Commit b1d4c6ca authored by James Hogan's avatar James Hogan Committed by Paul Burton
Browse files

MIPS: PM: Add CPU PM callbacks for general CPU context 



Add a CPU power management notifier callback for preserving general CPU
context. The CPU PM callbacks will be triggered by the powering down of
CPU cores, for example by cpuidle drivers & in the future by suspend to
RAM implementations.

The current state preserved is mostly related to the process context:
- FPU
- DSP
- ASID
- UserLocal
- Watch registers

Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Signed-off-by: default avatarPaul Burton <paul.burton@imgtec.com>
parent a798c10f

arch/mips/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -50,6 +50,7 @@ config MIPS 
	select CLONE_BACKWARDS

	select HAVE_DEBUG_STACKOVERFLOW

	select HAVE_CC_STACKPROTECTOR

	select CPU_PM if CPU_IDLE



menu "Machine selection"

arch/mips/kernel/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -107,6 +107,8 @@ obj-$(CONFIG_JUMP_LABEL) += jump_label.o 
obj-$(CONFIG_MIPS_CM)		+= mips-cm.o

obj-$(CONFIG_MIPS_CPC)		+= mips-cpc.o



obj-$(CONFIG_CPU_PM)		+= pm.o



#

# DSP ASE supported for MIPS32 or MIPS64 Release 2 cores only. It is not

# safe to unconditionnaly use the assembler -mdsp / -mdspr2 switches

arch/mips/kernel/pm.c

0 → 100644
+95 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2014 Imagination Technologies Ltd.

 *

 * This program is free software; you can redistribute	it and/or modify it

 * under  the terms of	the GNU General	 Public License as published by the

 * Free Software Foundation;  either version 2 of the  License, or (at your

 * option) any later version.

 *

 * CPU PM notifiers for saving/restoring general CPU state.

 */



#include <linux/cpu_pm.h>

#include <linux/init.h>



#include <asm/dsp.h>

#include <asm/fpu.h>

#include <asm/mmu_context.h>

#include <asm/watch.h>



/**

 * mips_cpu_save() - Save general CPU state.

 * Ensures that general CPU context is saved, notably FPU and DSP.

 */

static int mips_cpu_save(void)

{

	/* Save FPU state */

	lose_fpu(1);



	/* Save DSP state */

	save_dsp(current);



	return 0;

}



/**

 * mips_cpu_restore() - Restore general CPU state.

 * Restores important CPU context.

 */

static void mips_cpu_restore(void)

{

	unsigned int cpu = smp_processor_id();



	/* Restore ASID */

	if (current->mm)

		write_c0_entryhi(cpu_asid(cpu, current->mm));



	/* Restore DSP state */

	restore_dsp(current);



	/* Restore UserLocal */

	if (cpu_has_userlocal)

		write_c0_userlocal(current_thread_info()->tp_value);



	/* Restore watch registers */

	__restore_watch();

}



/**

 * mips_pm_notifier() - Notifier for preserving general CPU context.

 * @self:	Notifier block.

 * @cmd:	CPU PM event.

 * @v:		Private data (unused).

 *

 * This is called when a CPU power management event occurs, and is used to

 * ensure that important CPU context is preserved across a CPU power down.

 */

static int mips_pm_notifier(struct notifier_block *self, unsigned long cmd,

			    void *v)

{

	int ret;



	switch (cmd) {

	case CPU_PM_ENTER:

		ret = mips_cpu_save();

		if (ret)

			return NOTIFY_STOP;

		break;

	case CPU_PM_ENTER_FAILED:

	case CPU_PM_EXIT:

		mips_cpu_restore();

		break;

	}



	return NOTIFY_OK;

}



static struct notifier_block mips_pm_notifier_block = {

	.notifier_call = mips_pm_notifier,

};



static int __init mips_pm_init(void)

{

	return cpu_pm_register_notifier(&mips_pm_notifier_block);

}

arch_initcall(mips_pm_init);

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