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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2002 ARM Ltd.
* All Rights Reserved
*
* This hotplug implementation is _specific_ to the situation found on
* ARM development platforms where there is _no_ possibility of actually
* taking a CPU offline, resetting it, or otherwise. Real platforms must
* NOT copy this code.
*/
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/smp.h>
#include <asm/smp_plat.h>
#include <asm/cp15.h>
#include "platsmp.h"
static inline void versatile_immitation_enter_lowpower(unsigned int actrl_mask)
{
unsigned int v;
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" (actrl_mask)
: "cc");
}
static inline void versatile_immitation_leave_lowpower(unsigned int actrl_mask)
{
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" (actrl_mask)
: "cc");
}
static inline void versatile_immitation_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.
*
* This code should not be used outside Versatile platforms.
*/
for (;;) {
wfi();
if (versatile_cpu_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.
* This code supports immitation-style CPU hotplug for Versatile/Realview/
* Versatile Express platforms that are unable to do real CPU hotplug.
*/
void versatile_immitation_cpu_die(unsigned int cpu, unsigned int actrl_mask)
{
int spurious = 0;
versatile_immitation_enter_lowpower(actrl_mask);
versatile_immitation_do_lowpower(cpu, &spurious);
versatile_immitation_leave_lowpower(actrl_mask);
if (spurious)
pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
}
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