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/cp15.h>
  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, %3\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), "Ir" (0x40)
  38           : "cc");
  39 }
  40
  41 static inline void cpu_leave_lowpower(void)
  42 {
  43         unsigned int v;
  44
  45         asm volatile(
  46                 "mrc    p15, 0, %0, c1, c0, 0\n"
  47         "       orr     %0, %0, %1\n"
  48         "       mcr     p15, 0, %0, c1, c0, 0\n"
  49         "       mrc     p15, 0, %0, c1, c0, 1\n"
  50         "       orr     %0, %0, %2\n"
  51         "       mcr     p15, 0, %0, c1, c0, 1\n"
  52           : "=&r" (v)
  53           : "Ir" (CR_C), "Ir" (0x40)
  54           : "cc");
  55 }
  56
  57 static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
  58 {
  59         /*
  60          * there is no power-control hardware on this platform, so all
  61          * we can do is put the core into WFI; this is safe as the calling
  62          * code will have already disabled interrupts
  63          */
  64         for (;;) {
  65                 wfi();
  66
  67                 if (pen_release == cpu_logical_map(cpu)) {
  68                         /*
  69                          * OK, proper wakeup, we're done
  70                          */
  71                         break;
  72                 }
  73
  74                 /*
  75                  * Getting here, means that we have come out of WFI without
  76                  * having been woken up - this shouldn't happen
  77                  *
  78                  * Just note it happening - when we're woken, we can report
  79                  * its occurrence.
  80                  */
  81                 (*spurious)++;
  82         }
  83 }
  84
  85 /*
  86  * platform-specific code to shutdown a CPU
  87  *
  88  * Called with IRQs disabled
  89  */
  90 void __ref vexpress_cpu_die(unsigned int cpu)
  91 {
  92         int spurious = 0;
  93
  94         /*
  95          * we're ready for shutdown now, so do it
  96          */
  97         cpu_enter_lowpower();
  98         platform_do_lowpower(cpu, &spurious);
  99
 100         /*
 101          * bring this CPU back into the world of cache
 102          * coherency, and then restore interrupts
 103          */
 104         cpu_leave_lowpower();
 105
 106         if (spurious)
 107                 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
 108 }