Commit 05ef983e authored by Saravana Kannan's avatar Saravana Kannan Committed by Greg Kroah-Hartman
Browse files

driver core: Add device link support for SYNC_STATE_ONLY flag 



Parent devices might need to create "proxy" device links from themselves
to supplier devices to make sure the supplier devices don't get a
sync_state() before the child consumer devices get a chance to add
device links to the supplier devices.

However, the parent device has no real dependency on the supplier device
and probing, suspend/resume or runtime PM don't need to be affected by
the supplier device.  To capture these cases, create a SYNC_STATE_ONLY
device link flag that only affects sync_state() behavior and doesn't
affect probing, suspend/resume or runtime PM.

Signed-off-by: default avatarSaravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20191028220027.251605-2-saravanak@google.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8f677bc8

drivers/base/core.c

+41 −9
Original line number Diff line number Diff line
@@ -131,6 +131,9 @@ static int device_is_dependent(struct device *dev, void *target) 
		return ret;



	list_for_each_entry(link, &dev->links.consumers, s_node) {

		if (link->flags == (DL_FLAG_SYNC_STATE_ONLY | DL_FLAG_MANAGED))

			continue;



		if (link->consumer == target)

			return 1;
@@ -200,8 +203,11 @@ static int device_reorder_to_tail(struct device *dev, void *not_used) 
		device_pm_move_last(dev);



	device_for_each_child(dev, NULL, device_reorder_to_tail);

	list_for_each_entry(link, &dev->links.consumers, s_node)

	list_for_each_entry(link, &dev->links.consumers, s_node) {

		if (link->flags == (DL_FLAG_SYNC_STATE_ONLY | DL_FLAG_MANAGED))

			continue;

		device_reorder_to_tail(link->consumer, NULL);

	}



	return 0;

}
@@ -228,7 +234,8 @@ void device_pm_move_to_tail(struct device *dev) 


#define DL_MANAGED_LINK_FLAGS (DL_FLAG_AUTOREMOVE_CONSUMER | \

			       DL_FLAG_AUTOREMOVE_SUPPLIER | \

			       DL_FLAG_AUTOPROBE_CONSUMER)

			       DL_FLAG_AUTOPROBE_CONSUMER  | \

			       DL_FLAG_SYNC_STATE_ONLY)



#define DL_ADD_VALID_FLAGS (DL_MANAGED_LINK_FLAGS | DL_FLAG_STATELESS | \

			    DL_FLAG_PM_RUNTIME | DL_FLAG_RPM_ACTIVE)
@@ -296,6 +303,8 @@ struct device_link *device_link_add(struct device *consumer, 


	if (!consumer || !supplier || flags & ~DL_ADD_VALID_FLAGS ||

	    (flags & DL_FLAG_STATELESS && flags & DL_MANAGED_LINK_FLAGS) ||

	    (flags & DL_FLAG_SYNC_STATE_ONLY &&

	     flags != DL_FLAG_SYNC_STATE_ONLY) ||

	    (flags & DL_FLAG_AUTOPROBE_CONSUMER &&

	     flags & (DL_FLAG_AUTOREMOVE_CONSUMER |

		      DL_FLAG_AUTOREMOVE_SUPPLIER)))
@@ -316,11 +325,14 @@ struct device_link *device_link_add(struct device *consumer, 


	/*

	 * If the supplier has not been fully registered yet or there is a

	 * reverse dependency between the consumer and the supplier already in

	 * the graph, return NULL.

	 * reverse (non-SYNC_STATE_ONLY) dependency between the consumer and

	 * the supplier already in the graph, return NULL. If the link is a

	 * SYNC_STATE_ONLY link, we don't check for reverse dependencies

	 * because it only affects sync_state() callbacks.

	 */

	if (!device_pm_initialized(supplier)

	    || device_is_dependent(consumer, supplier)) {

	    || (!(flags & DL_FLAG_SYNC_STATE_ONLY) &&

		  device_is_dependent(consumer, supplier))) {

		link = NULL;

		goto out;

	}
@@ -347,10 +359,15 @@ struct device_link *device_link_add(struct device *consumer, 
		}



		if (flags & DL_FLAG_STATELESS) {

			link->flags |= DL_FLAG_STATELESS;

			kref_get(&link->kref);

			if (link->flags & DL_FLAG_SYNC_STATE_ONLY &&

			    !(link->flags & DL_FLAG_STATELESS)) {

				link->flags |= DL_FLAG_STATELESS;

				goto reorder;

			} else {

				goto out;

			}

		}



		/*

		 * If the life time of the link following from the new flags is
@@ -371,6 +388,12 @@ struct device_link *device_link_add(struct device *consumer, 
			link->flags |= DL_FLAG_MANAGED;

			device_link_init_status(link, consumer, supplier);

		}

		if (link->flags & DL_FLAG_SYNC_STATE_ONLY &&

		    !(flags & DL_FLAG_SYNC_STATE_ONLY)) {

			link->flags &= ~DL_FLAG_SYNC_STATE_ONLY;

			goto reorder;

		}



		goto out;

	}
@@ -410,6 +433,13 @@ struct device_link *device_link_add(struct device *consumer, 
	    flags & DL_FLAG_PM_RUNTIME)

		pm_runtime_resume(supplier);



	if (flags & DL_FLAG_SYNC_STATE_ONLY) {

		dev_dbg(consumer,

			"Linked as a sync state only consumer to %s\n",

			dev_name(supplier));

		goto out;

	}

reorder:

	/*

	 * Move the consumer and all of the devices depending on it to the end

	 * of dpm_list and the devices_kset list.
@@ -635,7 +665,8 @@ int device_links_check_suppliers(struct device *dev) 
	device_links_write_lock();



	list_for_each_entry(link, &dev->links.suppliers, c_node) {

		if (!(link->flags & DL_FLAG_MANAGED))

		if (!(link->flags & DL_FLAG_MANAGED) ||

		    link->flags & DL_FLAG_SYNC_STATE_ONLY)

			continue;



		if (link->status != DL_STATE_AVAILABLE) {
@@ -949,7 +980,8 @@ void device_links_unbind_consumers(struct device *dev) 
	list_for_each_entry(link, &dev->links.consumers, s_node) {

		enum device_link_state status;



		if (!(link->flags & DL_FLAG_MANAGED))

		if (!(link->flags & DL_FLAG_MANAGED) ||

		    link->flags & DL_FLAG_SYNC_STATE_ONLY)

			continue;



		status = link->status;

include/linux/device.h

+2 −0
Original line number Diff line number Diff line
@@ -1096,6 +1096,7 @@ enum device_link_state { 
 * AUTOREMOVE_SUPPLIER: Remove the link automatically on supplier driver unbind.

 * AUTOPROBE_CONSUMER: Probe consumer driver automatically after supplier binds.

 * MANAGED: The core tracks presence of supplier/consumer drivers (internal).

 * SYNC_STATE_ONLY: Link only affects sync_state() behavior.

 */

#define DL_FLAG_STATELESS		BIT(0)

#define DL_FLAG_AUTOREMOVE_CONSUMER	BIT(1)
@@ -1104,6 +1105,7 @@ enum device_link_state { 
#define DL_FLAG_AUTOREMOVE_SUPPLIER	BIT(4)

#define DL_FLAG_AUTOPROBE_CONSUMER	BIT(5)

#define DL_FLAG_MANAGED			BIT(6)

#define DL_FLAG_SYNC_STATE_ONLY		BIT(7)



/**

 * struct device_link - Device link representation.

CRA Git | Maintained and supported by SUSTech CRA and CCSE