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/smp_plat.h>
  16 #include <asm/cp15.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, %3\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), "Ir" (0x40)
  36           : "cc");
  37 }
  38
  39 static inline void cpu_leave_lowpower(void)
  40 {
  41         unsigned int v;
  42
  43         asm volatile(
  44                 "mrc    p15, 0, %0, c1, c0, 0\n"
  45         "       orr     %0, %0, %1\n"
  46         "       mcr     p15, 0, %0, c1, c0, 0\n"
  47         "       mrc     p15, 0, %0, c1, c0, 1\n"
  48         "       orr     %0, %0, %2\n"
  49         "       mcr     p15, 0, %0, c1, c0, 1\n"
  50           : "=&r" (v)
  51           : "Ir" (CR_C), "Ir" (0x40)
  52           : "cc");
  53 }
  54
  55 static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
  56 {
  57         /*
  58          * there is no power-control hardware on this platform, so all
  59          * we can do is put the core into WFI; this is safe as the calling
  60          * code will have already disabled interrupts
  61          */
  62         for (;;) {
  63                 wfi();
  64
  65                 if (pen_release == cpu_logical_map(cpu)) {
  66                         /*
  67                          * OK, proper wakeup, we're done
  68                          */
  69                         break;
  70                 }
  71
  72                 /*
  73                  * Getting here, means that we have come out of WFI without
  74                  * having been woken up - this shouldn't happen
  75                  *
  76                  * Just note it happening - when we're woken, we can report
  77                  * its occurrence.
  78                  */
  79                 (*spurious)++;
  80         }
  81 }
  82
  83 /*
  84  * platform-specific code to shutdown a CPU
  85  *
  86  * Called with IRQs disabled
  87  */
  88 void vexpress_cpu_die(unsigned int cpu)
  89 {
  90         int spurious = 0;
  91
  92         /*
  93          * we're ready for shutdown now, so do it
  94          */
  95         cpu_enter_lowpower();
  96         platform_do_lowpower(cpu, &spurious);
  97
  98         /*
  99          * bring this CPU back into the world of cache
 100          * coherency, and then restore interrupts
 101          */
 102         cpu_leave_lowpower();
 103
 104         if (spurious)
 105                 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
 106 }