arch/arm/mach-spear/hotplug.c

   1 /*
   2  * linux/arch/arm/mach-spear13xx/hotplug.c
   3  *
   4  * Copyright (C) 2012 ST Microelectronics Ltd.
   5  * Deepak Sikri <deepak.sikri@st.com>
   6  *
   7  * based upon linux/arch/arm/mach-realview/hotplug.c
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  */
  13 #include <linux/kernel.h>
  14 #include <linux/errno.h>
  15 #include <linux/smp.h>
  16 #include <asm/cp15.h>
  17 #include <asm/smp_plat.h>
  18
  19 static inline void cpu_enter_lowpower(void)
  20 {
  21         unsigned int v;
  22
  23         asm volatile(
  24         "       mcr     p15, 0, %1, c7, c5, 0\n"
  25         "       dsb\n"
  26         /*
  27          * Turn off coherency
  28          */
  29         "       mrc     p15, 0, %0, c1, c0, 1\n"
  30         "       bic     %0, %0, #0x20\n"
  31         "       mcr     p15, 0, %0, c1, c0, 1\n"
  32         "       mrc     p15, 0, %0, c1, c0, 0\n"
  33         "       bic     %0, %0, %2\n"
  34         "       mcr     p15, 0, %0, c1, c0, 0\n"
  35         : "=&r" (v)
  36         : "r" (0), "Ir" (CR_C)
  37         : "cc", "memory");
  38 }
  39
  40 static inline void cpu_leave_lowpower(void)
  41 {
  42         unsigned int v;
  43
  44         asm volatile("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, #0x20\n"
  49         "       mcr     p15, 0, %0, c1, c0, 1\n"
  50         : "=&r" (v)
  51         : "Ir" (CR_C)
  52         : "cc");
  53 }
  54
  55 static inline void spear13xx_do_lowpower(unsigned int cpu, int *spurious)
  56 {
  57         for (;;) {
  58                 wfi();
  59
  60                 if (pen_release == cpu) {
  61                         /*
  62                          * OK, proper wakeup, we're done
  63                          */
  64                         break;
  65                 }
  66
  67                 /*
  68                  * Getting here, means that we have come out of WFI without
  69                  * having been woken up - this shouldn't happen
  70                  *
  71                  * Just note it happening - when we're woken, we can report
  72                  * its occurrence.
  73                  */
  74                 (*spurious)++;
  75         }
  76 }
  77
  78 /*
  79  * platform-specific code to shutdown a CPU
  80  *
  81  * Called with IRQs disabled
  82  */
  83 void __ref spear13xx_cpu_die(unsigned int cpu)
  84 {
  85         int spurious = 0;
  86
  87         /*
  88          * we're ready for shutdown now, so do it
  89          */
  90         cpu_enter_lowpower();
  91         spear13xx_do_lowpower(cpu, &spurious);
  92
  93         /*
  94          * bring this CPU back into the world of cache
  95          * coherency, and then restore interrupts
  96          */
  97         cpu_leave_lowpower();
  98
  99         if (spurious)
 100                 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
 101 }