[PATCH v4 8/9] cxl: Create an xarray to tie a host bridge to the cxl_root

[Dave Jiang <dave.jiang@intel.com>]

Add helper functions to setup association of a host bridge device to a
related cxl_root. Functions are in preparation to support the moving
of host bridge ports creation from cxl_acpi to cxl_memdev probe path.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
---
 drivers/cxl/core/port.c | 53 +++++++++++++++++++++++++++++++++++++++++
 drivers/cxl/cxl.h       |  4 ++++
 2 files changed, 57 insertions(+)

diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 4f7ac4f0d3cf..20d2f834bf94 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -38,6 +38,7 @@ DECLARE_RWSEM(cxl_region_rwsem);
 
 static DEFINE_IDA(cxl_port_ida);
 static DEFINE_XARRAY(cxl_root_buses);
+static DEFINE_XARRAY(cxl_root_ports);
 
 /*
  * The terminal device in PCI is NULL and @platform_bus
@@ -1014,6 +1015,58 @@ int devm_cxl_register_pci_bus(struct device *host, struct device *uport_dev,
 }
 EXPORT_SYMBOL_NS_GPL(devm_cxl_register_pci_bus, "CXL");
 
+/**
+ * cxl_hb_uport_dev_to_root - Retrieve cxl_root tied to the host bridge device
+ * @hb_uport_dev: host bridge upstream port device
+ *
+ * Return cxl_root on success or NULL on failure
+ *
+ * A reference is taken on the port device. Caller needs to call put_device()
+ * when done.
+ */
+struct cxl_root *cxl_hb_uport_dev_to_root(struct device *hb_uport_dev)
+{
+	struct cxl_root *root;
+
+	root = xa_load(&cxl_root_ports, (unsigned long)hb_uport_dev);
+	if (!root)
+		return NULL;
+
+	get_device(&root->port.dev);
+
+	return root;
+}
+EXPORT_SYMBOL_NS_GPL(cxl_hb_uport_dev_to_root, "CXL");
+
+static void unregister_hb_uport_root_ports(void *hb_uport_dev)
+{
+	xa_erase(&cxl_root_ports, (unsigned long)hb_uport_dev);
+}
+
+/**
+ * devm_cxl_register_hb_uport_root_port - Tie a hostbridge device to a root port
+ * @host: device that hosts the memory for the xarray entries
+ * @hb_uport_dev: host bridge device that serves as the xarray index
+ * @root: cxl_root that serves as the xarray entry data
+ *
+ * Return 0 on success or -errno on failure.
+ */
+int devm_cxl_register_hb_uport_root_port(struct device *host,
+					 struct device *hb_uport_dev,
+					 struct cxl_root *root)
+{
+	int rc;
+
+	rc = xa_insert(&cxl_root_ports, (unsigned long)hb_uport_dev, root,
+		       GFP_KERNEL);
+	if (rc)
+		return rc;
+
+	return devm_add_action_or_reset(host, unregister_hb_uport_root_ports,
+					hb_uport_dev);
+}
+EXPORT_SYMBOL_NS_GPL(devm_cxl_register_hb_uport_root_port, "CXL");
+
 static bool dev_is_cxl_root_child(struct device *dev)
 {
 	struct cxl_port *port, *parent;
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 2b06f6099959..3973bf11043f 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -734,6 +734,10 @@ struct pci_bus;
 int devm_cxl_register_pci_bus(struct device *host, struct device *uport_dev,
 			      struct pci_bus *bus);
 struct pci_bus *cxl_port_to_pci_bus(struct cxl_port *port);
+int devm_cxl_register_hb_uport_root_port(struct device *host,
+					 struct device *hb_uport_dev,
+					 struct cxl_root *root);
+struct cxl_root *cxl_hb_uport_dev_to_root(struct device *uport_dev);
 struct cxl_port *devm_cxl_add_port(struct device *host,
 				   struct device *uport_dev,
 				   resource_size_t component_reg_phys,
-- 
2.49.0