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

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
......@@ -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"
......
......@@ -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
......
/*
* 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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