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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 <asm/cacheflush.h>

extern volatile int pen_release;

static inline void cpu_enter_lowpower(void)
{
      /* Just flush the cache. Changing the coherency is not yet
       * available on msm. */
      flush_cache_all();
}

static inline void cpu_leave_lowpower(void)
{
}

static inline void platform_do_lowpower(unsigned int cpu)
{
      /* Just enter wfi for now. TODO: Properly shut off the cpu. */
      for (;;) {
            /*
             * here's the WFI
             */
            asm("wfi"
                :
                :
                : "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
             */
            pr_debug("CPU%u: spurious wakeup call\n", cpu);
      }
}

int platform_cpu_kill(unsigned int cpu)
{
      return 1;
}

/*
 * platform-specific code to shutdown a CPU
 *
 * Called with IRQs disabled
 */
void platform_cpu_die(unsigned int cpu)
{
      /*
       * 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 platform_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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