ARM: ux500: add the cpuidle driver for WFI and ARM retention

This patch adds the cpuidle driver for the ux500 SoC.
The boards saves 12mA with these states. It is based on the latest
cpuidle consolidation from Robert Lee.

The cpu can go to retention only if the other core is in WFI.

If the other cpu is in WFI and we decoupled the gic from the cores,
then we have the guarantee, it won't be wake up.

It is up to the prcmu firmware to recouple the gic automatically
after the power state mode is selected.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

arch/arm/mach-ux500/Makefile

@@ -4,6 +4,7 @@
 
 obj-y				:= clock.o cpu.o devices.o devices-common.o \
 				   id.o usb.o timer.o
+obj-$(CONFIG_CPU_IDLE)          += cpuidle.o
 obj-$(CONFIG_CACHE_L2X0)	+= cache-l2x0.o
 obj-$(CONFIG_UX500_SOC_DB5500)	+= cpu-db5500.o dma-db5500.o
 obj-$(CONFIG_UX500_SOC_DB8500)	+= cpu-db8500.o devices-db8500.o

arch/arm/mach-ux500/cpuidle.c

@@ -0,0 +1,171 @@
+/*
+ * 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/clockchips.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 DEFINE_PER_CPU(struct cpuidle_device, ux500_cpuidle_device);
+
+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;
+
+	clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &this_cpu);
+
+	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())
+			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);
+	}
+
+	clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &this_cpu);
+
+	return index;
+}
+
+static struct cpuidle_driver ux500_idle_driver = {
+	.name = "ux500_idle",
+	.owner = THIS_MODULE,
+	.en_core_tk_irqen = 1,
+	.states = {
+		ARM_CPUIDLE_WFI_STATE,
+		{
+			.enter		  = ux500_enter_idle,
+			.exit_latency	  = 70,
+			.target_residency = 260,
+			.flags		  = CPUIDLE_FLAG_TIME_VALID,
+			.name		  = "ApIdle",
+			.desc		  = "ARM Retention",
+		},
+	},
+	.safe_state_index = 0,
+	.state_count = 2,
+};
+
+/*
+ * For each cpu, setup the broadcast timer because we will
+ * need to migrate the timers for the states >= ApIdle.
+ */
+static void ux500_setup_broadcast_timer(void *arg)
+{
+	int cpu = smp_processor_id();
+	clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ON, &cpu);
+}
+
+int __init ux500_idle_init(void)
+{
+	int ret, cpu;
+	struct cpuidle_device *device;
+
+        /* Configure wake up reasons */
+	prcmu_enable_wakeups(PRCMU_WAKEUP(ARM) | PRCMU_WAKEUP(RTC) |
+			     PRCMU_WAKEUP(ABB));
+
+	/*
+	 * Configure the timer broadcast for each cpu, that must
+	 * be done from the cpu context, so we use a smp cross
+	 * call with 'on_each_cpu'.
+	 */
+	on_each_cpu(ux500_setup_broadcast_timer, NULL, 1);
+
+	ret = cpuidle_register_driver(&ux500_idle_driver);
+	if (ret) {
+		printk(KERN_ERR "failed to register ux500 idle driver\n");
+		return ret;
+	}
+
+	for_each_online_cpu(cpu) {
+		device = &per_cpu(ux500_cpuidle_device, cpu);
+		device->cpu = cpu;
+		ret = cpuidle_register_device(device);
+		if (ret) {
+			printk(KERN_ERR "Failed to register cpuidle "
+			       "device for cpu%d\n", cpu);
+			goto out_unregister;
+		}
+	}
+out:
+	return ret;
+
+out_unregister:
+	for_each_online_cpu(cpu) {
+		device = &per_cpu(ux500_cpuidle_device, cpu);
+		cpuidle_unregister_device(device);
+	}
+
+	cpuidle_unregister_driver(&ux500_idle_driver);
+	goto out;
+}
+
+device_initcall(ux500_idle_init);