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ARM: CPU hotplug: add Versatile Express hotplug CPU support
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Russell King
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Dec 20, 2010
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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> | ||
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#include <asm/cacheflush.h> | ||
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extern volatile int pen_release; | ||
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static inline void cpu_enter_lowpower(void) | ||
{ | ||
unsigned int v; | ||
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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"); | ||
} | ||
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static inline void cpu_leave_lowpower(void) | ||
{ | ||
unsigned int v; | ||
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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"); | ||
} | ||
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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"); | ||
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if (pen_release == cpu) { | ||
/* | ||
* OK, proper wakeup, we're done | ||
*/ | ||
break; | ||
} | ||
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/* | ||
* 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)++; | ||
} | ||
} | ||
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int platform_cpu_kill(unsigned int cpu) | ||
{ | ||
return 1; | ||
} | ||
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/* | ||
* platform-specific code to shutdown a CPU | ||
* | ||
* Called with IRQs disabled | ||
*/ | ||
void platform_cpu_die(unsigned int cpu) | ||
{ | ||
int spurious = 0; | ||
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/* | ||
* we're ready for shutdown now, so do it | ||
*/ | ||
cpu_enter_lowpower(); | ||
platform_do_lowpower(cpu, &spurious); | ||
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/* | ||
* bring this CPU back into the world of cache | ||
* coherency, and then restore interrupts | ||
*/ | ||
cpu_leave_lowpower(); | ||
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if (spurious) | ||
pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious); | ||
} | ||
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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; | ||
} |