arch/arm/mach-spear/hotplug.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * linux/arch/arm/mach-spear13xx/hotplug.c
   4  *
   5  * Copyright (C) 2012 ST Microelectronics Ltd.
   6  * Deepak Sikri <deepak.sikri@st.com>
   7  *
   8  * based upon linux/arch/arm/mach-realview/hotplug.c
   9  */
  10 #include <linux/kernel.h>
  11 #include <linux/errno.h>
  12 #include <linux/smp.h>
  13 #include <asm/cp15.h>
  14 #include <asm/smp_plat.h>
  15
  16 #include "generic.h"
  17
  18 static inline void cpu_enter_lowpower(void)
  19 {
  20         unsigned int v;
  21
  22         asm volatile(
  23         "       mcr     p15, 0, %1, c7, c5, 0\n"
  24         "       dsb\n"
  25         /*
  26          * Turn off coherency
  27          */
  28         "       mrc     p15, 0, %0, c1, c0, 1\n"
  29         "       bic     %0, %0, #0x20\n"
  30         "       mcr     p15, 0, %0, c1, c0, 1\n"
  31         "       mrc     p15, 0, %0, c1, c0, 0\n"
  32         "       bic     %0, %0, %2\n"
  33         "       mcr     p15, 0, %0, c1, c0, 0\n"
  34         : "=&r" (v)
  35         : "r" (0), "Ir" (CR_C)
  36         : "cc", "memory");
  37 }
  38
  39 static inline void cpu_leave_lowpower(void)
  40 {
  41         unsigned int v;
  42
  43         asm volatile("mrc       p15, 0, %0, c1, c0, 0\n"
  44         "       orr     %0, %0, %1\n"
  45         "       mcr     p15, 0, %0, c1, c0, 0\n"
  46         "       mrc     p15, 0, %0, c1, c0, 1\n"
  47         "       orr     %0, %0, #0x20\n"
  48         "       mcr     p15, 0, %0, c1, c0, 1\n"
  49         : "=&r" (v)
  50         : "Ir" (CR_C)
  51         : "cc");
  52 }
  53
  54 static inline void spear13xx_do_lowpower(unsigned int cpu, int *spurious)
  55 {
  56         for (;;) {
  57                 wfi();
  58
  59                 if (spear_pen_release == cpu) {
  60                         /*
  61                          * OK, proper wakeup, we're done
  62                          */
  63                         break;
  64                 }
  65
  66                 /*
  67                  * Getting here, means that we have come out of WFI without
  68                  * having been woken up - this shouldn't happen
  69                  *
  70                  * Just note it happening - when we're woken, we can report
  71                  * its occurrence.
  72                  */
  73                 (*spurious)++;
  74         }
  75 }
  76
  77 /*
  78  * platform-specific code to shutdown a CPU
  79  *
  80  * Called with IRQs disabled
  81  */
  82 void spear13xx_cpu_die(unsigned int cpu)
  83 {
  84         int spurious = 0;
  85
  86         /*
  87          * we're ready for shutdown now, so do it
  88          */
  89         cpu_enter_lowpower();
  90         spear13xx_do_lowpower(cpu, &spurious);
  91
  92         /*
  93          * bring this CPU back into the world of cache
  94          * coherency, and then restore interrupts
  95          */
  96         cpu_leave_lowpower();
  97
  98         if (spurious)
  99                 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
 100 }