[v1,1/5] driver core: Add device link support for SYNC_STATE_ONLY flag
diff mbox series

Message ID 20191028220027.251605-2-saravanak@google.com
State Accepted
Commit 05ef983e0d65a31b370a4e1b93c1efd490ae778f
Headers show
Series
  • Improve of_devlink to handle "proxy cycles"
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Commit Message

Saravana Kannan Oct. 28, 2019, 10 p.m. UTC
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: Saravana Kannan <saravanak@google.com>
---
 drivers/base/core.c    | 50 ++++++++++++++++++++++++++++++++++--------
 include/linux/device.h |  2 ++
 2 files changed, 43 insertions(+), 9 deletions(-)

Patch
diff mbox series

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 7ea665a97da2..17ed054c4132 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -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;
 	}
@@ -347,9 +359,14 @@  struct device_link *device_link_add(struct device *consumer,
 		}
 
 		if (flags & DL_FLAG_STATELESS) {
-			link->flags |= DL_FLAG_STATELESS;
 			kref_get(&link->kref);
-			goto out;
+			if (link->flags & DL_FLAG_SYNC_STATE_ONLY &&
+			    !(link->flags & DL_FLAG_STATELESS)) {
+				link->flags |= DL_FLAG_STATELESS;
+				goto reorder;
+			} else {
+				goto out;
+			}
 		}
 
 		/*
@@ -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;
diff --git a/include/linux/device.h b/include/linux/device.h
index 9f2f2e169f95..f1f2aa0b19da 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1097,6 +1097,7 @@  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)
@@ -1105,6 +1106,7 @@  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.