PCI: endpoint: Assign function number for each PF in EPC core

The PCIe endpoint core relies on the drivers that invoke the
pci_epc_add_epf() API to allocate and assign a function number
to each physical function (PF). Since endpoint function device can
be created by multiple mechanisms (configfs, devicetree, etc..),
allowing each of these mechanisms to assign a function number
would result in mutliple endpoint function devices having the
same function number. In order to avoid this, let EPC core assign
a function number to the endpoint device.
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

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

@@ -29,7 +29,6 @@ struct pci_epc_group {
 	struct config_group group;
 	struct pci_epc *epc;
 	bool start;
-	unsigned long function_num_map;
 };
 
 static inline struct pci_epf_group *to_pci_epf_group(struct config_item *item)
@@ -89,37 +88,22 @@ static int pci_epc_epf_link(struct config_item *epc_item,
 			    struct config_item *epf_item)
 {
 	int ret;
-	u32 func_no = 0;
 	struct pci_epf_group *epf_group = to_pci_epf_group(epf_item);
 	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;
 
-	func_no = find_first_zero_bit(&epc_group->function_num_map,
-				      BITS_PER_LONG);
-	if (func_no >= BITS_PER_LONG)
-		return -EINVAL;
-
-	set_bit(func_no, &epc_group->function_num_map);
-	epf->func_no = func_no;
-
 	ret = pci_epc_add_epf(epc, epf);
 	if (ret)
-		goto err_add_epf;
+		return ret;
 
 	ret = pci_epf_bind(epf);
-	if (ret)
-		goto err_epf_bind;
-
-	return 0;
-
-err_epf_bind:
+	if (ret) {
 		pci_epc_remove_epf(epc, epf);
-
-err_add_epf:
-	clear_bit(func_no, &epc_group->function_num_map);
-
 		return ret;
+	}
+
+	return 0;
 }
 
 static void pci_epc_epf_unlink(struct config_item *epc_item,
@@ -134,7 +118,6 @@ static void pci_epc_epf_unlink(struct config_item *epc_item,
 
 	epc = epc_group->epc;
 	epf = epf_group->epf;
-	clear_bit(epf->func_no, &epc_group->function_num_map);
 	pci_epf_unbind(epf);
 	pci_epc_remove_epf(epc, epf);
 }

drivers/pci/endpoint/pci-epc-core.c

@@ -471,22 +471,39 @@ EXPORT_SYMBOL_GPL(pci_epc_write_header);
  */
 int pci_epc_add_epf(struct pci_epc *epc, struct pci_epf *epf)
 {
+	u32 func_no;
+	int ret = 0;
+
 	if (epf->epc)
 		return -EBUSY;
 
 	if (IS_ERR(epc))
 		return -EINVAL;
 
-	if (epf->func_no > epc->max_functions - 1)
-		return -EINVAL;
+	mutex_lock(&epc->lock);
+	func_no = find_first_zero_bit(&epc->function_num_map,
+				      BITS_PER_LONG);
+	if (func_no >= BITS_PER_LONG) {
+		ret = -EINVAL;
+		goto ret;
+	}
+
+	if (func_no > epc->max_functions - 1) {
+		dev_err(&epc->dev, "Exceeding max supported Function Number\n");
+		ret = -EINVAL;
+		goto ret;
+	}
 
+	set_bit(func_no, &epc->function_num_map);
+	epf->func_no = func_no;
 	epf->epc = epc;
 
-	mutex_lock(&epc->lock);
 	list_add_tail(&epf->list, &epc->pci_epf);
+
+ret:
 	mutex_unlock(&epc->lock);
 
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(pci_epc_add_epf);
 
@@ -503,6 +520,7 @@ void pci_epc_remove_epf(struct pci_epc *epc, struct pci_epf *epf)
 		return;
 
 	mutex_lock(&epc->lock);
+	clear_bit(epf->func_no, &epc->function_num_map);
 	list_del(&epf->list);
 	epf->epc = NULL;
 	mutex_unlock(&epc->lock);

include/linux/pci-epc.h

@@ -92,6 +92,7 @@ struct pci_epc_mem {
  * @max_functions: max number of functions that can be configured in this EPC
  * @group: configfs group representing the PCI EPC device
  * @lock: mutex to protect pci_epc ops
+ * @function_num_map: bitmap to manage physical function number
  * @notifier: used to notify EPF of any EPC events (like linkup)
  */
 struct pci_epc {
@@ -103,6 +104,7 @@ struct pci_epc {
 	struct config_group		*group;
 	/* mutex to protect against concurrent access of EP controller */
 	struct mutex			lock;
+	unsigned long			function_num_map;
 	struct atomic_notifier_head	notifier;
 };