1 files changed, 298 insertions, 10 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 7bd9cd366d41..42a672456432 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -45,6 +45,10 @@ early_param("sysfs.deprecated", sysfs_deprecated_setup);
 #endif
 
 /* Device links support. */
+static LIST_HEAD(wait_for_suppliers);
+static DEFINE_MUTEX(wfs_lock);
+static LIST_HEAD(deferred_sync);
+static unsigned int defer_sync_state_count = 1;
 
 #ifdef CONFIG_SRCU
 static DEFINE_MUTEX(device_links_lock);
@@ -127,6 +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;
 
@@ -196,8 +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;
 }
@@ -224,7 +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)
@@ -292,6 +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)))
@@ -312,11 +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;
 	}
@@ -343,9 +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;
+			}
 		}
 
 		/*
@@ -367,6 +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;
 	}
 
@@ -406,6 +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.
@@ -431,6 +465,70 @@ struct device_link *device_link_add(struct device *consumer,
 }
 EXPORT_SYMBOL_GPL(device_link_add);
 
+/**
+ * device_link_wait_for_supplier - Add device to wait_for_suppliers list
+ * @consumer: Consumer device
+ *
+ * Marks the @consumer device as waiting for suppliers to become available by
+ * adding it to the wait_for_suppliers list. The consumer device will never be
+ * probed until it's removed from the wait_for_suppliers list.
+ *
+ * The caller is responsible for adding the links to the supplier devices once
+ * they are available and removing the @consumer device from the
+ * wait_for_suppliers list once links to all the suppliers have been created.
+ *
+ * This function is NOT meant to be called from the probe function of the
+ * consumer but rather from code that creates/adds the consumer device.
+ */
+static void device_link_wait_for_supplier(struct device *consumer,
+					  bool need_for_probe)
+{
+	mutex_lock(&wfs_lock);
+	list_add_tail(&consumer->links.needs_suppliers, &wait_for_suppliers);
+	consumer->links.need_for_probe = need_for_probe;
+	mutex_unlock(&wfs_lock);
+}
+
+static void device_link_wait_for_mandatory_supplier(struct device *consumer)
+{
+	device_link_wait_for_supplier(consumer, true);
+}
+
+static void device_link_wait_for_optional_supplier(struct device *consumer)
+{
+	device_link_wait_for_supplier(consumer, false);
+}
+
+/**
+ * device_link_add_missing_supplier_links - Add links from consumer devices to
+ *					    supplier devices, leaving any
+ *					    consumer with inactive suppliers on
+ *					    the wait_for_suppliers list
+ *
+ * Loops through all consumers waiting on suppliers and tries to add all their
+ * supplier links. If that succeeds, the consumer device is removed from
+ * wait_for_suppliers list. Otherwise, they are left in the wait_for_suppliers
+ * list.  Devices left on the wait_for_suppliers list will not be probed.
+ *
+ * The fwnode add_links callback is expected to return 0 if it has found and
+ * added all the supplier links for the consumer device. It should return an
+ * error if it isn't able to do so.
+ *
+ * The caller of device_link_wait_for_supplier() is expected to call this once
+ * it's aware of potential suppliers becoming available.
+ */
+static void device_link_add_missing_supplier_links(void)
+{
+	struct device *dev, *tmp;
+
+	mutex_lock(&wfs_lock);
+	list_for_each_entry_safe(dev, tmp, &wait_for_suppliers,
+				 links.needs_suppliers)
+		if (!fwnode_call_int_op(dev->fwnode, add_links, dev))
+			list_del_init(&dev->links.needs_suppliers);
+	mutex_unlock(&wfs_lock);
+}
+
 static void device_link_free(struct device_link *link)
 {
 	while (refcount_dec_not_one(&link->rpm_active))
@@ -565,10 +663,23 @@ int device_links_check_suppliers(struct device *dev)
 	struct device_link *link;
 	int ret = 0;
 
+	/*
+	 * Device waiting for supplier to become available is not allowed to
+	 * probe.
+	 */
+	mutex_lock(&wfs_lock);
+	if (!list_empty(&dev->links.needs_suppliers) &&
+	    dev->links.need_for_probe) {
+		mutex_unlock(&wfs_lock);
+		return -EPROBE_DEFER;
+	}
+	mutex_unlock(&wfs_lock);
+
 	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) {
@@ -585,6 +696,128 @@ int device_links_check_suppliers(struct device *dev)
 }
 
 /**
+ * __device_links_queue_sync_state - Queue a device for sync_state() callback
+ * @dev: Device to call sync_state() on
+ * @list: List head to queue the @dev on
+ *
+ * Queues a device for a sync_state() callback when the device links write lock
+ * isn't held. This allows the sync_state() execution flow to use device links
+ * APIs.  The caller must ensure this function is called with
+ * device_links_write_lock() held.
+ *
+ * This function does a get_device() to make sure the device is not freed while
+ * on this list.
+ *
+ * So the caller must also ensure that device_links_flush_sync_list() is called
+ * as soon as the caller releases device_links_write_lock().  This is necessary
+ * to make sure the sync_state() is called in a timely fashion and the
+ * put_device() is called on this device.
+ */
+static void __device_links_queue_sync_state(struct device *dev,
+					    struct list_head *list)
+{
+	struct device_link *link;
+
+	if (dev->state_synced)
+		return;
+
+	list_for_each_entry(link, &dev->links.consumers, s_node) {
+		if (!(link->flags & DL_FLAG_MANAGED))
+			continue;
+		if (link->status != DL_STATE_ACTIVE)
+			return;
+	}
+
+	/*
+	 * Set the flag here to avoid adding the same device to a list more
+	 * than once. This can happen if new consumers get added to the device
+	 * and probed before the list is flushed.
+	 */
+	dev->state_synced = true;
+
+	if (WARN_ON(!list_empty(&dev->links.defer_sync)))
+		return;
+
+	get_device(dev);
+	list_add_tail(&dev->links.defer_sync, list);
+}
+
+/**
+ * device_links_flush_sync_list - Call sync_state() on a list of devices
+ * @list: List of devices to call sync_state() on
+ *
+ * Calls sync_state() on all the devices that have been queued for it. This
+ * function is used in conjunction with __device_links_queue_sync_state().
+ */
+static void device_links_flush_sync_list(struct list_head *list)
+{
+	struct device *dev, *tmp;
+
+	list_for_each_entry_safe(dev, tmp, list, links.defer_sync) {
+		list_del_init(&dev->links.defer_sync);
+
+		device_lock(dev);
+
+		if (dev->bus->sync_state)
+			dev->bus->sync_state(dev);
+		else if (dev->driver && dev->driver->sync_state)
+			dev->driver->sync_state(dev);
+
+		device_unlock(dev);
+
+		put_device(dev);
+	}
+}
+
+void device_links_supplier_sync_state_pause(void)
+{
+	device_links_write_lock();
+	defer_sync_state_count++;
+	device_links_write_unlock();
+}
+
+void device_links_supplier_sync_state_resume(void)
+{
+	struct device *dev, *tmp;
+	LIST_HEAD(sync_list);
+
+	device_links_write_lock();
+	if (!defer_sync_state_count) {
+		WARN(true, "Unmatched sync_state pause/resume!");
+		goto out;
+	}
+	defer_sync_state_count--;
+	if (defer_sync_state_count)
+		goto out;
+
+	list_for_each_entry_safe(dev, tmp, &deferred_sync, links.defer_sync) {
+		/*
+		 * Delete from deferred_sync list before queuing it to
+		 * sync_list because defer_sync is used for both lists.
+		 */
+		list_del_init(&dev->links.defer_sync);
+		__device_links_queue_sync_state(dev, &sync_list);
+	}
+out:
+	device_links_write_unlock();
+
+	device_links_flush_sync_list(&sync_list);
+}
+
+static int sync_state_resume_initcall(void)
+{
+	device_links_supplier_sync_state_resume();
+	return 0;
+}
+late_initcall(sync_state_resume_initcall);
+
+static void __device_links_supplier_defer_sync(struct device *sup)
+{
+	if (list_empty(&sup->links.defer_sync))
+		list_add_tail(&sup->links.defer_sync, &deferred_sync);
+}
+
+/**
  * device_links_driver_bound - Update device links after probing its driver.
  * @dev: Device to update the links for.
  *
@@ -598,6 +831,16 @@ int device_links_check_suppliers(struct device *dev)
 void device_links_driver_bound(struct device *dev)
 {
 	struct device_link *link;
+	LIST_HEAD(sync_list);
+
+	/*
+	 * If a device probes successfully, it's expected to have created all
+	 * the device links it needs to or make new device links as it needs
+	 * them. So, it no longer needs to wait on any suppliers.
+	 */
+	mutex_lock(&wfs_lock);
+	list_del_init(&dev->links.needs_suppliers);
+	mutex_unlock(&wfs_lock);
 
 	device_links_write_lock();
 
@@ -628,11 +871,19 @@ void device_links_driver_bound(struct device *dev)
 
 		WARN_ON(link->status != DL_STATE_CONSUMER_PROBE);
 		WRITE_ONCE(link->status, DL_STATE_ACTIVE);
+
+		if (defer_sync_state_count)
+			__device_links_supplier_defer_sync(link->supplier);
+		else
+			__device_links_queue_sync_state(link->supplier,
+							&sync_list);
 	}
 
 	dev->links.status = DL_DEV_DRIVER_BOUND;
 
 	device_links_write_unlock();
+
+	device_links_flush_sync_list(&sync_list);
 }
 
 static void device_link_drop_managed(struct device_link *link)
@@ -744,6 +995,7 @@ void device_links_driver_cleanup(struct device *dev)
 		WRITE_ONCE(link->status, DL_STATE_DORMANT);
 	}
 
+	list_del_init(&dev->links.defer_sync);
 	__device_links_no_driver(dev);
 
 	device_links_write_unlock();
@@ -813,7 +1065,8 @@ 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;
@@ -849,6 +1102,10 @@ static void device_links_purge(struct device *dev)
 {
 	struct device_link *link, *ln;
 
+	mutex_lock(&wfs_lock);
+	list_del(&dev->links.needs_suppliers);
+	mutex_unlock(&wfs_lock);
+
 	/*
 	 * Delete all of the remaining links from this device to any other
 	 * devices (either consumers or suppliers).
@@ -1713,6 +1970,8 @@ void device_initialize(struct device *dev)
 #endif
 	INIT_LIST_HEAD(&dev->links.consumers);
 	INIT_LIST_HEAD(&dev->links.suppliers);
+	INIT_LIST_HEAD(&dev->links.needs_suppliers);
+	INIT_LIST_HEAD(&dev->links.defer_sync);
 	dev->links.status = DL_DEV_NO_DRIVER;
 }
 EXPORT_SYMBOL_GPL(device_initialize);
@@ -2101,7 +2360,7 @@ int device_add(struct device *dev)
 	struct device *parent;
 	struct kobject *kobj;
 	struct class_interface *class_intf;
-	int error = -EINVAL;
+	int error = -EINVAL, fw_ret;
 	struct kobject *glue_dir = NULL;
 
 	dev = get_device(dev);
@@ -2199,6 +2458,32 @@ int device_add(struct device *dev)
 					     BUS_NOTIFY_ADD_DEVICE, dev);
 
 	kobject_uevent(&dev->kobj, KOBJ_ADD);
+
+	if (dev->fwnode && !dev->fwnode->dev)
+		dev->fwnode->dev = dev;
+
+	/*
+	 * Check if any of the other devices (consumers) have been waiting for
+	 * this device (supplier) to be added so that they can create a device
+	 * link to it.
+	 *
+	 * This needs to happen after device_pm_add() because device_link_add()
+	 * requires the supplier be registered before it's called.
+	 *
+	 * But this also needs to happe before bus_probe_device() to make sure
+	 * waiting consumers can link to it before the driver is bound to the
+	 * device and the driver sync_state callback is called for this device.
+	 */
+	device_link_add_missing_supplier_links();
+
+	if (fwnode_has_op(dev->fwnode, add_links)) {
+		fw_ret = fwnode_call_int_op(dev->fwnode, add_links, dev);
+		if (fw_ret == -ENODEV)
+			device_link_wait_for_mandatory_supplier(dev);
+		else if (fw_ret)
+			device_link_wait_for_optional_supplier(dev);
+	}
+
 	bus_probe_device(dev);
 	if (parent)
 		klist_add_tail(&dev->p->knode_parent,
@@ -2343,6 +2628,9 @@ void device_del(struct device *dev)
 	kill_device(dev);
 	device_unlock(dev);
 
+	if (dev->fwnode && dev->fwnode->dev == dev)
+		dev->fwnode->dev = NULL;
+
 	/* Notify clients of device removal.  This call must come
 	 * before dpm_sysfs_remove().
 	 */