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

Colin Cross
2011-06-13T00:44:37Z

During some CPU power modes entered during idle, hotplug and
suspend, peripherals located in the CPU power domain, such as
the GIC 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/Kconfig | 7 ++
arch/arm/include/asm/cpu_pm.h | 54 ++++++++++++
arch/arm/kernel/Makefile | 1 +
arch/arm/kernel/cpu_pm.c | 181 +++++++++++++++++++++++++++++++++++++++++
4 files changed, 243 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/Kconfig b/arch/arm/Kconfig
index 9adc278..356f266 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -183,6 +183,13 @@ config FIQ
config ARCH_MTD_XIP
bool

+config ARCH_USES_CPU_PM
+ bool
+
+config CPU_PM
+ def_bool y
+ depends on ARCH_USES_CPU_PM && (PM || CPU_IDLE)
+
config VECTORS_BASE
hex
default 0xffff0000 if MMU || CPU_HIGH_VECTOR
diff --git a/arch/arm/include/asm/cpu_pm.h b/arch/arm/include/asm/cpu_pm.h
new file mode 100644
index 0000000..b4bb715
--- /dev/null
+++ b/arch/arm/include/asm/cpu_pm.h
@@ -0,0 +1,54 @@
+/*
+ * 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>
+
+/* 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);
+
+int cpu_pm_enter(void);
+int cpu_pm_exit(void);
+
+int cpu_complex_pm_enter(void);
+int cpu_complex_pm_exit(void);
+
+#endif
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index a5b31af..8b42d58 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -60,6 +60,7 @@ 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_PM) += 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..48a5b53
--- /dev/null
+++ b/arch/arm/kernel/cpu_pm.c
@@ -0,0 +1,181 @@
+/*
+ * 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/module.h>
+#include <linux/notifier.h>
+#include <linux/spinlock.h>
+
+#include <asm/cpu_pm.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.
+ *
+ */
+
+static DEFINE_RWLOCK(cpu_pm_notifier_lock);
+static RAW_NOTIFIER_HEAD(cpu_pm_notifier_chain);
+
+int cpu_pm_register_notifier(struct notifier_block *nb)
+{
+ unsigned long flags;
+ int ret;
+
+ write_lock_irqsave(&cpu_pm_notifier_lock, flags);
+ ret = raw_notifier_chain_register(&cpu_pm_notifier_chain, nb);
+ write_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(cpu_pm_register_notifier);
+
+int cpu_pm_unregister_notifier(struct notifier_block *nb)
+{
+ unsigned long flags;
+ int ret;
+
+ write_lock_irqsave(&cpu_pm_notifier_lock, flags);
+ ret = raw_notifier_chain_unregister(&cpu_pm_notifier_chain, nb);
+ write_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(cpu_pm_unregister_notifier);
+
+static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls)
+{
+ int ret;
+
+ ret = __raw_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL,
+ nr_to_call, nr_calls);
+
+ return notifier_to_errno(ret);
+}
+
+/**
+ * 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)
+{
+ int nr_calls;
+ int ret = 0;
+
+ read_lock(&cpu_pm_notifier_lock);
+ ret = cpu_pm_notify(CPU_PM_ENTER, -1, &nr_calls);
+ if (ret)
+ cpu_pm_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL);
+ read_unlock(&cpu_pm_notifier_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(cpu_pm_enter);
+
+/**
+ * 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)
+{
+ int ret;
+
+ read_lock(&cpu_pm_notifier_lock);
+ ret = cpu_pm_notify(CPU_PM_EXIT, -1, NULL);
+ read_unlock(&cpu_pm_notifier_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(cpu_pm_exit);
+
+/**
+ * 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)
+{
+ int nr_calls;
+ int ret = 0;
+
+ read_lock(&cpu_pm_notifier_lock);
+ ret = cpu_pm_notify(CPU_COMPLEX_PM_ENTER, -1, &nr_calls);
+ if (ret)
+ cpu_pm_notify(CPU_COMPLEX_PM_ENTER_FAILED, nr_calls - 1, NULL);
+ read_unlock(&cpu_pm_notifier_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(cpu_complex_pm_enter);
+
+/**
+ * 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)
+{
+ int ret;
+
+ read_lock(&cpu_pm_notifier_lock);
+ ret = cpu_pm_notify(CPU_COMPLEX_PM_EXIT, -1, NULL);
+ read_unlock(&cpu_pm_notifier_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(cpu_complex_pm_exit);
--
1.7.4.1