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Message-ID: <CAPDyKFoYsKunfo1Vzp3U-QDZVg97m31taKG3ZuW_86Bt3xWPog@mail.gmail.com>
Date: Thu, 8 May 2014 09:49:36 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Alan Stern <stern@...land.harvard.edu>,
Linux PM list <linux-pm@...r.kernel.org>,
Mika Westerberg <mika.westerberg@...ux.intel.com>,
Aaron Lu <aaron.lu@...el.com>,
ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 1/3] PM / sleep: Flag to speed up suspend-resume of
runtime-suspended devices
On 8 May 2014 01:29, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Currently, some subsystems (e.g. PCI and the ACPI PM domain) have to
> resume all runtime-suspended devices during system suspend, mostly
> because those devices may need to be reprogrammed due to different
> wakeup settings for system sleep and for runtime PM.
>
> For some devices, though, it's OK to remain in runtime suspend
> throughout a complete system suspend/resume cycle (if the device was in
> runtime suspend at the start of the cycle). We would like to do this
> whenever possible, to avoid the overhead of extra power-up and power-down
> events.
>
> However, problems may arise because the device's descendants may require
> it to be at full power at various points during the cycle. Therefore the
> most straightforward way to do this safely is if the device and all its
> descendants can remain runtime suspended until the resume stage of system
> resume.
>
> To this end, introduce dev->power.leave_runtime_suspended.
> If a subsystem or driver sets this flag during the ->prepare() callback,
> and if the flag is set in all of the device's descendants, and if the
> device is still in runtime suspend at the beginning of the ->suspend()
> callback, that callback is allowed to return 0 without clearing
> power.leave_runtime_suspended and without changing the state of the
> device, unless the current state of the device is not appropriate for
> the upcoming system sleep state (for example, the device is supposed to
> wake up the system from that state and its current wakeup settings are
> not suitable for that). Then, the PM core will not invoke the device's
> ->suspend_late(), ->suspend_irq(), ->resume_irq(), ->resume_early(), or
> ->resume() callbacks. Instead, it will invoke ->runtime_resume() during
> the device resume stage of system resume.
>
> By leaving this flag set after ->suspend(), a driver or subsystem tells
> the PM core that the device is runtime suspended, it is in a suitable
> state for system suspend (for example, the wakeup setting does not
> need to be changed), and it does not need to return to full
> power until the resume stage.
>
> Changelog based on an Alan Stern's description of the idea
> (http://marc.info/?l=linux-pm&m=139940466625569&w=2).
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> drivers/base/power/main.c | 31 ++++++++++++++++++++++++-------
> drivers/base/power/runtime.c | 10 ++++++++++
> include/linux/pm.h | 3 +++
> include/linux/pm_runtime.h | 16 ++++++++++++++++
> kernel/power/Kconfig | 4 ++++
> 5 files changed, 57 insertions(+), 7 deletions(-)
>
> Index: linux-pm/kernel/power/Kconfig
> ===================================================================
> --- linux-pm.orig/kernel/power/Kconfig
> +++ linux-pm/kernel/power/Kconfig
> @@ -147,6 +147,10 @@ config PM
> def_bool y
> depends on PM_SLEEP || PM_RUNTIME
>
> +config PM_BOTH
> + def_bool y
> + depends on PM_SLEEP && PM_RUNTIME
> +
Should we not depend on PM_RUNTIME only? Thus we don't need the new
Kconfig, and then we could rename the new APIs to pm_runtime_*
instead.
> config PM_DEBUG
> bool "Power Management Debug Support"
> depends on PM
> Index: linux-pm/include/linux/pm.h
> ===================================================================
> --- linux-pm.orig/include/linux/pm.h
> +++ linux-pm/include/linux/pm.h
> @@ -583,6 +583,9 @@ struct dev_pm_info {
> unsigned long suspended_jiffies;
> unsigned long accounting_timestamp;
> #endif
> +#ifdef CONFIG_PM_BOTH
> + bool leave_runtime_suspended:1;
> +#endif
> struct pm_subsys_data *subsys_data; /* Owned by the subsystem. */
> void (*set_latency_tolerance)(struct device *, s32);
> struct dev_pm_qos *qos;
> Index: linux-pm/include/linux/pm_runtime.h
> ===================================================================
> --- linux-pm.orig/include/linux/pm_runtime.h
> +++ linux-pm/include/linux/pm_runtime.h
> @@ -264,4 +264,20 @@ static inline void pm_runtime_dont_use_a
> __pm_runtime_use_autosuspend(dev, false);
> }
>
> +#ifdef CONFIG_PM_BOTH
> +static inline void __set_leave_runtime_suspended(struct device *dev, bool val)
> +{
> + dev->power.leave_runtime_suspended = val;
> +}
> +extern void pm_set_leave_runtime_suspended(struct device *dev, bool val);
> +static inline bool pm_leave_runtime_suspended(struct device *dev)
> +{
> + return dev->power.leave_runtime_suspended;
> +}
> +#else
> +static inline void __set_leave_runtime_suspended(struct device *dev, bool val) {}
> +static inline void pm_set_leave_runtime_suspended(struct device *dev, bool val) {}
> +static inline bool pm_leave_runtime_suspended(struct device *dev) { return false; }
> +#endif
> +
> #endif
> Index: linux-pm/drivers/base/power/runtime.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/runtime.c
> +++ linux-pm/drivers/base/power/runtime.c
> @@ -732,6 +732,7 @@ static int rpm_resume(struct device *dev
> }
> skip_parent:
>
> + __set_leave_runtime_suspended(dev, false);
> if (dev->power.no_callbacks)
> goto no_callback; /* Assume success. */
>
> @@ -1485,3 +1486,12 @@ out:
> return ret;
> }
> EXPORT_SYMBOL_GPL(pm_runtime_force_resume);
> +
> +#ifdef CONFIG_PM_BOTH
> +void pm_set_leave_runtime_suspended(struct device *dev, bool val)
> +{
> + spin_lock_irq(&dev->power.lock);
> + __set_leave_runtime_suspended(dev, val);
> + spin_unlock_irq(&dev->power.lock);
> +}
> +#endif
> Index: linux-pm/drivers/base/power/main.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/main.c
> +++ linux-pm/drivers/base/power/main.c
> @@ -479,7 +479,7 @@ static int device_resume_noirq(struct de
> TRACE_DEVICE(dev);
> TRACE_RESUME(0);
>
> - if (dev->power.syscore)
> + if (dev->power.syscore || pm_leave_runtime_suspended(dev))
> goto Out;
>
> if (!dev->power.is_noirq_suspended)
> @@ -605,7 +605,7 @@ static int device_resume_early(struct de
> TRACE_DEVICE(dev);
> TRACE_RESUME(0);
>
> - if (dev->power.syscore)
> + if (dev->power.syscore || pm_leave_runtime_suspended(dev))
> goto Out;
>
> if (!dev->power.is_late_suspended)
> @@ -735,6 +735,11 @@ static int device_resume(struct device *
> if (dev->power.syscore)
> goto Complete;
>
> + if (pm_leave_runtime_suspended(dev)) {
> + pm_runtime_resume(dev);
> + goto Complete;
> + }
> +
> dpm_wait(dev->parent, async);
> dpm_watchdog_set(&wd, dev);
> device_lock(dev);
> @@ -1007,7 +1012,7 @@ static int __device_suspend_noirq(struct
> goto Complete;
> }
>
> - if (dev->power.syscore)
> + if (dev->power.syscore || pm_leave_runtime_suspended(dev))
> goto Complete;
>
> dpm_wait_for_children(dev, async);
> @@ -1146,7 +1151,7 @@ static int __device_suspend_late(struct
> goto Complete;
> }
>
> - if (dev->power.syscore)
> + if (dev->power.syscore || pm_leave_runtime_suspended(dev))
> goto Complete;
>
> dpm_wait_for_children(dev, async);
> @@ -1382,10 +1387,21 @@ static int __device_suspend(struct devic
>
> End:
> if (!error) {
> + struct device *parent = dev->parent;
> +
> dev->power.is_suspended = true;
> - if (dev->power.wakeup_path
> - && dev->parent && !dev->parent->power.ignore_children)
> - dev->parent->power.wakeup_path = true;
> + if (parent) {
> + spin_lock_irq(&parent->power.lock);
> +
> + if (dev->power.wakeup_path
> + && !parent->power.ignore_children)
> + parent->power.wakeup_path = true;
> +
> + if (!pm_leave_runtime_suspended(dev))
I suppose this is the reason to why you think you need CONFIG_PM_BOTH?
But won't this would work nicely even if we just had CONFIG_PM_RUNTIME?
> + __set_leave_runtime_suspended(parent, false);
> +
> + spin_unlock_irq(&parent->power.lock);
> + }
> }
>
> device_unlock(dev);
> @@ -1553,6 +1569,7 @@ int dpm_prepare(pm_message_t state)
> struct device *dev = to_device(dpm_list.next);
>
> get_device(dev);
> + pm_set_leave_runtime_suspended(dev, false);
Is this needed?
> mutex_unlock(&dpm_list_mtx);
>
> error = device_prepare(dev, state);
>
> --
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Kind regards
Ulf Hansson
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