PM / runtime: Use device links

Modify the runtime PM framework to use device links to ensure that
supplier devices will not be suspended if any of their consumer
devices are active.

The idea is to reference count suppliers on the consumer's resume
and drop references to them on its suspend.  The information on
whether or not the supplier has been reference counted by the
consumer's (runtime) resume is stored in a new field (rpm_active)
in the link object for each link.

It may be necessary to clean up those references when the
supplier is unbinding and that's why the links whose status is
DEVICE_LINK_SUPPLIER_UNBIND are skipped by the runtime suspend
and resume code.

The above means that if the consumer device is probed in the
runtime-active state, the supplier has to be resumed and reference
counted by device_link_add() so the code works as expected on its
(runtime) suspend.  There is a new flag, DEVICE_LINK_RPM_ACTIVE,
to tell device_link_add() about that (in which case the caller
is responsible for making sure that the consumer really will
be runtime-active when runtime PM is enabled for it).

The other new link flag, DEVICE_LINK_PM_RUNTIME, tells the core
whether or not the link should be used for runtime PM at all.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/device.h b/include/linux/device.h
index 9cae2feaf5cb..49f453892ca5 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -730,9 +730,13 @@ enum device_link_state {
  *
  * STATELESS: The core won't track the presence of supplier/consumer drivers.
  * AUTOREMOVE: Remove this link automatically on consumer driver unbind.
+ * PM_RUNTIME: If set, the runtime PM framework will use this link.
+ * RPM_ACTIVE: Run pm_runtime_get_sync() on the supplier during link creation.
  */
 #define DL_FLAG_STATELESS	BIT(0)
 #define DL_FLAG_AUTOREMOVE	BIT(1)
+#define DL_FLAG_PM_RUNTIME	BIT(2)
+#define DL_FLAG_RPM_ACTIVE	BIT(3)
 
 /**
  * struct device_link - Device link representation.
@@ -742,6 +746,7 @@ enum device_link_state {
  * @c_node: Hook to the consumer device's list of links to suppliers.
  * @status: The state of the link (with respect to the presence of drivers).
  * @flags: Link flags.
+ * @rpm_active: Whether or not the consumer device is runtime-PM-active.
  * @rcu_head: An RCU head to use for deferred execution of SRCU callbacks.
  */
 struct device_link {
@@ -751,6 +756,7 @@ struct device_link {
 	struct list_head c_node;
 	enum device_link_state status;
 	u32 flags;
+	bool rpm_active;
 #ifdef CONFIG_SRCU
 	struct rcu_head rcu_head;
 #endif