arch/arm/mach-realview/hotplug.c

   1 /*
   2  *  linux/arch/arm/mach-realview/hotplug.c
   3  *
   4  *  Copyright (C) 2002 ARM Ltd.
   5  *  All Rights Reserved
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11 #include <linux/kernel.h>
  12 #include <linux/errno.h>
  13 #include <linux/smp.h>
  14 #include <linux/completion.h>
  15
  16 #include <asm/cacheflush.h>
  17
  18 extern volatile int pen_release;
  19
  20 static DECLARE_COMPLETION(cpu_killed);
  21
  22 static inline void cpu_enter_lowpower(void)
  23 {
  24         unsigned int v;
  25
  26         flush_cache_all();
  27         asm volatile(
  28         "       mcr     p15, 0, %1, c7, c5, 0\n"
  29         "       mcr     p15, 0, %1, c7, c10, 4\n"
  30         /*
  31          * Turn off coherency
  32          */
  33         "       mrc     p15, 0, %0, c1, c0, 1\n"
  34         "       bic     %0, %0, #0x20\n"
  35         "       mcr     p15, 0, %0, c1, c0, 1\n"
  36         "       mrc     p15, 0, %0, c1, c0, 0\n"
  37         "       bic     %0, %0, #0x04\n"
  38         "       mcr     p15, 0, %0, c1, c0, 0\n"
  39           : "=&r" (v)
  40           : "r" (0)
  41           : "cc");
  42 }
  43
  44 static inline void cpu_leave_lowpower(void)
  45 {
  46         unsigned int v;
  47
  48         asm volatile(   "mrc    p15, 0, %0, c1, c0, 0\n"
  49         "       orr     %0, %0, #0x04\n"
  50         "       mcr     p15, 0, %0, c1, c0, 0\n"
  51         "       mrc     p15, 0, %0, c1, c0, 1\n"
  52         "       orr     %0, %0, #0x20\n"
  53         "       mcr     p15, 0, %0, c1, c0, 1\n"
  54           : "=&r" (v)
  55           :
  56           : "cc");
  57 }
  58
  59 static inline void platform_do_lowpower(unsigned int cpu)
  60 {
  61         /*
  62          * there is no power-control hardware on this platform, so all
  63          * we can do is put the core into WFI; this is safe as the calling
  64          * code will have already disabled interrupts
  65          */
  66         for (;;) {
  67                 /*
  68                  * here's the WFI
  69                  */
  70                 asm(".word      0xe320f003\n"
  71                     :
  72                     :
  73                     : "memory", "cc");
  74
  75                 if (pen_release == cpu) {
  76                         /*
  77                          * OK, proper wakeup, we're done
  78                          */
  79                         break;
  80                 }
  81
  82                 /*
  83                  * getting here, means that we have come out of WFI without
  84                  * having been woken up - this shouldn't happen
  85                  *
  86                  * The trouble is, letting people know about this is not really
  87                  * possible, since we are currently running incoherently, and
  88                  * therefore cannot safely call printk() or anything else
  89                  */
  90 #ifdef DEBUG
  91                 printk("CPU%u: spurious wakeup call\n", cpu);
  92 #endif
  93         }
  94 }
  95
  96 int platform_cpu_kill(unsigned int cpu)
  97 {
  98         return wait_for_completion_timeout(&cpu_killed, 5000);
  99 }
 100
 101 /*
 102  * platform-specific code to shutdown a CPU
 103  *
 104  * Called with IRQs disabled
 105  */
 106 void platform_cpu_die(unsigned int cpu)
 107 {
 108 #ifdef DEBUG
 109         unsigned int this_cpu = hard_smp_processor_id();
 110
 111         if (cpu != this_cpu) {
 112                 printk(KERN_CRIT "Eek! platform_cpu_die running on %u, should be %u\n",
 113                            this_cpu, cpu);
 114                 BUG();
 115         }
 116 #endif
 117
 118         printk(KERN_NOTICE "CPU%u: shutdown\n", cpu);
 119         complete(&cpu_killed);
 120
 121         /*
 122          * we're ready for shutdown now, so do it
 123          */
 124         cpu_enter_lowpower();
 125         platform_do_lowpower(cpu);
 126
 127         /*
 128          * bring this CPU back into the world of cache
 129          * coherency, and then restore interrupts
 130          */
 131         cpu_leave_lowpower();
 132 }
 133
 134 int mach_cpu_disable(unsigned int cpu)
 135 {
 136         /*
 137          * we don't allow CPU 0 to be shutdown (it is still too special
 138          * e.g. clock tick interrupts)
 139          */
 140         return cpu == 0 ? -EPERM : 0;
 141 }