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Date: Fri, 2 Oct 2015 10:10:15 +0200
From: Tomeu Vizoso <tomeu.vizoso@...labora.com>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
Alan Stern <stern@...land.harvard.edu>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
martyn.welch@...labora.co.uk,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Len Brown <len.brown@...el.com>,
Kevin Hilman <khilman@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Pavel Machek <pavel@....cz>
Subject: Re: [PATCH v8 3/4] PM / sleep: Go direct_complete if driver has no callbacks
On 2 October 2015 at 09:48, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> On 2 October 2015 at 09:14, Tomeu Vizoso <tomeu.vizoso@...labora.com> wrote:
>> If a suitable prepare callback cannot be found for a given device and
>> its driver has no PM callbacks at all, assume that it can go direct to
>> complete when the system goes to sleep.
>>
>> The reason for this is that there's lots of devices in a system that do
>> no PM at all and there's no reason for them to prevent their ancestors
>> to do direct_complete if they can support it.
>>
>> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
>> ---
>>
>> Changes in v8:
>> - Move no_pm_callbacks field into CONFIG_PM_SLEEP
>> - Call device_check_pm_callbacks only after a device is bound or unbound
>
> Devices that don't use a driver, will not get this feature for "free".
> I expect in those cases, they will have to call
> device_check_pm_callbacks() themselves, right?
You are right, but wonder if we shouldn't go back to calling
device_check_pm_callbacks() from device_pm_add() and
dev_pm_domain_set() so they don't have to.
Thanks,
Tomeu
> Perhaps we should mention that, at least in the change log.
>
>>
>> Changes in v7:
>> - Reduce indentation by adding a label in device_prepare()
>>
>> Changes in v6:
>> - Add stub for !CONFIG_PM.
>> - Move implementation of device_check_pm_callbacks to power/main.c as it
>> doesn't belong to CONFIG_PM_SLEEP.
>> - Take dev->power.lock before modifying flag.
>>
>> Changes in v5:
>> - Check for all dev_pm_ops instances associated to a device, updating a
>> no_pm_callbacks flag at the times when that could change.
>>
>> drivers/base/dd.c | 3 +++
>> drivers/base/power/domain.c | 2 ++
>> drivers/base/power/main.c | 33 +++++++++++++++++++++++++++++++++
>> drivers/base/power/power.h | 6 ++++++
>> include/linux/pm.h | 1 +
>> 5 files changed, 45 insertions(+)
>>
>> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
>> index f2007fa7316f..2e3809affb06 100644
>> --- a/drivers/base/dd.c
>> +++ b/drivers/base/dd.c
>> @@ -210,6 +210,8 @@ static void driver_bound(struct device *dev)
>>
>> klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
>>
>> + device_check_pm_callbacks(dev);
>> +
>> /*
>> * Make sure the device is no longer in one of the deferred lists and
>> * kick off retrying all pending devices
>> @@ -700,6 +702,7 @@ static void __device_release_driver(struct device *dev)
>> dev->pm_domain->dismiss(dev);
>>
>> klist_remove(&dev->p->knode_driver);
>> + device_check_pm_callbacks(dev);
>> if (dev->bus)
>> blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
>> BUS_NOTIFY_UNBOUND_DRIVER,
>> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>> index b75d02aa8d93..9dc1ce9c573b 100644
>> --- a/drivers/base/power/domain.c
>> +++ b/drivers/base/power/domain.c
>> @@ -20,6 +20,8 @@
>> #include <linux/suspend.h>
>> #include <linux/export.h>
>>
>> +#include "power.h"
>> +
>
> Seems like a leftover from the earlier version of the patch...
>
>> #define GENPD_RETRY_MAX_MS 250 /* Approximate */
>>
>> #define GENPD_DEV_CALLBACK(genpd, type, callback, dev) \
>> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
>> index 1710c26ba097..43b44f8251c7 100644
>> --- a/drivers/base/power/main.c
>> +++ b/drivers/base/power/main.c
>> @@ -1569,6 +1569,11 @@ static int device_prepare(struct device *dev, pm_message_t state)
>>
>> dev->power.wakeup_path = device_may_wakeup(dev);
>>
>> + if (dev->power.no_pm_callbacks) {
>> + ret = 1; /* Let device go direct_complete */
>> + goto unlock;
>> + }
>> +
>> if (dev->pm_domain) {
>> info = "preparing power domain ";
>> callback = dev->pm_domain->ops.prepare;
>> @@ -1591,6 +1596,7 @@ static int device_prepare(struct device *dev, pm_message_t state)
>> if (callback)
>> ret = callback(dev);
>>
>> +unlock:
>> device_unlock(dev);
>>
>> if (ret < 0) {
>> @@ -1719,3 +1725,30 @@ void dpm_for_each_dev(void *data, void (*fn)(struct device *, void *))
>> device_pm_unlock();
>> }
>> EXPORT_SYMBOL_GPL(dpm_for_each_dev);
>> +
>> +static bool pm_ops_is_empty(const struct dev_pm_ops *ops)
>> +{
>> + if (!ops)
>> + return true;
>> +
>> + return !ops->prepare &&
>> + !ops->suspend &&
>> + !ops->suspend_late &&
>> + !ops->suspend_noirq &&
>> + !ops->resume_noirq &&
>> + !ops->resume_early &&
>> + !ops->resume &&
>> + !ops->complete;
>> +}
>> +
>> +void device_check_pm_callbacks(struct device *dev)
>> +{
>> + spin_lock_irq(&dev->power.lock);
>> + dev->power.no_pm_callbacks =
>> + (!dev->bus || pm_ops_is_empty(dev->bus->pm)) &&
>> + (!dev->class || pm_ops_is_empty(dev->class->pm)) &&
>> + (!dev->type || pm_ops_is_empty(dev->type->pm)) &&
>> + (!dev->pm_domain || pm_ops_is_empty(&dev->pm_domain->ops)) &&
>> + (!dev->driver || pm_ops_is_empty(dev->driver->pm));
>> + spin_unlock_irq(&dev->power.lock);
>> +}
>> diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h
>> index 998fa6b23084..b3e35e825cd8 100644
>> --- a/drivers/base/power/power.h
>> +++ b/drivers/base/power/power.h
>> @@ -37,6 +37,8 @@ extern void device_wakeup_detach_irq(struct device *dev);
>> extern void device_wakeup_arm_wake_irqs(void);
>> extern void device_wakeup_disarm_wake_irqs(void);
>>
>> +extern void device_check_pm_callbacks(struct device *dev);
>> +
>> #else
>>
>> static inline int
>> @@ -58,6 +60,10 @@ static inline void device_wakeup_disarm_wake_irqs(void)
>> {
>> }
>>
>> +static inline void device_check_pm_callbacks(struct device *dev)
>> +{
>> +}
>> +
>> #endif /* CONFIG_PM_SLEEP */
>>
>> /*
>> diff --git a/include/linux/pm.h b/include/linux/pm.h
>> index 35d599e7250d..7943acb74ae4 100644
>> --- a/include/linux/pm.h
>> +++ b/include/linux/pm.h
>> @@ -573,6 +573,7 @@ struct dev_pm_info {
>> struct wakeup_source *wakeup;
>> bool wakeup_path:1;
>> bool syscore:1;
>> + bool no_pm_callbacks:1; /* Owned by the PM core */
>> #else
>> unsigned int should_wakeup:1;
>> #endif
>> --
>> 2.4.3
>>
>
> Kind regards
> Uffe
> --
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