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/smp_plat.h>
  17 #include <asm/system.h>
  18
  19 extern volatile int pen_release;
  20
  21 static inline void cpu_enter_lowpower(void)
  22 {
  23         unsigned int v;
  24
  25         flush_cache_all();
  26         asm volatile(
  27                 "mcr    p15, 0, %1, c7, c5, 0\n"
  28         "       mcr     p15, 0, %1, c7, c10, 4\n"
  29         /*
  30          * Turn off coherency
  31          */
  32         "       mrc     p15, 0, %0, c1, c0, 1\n"
  33         "       bic     %0, %0, %3\n"
  34         "       mcr     p15, 0, %0, c1, c0, 1\n"
  35         "       mrc     p15, 0, %0, c1, c0, 0\n"
  36         "       bic     %0, %0, %2\n"
  37         "       mcr     p15, 0, %0, c1, c0, 0\n"
  38           : "=&r" (v)
  39           : "r" (0), "Ir" (CR_C), "Ir" (0x40)
  40           : "cc");
  41 }
  42
  43 static inline void cpu_leave_lowpower(void)
  44 {
  45         unsigned int v;
  46
  47         asm volatile(
  48                 "mrc    p15, 0, %0, c1, c0, 0\n"
  49         "       orr     %0, %0, %1\n"
  50         "       mcr     p15, 0, %0, c1, c0, 0\n"
  51         "       mrc     p15, 0, %0, c1, c0, 1\n"
  52         "       orr     %0, %0, %2\n"
  53         "       mcr     p15, 0, %0, c1, c0, 1\n"
  54           : "=&r" (v)
  55           : "Ir" (CR_C), "Ir" (0x40)
  56           : "cc");
  57 }
  58
  59 static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
  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                 wfi();
  68
  69                 if (pen_release == cpu_logical_map(cpu)) {
  70                         /*
  71                          * OK, proper wakeup, we're done
  72                          */
  73                         break;
  74                 }
  75
  76                 /*
  77                  * Getting here, means that we have come out of WFI without
  78                  * having been woken up - this shouldn't happen
  79                  *
  80                  * Just note it happening - when we're woken, we can report
  81                  * its occurrence.
  82                  */
  83                 (*spurious)++;
  84         }
  85 }
  86
  87 int platform_cpu_kill(unsigned int cpu)
  88 {
  89         return 1;
  90 }
  91
  92 /*
  93  * platform-specific code to shutdown a CPU
  94  *
  95  * Called with IRQs disabled
  96  */
  97 void platform_cpu_die(unsigned int cpu)
  98 {
  99         int spurious = 0;
 100
 101         /*
 102          * we're ready for shutdown now, so do it
 103          */
 104         cpu_enter_lowpower();
 105         platform_do_lowpower(cpu, &spurious);
 106
 107         /*
 108          * bring this CPU back into the world of cache
 109          * coherency, and then restore interrupts
 110          */
 111         cpu_leave_lowpower();
 112
 113         if (spurious)
 114                 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
 115 }
 116
 117 int platform_cpu_disable(unsigned int cpu)
 118 {
 119         /*
 120          * we don't allow CPU 0 to be shutdown (it is still too special
 121          * e.g. clock tick interrupts)
 122          */
 123         return cpu == 0 ? -EPERM : 0;
 124 }