kernel/linux.git/drivers/base/power/runtime.c, branch v4.19.112

driver core: Remove device link creation limitation

2020-03-20T10:55:58+00:00

commit 515db266a9dace92b0cbaed9a6044dd5304b8ca9 upstream. If device_link_add() is called for a consumer/supplier pair with an existing device link between them and the existing link's type is not in agreement with the flags passed to that function by its caller, NULL will be returned. That is seriously inconvenient, because it forces the callers of device_link_add() to worry about what others may or may not do even if that is not relevant to them for any other reasons. It turns out, however, that this limitation can be made go away relatively easily. The underlying observation is that if DL_FLAG_STATELESS has been passed to device_link_add() in flags for the given consumer/supplier pair at least once, calling either device_link_del() or device_link_remove() to release the link returned by it should work, but there are no other requirements associated with that flag. In turn, if at least one of the callers of device_link_add() for the given consumer/supplier pair has not passed DL_FLAG_STATELESS to it in flags, the driver core should track the status of the link and act on it as appropriate (ie. the link should be treated as "managed"). This means that DL_FLAG_STATELESS needs to be set for managed device links and it should be valid to call device_link_del() or device_link_remove() to drop references to them in certain sutiations. To allow that to happen, introduce a new (internal) device link flag called DL_FLAG_MANAGED and make device_link_add() set it automatically whenever DL_FLAG_STATELESS is not passed to it. Also make it take additional references to existing device links that were previously stateless (that is, with DL_FLAG_STATELESS set and DL_FLAG_MANAGED unset) and will need to be managed going forward and initialize their status (which has been DL_STATE_NONE so far). Accordingly, when a managed device link is dropped automatically by the driver core, make it clear DL_FLAG_MANAGED, reset the link's status back to DL_STATE_NONE and drop the reference to it associated with DL_FLAG_MANAGED instead of just deleting it right away (to allow it to stay around in case it still needs to be released explicitly by someone). With that, since setting DL_FLAG_STATELESS doesn't mean that the device link in question is not managed any more, replace all of the status-tracking checks against DL_FLAG_STATELESS with analogous checks against DL_FLAG_MANAGED and update the documentation to reflect these changes. While at it, make device_link_add() reject flags that it does not recognize, including DL_FLAG_MANAGED. Signed-off-by: Rafael J. Wysocki Reviewed-by: Saravana Kannan Tested-by: Marek Szyprowski Review-by: Saravana Kannan Link: https://lore.kernel.org/r/2305283.AStDPdUUnE@kreacher Signed-off-by: Saravana Kannan Signed-off-by: Greg Kroah-Hartman

driver core: Fix PM-runtime for links added during consumer probe

2020-01-27T13:50:26+00:00

[ Upstream commit 36003d4cf57ca431fb3f94d317bcca426a2394d6 ] Commit 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance") introduced a regression that causes suppliers to be suspended prematurely for device links added during consumer driver probe if the initial PM-runtime status of the consumer is "suspended" and the consumer is resumed after adding the link and before pm_runtime_put_suppliers() is called. In that case, pm_runtime_put_suppliers() will drop the rpm_active refcount for the link by one and (since rpm_active is equal to two after the preceding consumer resume) the supplier's PM-runtime usage counter will be decremented, which may cause the supplier to suspend even though the consumer's PM-runtime status is "active". For this reason, partially revert commit 4c06c4e6cf63 as the problem it tried to fix needs to be addressed somewhat differently, and change pm_runtime_get_suppliers() and pm_runtime_put_suppliers() so that the latter only drops rpm_active references acquired by the former. [This requires adding a new field to struct device_link, but I coulnd't find a cleaner way to address the issue that would work in all cases.] This causes pm_runtime_put_suppliers() to effectively ignore device links added during consumer probe, so device_link_add() doesn't need to worry about ensuring that suppliers will remain active after pm_runtime_put_suppliers() for links created with DL_FLAG_RPM_ACTIVE set and it only needs to bump up rpm_active by one for those links, so pm_runtime_active_link() is not necessary any more. Fixes: 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance") Reported-by: Jon Hunter Tested-by: Jon Hunter Tested-by: Ulf Hansson Reviewed-by: Ulf Hansson Signed-off-by: Rafael J. Wysocki Tested-by: Thierry Reding Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

driver core: Fix possible supplier PM-usage counter imbalance

2020-01-27T13:50:22+00:00

[ 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 Signed-off-by: Rafael J. Wysocki Reviewed-by: Ulf Hansson Tested-by: Ulf Hansson Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

driver core: Do not call rpm_put_suppliers() in pm_runtime_drop_link()

2020-01-27T13:50:17+00:00

[ Upstream commit a1fdbfbb1da2063ba98a12eb6f1bdd07451c7145 ] Calling rpm_put_suppliers() from pm_runtime_drop_link() is excessive as it affects all suppliers of the consumer device and not just the one pointed to by the device link being dropped. Worst case it may cause the consumer device to stop working unexpectedly. Moreover, in principle it is racy with respect to runtime PM of the consumer device. To avoid these problems drop runtime PM references on the particular supplier pointed to by the link in question only and do that after the link has been dropped from the consumer device's list of links to suppliers, which is in device_link_free(). Fixes: a0504aecba76 ("PM / runtime: Drop usage count for suppliers at device link removal") Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

driver core: Fix handling of runtime PM flags in device_link_add()

2020-01-27T13:50:17+00:00

[ Upstream commit e2f3cd831a280fc226118d9369bf3f77aab58c56 ] After commit ead18c23c263 ("driver core: Introduce device links reference counting"), if there is a link between the given supplier and the given consumer already, device_link_add() will refcount it and return it unconditionally without updating its flags. It is possible, however, that the second (or any subsequent) caller of device_link_add() for the same consumer-supplier pair will pass DL_FLAG_PM_RUNTIME, possibly along with DL_FLAG_RPM_ACTIVE, in flags to it and the existing link may not behave as expected then. First, if DL_FLAG_PM_RUNTIME is not set in the existing link's flags at all, it needs to be set like during the original initialization of the link. Second, if DL_FLAG_RPM_ACTIVE is passed to device_link_add() in flags (in addition to DL_FLAG_PM_RUNTIME), the existing link should to be updated to reflect the "active" runtime PM configuration of the consumer-supplier pair and extra care must be taken here to avoid possible destructive races with runtime PM of the consumer. To that end, redefine the rpm_active field in struct device_link as a refcount, initialize it to 1 and make rpm_resume() (for the consumer) and device_link_add() increment it whenever they acquire a runtime PM reference on the supplier device. Accordingly, make rpm_suspend() (for the consumer) and pm_runtime_clean_up_links() decrement it and drop runtime PM references to the supplier device in a loop until rpm_active becones 1 again. Fixes: ead18c23c263 ("driver core: Introduce device links reference counting") Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

Revert "PM / runtime: Fixup reference counting of device link suppliers at probe"

2018-06-12T08:24:13+00:00

Revert commit 1e8378619841 (PM / runtime: Fixup reference counting of device link suppliers at probe), as it has introduced a regression and the condition it was designed to address should be covered by the existing code. Reported-by: Marek Szyprowski Signed-off-by: Rafael J. Wysocki

PM / runtime: Drop usage count for suppliers at device link removal

2018-05-27T10:18:55+00:00

In the case consumer device is runtime resumed, while the link to the supplier is removed, the earlier call to pm_runtime_get_sync() made from rpm_get_suppliers() does not get properly balanced with a corresponding call to pm_runtime_put(). This leads to that suppliers remains to be runtime resumed forever, while they don't need to. Let's fix the behaviour by calling rpm_put_suppliers() when dropping a device link. Not that, since rpm_put_suppliers() checks the link->rpm_active flag, we can correctly avoid to call pm_runtime_put() in cases when we shouldn't. Reported-by: Todor Tomov Fixes: 21d5c57b3726 (PM / runtime: Use device links) Signed-off-by: Ulf Hansson Signed-off-by: Rafael J. Wysocki

PM / runtime: Fixup reference counting of device link suppliers at probe

2018-05-27T10:10:32+00:00

In the driver core, before it invokes really_probe() it runtime resumes the suppliers for the device via calling pm_runtime_get_suppliers(), which also increases the runtime PM usage count for each of the available supplier. This makes sense, as to be able to allow the consumer device to be probed by its driver. However, if the driver decides to add a new supplier link during ->probe(), hence updating the list of suppliers, the following call to pm_runtime_put_suppliers(), invoked after really_probe() in the driver core, we get into trouble. More precisely, pm_runtime_put() gets called also for the new supplier(s), which is wrong as the driver core, didn't trigger pm_runtime_get_sync() to be called for it in the first place. In other words, the new supplier may be runtime suspended even in cases when it shouldn't. Fix this behaviour, by runtime resume suppliers according to the same conditions as managed by the runtime PM core, when runtime resume callbacks are being invoked. Additionally, don't try to runtime suspend any of the suppliers after really_probe(), but instead rely on that to happen via the consumer device, when it becomes runtime suspended. Fixes: 21d5c57b3726 (PM / runtime: Use device links) Signed-off-by: Ulf Hansson Signed-off-by: Rafael J. Wysocki

PM / runtime: Allow no callbacks in pm_runtime_force_suspend|resume()

2018-01-17T11:42:49+00:00

The pm_runtime_force_suspend|resume() helpers currently requires the device to at some level (PM domain, bus, etc), have the ->runtime_suspend|resume() callbacks assigned for it, else -ENOSYS is returned as an error. However, there are no reason for this requirement, so let's simply remove it by allowing these callbacks to be NULL. Signed-off-by: Ulf Hansson Signed-off-by: Rafael J. Wysocki

PM / runtime: Check ignore_children in pm_runtime_need_not_resume()

2018-01-15T16:21:19+00:00

Modify pm_runtime_need_not_resume() to make it avoid taking power.child_count for devices with power.ignore_children which is consistent with the runtime PM usage of these fields. Suggested-by: Ulf Hansson Signed-off-by: Rafael J. Wysocki Reviewed-by: Ulf Hansson