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 extern volatile int pen_release;
  17
  18 static DECLARE_COMPLETION(cpu_killed);
  19
  20 static inline void cpu_enter_lowpower(void)
  21 {
  22         unsigned int v;
  23
  24         asm volatile(   "mcr    p15, 0, %1, c7, c14, 0\n"
  25         "       mcr     p15, 0, %1, c7, c5, 0\n"
  26         "       mcr     p15, 0, %1, c7, c10, 4\n"
  27         /*
  28          * Turn off coherency
  29          */
  30         "       mrc     p15, 0, %0, c1, c0, 1\n"
  31         "       bic     %0, %0, #0x20\n"
  32         "       mcr     p15, 0, %0, c1, c0, 1\n"
  33         "       mrc     p15, 0, %0, c1, c0, 0\n"
  34         "       bic     %0, %0, #0x04\n"
  35         "       mcr     p15, 0, %0, c1, c0, 0\n"
  36           : "=&r" (v)
  37           : "r" (0)
  38           : "cc");
  39 }
  40
  41 static inline void cpu_leave_lowpower(void)
  42 {
  43         unsigned int v;
  44
  45         asm volatile(   "mrc    p15, 0, %0, c1, c0, 0\n"
  46         "       orr     %0, %0, #0x04\n"
  47         "       mcr     p15, 0, %0, c1, c0, 0\n"
  48         "       mrc     p15, 0, %0, c1, c0, 1\n"
  49         "       orr     %0, %0, #0x20\n"
  50         "       mcr     p15, 0, %0, c1, c0, 1\n"
  51           : "=&r" (v)
  52           :
  53           : "cc");
  54 }
  55
  56 static inline void platform_do_lowpower(unsigned int cpu)
  57 {
  58         /*
  59          * there is no power-control hardware on this platform, so all
  60          * we can do is put the core into WFI; this is safe as the calling
  61          * code will have already disabled interrupts
  62          */
  63         for (;;) {
  64                 /*
  65                  * here's the WFI
  66                  */
  67                 asm(".word      0xe320f003\n"
  68                     :
  69                     :
  70                     : "memory", "cc");
  71
  72                 if (pen_release == cpu) {
  73                         /*
  74                          * OK, proper wakeup, we're done
  75                          */
  76                         break;
  77                 }
  78
  79                 /*
  80                  * getting here, means that we have come out of WFI without
  81                  * having been woken up - this shouldn't happen
  82                  *
  83                  * The trouble is, letting people know about this is not really
  84                  * possible, since we are currently running incoherently, and
  85                  * therefore cannot safely call printk() or anything else
  86                  */
  87 #ifdef DEBUG
  88                 printk("CPU%u: spurious wakeup call\n", cpu);
  89 #endif
  90         }
  91 }
  92
  93 int platform_cpu_kill(unsigned int cpu)
  94 {
  95         return wait_for_completion_timeout(&cpu_killed, 5000);
  96 }
  97
  98 /*
  99  * platform-specific code to shutdown a CPU
 100  *
 101  * Called with IRQs disabled
 102  */
 103 void platform_cpu_die(unsigned int cpu)
 104 {
 105 #ifdef DEBUG
 106         unsigned int this_cpu = hard_smp_processor_id();
 107
 108         if (cpu != this_cpu) {
 109                 printk(KERN_CRIT "Eek! platform_cpu_die running on %u, should be %u\n",
 110                            this_cpu, cpu);
 111                 BUG();
 112         }
 113 #endif
 114
 115         printk(KERN_NOTICE "CPU%u: shutdown\n", cpu);
 116         complete(&cpu_killed);
 117
 118         /*
 119          * we're ready for shutdown now, so do it
 120          */
 121         cpu_enter_lowpower();
 122         platform_do_lowpower(cpu);
 123
 124         /*
 125          * bring this CPU back into the world of cache
 126          * coherency, and then restore interrupts
 127          */
 128         cpu_leave_lowpower();
 129 }
 130
 131 int mach_cpu_disable(unsigned int cpu)
 132 {
 133         /*
 134          * we don't allow CPU 0 to be shutdown (it is still too special
 135          * e.g. clock tick interrupts)
 136          */
 137         return cpu == 0 ? -EPERM : 0;
 138 }