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ARM: CPU hotplug: add Versatile Express hotplug CPU support
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Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Russell King committed Dec 20, 2010
1 parent d445026 commit e988277
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1 change: 1 addition & 0 deletions arch/arm/mach-vexpress/Makefile
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Expand Up @@ -5,4 +5,5 @@
obj-y := v2m.o
obj-$(CONFIG_ARCH_VEXPRESS_CA9X4) += ct-ca9x4.o
obj-$(CONFIG_SMP) += platsmp.o headsmp.o
obj-$(CONFIG_HOTPLUG_CPU) += hotplug.o
obj-$(CONFIG_LOCAL_TIMERS) += localtimer.o
128 changes: 128 additions & 0 deletions arch/arm/mach-vexpress/hotplug.c
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@@ -0,0 +1,128 @@
/*
* 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>

extern volatile int pen_release;

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 (;;) {
/*
* here's the WFI
*/
asm(".word 0xe320f003\n"
:
:
: "memory", "cc");

if (pen_release == 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)++;
}
}

int platform_cpu_kill(unsigned int cpu)
{
return 1;
}

/*
* platform-specific code to shutdown a CPU
*
* Called with IRQs disabled
*/
void platform_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);
}

int platform_cpu_disable(unsigned int cpu)
{
/*
* we don't allow CPU 0 to be shutdown (it is still too special
* e.g. clock tick interrupts)
*/
return cpu == 0 ? -EPERM : 0;
}

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