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Message-ID: <20151004151621.GA12684@xo-6d-61-c0.localdomain>
Date: Sun, 4 Oct 2015 17:16:21 +0200
From: Pavel Machek <pavel@....cz>
To: Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc: 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,
Len Brown <len.brown@...el.com>,
Kevin Hilman <khilman@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v5 1/2] PM / sleep: Go direct_complete if driver has no
callbacks
On Tue 2015-09-29 14:29:19, 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.
Dunno. This sounds like asking for trouble. Even if most devices can handle
this, is not this bound to introduce some bugs?
Thanks,
Pavel
>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
> ---
>
> 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 | 5 ++++
> drivers/base/power/main.c | 69 ++++++++++++++++++++++++++++++++-------------
> drivers/base/power/power.h | 2 ++
> include/linux/pm.h | 1 +
> 5 files changed, 61 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/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..b6eaa00b2540 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -117,6 +117,31 @@ void device_pm_unlock(void)
> mutex_unlock(&dpm_list_mtx);
> }
>
> +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)
> +{
> + 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));
> +}
> +
> /**
> * device_pm_add - Add a device to the PM core's list of active devices.
> * @dev: Device to add to the list.
> @@ -131,6 +156,8 @@ 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 +1596,31 @@ 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 */
> + 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..518a8fc84e8d 100644
> --- a/drivers/base/power/power.h
> +++ b/drivers/base/power/power.h
> @@ -9,6 +9,8 @@ static inline void device_pm_init_common(struct device *dev)
> }
> }
>
> +extern void device_check_pm_callbacks(struct device *dev);
> +
> #ifdef CONFIG_PM
>
> static inline void pm_runtime_early_init(struct device *dev)
> 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;
> --
> 2.4.3
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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