[RFC PATCH 1/3] ARM: Add cpu power management notifiers

[ccross@android.com (Colin Cross)]

During some CPU power modes entered during idle, hotplug and
suspend, peripherals located in the CPU power domain, such as
the GIC, localtimers, and VFP, may be powered down.  Add a
notifier chain that allows drivers for those peripherals to
be notified before and after they may be reset.

Signed-off-by: Colin Cross <ccross@android.com>
---
 arch/arm/include/asm/cpu_pm.h |  123 +++++++++++++++++++++++++++++++++++++++++
 arch/arm/kernel/Makefile      |    1 +
 arch/arm/kernel/cpu_pm.c      |  116 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 240 insertions(+), 0 deletions(-)
 create mode 100644 arch/arm/include/asm/cpu_pm.h
 create mode 100644 arch/arm/kernel/cpu_pm.c

diff --git a/arch/arm/include/asm/cpu_pm.h b/arch/arm/include/asm/cpu_pm.h
new file mode 100644
index 0000000..07b1b6e
--- /dev/null
+++ b/arch/arm/include/asm/cpu_pm.h
@@ -0,0 +1,123 @@
+/*
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * Author:
+ *	Colin Cross <ccross@android.com>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _ASMARM_CPU_PM_H
+#define _ASMARM_CPU_PM_H
+
+#include <linux/kernel.h>
+#include <linux/notifier.h>
+
+/*
+ * When a CPU goes to a low power state that turns off power to the CPU's
+ * power domain, the contents of some blocks (floating point coprocessors,
+ * interrutp controllers, caches, timers) in the same power domain can
+ * be lost.  The cpm_pm notifiers provide a method for platform idle, suspend,
+ * and hotplug implementations to notify the drivers for these blocks that
+ * they may be reset.
+ *
+ * All cpu_pm notifications must be called with interrupts disabled.
+ *
+ * The notifications are split into two classes, CPU notifications and CPU
+ * complex notifications.
+ *
+ * CPU notifications apply to a single CPU, and must be called on the affected
+ * CPU.  They are used to save per-cpu context for affected blocks.
+ *
+ * CPU complex notifications apply to all CPUs in a single power domain. They
+ * are used to save any global context for affected blocks, and must be called
+ * after all the CPUs in the power domain have been notified of the low power
+ * state.
+ *
+ */
+
+/*
+ * Event codes passed as unsigned long val to notifier calls
+ */
+enum cpu_pm_event {
+	/* A single cpu is entering a low power state */
+	CPU_PM_ENTER,
+
+	/* A single cpu failed to enter a low power state */
+	CPU_PM_ENTER_FAILED,
+
+	/* A single cpu is exiting a low power state */
+	CPU_PM_EXIT,
+
+	/* A cpu power domain is entering a low power state */
+	CPU_COMPLEX_PM_ENTER,
+
+	/* A cpu power domain failed to enter a low power state */
+	CPU_COMPLEX_PM_ENTER_FAILED,
+
+	/* A cpu power domain is exiting a low power state */
+	CPU_COMPLEX_PM_EXIT,
+};
+
+int cpu_pm_register_notifier(struct notifier_block *nb);
+int cpu_pm_unregister_notifier(struct notifier_block *nb);
+
+/*
+ * cpm_pm_enter
+ *
+ * Notifies listeners that a single cpu is entering a low power state that may
+ * cause some blocks in the same power domain as the cpu to reset.
+ *
+ * Must be called on the affected cpu with interrupts disabled.  Platform is
+ * responsible for ensuring that cpu_pm_enter is not called twice on the same
+ * cpu before cpu_pm_exit is called.
+ */
+int cpu_pm_enter(void);
+
+/*
+ * cpm_pm_exit
+ *
+ * Notifies listeners that a single cpu is exiting a low power state that may
+ * have caused some blocks in the same power domain as the cpu to reset.
+ *
+ * Must be called on the affected cpu with interrupts disabled.
+ */
+int cpu_pm_exit(void);
+
+/*
+ * cpm_complex_pm_enter
+ *
+ * Notifies listeners that all cpus in a power domain are entering a low power
+ * state that may cause some blocks in the same power domain to reset.
+ *
+ * Must be called after cpu_pm_enter has been called on all cpus in the power
+ * domain, and before cpu_pm_exit has been called on any cpu in the power
+ * domain.
+ *
+ * Must be called with interrupts disabled.
+ */
+int cpu_complex_pm_enter(void);
+
+/*
+ * cpm_pm_enter
+ *
+ * Notifies listeners that a single cpu is entering a low power state that may
+ * cause some blocks in the same power domain as the cpu to reset.
+ *
+ * Must be called after cpu_pm_enter has been called on all cpus in the power
+ * domain, and before cpu_pm_exit has been called on any cpu in the power
+ * domain.
+ *
+ * Must be called with interrupts disabled.
+ */
+int cpu_complex_pm_exit(void);
+
+#endif
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 185ee82..b0f25cb 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -58,6 +58,7 @@ obj-$(CONFIG_CPU_PJ4)		+= pj4-cp0.o
 obj-$(CONFIG_IWMMXT)		+= iwmmxt.o
 obj-$(CONFIG_CPU_HAS_PMU)	+= pmu.o
 obj-$(CONFIG_HW_PERF_EVENTS)	+= perf_event.o
+obj-$(CONFIG_CPU_IDLE)		+= cpu_pm.o
 AFLAGS_iwmmxt.o			:= -Wa,-mcpu=iwmmxt
 
 ifneq ($(CONFIG_ARCH_EBSA110),y)
diff --git a/arch/arm/kernel/cpu_pm.c b/arch/arm/kernel/cpu_pm.c
new file mode 100644
index 0000000..9a04ba1
--- /dev/null
+++ b/arch/arm/kernel/cpu_pm.c
@@ -0,0 +1,116 @@
+/*
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * Author:
+ *	Colin Cross <ccross@android.com>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/notifier.h>
+#include <linux/smp.h>
+
+#include <asm/cpu_pm.h>
+
+static DEFINE_SPINLOCK(idle_notifier_lock);
+static RAW_NOTIFIER_HEAD(idle_notifier_chain);
+
+int cpu_pm_register_notifier(struct notifier_block *nb)
+{
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&idle_notifier_lock, flags);
+	ret = raw_notifier_chain_register(&idle_notifier_chain, nb);
+	spin_unlock_irqrestore(&idle_notifier_lock, flags);
+
+	return ret;
+}
+
+int cpu_pm_unregister_notifier(struct notifier_block *nb)
+{
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&idle_notifier_lock, flags);
+	ret = raw_notifier_chain_unregister(&idle_notifier_chain, nb);
+	spin_unlock_irqrestore(&idle_notifier_lock, flags);
+
+	return ret;
+}
+
+static int __idle_notify(enum cpu_pm_event event, int nr_to_call,
+	int *nr_calls)
+{
+	int ret;
+
+	ret = __raw_notifier_call_chain(&idle_notifier_chain, event, NULL,
+		nr_to_call, nr_calls);
+
+	return notifier_to_errno(ret);
+}
+
+int cpu_pm_enter(void)
+{
+	int nr_calls;
+	int ret;
+
+	spin_lock(&idle_notifier_lock);
+	ret = __idle_notify(CPU_PM_ENTER, -1, &nr_calls);
+	if (ret) {
+		__idle_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL);
+		spin_unlock(&idle_notifier_lock);
+		return ret;
+	}
+	spin_unlock(&idle_notifier_lock);
+
+	return 0;
+}
+
+int cpu_pm_exit(void)
+{
+	int ret;
+
+	spin_lock(&idle_notifier_lock);
+	ret = __idle_notify(CPU_PM_EXIT, -1, NULL);
+	spin_unlock(&idle_notifier_lock);
+
+	return ret;
+}
+
+int cpu_complex_pm_enter(void)
+{
+	int nr_calls;
+	int ret;
+
+	spin_lock(&idle_notifier_lock);
+	ret = __idle_notify(CPU_COMPLEX_PM_ENTER, -1, &nr_calls);
+	if (ret) {
+		__idle_notify(CPU_COMPLEX_PM_ENTER_FAILED, nr_calls - 1, NULL);
+		spin_unlock(&idle_notifier_lock);
+		return ret;
+	}
+	spin_unlock(&idle_notifier_lock);
+
+	return 0;
+}
+
+int cpu_complex_pm_exit(void)
+{
+	int ret;
+
+	spin_lock(&idle_notifier_lock);
+	ret = __idle_notify(CPU_COMPLEX_PM_EXIT, -1, NULL);
+	spin_unlock(&idle_notifier_lock);
+
+	return ret;
+}
-- 
1.7.3.1