arch/arm/mach-msm/hotplug.c

   1 /*
   2  *  Copyright (C) 2002 ARM Ltd.
   3  *  All Rights Reserved
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9 #include <linux/kernel.h>
  10 #include <linux/errno.h>
  11 #include <linux/smp.h>
  12
  13 #include <asm/cacheflush.h>
  14
  15 extern volatile int pen_release;
  16
  17 static inline void cpu_enter_lowpower(void)
  18 {
  19         /* Just flush the cache. Changing the coherency is not yet
  20          * available on msm. */
  21         flush_cache_all();
  22 }
  23
  24 static inline void cpu_leave_lowpower(void)
  25 {
  26 }
  27
  28 static inline void platform_do_lowpower(unsigned int cpu)
  29 {
  30         /* Just enter wfi for now. TODO: Properly shut off the cpu. */
  31         for (;;) {
  32                 /*
  33                  * here's the WFI
  34                  */
  35                 asm("wfi"
  36                     :
  37                     :
  38                     : "memory", "cc");
  39
  40                 if (pen_release == cpu) {
  41                         /*
  42                          * OK, proper wakeup, we're done
  43                          */
  44                         break;
  45                 }
  46
  47                 /*
  48                  * getting here, means that we have come out of WFI without
  49                  * having been woken up - this shouldn't happen
  50                  *
  51                  * The trouble is, letting people know about this is not really
  52                  * possible, since we are currently running incoherently, and
  53                  * therefore cannot safely call printk() or anything else
  54                  */
  55                 pr_debug("CPU%u: spurious wakeup call\n", cpu);
  56         }
  57 }
  58
  59 int platform_cpu_kill(unsigned int cpu)
  60 {
  61         return 1;
  62 }
  63
  64 /*
  65  * platform-specific code to shutdown a CPU
  66  *
  67  * Called with IRQs disabled
  68  */
  69 void platform_cpu_die(unsigned int cpu)
  70 {
  71         /*
  72          * we're ready for shutdown now, so do it
  73          */
  74         cpu_enter_lowpower();
  75         platform_do_lowpower(cpu);
  76
  77         /*
  78          * bring this CPU back into the world of cache
  79          * coherency, and then restore interrupts
  80          */
  81         cpu_leave_lowpower();
  82 }
  83
  84 int platform_cpu_disable(unsigned int cpu)
  85 {
  86         /*
  87          * we don't allow CPU 0 to be shutdown (it is still too special
  88          * e.g. clock tick interrupts)
  89          */
  90         return cpu == 0 ? -EPERM : 0;
  91 }