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
  15 #include <asm/cacheflush.h>
  16
  17 extern volatile int pen_release;
  18
  19 static inline void cpu_enter_lowpower(void)
  20 {
  21         unsigned int v;
  22
  23         flush_cache_all();
  24         asm volatile(
  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, %2\n"
  35         "       mcr     p15, 0, %0, c1, c0, 0\n"
  36           : "=&r" (v)
  37           : "r" (0), "Ir" (CR_C)
  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, %1\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           : "Ir" (CR_C)
  53           : "cc");
  54 }
  55
  56 static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
  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                  * Just note it happening - when we're woken, we can report
  84                  * its occurrence.
  85                  */
  86                 (*spurious)++;
  87         }
  88 }
  89
  90 int platform_cpu_kill(unsigned int cpu)
  91 {
  92         return 1;
  93 }
  94
  95 /*
  96  * platform-specific code to shutdown a CPU
  97  *
  98  * Called with IRQs disabled
  99  */
 100 void platform_cpu_die(unsigned int cpu)
 101 {
 102         int spurious = 0;
 103
 104         /*
 105          * we're ready for shutdown now, so do it
 106          */
 107         cpu_enter_lowpower();
 108         platform_do_lowpower(cpu, &spurious);
 109
 110         /*
 111          * bring this CPU back into the world of cache
 112          * coherency, and then restore interrupts
 113          */
 114         cpu_leave_lowpower();
 115
 116         if (spurious)
 117                 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
 118 }
 119
 120 int platform_cpu_disable(unsigned int cpu)
 121 {
 122         /*
 123          * we don't allow CPU 0 to be shutdown (it is still too special
 124          * e.g. clock tick interrupts)
 125          */
 126         return cpu == 0 ? -EPERM : 0;
 127 }