PCI: endpoint: Add support in configfs to associate two EPCs with EPF

Now that PCI endpoint core supports to add secondary endpoint controller
(EPC) with endpoint function (EPF), Add support in configfs to associate
two EPCs with EPF. This creates "primary" and "secondary" directory inside
the directory created by users for EPF device. Users have to add a symlink
of endpoint controller (pci_ep/controllers/) to "primary" or "secondary"
directory to bind EPF to primary and secondary EPF interfaces respectively.
Existing method of linking directory representing EPF device to directory
representing EPC device to associate a single EPC device with a EPF device
will continue to work.

Link: https://lore.kernel.org/r/20210201195809.7342-8-kishon@ti.comSigned-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Documentation/PCI/endpoint/pci-endpoint-cfs.rst

@@ -68,6 +68,16 @@ created)
 				... subsys_vendor_id
 				... subsys_id
 				... interrupt_pin
+                                ... primary/
+			                ... <Symlink EPC Device1>/
+                                ... secondary/
+			                ... <Symlink EPC Device2>/
+
+If an EPF device has to be associated with 2 EPCs (like in the case of
+Non-transparent bridge), symlink of endpoint controller connected to primary
+interface should be added in 'primary' directory and symlink of endpoint
+controller connected to secondary interface should be added in 'secondary'
+directory.
 
 EPC Device
 ==========

drivers/pci/endpoint/pci-ep-cfs.c

@@ -21,6 +21,9 @@ static struct config_group *controllers_group;
 
 struct pci_epf_group {
 	struct config_group group;
+	struct config_group primary_epc_group;
+	struct config_group secondary_epc_group;
+	struct delayed_work cfs_work;
 	struct pci_epf *epf;
 	int index;
 };
@@ -41,6 +44,127 @@ static inline struct pci_epc_group *to_pci_epc_group(struct config_item *item)
 	return container_of(to_config_group(item), struct pci_epc_group, group);
 }
 
+static int pci_secondary_epc_epf_link(struct config_item *epf_item,
+				      struct config_item *epc_item)
+{
+	int ret;
+	struct pci_epf_group *epf_group = to_pci_epf_group(epf_item->ci_parent);
+	struct pci_epc_group *epc_group = to_pci_epc_group(epc_item);
+	struct pci_epc *epc = epc_group->epc;
+	struct pci_epf *epf = epf_group->epf;
+
+	ret = pci_epc_add_epf(epc, epf, SECONDARY_INTERFACE);
+	if (ret)
+		return ret;
+
+	ret = pci_epf_bind(epf);
+	if (ret) {
+		pci_epc_remove_epf(epc, epf, SECONDARY_INTERFACE);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void pci_secondary_epc_epf_unlink(struct config_item *epc_item,
+					 struct config_item *epf_item)
+{
+	struct pci_epf_group *epf_group = to_pci_epf_group(epf_item->ci_parent);
+	struct pci_epc_group *epc_group = to_pci_epc_group(epc_item);
+	struct pci_epc *epc;
+	struct pci_epf *epf;
+
+	WARN_ON_ONCE(epc_group->start);
+
+	epc = epc_group->epc;
+	epf = epf_group->epf;
+	pci_epf_unbind(epf);
+	pci_epc_remove_epf(epc, epf, SECONDARY_INTERFACE);
+}
+
+static struct configfs_item_operations pci_secondary_epc_item_ops = {
+	.allow_link	= pci_secondary_epc_epf_link,
+	.drop_link	= pci_secondary_epc_epf_unlink,
+};
+
+static const struct config_item_type pci_secondary_epc_type = {
+	.ct_item_ops	= &pci_secondary_epc_item_ops,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct config_group
+*pci_ep_cfs_add_secondary_group(struct pci_epf_group *epf_group)
+{
+	struct config_group *secondary_epc_group;
+
+	secondary_epc_group = &epf_group->secondary_epc_group;
+	config_group_init_type_name(secondary_epc_group, "secondary",
+				    &pci_secondary_epc_type);
+	configfs_register_group(&epf_group->group, secondary_epc_group);
+
+	return secondary_epc_group;
+}
+
+static int pci_primary_epc_epf_link(struct config_item *epf_item,
+				    struct config_item *epc_item)
+{
+	int ret;
+	struct pci_epf_group *epf_group = to_pci_epf_group(epf_item->ci_parent);
+	struct pci_epc_group *epc_group = to_pci_epc_group(epc_item);
+	struct pci_epc *epc = epc_group->epc;
+	struct pci_epf *epf = epf_group->epf;
+
+	ret = pci_epc_add_epf(epc, epf, PRIMARY_INTERFACE);
+	if (ret)
+		return ret;
+
+	ret = pci_epf_bind(epf);
+	if (ret) {
+		pci_epc_remove_epf(epc, epf, PRIMARY_INTERFACE);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void pci_primary_epc_epf_unlink(struct config_item *epc_item,
+				       struct config_item *epf_item)
+{
+	struct pci_epf_group *epf_group = to_pci_epf_group(epf_item->ci_parent);
+	struct pci_epc_group *epc_group = to_pci_epc_group(epc_item);
+	struct pci_epc *epc;
+	struct pci_epf *epf;
+
+	WARN_ON_ONCE(epc_group->start);
+
+	epc = epc_group->epc;
+	epf = epf_group->epf;
+	pci_epf_unbind(epf);
+	pci_epc_remove_epf(epc, epf, PRIMARY_INTERFACE);
+}
+
+static struct configfs_item_operations pci_primary_epc_item_ops = {
+	.allow_link	= pci_primary_epc_epf_link,
+	.drop_link	= pci_primary_epc_epf_unlink,
+};
+
+static const struct config_item_type pci_primary_epc_type = {
+	.ct_item_ops	= &pci_primary_epc_item_ops,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct config_group
+*pci_ep_cfs_add_primary_group(struct pci_epf_group *epf_group)
+{
+	struct config_group *primary_epc_group = &epf_group->primary_epc_group;
+
+	config_group_init_type_name(primary_epc_group, "primary",
+				    &pci_primary_epc_type);
+	configfs_register_group(&epf_group->group, primary_epc_group);
+
+	return primary_epc_group;
+}
+
 static ssize_t pci_epc_start_store(struct config_item *item, const char *page,
 				   size_t len)
 {
@@ -372,6 +496,25 @@ static const struct config_item_type pci_epf_type = {
 	.ct_owner	= THIS_MODULE,
 };
 
+static void pci_epf_cfs_work(struct work_struct *work)
+{
+	struct pci_epf_group *epf_group;
+	struct config_group *group;
+
+	epf_group = container_of(work, struct pci_epf_group, cfs_work.work);
+	group = pci_ep_cfs_add_primary_group(epf_group);
+	if (IS_ERR(group)) {
+		pr_err("failed to create 'primary' EPC interface\n");
+		return;
+	}
+
+	group = pci_ep_cfs_add_secondary_group(epf_group);
+	if (IS_ERR(group)) {
+		pr_err("failed to create 'secondary' EPC interface\n");
+		return;
+	}
+}
+
 static struct config_group *pci_epf_make(struct config_group *group,
 					 const char *name)
 {
@@ -414,6 +557,10 @@ static struct config_group *pci_epf_make(struct config_group *group,
 
 	kfree(epf_name);
 
+	INIT_DELAYED_WORK(&epf_group->cfs_work, pci_epf_cfs_work);
+	queue_delayed_work(system_wq, &epf_group->cfs_work,
+			   msecs_to_jiffies(1));
+
 	return &epf_group->group;
 
 free_name: