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/cp15.h>
  16 #include <asm/smp_plat.h>
  17
  18 static inline void cpu_enter_lowpower(void)
  19 {
  20         unsigned int v;
  21
  22         asm volatile(
  23         "       mcr     p15, 0, %1, c7, c5, 0\n"
  24         "       mcr     p15, 0, %1, c7, c10, 4\n"
  25         /*
  26          * Turn off coherency
  27          */
  28         "       mrc     p15, 0, %0, c1, c0, 1\n"
  29         "       bic     %0, %0, #0x20\n"
  30         "       mcr     p15, 0, %0, c1, c0, 1\n"
  31         "       mrc     p15, 0, %0, c1, c0, 0\n"
  32         "       bic     %0, %0, %2\n"
  33         "       mcr     p15, 0, %0, c1, c0, 0\n"
  34           : "=&r" (v)
  35           : "r" (0), "Ir" (CR_C)
  36           : "cc");
  37 }
  38
  39 static inline void cpu_leave_lowpower(void)
  40 {
  41         unsigned int v;
  42
  43         asm volatile(   "mrc    p15, 0, %0, c1, c0, 0\n"
  44         "       orr     %0, %0, %1\n"
  45         "       mcr     p15, 0, %0, c1, c0, 0\n"
  46         "       mrc     p15, 0, %0, c1, c0, 1\n"
  47         "       orr     %0, %0, #0x20\n"
  48         "       mcr     p15, 0, %0, c1, c0, 1\n"
  49           : "=&r" (v)
  50           : "Ir" (CR_C)
  51           : "cc");
  52 }
  53
  54 static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
  55 {
  56         /*
  57          * there is no power-control hardware on this platform, so all
  58          * we can do is put the core into WFI; this is safe as the calling
  59          * code will have already disabled interrupts
  60          */
  61         for (;;) {
  62                 /*
  63                  * here's the WFI
  64                  */
  65                 asm(".word      0xe320f003\n"
  66                     :
  67                     :
  68                     : "memory", "cc");
  69
  70                 if (pen_release == cpu_logical_map(cpu)) {
  71                         /*
  72                          * OK, proper wakeup, we're done
  73                          */
  74                         break;
  75                 }
  76
  77                 /*
  78                  * Getting here, means that we have come out of WFI without
  79                  * having been woken up - this shouldn't happen
  80                  *
  81                  * Just note it happening - when we're woken, we can report
  82                  * its occurrence.
  83                  */
  84                 (*spurious)++;
  85         }
  86 }
  87
  88 /*
  89  * platform-specific code to shutdown a CPU
  90  *
  91  * Called with IRQs disabled
  92  */
  93 void realview_cpu_die(unsigned int cpu)
  94 {
  95         int spurious = 0;
  96
  97         /*
  98          * we're ready for shutdown now, so do it
  99          */
 100         cpu_enter_lowpower();
 101         platform_do_lowpower(cpu, &spurious);
 102
 103         /*
 104          * bring this CPU back into the world of cache
 105          * coherency, and then restore interrupts
 106          */
 107         cpu_leave_lowpower();
 108
 109         if (spurious)
 110                 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
 111 }