From: Rafael J. Wysocki rafael.j.wysocki@intel.com
[ Upstream commit 4c06c4e6cf63d7f3d5dfe62593a073253d750a59 ]
If a stateless device link to a certain supplier with DL_FLAG_PM_RUNTIME set in the flags is added and then removed by the consumer driver's probe callback, the supplier's PM-runtime usage counter will be nonzero after that which effectively causes the supplier to remain "always on" going forward.
Namely, device_link_add() called to add the link invokes device_link_rpm_prepare() which notices that the consumer driver is probing, so it increments the supplier's PM-runtime usage counter with the assumption that the link will stay around until pm_runtime_put_suppliers() is called by driver_probe_device(), but if the link goes away before that point, the supplier's PM-runtime usage counter will remain nonzero.
To prevent that from happening, first rework pm_runtime_get_suppliers() and pm_runtime_put_suppliers() to use the rpm_active refounts of device links and make the latter only drop rpm_active and the supplier's PM-runtime usage counter for each link by one, unless rpm_active is one already for it. Next, modify device_link_add() to bump up the new link's rpm_active refcount and the suppliers PM-runtime usage counter by two, to prevent pm_runtime_put_suppliers(), if it is called subsequently, from suspending the supplier prematurely (in case its PM-runtime usage counter goes down to 0 in there).
Due to the way rpm_put_suppliers() works, this change does not affect runtime suspend of the consumer ends of new device links (or, generally, device links for which DL_FLAG_PM_RUNTIME has just been set).
Fixes: e2f3cd831a28 ("driver core: Fix handling of runtime PM flags in device_link_add()") Reported-by: Ulf Hansson ulf.hansson@linaro.org Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Ulf Hansson ulf.hansson@linaro.org Tested-by: Ulf Hansson ulf.hansson@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/base/core.c | 21 ++++----------------- drivers/base/power/runtime.c | 27 +++++++++++++++++++++++++-- include/linux/pm_runtime.h | 4 ++++ 3 files changed, 33 insertions(+), 19 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c index 7599147d5f83c..ab08211ba5d2d 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -165,19 +165,6 @@ void device_pm_move_to_tail(struct device *dev) device_links_read_unlock(idx); }
-static void device_link_rpm_prepare(struct device *consumer, - struct device *supplier) -{ - pm_runtime_new_link(consumer); - /* - * If the link is being added by the consumer driver at probe time, - * balance the decrementation of the supplier's runtime PM usage counter - * after consumer probe in driver_probe_device(). - */ - if (consumer->links.status == DL_DEV_PROBING) - pm_runtime_get_noresume(supplier); -} - /** * device_link_add - Create a link between two devices. * @consumer: Consumer end of the link. @@ -262,11 +249,11 @@ struct device_link *device_link_add(struct device *consumer,
if (flags & DL_FLAG_PM_RUNTIME) { if (!(link->flags & DL_FLAG_PM_RUNTIME)) { - device_link_rpm_prepare(consumer, supplier); + pm_runtime_new_link(consumer); link->flags |= DL_FLAG_PM_RUNTIME; } if (flags & DL_FLAG_RPM_ACTIVE) - refcount_inc(&link->rpm_active); + pm_runtime_active_link(link, supplier); }
kref_get(&link->kref); @@ -281,9 +268,9 @@ struct device_link *device_link_add(struct device *consumer,
if (flags & DL_FLAG_PM_RUNTIME) { if (flags & DL_FLAG_RPM_ACTIVE) - refcount_inc(&link->rpm_active); + pm_runtime_active_link(link, supplier);
- device_link_rpm_prepare(consumer, supplier); + pm_runtime_new_link(consumer); }
get_device(supplier); diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index ab454c4533ba1..0527890b4c191 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -1570,8 +1570,10 @@ void pm_runtime_get_suppliers(struct device *dev) idx = device_links_read_lock();
list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) - if (link->flags & DL_FLAG_PM_RUNTIME) + if (link->flags & DL_FLAG_PM_RUNTIME) { + refcount_inc(&link->rpm_active); pm_runtime_get_sync(link->supplier); + }
device_links_read_unlock(idx); } @@ -1588,7 +1590,8 @@ void pm_runtime_put_suppliers(struct device *dev) idx = device_links_read_lock();
list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) - if (link->flags & DL_FLAG_PM_RUNTIME) + if (link->flags & DL_FLAG_PM_RUNTIME && + refcount_dec_not_one(&link->rpm_active)) pm_runtime_put(link->supplier);
device_links_read_unlock(idx); @@ -1601,6 +1604,26 @@ void pm_runtime_new_link(struct device *dev) spin_unlock_irq(&dev->power.lock); }
+/** + * pm_runtime_active_link - Set up new device link as active for PM-runtime. + * @link: Device link to be set up as active. + * @supplier: Supplier end of the link. + * + * Add 2 to the rpm_active refcount of @link and increment the PM-runtime + * usage counter of @supplier once more in case the link is being added while + * the consumer driver is probing and pm_runtime_put_suppliers() will be called + * subsequently. + * + * Note that this doesn't prevent rpm_put_suppliers() from decreasing the link's + * rpm_active refcount down to one, so runtime suspend of the consumer end of + * @link is not affected. + */ +void pm_runtime_active_link(struct device_link *link, struct device *supplier) +{ + refcount_add(2, &link->rpm_active); + pm_runtime_get_noresume(supplier); +} + void pm_runtime_drop_link(struct device *dev) { spin_lock_irq(&dev->power.lock); diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h index f0fc4700b6ff5..bace7df51af4d 100644 --- a/include/linux/pm_runtime.h +++ b/include/linux/pm_runtime.h @@ -59,6 +59,8 @@ extern void pm_runtime_clean_up_links(struct device *dev); extern void pm_runtime_get_suppliers(struct device *dev); extern void pm_runtime_put_suppliers(struct device *dev); extern void pm_runtime_new_link(struct device *dev); +extern void pm_runtime_active_link(struct device_link *link, + struct device *supplier); extern void pm_runtime_drop_link(struct device *dev);
static inline void pm_suspend_ignore_children(struct device *dev, bool enable) @@ -176,6 +178,8 @@ static inline void pm_runtime_clean_up_links(struct device *dev) {} static inline void pm_runtime_get_suppliers(struct device *dev) {} static inline void pm_runtime_put_suppliers(struct device *dev) {} static inline void pm_runtime_new_link(struct device *dev) {} +static inline void pm_runtime_active_link(struct device_link *link, + struct device *supplier) {} static inline void pm_runtime_drop_link(struct device *dev) {}
#endif /* !CONFIG_PM */