Message-ID: <4E6EED5B.3050304@ti.com>
Date:	Tue, 13 Sep 2011 11:12:51 +0530
From:	Santosh <santosh.shilimkar@...com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux@....linux.org.uk, ccross@...roid.com, rjw@...k.pl,
	khilman@...com, linux-arch@...r.kernel.org
Subject: Re: [PATCH v2 1/5] cpu_pm: Add cpu power management notifiers

( CC'ing linux-arch@...r.kernel.org)

On Monday 12 September 2011 10:32 AM, Santosh wrote:
> On Saturday 10 September 2011 03:01 PM, Santosh wrote:
>> Andrew,
>>
>> On Saturday 10 September 2011 04:26 AM, Andrew Morton wrote:
>>> On Sat, 3 Sep 2011 20:09:11 +0530
>>> Santosh Shilimkar<santosh.shilimkar@...com> wrote:
>>
>> [...]
>>
>>>
>>> Have you identified which indivudual you hope/expect to merge this into
>>> mainline?
>>>
>>> The code is presumably and hopefully applicable to architectures other
>>> than ARM, yes? Can you suggest likely candidate architectures so we
>>> can go off and bug the relevant maintainers to review it?
>>>
>> Sorry I missed above question in last email. Am not too sure but any
>> arch which has CPU local timers, interrupt controller, Floating point
>> co-processor etc, should be able to make use of it. So it's applicable
>> to any architecture, but whether they want to use it, i don't know.
>>
>> As you noticed most of the ARM machine's are adapting to it.
>> Along with generic patch, there are couple ARM drivers adapting
>> to make use of it. That was the reason I was pushing this series
>> via Russell's tree.
>>
> Here is an updated patch addressing your comments.
> Attaching the same in case mailer eats spaces.
>
>  From 6a0ef5d42da459d9eba0a5f396e6d9a95d3f94ff Mon Sep 17 00:00:00 2001
> From: Colin Cross <ccross@...roid.com>
> Date: Thu, 10 Feb 2011 02:04:45 -0800
> Subject: [PATCH 1/5] cpu_pm: Add cpu power management notifiers
>
> 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.
>
> Notified drivers can include VFP co-processor, interrupt controller
> and it's PM extensions, local CPU timers context save/restore which
> shouldn't be interrupted. Hence CPU PM event APIs must be called
> with interrupts disabled.
>
> Signed-off-by: Colin Cross <ccross@...roid.com>
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...com>
> Reviewed-by: Kevin Hilman <khilman@...com>
> Tested-and-Acked-by: Shawn Guo <shawn.guo@...aro.org>
> Tested-by: Kevin Hilman <khilman@...com>
> ---
> include/linux/cpu_pm.h | 109 ++++++++++++++++++++++++++
> kernel/Makefile | 1 +
> kernel/cpu_pm.c | 200 ++++++++++++++++++++++++++++++++++++++++++++++++
> kernel/power/Kconfig | 4 +
> 4 files changed, 314 insertions(+), 0 deletions(-)
> create mode 100644 include/linux/cpu_pm.h
> create mode 100644 kernel/cpu_pm.c
>
> diff --git a/include/linux/cpu_pm.h b/include/linux/cpu_pm.h
> new file mode 100644
> index 0000000..455b233
> --- /dev/null
> +++ b/include/linux/cpu_pm.h
> @@ -0,0 +1,109 @@
> +/*
> + * Copyright (C) 2011 Google, Inc.
> + *
> + * Author:
> + * Colin Cross <ccross@...roid.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 _LINUX_CPU_PM_H
> +#define _LINUX_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,
> + * interrupt 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
> + * cluster 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 cluster 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_CLUSTER_PM_ENTER,
> +
> + /* A cpu power domain failed to enter a low power state */
> + CPU_CLUSTER_PM_ENTER_FAILED,
> +
> + /* A cpu power domain is exiting a low power state */
> + CPU_CLUSTER_PM_EXIT,
> +};
> +
> +#ifdef CONFIG_CPU_PM
> +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_cluster_pm_enter(void);
> +int cpu_cluster_pm_exit(void);
> +
> +#else
> +
> +static inline int cpu_pm_register_notifier(struct notifier_block *nb)
> +{
> + return 0;
> +}
> +
> +static inline int cpu_pm_unregister_notifier(struct notifier_block *nb)
> +{
> + return 0;
> +}
> +
> +static inline int cpu_pm_enter(void)
> +{
> + return 0;
> +}
> +
> +static inline int cpu_pm_exit(void)
> +{
> + return 0;
> +}
> +
> +static inline int cpu_cluster_pm_enter(void)
> +{
> + return 0;
> +}
> +
> +static inline int cpu_cluster_pm_exit(void)
> +{
> + return 0;
> +}
> +#endif
> +#endif
> diff --git a/kernel/Makefile b/kernel/Makefile
> index eca595e..988cb3d 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -101,6 +101,7 @@ obj-$(CONFIG_RING_BUFFER) += trace/
> obj-$(CONFIG_TRACEPOINTS) += trace/
> obj-$(CONFIG_SMP) += sched_cpupri.o
> obj-$(CONFIG_IRQ_WORK) += irq_work.o
> +obj-$(CONFIG_CPU_PM) += cpu_pm.o
>
> obj-$(CONFIG_PERF_EVENTS) += events/
>
> diff --git a/kernel/cpu_pm.c b/kernel/cpu_pm.c
> new file mode 100644
> index 0000000..4d1ff4a
> --- /dev/null
> +++ b/kernel/cpu_pm.c
> @@ -0,0 +1,200 @@
> +/*
> + * Copyright (C) 2011 Google, Inc.
> + *
> + * Author:
> + * Colin Cross <ccross@...roid.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/cpu_pm.h>
> +#include <linux/module.h>
> +#include <linux/notifier.h>
> +#include <linux/spinlock.h>
> +
> +static DEFINE_RWLOCK(cpu_pm_notifier_lock);
> +static RAW_NOTIFIER_HEAD(cpu_pm_notifier_chain);
> +
> +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);
> +}
> +
> +/**
> + * cpu_pm_register_notifier - register a driver with cpu_pm
> + * @nb: notifier block to register
> + *
> + * Add a driver to a list of drivers that are notified about
> + * CPU and CPU cluster low power entry and exit.
> + *
> + * This function may sleep, and has the same return conditions as
> + * raw_notifier_chain_register.
> + */
> +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);
> +
> +/**
> + * cpu_pm_unregister_notifier - unregister a driver with cpu_pm
> + * @nb: notifier block to be unregistered
> + *
> + * Remove a driver from the CPU PM notifier list.
> + *
> + * This function may sleep, and has the same return conditions as
> + * raw_notifier_chain_unregister.
> + */
> +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);
> +
> +/**
> + * cpm_pm_enter - CPU low power entry notifier
> + *
> + * 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. Notified drivers can include VFP
> + * co-processor, interrupt controller and it's PM extensions, local CPU
> + * timers context save/restore which shouldn't be interrupted. Hence it
> + * must be called with interrupts disabled.
> + *
> + * Return conditions are same as __raw_notifier_call_chain.
> + */
> +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)
> + /*
> + * Inform listeners (nr_calls - 1) about failure of CPU PM
> + * PM entry who are notified earlier to prepare for it.
> + */
> + 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 - CPU low power exit notifier
> + *
> + * 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.
> + *
> + * Notified drivers can include VFP co-processor, interrupt controller
> + * and it's PM extensions, local CPU timers context save/restore which
> + * shouldn't be interrupted. Hence it must be called with interrupts
> disabled.
> + *
> + * Return conditions are same as __raw_notifier_call_chain.
> + */
> +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_cluster_pm_enter - CPU cluster low power entry notifier
> + *
> + * 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. Notified drivers can include VFP co-processor, interrupt
> controller
> + * and it's PM extensions, local CPU timers context save/restore which
> + * shouldn't be interrupted. Hence it must be called with interrupts
> disabled.
> + *
> + * Must be called with interrupts disabled.
> + *
> + * Return conditions are same as __raw_notifier_call_chain.
> + */
> +int cpu_cluster_pm_enter(void)
> +{
> + int nr_calls;
> + int ret = 0;
> +
> + read_lock(&cpu_pm_notifier_lock);
> + ret = cpu_pm_notify(CPU_CLUSTER_PM_ENTER, -1, &nr_calls);
> + if (ret)
> + /*
> + * Inform listeners (nr_calls - 1) about failure of CPU cluster
> + * PM entry who are notified earlier to prepare for it.
> + */
> + cpu_pm_notify(CPU_CLUSTER_PM_ENTER_FAILED, nr_calls - 1, NULL);
> + read_unlock(&cpu_pm_notifier_lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
> +
> +/**
> + * cpm_cluster_pm_exit - CPU cluster low power exit notifier
> + *
> + * Notifies listeners that all cpus in a power domain are exiting form a
> + * low power state that may have caused some blocks in the same power
> domain
> + * to reset.
> + *
> + * Must be called after cpu_pm_exit 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. Notified drivers can include VFP co-processor, interrupt
> controller
> + * and it's PM extensions, local CPU timers context save/restore which
> + * shouldn't be interrupted. Hence it must be called with interrupts
> disabled.
> + *
> + * Return conditions are same as __raw_notifier_call_chain.
> + */
> +int cpu_cluster_pm_exit(void)
> +{
> + int ret;
> +
> + read_lock(&cpu_pm_notifier_lock);
> + ret = cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL);
> + read_unlock(&cpu_pm_notifier_lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 3744c59..80a8597 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -235,3 +235,7 @@ config PM_GENERIC_DOMAINS
> config PM_GENERIC_DOMAINS_RUNTIME
> def_bool y
> depends on PM_RUNTIME && PM_GENERIC_DOMAINS
> +
> +config CPU_PM
> + bool
> + depends on SUSPEND || CPU_IDLE

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