PCI: endpoint: Add helper API to get the 'next' unreserved BAR

Add an API to get the next unreserved BAR starting from a given BAR number
that can be used by the endpoint function.

Link: https://lore.kernel.org/r/20210201195809.7342-4-kishon@ti.com
Signed-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>

Author: kishon

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

@@ -87,32 +87,50 @@ EXPORT_SYMBOL_GPL(pci_epc_get);
  * pci_epc_get_first_free_bar() - helper to get first unreserved BAR
  * @epc_features: pci_epc_features structure that holds the reserved bar bitmap
  *
- * Invoke to get the first unreserved BAR that can be used for endpoint
+ * Invoke to get the first unreserved BAR that can be used by the endpoint
  * function. For any incorrect value in reserved_bar return '0'.
  */
 unsigned int pci_epc_get_first_free_bar(const struct pci_epc_features
 					*epc_features)
+{
+	return pci_epc_get_next_free_bar(epc_features, BAR_0);
+}
+EXPORT_SYMBOL_GPL(pci_epc_get_first_free_bar);
+
+/**
+ * pci_epc_get_next_free_bar() - helper to get unreserved BAR starting from @bar
+ * @epc_features: pci_epc_features structure that holds the reserved bar bitmap
+ * @bar: the starting BAR number from where unreserved BAR should be searched
+ *
+ * Invoke to get the next unreserved BAR starting from @bar that can be used
+ * for endpoint function. For any incorrect value in reserved_bar return '0'.
+ */
+unsigned int pci_epc_get_next_free_bar(const struct pci_epc_features
+				       *epc_features, enum pci_barno bar)
 {
 	unsigned long free_bar;
 
 	if (!epc_features)
 		return 0;
 
+	/* If 'bar - 1' is a 64-bit BAR, move to the next BAR */
+	if ((epc_features->bar_fixed_64bit << 1) & 1 << bar)
+		bar++;
+
 	/* Find if the reserved BAR is also a 64-bit BAR */
 	free_bar = epc_features->reserved_bar & epc_features->bar_fixed_64bit;
 
 	/* Set the adjacent bit if the reserved BAR is also a 64-bit BAR */
 	free_bar <<= 1;
 	free_bar |= epc_features->reserved_bar;
 
-	/* Now find the free BAR */
-	free_bar = ffz(free_bar);
+	free_bar = find_next_zero_bit(&free_bar, 6, bar);
 	if (free_bar > 5)
 		return 0;
 
 	return free_bar;
 }
-EXPORT_SYMBOL_GPL(pci_epc_get_first_free_bar);
+EXPORT_SYMBOL_GPL(pci_epc_get_next_free_bar);
 
 /**
  * pci_epc_get_features() - get the features supported by EPC

include/linux/pci-epc.h

@@ -203,6 +203,8 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
 						    u8 func_no);
 unsigned int pci_epc_get_first_free_bar(const struct pci_epc_features
 					*epc_features);
+unsigned int pci_epc_get_next_free_bar(const struct pci_epc_features
+				       *epc_features, enum pci_barno bar);
 struct pci_epc *pci_epc_get(const char *epc_name);
 void pci_epc_put(struct pci_epc *epc);