hotplug.c

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/*
 *  linux/arch/arm/mach-realview/hotplug.c
 *
 *  Copyright (C) 2002 ARM Ltd.
 *  All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/smp.h>

#include <asm/cacheflush.h>
#include <asm/smp_plat.h>
#include <asm/cp15.h>

static inline void cpu_enter_lowpower(void)
{
    unsigned int v;

    flush_cache_all();
    asm volatile(
        "mcr    p15, 0, %1, c7, c5, 0\n"
    "   mcr p15, 0, %1, c7, c10, 4\n"
    /*
     * Turn off coherency
     */
    "   mrc p15, 0, %0, c1, c0, 1\n"
    "   bic %0, %0, %3\n"
    "   mcr p15, 0, %0, c1, c0, 1\n"
    "   mrc p15, 0, %0, c1, c0, 0\n"
    "   bic %0, %0, %2\n"
    "   mcr p15, 0, %0, c1, c0, 0\n"
      : "=&r" (v)
      : "r" (0), "Ir" (CR_C), "Ir" (0x40)
      : "cc");
}

static inline void cpu_leave_lowpower(void)
{
    unsigned int v;

    asm volatile(
        "mrc    p15, 0, %0, c1, c0, 0\n"
    "   orr %0, %0, %1\n"
    "   mcr p15, 0, %0, c1, c0, 0\n"
    "   mrc p15, 0, %0, c1, c0, 1\n"
    "   orr %0, %0, %2\n"
    "   mcr p15, 0, %0, c1, c0, 1\n"
      : "=&r" (v)
      : "Ir" (CR_C), "Ir" (0x40)
      : "cc");
}

static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
{
    /*
     * there is no power-control hardware on this platform, so all
     * we can do is put the core into WFI; this is safe as the calling
     * code will have already disabled interrupts
     */
    for (;;) {
        wfi();

        if (pen_release == cpu_logical_map(cpu)) {
            /*
             * OK, proper wakeup, we're done
             */
            break;
        }

        /*
         * Getting here, means that we have come out of WFI without
         * having been woken up - this shouldn't happen
         *
         * Just note it happening - when we're woken, we can report
         * its occurrence.
         */
        (*spurious)++;
    }
}

/*
 * platform-specific code to shutdown a CPU
 *
 * Called with IRQs disabled
 */
void __ref vexpress_cpu_die(unsigned int cpu)
{
    int spurious = 0;

    /*
     * we're ready for shutdown now, so do it
     */
    cpu_enter_lowpower();
    platform_do_lowpower(cpu, &spurious);

    /*
     * bring this CPU back into the world of cache
     * coherency, and then restore interrupts
     */
    cpu_leave_lowpower();

    if (spurious)
        pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
}