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Commit 0eb03799 authored by Russell King's avatar Russell King
Browse files

ARM: oxnas: remove CPU hotplug implementation 



The CPU hotplug implementation on this platform is cargo-culted from
the plat-versatile implementation, and is buggy.  Once a CPU hits the
"low power" loop, it will wait for pen_release to be set to the CPU
number to wake up again - but nothing in this implementation does that.

So, once a CPU has entered cpu_die() it will never, ever leave.

Remove this useless cargo-culted implementation.

Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
parent d0e22329

arch/arm/mach-oxnas/Makefile

+0 −1
Original line number Diff line number Diff line 
obj-$(CONFIG_SMP)		+= platsmp.o headsmp.o
 
obj-$(CONFIG_HOTPLUG_CPU) 	+= hotplug.o

arch/arm/mach-oxnas/hotplug.c

deleted100644 → 0
+0 −109
Original line number Diff line number Diff line 
/*

 *  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/cp15.h>

#include <asm/smp_plat.h>



static inline void cpu_enter_lowpower(void)

{

	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, #0x20\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)

	  : "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, #0x20\n"

	"	mcr	p15, 0, %0, c1, c0, 1\n"

	  : "=&r" (v)

	  : "Ir" (CR_C)

	  : "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_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 ox820_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);

}

arch/arm/mach-oxnas/platsmp.c

+0 −4
Original line number Diff line number Diff line
@@ -19,7 +19,6 @@ 
#include <asm/smp_scu.h>



extern void ox820_secondary_startup(void);

extern void ox820_cpu_die(unsigned int cpu);



static void __iomem *cpu_ctrl;

static void __iomem *gic_cpu_ctrl;
@@ -94,9 +93,6 @@ static void __init ox820_smp_prepare_cpus(unsigned int max_cpus) 
static const struct smp_operations ox820_smp_ops __initconst = {

	.smp_prepare_cpus	= ox820_smp_prepare_cpus,

	.smp_boot_secondary	= ox820_boot_secondary,

#ifdef CONFIG_HOTPLUG_CPU

	.cpu_die		= ox820_cpu_die,

#endif

};



CPU_METHOD_OF_DECLARE(ox820_smp, "oxsemi,ox820-smp", &ox820_smp_ops);