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Date: Mon, 05 May 2014 20:46:20 +0800
From: "Li, Aubrey" <aubrey.li@...ux.intel.com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Linux PM list <linux-pm@...r.kernel.org>
CC: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Zhang Rui <rui.zhang@...el.com>,
Aubrey Li <aubrey.li@...el.com>
Subject: Re: [PATCH] PM / suspend: Always use deepest C-state in the "freeze"
sleep state
On 2014/5/5 6:51, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> If freeze_enter() is called, we want to bypass the current cpuidle
> governor and always use the deepest available (that is, not disabled)
> C-state, because we want to save as much energy as reasonably possible
> then and runtime latency constraints don't matter at that point, since
> the system is in a sleep state anyway.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>
> This is on top of https://patchwork.kernel.org/patch/4071541/ .
>
> ---
> drivers/cpuidle/cpuidle.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
> include/linux/cpuidle.h | 2 ++
> kernel/power/suspend.c | 2 ++
> 3 files changed, 48 insertions(+), 1 deletion(-)
>
> Index: linux-pm/drivers/cpuidle/cpuidle.c
> ===================================================================
> --- linux-pm.orig/drivers/cpuidle/cpuidle.c
> +++ linux-pm/drivers/cpuidle/cpuidle.c
> @@ -32,6 +32,7 @@ LIST_HEAD(cpuidle_detected_devices);
> static int enabled_devices;
> static int off __read_mostly;
> static int initialized __read_mostly;
> +static bool use_deepest_state __read_mostly;
>
> int cpuidle_disabled(void)
> {
> @@ -65,6 +66,45 @@ int cpuidle_play_dead(void)
> }
>
> /**
> + * cpuidle_use_deepest_state - Enable/disable the "deepest idle" mode.
> + * @enable: Whether enable or disable the feature.
> + *
> + * If the "deepest idle" mode is enabled, cpuidle will ignore the governor and
> + * always use the state with the greatest exit latency (out of the states that
> + * are not disabled).
> + *
> + * This function can only be called after cpuidle_pause() to avoid races.
> + */
> +void cpuidle_use_deepest_state(bool enable)
> +{
> + use_deepest_state = enable;
> +}
> +
> +/**
> + * cpuidle_find_deepest_state - Find the state of the greatest exit latency.
> + * @drv: cpuidle driver for a given CPU.
> + * @dev: cpuidle device for a given CPU.
> + */
> +static int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
> + struct cpuidle_device *dev)
> +{
> + unsigned int latency_req = 0;
> + int i, ret = CPUIDLE_DRIVER_STATE_START - 1;
> +
> + for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) {
> + struct cpuidle_state *s = &drv->states[i];
> + struct cpuidle_state_usage *su = &dev->states_usage[i];
> +
> + if (s->disabled || su->disable || s->exit_latency <= latency_req)
> + continue;
> +
> + latency_req = s->exit_latency;
> + ret = i;
> + }
> + return ret;
> +}
> +
> +/**
> * cpuidle_enter_state - enter the state and update stats
> * @dev: cpuidle device for this cpu
> * @drv: cpuidle driver for this cpu
> @@ -124,6 +164,9 @@ int cpuidle_select(struct cpuidle_driver
> if (!drv || !dev || !dev->enabled)
> return -EBUSY;
>
> + if (unlikely(use_deepest_state))
> + return cpuidle_find_deepest_state(drv, dev);
> +
> return cpuidle_curr_governor->select(drv, dev);
> }
>
> @@ -155,7 +198,7 @@ int cpuidle_enter(struct cpuidle_driver
> */
> void cpuidle_reflect(struct cpuidle_device *dev, int index)
> {
> - if (cpuidle_curr_governor->reflect)
> + if (cpuidle_curr_governor->reflect && !unlikely(use_deepest_state))
> cpuidle_curr_governor->reflect(dev, index);
> }
>
> Index: linux-pm/include/linux/cpuidle.h
> ===================================================================
> --- linux-pm.orig/include/linux/cpuidle.h
> +++ linux-pm/include/linux/cpuidle.h
> @@ -143,6 +143,7 @@ extern void cpuidle_resume(void);
> extern int cpuidle_enable_device(struct cpuidle_device *dev);
> extern void cpuidle_disable_device(struct cpuidle_device *dev);
> extern int cpuidle_play_dead(void);
> +extern void cpuidle_use_deepest_state(bool enable);
>
> extern struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev);
> #else
> @@ -175,6 +176,7 @@ static inline int cpuidle_enable_device(
> {return -ENODEV; }
> static inline void cpuidle_disable_device(struct cpuidle_device *dev) { }
> static inline int cpuidle_play_dead(void) {return -ENODEV; }
> +static inline void cpuidle_use_deepest_state(bool enable) {}
> static inline struct cpuidle_driver *cpuidle_get_cpu_driver(
> struct cpuidle_device *dev) {return NULL; }
> #endif
> Index: linux-pm/kernel/power/suspend.c
> ===================================================================
> --- linux-pm.orig/kernel/power/suspend.c
> +++ linux-pm/kernel/power/suspend.c
> @@ -54,9 +54,11 @@ static void freeze_begin(void)
>
> static void freeze_enter(void)
> {
> + cpuidle_use_deepest_state(true);
> cpuidle_resume();
> wait_event(suspend_freeze_wait_head, suspend_freeze_wake);
> cpuidle_pause();
> + cpuidle_use_deepest_state(false);
> }
>
> void freeze_wake(void)
>
Tested-by: Aubrey Li <aubrey.li@...ux.intel.com>
I tested freeze mode on ASUS-T100, it works as expected. Thanks Rafael!
-Aubrey
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