Merge branch 'pci/host' into next

* pci/host:
  of/pci: Add of_pci_get_max_link_speed() to parse max-link-speed from DT
  Documentation/devicetree: Add PCIe max-link-speed property

Documentation/devicetree/bindings/pci/pci.txt

@@ -18,3 +18,9 @@ driver implementation may support the following properties:
    host bridges in the system, otherwise potentially conflicting domain numbers
    may be assigned to root buses behind different host bridges.  The domain
    number for each host bridge in the system must be unique.
+- max-link-speed:
+   If present this property specifies PCI gen for link capability.  Host
+   drivers could add this as a strategy to avoid unnecessary operation for
+   unsupported link speed, for instance, trying to do training for
+   unsupported link speed, etc.  Must be '4' for gen4, '3' for gen3, '2'
+   for gen2, and '1' for gen1. Any other values are invalid.

drivers/of/of_pci.c

@@ -119,6 +119,27 @@ int of_get_pci_domain_nr(struct device_node *node)
 }
 EXPORT_SYMBOL_GPL(of_get_pci_domain_nr);
 
+/**
+ * This function will try to find the limitation of link speed by finding
+ * a property called "max-link-speed" of the given device node.
+ *
+ * @node: device tree node with the max link speed information
+ *
+ * Returns the associated max link speed from DT, or a negative value if the
+ * required property is not found or is invalid.
+ */
+int of_pci_get_max_link_speed(struct device_node *node)
+{
+	u32 max_link_speed;
+
+	if (of_property_read_u32(node, "max-link-speed", &max_link_speed) ||
+	    max_link_speed > 4)
+		return -EINVAL;
+
+	return max_link_speed;
+}
+EXPORT_SYMBOL_GPL(of_pci_get_max_link_speed);
+
 /**
  * of_pci_check_probe_only - Setup probe only mode if linux,pci-probe-only
  *                           is present and valid

include/linux/of_pci.h

@@ -16,6 +16,7 @@ int of_pci_get_devfn(struct device_node *np);
 int of_irq_parse_and_map_pci(const struct pci_dev *dev, u8 slot, u8 pin);
 int of_pci_parse_bus_range(struct device_node *node, struct resource *res);
 int of_get_pci_domain_nr(struct device_node *node);
+int of_pci_get_max_link_speed(struct device_node *node);
 void of_pci_check_probe_only(void);
 int of_pci_map_rid(struct device_node *np, u32 rid,
 		   const char *map_name, const char *map_mask_name,
@@ -62,6 +63,12 @@ static inline int of_pci_map_rid(struct device_node *np, u32 rid,
 	return -EINVAL;
 }
 
+static inline int
+of_pci_get_max_link_speed(struct device_node *node)
+{
+	return -EINVAL;
+}
+
 static inline void of_pci_check_probe_only(void) { }
 #endif