arch/arm/plat-versatile/hotplug.c

   1 /*
   2  *  Copyright (C) 2002 ARM Ltd.
   3  *  All Rights Reserved
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * This hotplug implementation is _specific_ to the situation found on
  10  * ARM development platforms where there is _no_ possibility of actually
  11  * taking a CPU offline, resetting it, or otherwise.  Real platforms must
  12  * NOT copy this code.
  13  */
  14 #include <linux/kernel.h>
  15 #include <linux/errno.h>
  16 #include <linux/smp.h>
  17
  18 #include <asm/smp_plat.h>
  19 #include <asm/cp15.h>
  20
  21 #include <plat/platsmp.h>
  22
  23 static inline void versatile_immitation_enter_lowpower(unsigned int actrl_mask)
  24 {
  25         unsigned int v;
  26
  27         asm volatile(
  28                 "mcr    p15, 0, %1, c7, c5, 0\n"
  29         "       mcr     p15, 0, %1, c7, c10, 4\n"
  30         /*
  31          * Turn off coherency
  32          */
  33         "       mrc     p15, 0, %0, c1, c0, 1\n"
  34         "       bic     %0, %0, %3\n"
  35         "       mcr     p15, 0, %0, c1, c0, 1\n"
  36         "       mrc     p15, 0, %0, c1, c0, 0\n"
  37         "       bic     %0, %0, %2\n"
  38         "       mcr     p15, 0, %0, c1, c0, 0\n"
  39           : "=&r" (v)
  40           : "r" (0), "Ir" (CR_C), "Ir" (actrl_mask)
  41           : "cc");
  42 }
  43
  44 static inline void versatile_immitation_leave_lowpower(unsigned int actrl_mask)
  45 {
  46         unsigned int v;
  47
  48         asm volatile(
  49                 "mrc    p15, 0, %0, c1, c0, 0\n"
  50         "       orr     %0, %0, %1\n"
  51         "       mcr     p15, 0, %0, c1, c0, 0\n"
  52         "       mrc     p15, 0, %0, c1, c0, 1\n"
  53         "       orr     %0, %0, %2\n"
  54         "       mcr     p15, 0, %0, c1, c0, 1\n"
  55           : "=&r" (v)
  56           : "Ir" (CR_C), "Ir" (actrl_mask)
  57           : "cc");
  58 }
  59
  60 static inline void versatile_immitation_do_lowpower(unsigned int cpu, int *spurious)
  61 {
  62         /*
  63          * there is no power-control hardware on this platform, so all
  64          * we can do is put the core into WFI; this is safe as the calling
  65          * code will have already disabled interrupts.
  66          *
  67          * This code should not be used outside Versatile platforms.
  68          */
  69         for (;;) {
  70                 wfi();
  71
  72                 if (versatile_cpu_release == cpu_logical_map(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 /*
  91  * platform-specific code to shutdown a CPU.
  92  * This code supports immitation-style CPU hotplug for Versatile/Realview/
  93  * Versatile Express platforms that are unable to do real CPU hotplug.
  94  */
  95 void versatile_immitation_cpu_die(unsigned int cpu, unsigned int actrl_mask)
  96 {
  97         int spurious = 0;
  98
  99         versatile_immitation_enter_lowpower(actrl_mask);
 100         versatile_immitation_do_lowpower(cpu, &spurious);
 101         versatile_immitation_leave_lowpower(actrl_mask);
 102
 103         if (spurious)
 104                 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
 105 }