cpuidle.c

/*
 * Copyright (c) 2012 Linaro : Daniel Lezcano <daniel.lezcano@linaro.org> (IBM)
 *
 * Based on the work of Rickard Andersson <rickard.andersson@stericsson.com>
 * and Jonas Aaberg <jonas.aberg@stericsson.com>.
 *
 * 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/module.h>
#include <linux/cpuidle.h>
#include <linux/spinlock.h>
#include <linux/atomic.h>
#include <linux/smp.h>
#include <linux/mfd/dbx500-prcmu.h>

#include <asm/cpuidle.h>
#include <asm/proc-fns.h>

static atomic_t master = ATOMIC_INIT(0);
static DEFINE_SPINLOCK(master_lock);

static inline int ux500_enter_idle(struct cpuidle_device *dev,
				   struct cpuidle_driver *drv, int index)
{
	int this_cpu = smp_processor_id();
	bool recouple = false;

	if (atomic_inc_return(&master) == num_online_cpus()) {

		/* With this lock, we prevent the other cpu to exit and enter
		 * this function again and become the master */
		if (!spin_trylock(&master_lock))
			goto wfi;

		/* decouple the gic from the A9 cores */
		if (prcmu_gic_decouple()) {
			spin_unlock(&master_lock);
			goto out;
		}

		/* If an error occur, we will have to recouple the gic
		 * manually */
		recouple = true;

		/* At this state, as the gic is decoupled, if the other
		 * cpu is in WFI, we have the guarantee it won't be wake
		 * up, so we can safely go to retention */
		if (!prcmu_is_cpu_in_wfi(this_cpu ? 0 : 1))
			goto out;

		/* The prcmu will be in charge of watching the interrupts
		 * and wake up the cpus */
		if (prcmu_copy_gic_settings())
			goto out;

		/* Check in the meantime an interrupt did
		 * not occur on the gic ... */
		if (prcmu_gic_pending_irq())
			goto out;

		/* ... and the prcmu */
		if (prcmu_pending_irq())
			goto out;

		/* Go to the retention state, the prcmu will wait for the
		 * cpu to go WFI and this is what happens after exiting this
		 * 'master' critical section */
		if (prcmu_set_power_state(PRCMU_AP_IDLE, true, true))
			goto out;

		/* When we switch to retention, the prcmu is in charge
		 * of recoupling the gic automatically */
		recouple = false;

		spin_unlock(&master_lock);
	}
wfi:
	cpu_do_idle();
out:
	atomic_dec(&master);

	if (recouple) {
		prcmu_gic_recouple();
		spin_unlock(&master_lock);
	}

	return index;
}

static struct cpuidle_driver ux500_idle_driver = {
	.name = "ux500_idle",
	.owner = THIS_MODULE,
	.states = {
		ARM_CPUIDLE_WFI_STATE,
		{
			.enter		  = ux500_enter_idle,
			.exit_latency	  = 70,
			.target_residency = 260,
			.flags		  = CPUIDLE_FLAG_TIME_VALID |
			                    CPUIDLE_FLAG_TIMER_STOP,
			.name		  = "ApIdle",
			.desc		  = "ARM Retention",
		},
	},
	.safe_state_index = 0,
	.state_count = 2,
};

int __init ux500_idle_init(void)
{
        /* Configure wake up reasons */
	prcmu_enable_wakeups(PRCMU_WAKEUP(ARM) | PRCMU_WAKEUP(RTC) |
			     PRCMU_WAKEUP(ABB));

	return cpuidle_register(&ux500_idle_driver, NULL);
}

device_initcall(ux500_idle_init);