arch/arm/mach-spear13xx/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/cacheflush.h>
  17 #include <asm/cp15.h>
  18 #include <asm/smp_plat.h>
  19
  20 static inline void cpu_enter_lowpower(void)
  21 {
  22         unsigned int v;
  23
  24         flush_cache_all();
  25         asm volatile(
  26         "       mcr     p15, 0, %1, c7, c5, 0\n"
  27         "       dsb\n"
  28         /*
  29          * Turn off coherency
  30          */
  31         "       mrc     p15, 0, %0, c1, c0, 1\n"
  32         "       bic     %0, %0, #0x20\n"
  33         "       mcr     p15, 0, %0, c1, c0, 1\n"
  34         "       mrc     p15, 0, %0, c1, c0, 0\n"
  35         "       bic     %0, %0, %2\n"
  36         "       mcr     p15, 0, %0, c1, c0, 0\n"
  37         : "=&r" (v)
  38         : "r" (0), "Ir" (CR_C)
  39         : "cc", "memory");
  40 }
  41
  42 static inline void cpu_leave_lowpower(void)
  43 {
  44         unsigned int v;
  45
  46         asm volatile("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, #0x20\n"
  51         "       mcr     p15, 0, %0, c1, c0, 1\n"
  52         : "=&r" (v)
  53         : "Ir" (CR_C)
  54         : "cc");
  55 }
  56
  57 static inline void spear13xx_do_lowpower(unsigned int cpu, int *spurious)
  58 {
  59         for (;;) {
  60                 wfi();
  61
  62                 if (pen_release == cpu) {
  63                         /*
  64                          * OK, proper wakeup, we're done
  65                          */
  66                         break;
  67                 }
  68
  69                 /*
  70                  * Getting here, means that we have come out of WFI without
  71                  * having been woken up - this shouldn't happen
  72                  *
  73                  * Just note it happening - when we're woken, we can report
  74                  * its occurrence.
  75                  */
  76                 (*spurious)++;
  77         }
  78 }
  79
  80 /*
  81  * platform-specific code to shutdown a CPU
  82  *
  83  * Called with IRQs disabled
  84  */
  85 void __ref spear13xx_cpu_die(unsigned int cpu)
  86 {
  87         int spurious = 0;
  88
  89         /*
  90          * we're ready for shutdown now, so do it
  91          */
  92         cpu_enter_lowpower();
  93         spear13xx_do_lowpower(cpu, &spurious);
  94
  95         /*
  96          * bring this CPU back into the world of cache
  97          * coherency, and then restore interrupts
  98          */
  99         cpu_leave_lowpower();
 100
 101         if (spurious)
 102                 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
 103 }