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Date: Tue, 18 Feb 2014 13:59:36 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Linux PM list <linux-pm@...r.kernel.org>,
Alan Stern <stern@...land.harvard.edu>,
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: [PATCH 1/3] PM / sleep: New flag to speed up suspend-resume of
suspended devices
On 17 February 2014 00:50, 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. However, at
> least in some cases, that isn't really necessary, because the wakeup
> settings may not be really different.
>
> The idea here is that subsystems should know whether or not it is
> necessary to reprogram a given device during system suspend and they
> should be able to tell the PM core about that. For this reason,
> modify the PM core so that if the .prepare() callback returns a
> positive value for certain device, the core will set a new
> power.fast_suspend flag for it. Then, if that flag is set, the core
> will skip all of the subsequent suspend callbacks for that device.
> It also will skip all of the system resume callbacks for the device
> during the subsequent system resume and pm_request_resume() will be
> executed to trigger a runtime PM resume of the device after the
> system device resume sequence has been finished.
>
> However, since parents may need to be resumed so that their children
> can be reprogrammed, make the PM core clear power.fast_suspend for
> devices whose children don't have power.fast_suspend set (the
> power.ignore_children flag doesn't matter here, because a parent
> whose children are normally ignored for runtime PM may still need to
> be accessible for their children to be prepare for system suspend
> properly).
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> drivers/base/power/main.c | 49 +++++++++++++++++++++++++++++++---------------
> include/linux/pm.h | 1
> 2 files changed, 35 insertions(+), 15 deletions(-)
>
> Index: linux-pm/drivers/base/power/main.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/main.c
> +++ linux-pm/drivers/base/power/main.c
> @@ -478,7 +478,7 @@ static int device_resume_noirq(struct de
> TRACE_DEVICE(dev);
> TRACE_RESUME(0);
>
> - if (dev->power.syscore)
> + if (dev->power.syscore || dev->power.fast_suspend)
> goto Out;
>
> if (!dev->power.is_noirq_suspended)
> @@ -599,7 +599,7 @@ static int device_resume_early(struct de
> TRACE_DEVICE(dev);
> TRACE_RESUME(0);
>
> - if (dev->power.syscore)
> + if (dev->power.syscore || dev->power.fast_suspend)
> goto Out;
>
> if (!dev->power.is_late_suspended)
> @@ -724,6 +724,11 @@ static int device_resume(struct device *
> if (dev->power.syscore)
> goto Complete;
>
> + if (dev->power.fast_suspend) {
> + pm_request_resume(dev);
> + goto Complete;
So, this will trigger an async request to runtime resume the device.
At device_complete(), we do pm_runtime_put() to return the reference
we fetched at device_prepare(), thus likely causing the device to be
runtime suspended again. Is that the expected sequence you need? Could
you elaborate why?
Kind regards
Ulf Hansson
> + }
> +
> dpm_wait(dev->parent, async);
> dpm_watchdog_set(&wd, dev);
> device_lock(dev);
> @@ -994,7 +999,7 @@ static int __device_suspend_noirq(struct
> return async_error;
> }
>
> - if (dev->power.syscore)
> + if (dev->power.syscore || dev->power.fast_suspend)
> return 0;
>
> if (dev->pm_domain) {
> @@ -1127,7 +1132,7 @@ static int __device_suspend_late(struct
> return async_error;
> }
>
> - if (dev->power.syscore)
> + if (dev->power.syscore || dev->power.fast_suspend)
> return 0;
>
> if (dev->pm_domain) {
> @@ -1296,8 +1301,10 @@ static int __device_suspend(struct devic
> * for it, this is equivalent to the device signaling wakeup, so the
> * system suspend operation should be aborted.
> */
> - if (pm_runtime_barrier(dev) && device_may_wakeup(dev))
> + if (pm_runtime_barrier(dev) && device_may_wakeup(dev)) {
> pm_wakeup_event(dev, 0);
> + dev->power.fast_suspend = false;
> + }
>
> if (pm_wakeup_pending()) {
> async_error = -EBUSY;
> @@ -1310,6 +1317,9 @@ static int __device_suspend(struct devic
> dpm_watchdog_set(&wd, dev);
> device_lock(dev);
>
> + if (dev->power.fast_suspend)
> + goto End;
> +
> if (dev->pm_domain) {
> info = "power domain ";
> callback = pm_op(&dev->pm_domain->ops, state);
> @@ -1358,9 +1368,14 @@ static int __device_suspend(struct devic
> End:
> if (!error) {
> dev->power.is_suspended = true;
> - if (dev->power.wakeup_path
> - && dev->parent && !dev->parent->power.ignore_children)
> - dev->parent->power.wakeup_path = true;
> + if (dev->parent) {
> + if (!dev->parent->power.ignore_children
> + && dev->power.wakeup_path)
> + dev->parent->power.wakeup_path = true;
> +
> + if (!dev->power.fast_suspend)
> + dev->parent->power.fast_suspend = false;
> + }
> }
>
> device_unlock(dev);
> @@ -1460,7 +1475,7 @@ static int device_prepare(struct device
> {
> int (*callback)(struct device *) = NULL;
> char *info = NULL;
> - int error = 0;
> + int ret = 0;
>
> if (dev->power.syscore)
> return 0;
> @@ -1476,6 +1491,7 @@ static int device_prepare(struct device
> device_lock(dev);
>
> dev->power.wakeup_path = device_may_wakeup(dev);
> + dev->power.fast_suspend = false;
>
> if (dev->pm_domain) {
> info = "preparing power domain ";
> @@ -1497,16 +1513,19 @@ static int device_prepare(struct device
> }
>
> if (callback) {
> - error = callback(dev);
> - suspend_report_result(callback, error);
> + ret = callback(dev);
> + suspend_report_result(callback, ret);
> }
>
> device_unlock(dev);
>
> - if (error)
> + if (ret < 0) {
> pm_runtime_put(dev);
> -
> - return error;
> + return ret;
> + } else if (ret > 0) {
> + dev->power.fast_suspend = true;
> + }
> + return 0;
> }
>
> /**
> @@ -1575,7 +1594,7 @@ EXPORT_SYMBOL_GPL(dpm_suspend_start);
>
> void __suspend_report_result(const char *function, void *fn, int ret)
> {
> - if (ret)
> + if (ret < 0)
> printk(KERN_ERR "%s(): %pF returns %d\n", function, fn, ret);
> }
> EXPORT_SYMBOL_GPL(__suspend_report_result);
> Index: linux-pm/include/linux/pm.h
> ===================================================================
> --- linux-pm.orig/include/linux/pm.h
> +++ linux-pm/include/linux/pm.h
> @@ -546,6 +546,7 @@ struct dev_pm_info {
> bool is_late_suspended:1;
> bool ignore_children:1;
> bool early_init:1; /* Owned by the PM core */
> + bool fast_suspend:1; /* Owned by the PM core */
> spinlock_t lock;
> #ifdef CONFIG_PM_SLEEP
> struct list_head entry;
>
> --
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