arch/arm/plat-versatile/hotplug.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  Copyright (C) 2002 ARM Ltd.
   4  *  All Rights Reserved
   5  *
   6  * This hotplug implementation is _specific_ to the situation found on
   7  * ARM development platforms where there is _no_ possibility of actually
   8  * taking a CPU offline, resetting it, or otherwise.  Real platforms must
   9  * NOT copy this code.
  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 #include <plat/platsmp.h>
  19
  20 static inline void versatile_immitation_enter_lowpower(unsigned int actrl_mask)
  21 {
  22         unsigned int v;
  23
  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" (actrl_mask)
  38           : "cc");
  39 }
  40
  41 static inline void versatile_immitation_leave_lowpower(unsigned int actrl_mask)
  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" (actrl_mask)
  54           : "cc");
  55 }
  56
  57 static inline void versatile_immitation_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          * This code should not be used outside Versatile platforms.
  65          */
  66         for (;;) {
  67                 wfi();
  68
  69                 if (versatile_cpu_release == cpu_logical_map(cpu)) {
  70                         /*
  71                          * OK, proper wakeup, we're done
  72                          */
  73                         break;
  74                 }
  75
  76                 /*
  77                  * Getting here, means that we have come out of WFI without
  78                  * having been woken up - this shouldn't happen
  79                  *
  80                  * Just note it happening - when we're woken, we can report
  81                  * its occurrence.
  82                  */
  83                 (*spurious)++;
  84         }
  85 }
  86
  87 /*
  88  * platform-specific code to shutdown a CPU.
  89  * This code supports immitation-style CPU hotplug for Versatile/Realview/
  90  * Versatile Express platforms that are unable to do real CPU hotplug.
  91  */
  92 void versatile_immitation_cpu_die(unsigned int cpu, unsigned int actrl_mask)
  93 {
  94         int spurious = 0;
  95
  96         versatile_immitation_enter_lowpower(actrl_mask);
  97         versatile_immitation_do_lowpower(cpu, &spurious);
  98         versatile_immitation_leave_lowpower(actrl_mask);
  99
 100         if (spurious)
 101                 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
 102 }