

      /*
       * bring this CPU back into the world of cache
       * coherency, and then restore interrupts
       */
      cpu_leave_lowpower();
}

int mach_cpu_disable(unsigned int cpu)
{
      /*
       * we don't allow CPU 0 to be shutdown (it is still too special
       * e.g. clock tick interrupts)
       */
      return cpu == 0 ? -EPERM : 0;
}

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