arch/arm/mach-vexpress/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
  15 #include <asm/cacheflush.h>
  16 #include <asm/system.h>
  17
  18 extern volatile int pen_release;
  19
  20 static inline void cpu_enter_lowpower(void)
  21 {
  22         unsigned int v;
  23
  24         flush_cache_all();
  25         asm volatile(
  26                 "mcr    p15, 0, %1, c7, c5, 0\n"
  27         "       mcr     p15, 0, %1, c7, c10, 4\n"
  28         /*
  29          * Turn off coherency
  30          */
  31         "       mrc     p15, 0, %0, c1, c0, 1\n"
  32         "       bic     %0, %0, %3\n"
  33         "       mcr     p15, 0, %0, c1, c0, 1\n"
  34         "       mrc     p15, 0, %0, c1, c0, 0\n"
  35         "       bic     %0, %0, %2\n"
  36         "       mcr     p15, 0, %0, c1, c0, 0\n"
  37           : "=&r" (v)
  38           : "r" (0), "Ir" (CR_C), "Ir" (0x40)
  39           : "cc");
  40 }
  41
  42 static inline void cpu_leave_lowpower(void)
  43 {
  44         unsigned int v;
  45
  46         asm volatile(
  47                 "mrc    p15, 0, %0, c1, c0, 0\n"
  48         "       orr     %0, %0, %1\n"
  49         "       mcr     p15, 0, %0, c1, c0, 0\n"
  50         "       mrc     p15, 0, %0, c1, c0, 1\n"
  51         "       orr     %0, %0, %2\n"
  52         "       mcr     p15, 0, %0, c1, c0, 1\n"
  53           : "=&r" (v)
  54           : "Ir" (CR_C), "Ir" (0x40)
  55           : "cc");
  56 }
  57
  58 static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
  59 {
  60         /*
  61          * there is no power-control hardware on this platform, so all
  62          * we can do is put the core into WFI; this is safe as the calling
  63          * code will have already disabled interrupts
  64          */
  65         for (;;) {
  66                 wfi();
  67
  68                 if (pen_release == cpu) {
  69                         /*
  70                          * OK, proper wakeup, we're done
  71                          */
  72                         break;
  73                 }
  74
  75                 /*
  76                  * Getting here, means that we have come out of WFI without
  77                  * having been woken up - this shouldn't happen
  78                  *
  79                  * Just note it happening - when we're woken, we can report
  80                  * its occurrence.
  81                  */
  82                 (*spurious)++;
  83         }
  84 }
  85
  86 int platform_cpu_kill(unsigned int cpu)
  87 {
  88         return 1;
  89 }
  90
  91 /*
  92  * platform-specific code to shutdown a CPU
  93  *
  94  * Called with IRQs disabled
  95  */
  96 void platform_cpu_die(unsigned int cpu)
  97 {
  98         int spurious = 0;
  99
 100         /*
 101          * we're ready for shutdown now, so do it
 102          */
 103         cpu_enter_lowpower();
 104         platform_do_lowpower(cpu, &spurious);
 105
 106         /*
 107          * bring this CPU back into the world of cache
 108          * coherency, and then restore interrupts
 109          */
 110         cpu_leave_lowpower();
 111
 112         if (spurious)
 113                 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
 114 }
 115
 116 int platform_cpu_disable(unsigned int cpu)
 117 {
 118         /*
 119          * we don't allow CPU 0 to be shutdown (it is still too special
 120          * e.g. clock tick interrupts)
 121          */
 122         return cpu == 0 ? -EPERM : 0;
 123 }