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 #include <asm/smp_plat.h>
  15
  16 extern volatile int pen_release;
  17
  18 static inline void cpu_enter_lowpower(void)
  19 {
  20         /* Just flush the cache. Changing the coherency is not yet
  21          * available on msm. */
  22         flush_cache_all();
  23 }
  24
  25 static inline void cpu_leave_lowpower(void)
  26 {
  27 }
  28
  29 static inline void platform_do_lowpower(unsigned int cpu)
  30 {
  31         /* Just enter wfi for now. TODO: Properly shut off the cpu. */
  32         for (;;) {
  33                 /*
  34                  * here's the WFI
  35                  */
  36                 asm("wfi"
  37                     :
  38                     :
  39                     : "memory", "cc");
  40
  41                 if (pen_release == cpu_logical_map(cpu)) {
  42                         /*
  43                          * OK, proper wakeup, we're done
  44                          */
  45                         break;
  46                 }
  47
  48                 /*
  49                  * getting here, means that we have come out of WFI without
  50                  * having been woken up - this shouldn't happen
  51                  *
  52                  * The trouble is, letting people know about this is not really
  53                  * possible, since we are currently running incoherently, and
  54                  * therefore cannot safely call printk() or anything else
  55                  */
  56                 pr_debug("CPU%u: spurious wakeup call\n", cpu);
  57         }
  58 }
  59
  60 int platform_cpu_kill(unsigned int cpu)
  61 {
  62         return 1;
  63 }
  64
  65 /*
  66  * platform-specific code to shutdown a CPU
  67  *
  68  * Called with IRQs disabled
  69  */
  70 void platform_cpu_die(unsigned int cpu)
  71 {
  72         /*
  73          * we're ready for shutdown now, so do it
  74          */
  75         cpu_enter_lowpower();
  76         platform_do_lowpower(cpu);
  77
  78         /*
  79          * bring this CPU back into the world of cache
  80          * coherency, and then restore interrupts
  81          */
  82         cpu_leave_lowpower();
  83 }
  84
  85 int platform_cpu_disable(unsigned int cpu)
  86 {
  87         /*
  88          * we don't allow CPU 0 to be shutdown (it is still too special
  89          * e.g. clock tick interrupts)
  90          */
  91         return cpu == 0 ? -EPERM : 0;
  92 }