[PATCH v2 01/10] irqdomain: Add interface to request an irq domain

[Robert Richter]

This patch introduces a new interface to allow irq domain
initialization regardless of order dependencies. This is done by
requesting a domain and registering a callback function that is called
as soon as a domain becomes available.

A typical irq domain initialization code is the following:

Parent initialization:

	...
	domain = msi_create_irq_domain(fwnode, info, parent);
	if (domain)
		irq_domain_update_bus_token(domain, bus_token);
	...

Child initialization:

	...
	parent = irq_find_matching_fwnode(fwnode, bus_token);
	if (!parent)
		...
	create_irq_domain(parent, ...);
	...

In case the parent is not yet available, the child initialization
fails. Thus, the current implementation requires the parent domain
being initialized before the child domain. With a complex irq domain
hierarchy it becomes more and more difficult to grant that order as
irq domains are enabled in separate subsystems. Care must be taken
when initializing parent and child domains in the same initcall
level. E.g. Arm's gic-v3-its implementation might have the following
tree and dependencies:

	gic-v3
	âââ its-node-0
	â   âââ pci-host-0
	â   âââ platform-bus
	â   ...
	âââ its-node-1
	â   âââ pci-host-1
	...

All domains must be initialized in top-down order of the tree.

This patch introduces an interface that allows domain initialization
without any order requirements, e.g. to be able to initialize the irq
domains in the same initcall level. The following functions have been
introduced to allow the registration of a callback handler:

	irq_domain_request_fwnode()
	irq_domain_request_host()

Instead of using the irq_find_matching_fwnode() function and it's
variants the child code replaces them with the new functions and
looks e.g. like the following:

	...
	irq_domain_request_fwnode(fwnode, bus_token,
				create_irq_domain, name, priv);
	...

Here, the callback function create_irq_domain() is called as soon as
the parent becomes available. All registered handlers are stored in a
list. With each update of the bus token using irq_domain_update_bus_
token(), the list is checked if that domain is requested by a handler
and if that is the case it's callback function is called and the
request removed from the list.

With a late_initcall all requests from the list should already have
been handled, otherwise all remaining requests are removed with an
error reported.

Signed-off-by: Robert Richter <rrichter@xxxxxxxxxx>
---
 include/linux/irqdomain.h |  15 +++++
 kernel/irq/irqdomain.c    | 163 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 178 insertions(+)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index 068aa46f0d55..27e83803627d 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -311,6 +311,21 @@ static inline struct irq_domain *irq_find_host(struct device_node *node)
 	return d;
 }
 
+typedef int (*irq_domain_callback_t)(struct irq_domain *, void *);
+int irq_domain_request_fwnode(struct fwnode_handle *fwnode,
+			enum irq_domain_bus_token bus_token,
+			irq_domain_callback_t callback,
+			const char *name, void *priv);
+
+static inline int irq_domain_request_host(struct device_node *node,
+					enum irq_domain_bus_token bus_token,
+					irq_domain_callback_t callback,
+					void *priv)
+{
+	return irq_domain_request_fwnode(of_node_to_fwnode(node), bus_token,
+					callback, node->full_name, priv);
+}
+
 /**
  * irq_domain_add_linear() - Allocate and register a linear revmap irq_domain.
  * @of_node: pointer to interrupt controller's device tree node.
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 3366d11c3e02..ebe628dad568 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -21,6 +21,7 @@
 #include <linux/fs.h>
 
 static LIST_HEAD(irq_domain_list);
+static LIST_HEAD(irq_domain_requests);
 static DEFINE_MUTEX(irq_domain_mutex);
 
 static struct irq_domain *irq_default_domain;
@@ -45,6 +46,111 @@ static inline void debugfs_remove_domain_dir(struct irq_domain *d) { }
 const struct fwnode_operations irqchip_fwnode_ops;
 EXPORT_SYMBOL_GPL(irqchip_fwnode_ops);
 
+struct irq_domain_request {
+	struct list_head		list;
+	struct fwnode_handle		*fwnode;
+	enum irq_domain_bus_token	bus_token;
+	irq_domain_callback_t		callback;
+	char				*name;
+	void				*priv;
+};
+
+static void irq_domain_call_handler(struct irq_domain *domain,
+		irq_domain_callback_t callback, const char *name, void *priv)
+{
+	int ret;
+
+	ret = callback(domain, priv);
+	if (ret)
+		pr_err("%s: Domain request handler failed: %d\n",
+			name, ret);
+
+	of_node_put(irq_domain_get_of_node(domain));
+}
+
+static void irq_domain_free_request(struct irq_domain_request *request)
+{
+	kfree(request->name);
+	kfree(request);
+}
+
+static void irq_domain_handle_requests(struct fwnode_handle *fwnode,
+                        enum irq_domain_bus_token bus_token)
+{
+	struct irq_domain *domain;
+	struct irq_domain_request *request;
+
+	if (!fwnode)
+		return;
+redo:
+	domain = irq_find_matching_fwnode(fwnode, bus_token);
+	if (!domain)
+		return;
+
+	mutex_lock(&irq_domain_mutex);
+
+	/*
+	 * For serialization of irq domain updates make sure to handle
+	 * (and remove) the request only if the domain still matches
+	 * the request.
+	 */
+	if ((domain->fwnode != fwnode) || (domain->bus_token != bus_token)) {
+		mutex_unlock(&irq_domain_mutex);
+		goto redo;
+	}
+
+	list_for_each_entry(request, &irq_domain_requests, list) {
+		if (request->fwnode != fwnode ||
+		    request->bus_token != bus_token)
+			continue;
+
+		list_del(&request->list);
+		mutex_unlock(&irq_domain_mutex);
+
+		irq_domain_call_handler(domain, request->callback,
+					request->name, request->priv);
+		irq_domain_free_request(request);
+
+		goto redo;
+	}
+
+	mutex_unlock(&irq_domain_mutex);
+}
+
+static int __init irq_domain_drain_requests(void)
+{
+	struct irq_domain_request *request;
+	struct irq_domain *domain;
+	int ret = 0;
+redo:
+	mutex_lock(&irq_domain_mutex);
+
+	list_for_each_entry(request, &irq_domain_requests, list) {
+		list_del(&request->list);
+		mutex_unlock(&irq_domain_mutex);
+
+		domain = irq_find_matching_fwnode(request->fwnode,
+						request->bus_token);
+		if (domain) {
+			irq_domain_call_handler(domain, request->callback,
+						request->name, request->priv);
+		} else {
+			ret = -ENODEV;
+			pr_err("%s-%d: Unhandled domain request\n",
+				request->name, request->bus_token);
+		}
+
+		irq_domain_free_request(request);
+
+		goto redo;
+	}
+
+	mutex_unlock(&irq_domain_mutex);
+
+	return ret;
+}
+late_initcall(irq_domain_drain_requests);
+
 /**
  * irq_domain_alloc_fwnode - Allocate a fwnode_handle suitable for
  *                           identifying an irq domain
@@ -293,6 +399,8 @@ void irq_domain_update_bus_token(struct irq_domain *domain,
 	debugfs_add_domain_dir(domain);
 
 	mutex_unlock(&irq_domain_mutex);
+
+	irq_domain_handle_requests(domain->fwnode, bus_token);
 }
 
 /**
@@ -417,6 +525,61 @@ struct irq_domain *irq_find_matching_fwspec(struct irq_fwspec *fwspec,
 EXPORT_SYMBOL_GPL(irq_find_matching_fwspec);
 
 /**
+ * irq_domain_request_fwnode() - Requests a domain for a given fwspec
+ * @fwspec: FW specifier for an interrupt
+ * @bus_token: domain-specific data
+ * @callback: function to be called once domain becomes available
+ * @name: name to be used for fwnode
+ * @priv: private data to be passed to callback
+ *
+ * The callback function is called as soon as the domain is available.
+ */
+int irq_domain_request_fwnode(struct fwnode_handle *fwnode,
+			enum irq_domain_bus_token bus_token,
+			irq_domain_callback_t callback,
+			const char *name, void *priv)
+{
+	struct irq_domain *parent;
+	struct irq_domain_request *request;
+
+	if (!fwnode || bus_token == DOMAIN_BUS_ANY || !callback || !name)
+		return -EINVAL;
+
+	parent = irq_find_matching_fwnode(fwnode, bus_token);
+	if (parent) {
+		irq_domain_call_handler(parent, callback, name, priv);
+		return 0;
+	}
+
+	request = kzalloc(sizeof(*request), GFP_KERNEL);
+	if (!request)
+		return -ENOMEM;
+
+	request->fwnode = fwnode;
+	request->bus_token = bus_token;
+	request->callback = callback;
+	request->name = kstrdup(name, GFP_KERNEL);
+	request->priv = priv;
+	INIT_LIST_HEAD(&request->list);
+
+	if (!request->name) {
+		kfree(request);
+		return -ENOMEM;
+	}
+
+	of_node_get(to_of_node(fwnode));
+
+	mutex_lock(&irq_domain_mutex);
+	list_add_tail(&request->list, &irq_domain_requests);
+	mutex_unlock(&irq_domain_mutex);
+
+	/* recheck in case list changed */
+	irq_domain_handle_requests(fwnode, bus_token);
+
+	return 0;
+}
+
+/**
  * irq_domain_check_msi_remap - Check whether all MSI irq domains implement
  * IRQ remapping
  *
-- 
2.11.0