Re: [PATCH v6 1/2] PM / sleep: Go direct_complete if driver has no callbacks

[Rafael J. Wysocki]

On Tuesday, September 29, 2015 05:32:53 PM Tomeu Vizoso 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@xxxxxxxxxxxxx>
> ---
> 
> 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/common.c | 27 +++++++++++++++++++++++++++
>  drivers/base/power/domain.c |  5 +++++
>  drivers/base/power/main.c   | 44 +++++++++++++++++++++++++-------------------
>  drivers/base/power/power.h  |  6 ++++++
>  include/linux/pm.h          |  1 +
>  6 files changed, 67 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index be0eb4639128..fe0e9cb684b8 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -205,6 +205,8 @@ 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
> @@ -695,6 +697,7 @@ 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/common.c b/drivers/base/power/common.c
> index f32b802b98f4..1bba85f8bf8a 100644
> --- a/drivers/base/power/common.c
> +++ b/drivers/base/power/common.c
> @@ -128,3 +128,30 @@ void dev_pm_domain_detach(struct device *dev, bool power_off)
>  		dev->pm_domain->detach(dev, power_off);
>  }
>  EXPORT_SYMBOL_GPL(dev_pm_domain_detach);
> +
> +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/domain.c b/drivers/base/power/domain.c
> index 16550c63d611..3cae1aa1885b 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"
> +
>  #define GENPD_RETRY_MAX_MS	250		/* Approximate */
>  
>  #define GENPD_DEV_CALLBACK(genpd, type, callback, dev)		\
> @@ -1305,6 +1307,7 @@ int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
>  
>  	list_add_tail(&gpd_data->base.list_node, &genpd->dev_list);
>  
> +	device_check_pm_callbacks(dev);
>   out:
>  	mutex_unlock(&genpd->lock);
>  
> @@ -1369,6 +1372,8 @@ int pm_genpd_remove_device(struct generic_pm_domain *genpd,
>  
>  	genpd_free_dev_data(dev, gpd_data);
>  
> +	device_check_pm_callbacks(dev);
> +
>  	return 0;
>  
>   out:
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index 1710c26ba097..8f9cdaf21ee4 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -131,6 +131,8 @@ void device_pm_add(struct device *dev)
>  			dev_name(dev->parent));
>  	list_add_tail(&dev->power.entry, &dpm_list);
>  	mutex_unlock(&dpm_list_mtx);
> +
> +	device_check_pm_callbacks(dev);
>  }
>  
>  /**
> @@ -1569,27 +1571,31 @@ static int device_prepare(struct device *dev, pm_message_t state)
>  
>  	dev->power.wakeup_path = device_may_wakeup(dev);
>  
> -	if (dev->pm_domain) {
> -		info = "preparing power domain ";
> -		callback = dev->pm_domain->ops.prepare;
> -	} else if (dev->type && dev->type->pm) {
> -		info = "preparing type ";
> -		callback = dev->type->pm->prepare;
> -	} else if (dev->class && dev->class->pm) {
> -		info = "preparing class ";
> -		callback = dev->class->pm->prepare;
> -	} else if (dev->bus && dev->bus->pm) {
> -		info = "preparing bus ";
> -		callback = dev->bus->pm->prepare;
> -	}
> +	if (dev->power.no_pm_callbacks)
> +		ret = 1;	/* Let device go direct_complete */

Braces here, please.

Plus I'd rather jump to a new label from here to avoid the extra indentation
and the patch would be simpler then.

> +	else {
> +		if (dev->pm_domain) {
> +			info = "preparing power domain ";
> +			callback = dev->pm_domain->ops.prepare;
> +		} else if (dev->type && dev->type->pm) {
> +			info = "preparing type ";
> +			callback = dev->type->pm->prepare;
> +		} else if (dev->class && dev->class->pm) {
> +			info = "preparing class ";
> +			callback = dev->class->pm->prepare;
> +		} else if (dev->bus && dev->bus->pm) {
> +			info = "preparing bus ";
> +			callback = dev->bus->pm->prepare;
> +		}
>  
> -	if (!callback && dev->driver && dev->driver->pm) {
> -		info = "preparing driver ";
> -		callback = dev->driver->pm->prepare;
> -	}
> +		if (!callback && dev->driver && dev->driver->pm) {
> +			info = "preparing driver ";
> +			callback = dev->driver->pm->prepare;
> +		}
>  
> -	if (callback)
> -		ret = callback(dev);
> +		if (callback)
> +			ret = callback(dev);
> +	}
>  
>  	device_unlock(dev);
>  
> diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h
> index 998fa6b23084..f665a7850016 100644
> --- a/drivers/base/power/power.h
> +++ b/drivers/base/power/power.h
> @@ -29,6 +29,8 @@ struct wake_irq {
>  extern void dev_pm_arm_wake_irq(struct wake_irq *wirq);
>  extern void dev_pm_disarm_wake_irq(struct wake_irq *wirq);
>  
> +extern void device_check_pm_callbacks(struct device *dev);
> +
>  #ifdef CONFIG_PM_SLEEP
>  
>  extern int device_wakeup_attach_irq(struct device *dev,
> @@ -102,6 +104,10 @@ static inline void dev_pm_disarm_wake_irq(struct wake_irq *wirq)
>  {
>  }
>  
> +static inline void device_check_pm_callbacks(struct device *dev)
> +{
> +}
> +
>  #endif
>  
>  #ifdef CONFIG_PM_SLEEP
> diff --git a/include/linux/pm.h b/include/linux/pm.h
> index 35d599e7250d..e334b9b8cd46 100644
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -566,6 +566,7 @@ struct dev_pm_info {
>  	bool			ignore_children:1;
>  	bool			early_init:1;	/* Owned by the PM core */
>  	bool			direct_complete:1;	/* Owned by the PM core */
> +	bool			no_pm_callbacks:1;	/* Owned by the PM core */
>  	spinlock_t		lock;
>  #ifdef CONFIG_PM_SLEEP
>  	struct list_head	entry;
> 

Thanks,
Rafael

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