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Linux/arch/arm/mach-vexpress/hotplug.c

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  1 /*
  2  *  linux/arch/arm/mach-realview/hotplug.c
  3  *
  4  *  Copyright (C) 2002 ARM Ltd.
  5  *  All Rights Reserved
  6  *
  7  * This program is free software; you can redistribute it and/or modify
  8  * it under the terms of the GNU General Public License version 2 as
  9  * published by the Free Software Foundation.
 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 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         "       mcr     p15, 0, %1, c7, c10, 4\n"
 25         /*
 26          * Turn off coherency
 27          */
 28         "       mrc     p15, 0, %0, c1, c0, 1\n"
 29         "       bic     %0, %0, %3\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), "Ir" (0x40)
 36           : "cc");
 37 }
 38 
 39 static inline void cpu_leave_lowpower(void)
 40 {
 41         unsigned int v;
 42 
 43         asm volatile(
 44                 "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, %2\n"
 49         "       mcr     p15, 0, %0, c1, c0, 1\n"
 50           : "=&r" (v)
 51           : "Ir" (CR_C), "Ir" (0x40)
 52           : "cc");
 53 }
 54 
 55 static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
 56 {
 57         /*
 58          * there is no power-control hardware on this platform, so all
 59          * we can do is put the core into WFI; this is safe as the calling
 60          * code will have already disabled interrupts
 61          */
 62         for (;;) {
 63                 wfi();
 64 
 65                 if (pen_release == cpu_logical_map(cpu)) {
 66                         /*
 67                          * OK, proper wakeup, we're done
 68                          */
 69                         break;
 70                 }
 71 
 72                 /*
 73                  * Getting here, means that we have come out of WFI without
 74                  * having been woken up - this shouldn't happen
 75                  *
 76                  * Just note it happening - when we're woken, we can report
 77                  * its occurrence.
 78                  */
 79                 (*spurious)++;
 80         }
 81 }
 82 
 83 /*
 84  * platform-specific code to shutdown a CPU
 85  *
 86  * Called with IRQs disabled
 87  */
 88 void __ref vexpress_cpu_die(unsigned int cpu)
 89 {
 90         int spurious = 0;
 91 
 92         /*
 93          * we're ready for shutdown now, so do it
 94          */
 95         cpu_enter_lowpower();
 96         platform_do_lowpower(cpu, &spurious);
 97 
 98         /*
 99          * bring this CPU back into the world of cache
100          * coherency, and then restore interrupts
101          */
102         cpu_leave_lowpower();
103 
104         if (spurious)
105                 pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
106 }
107 

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