static int add_host_bridge_uport()

in acpi.c [201:284]

• 59 lines of code
• 10 McCabe index (conditional complexity)

static int add_host_bridge_uport(struct device *match, void *arg)
{
	struct cxl_port *root_port = arg;
	struct device *host = root_port->dev.parent;
	struct acpi_device *bridge = to_cxl_host_bridge(host, match);
	struct acpi_pci_root *pci_root;
	struct cxl_walk_context ctx;
	int single_port_map[1], rc;
	struct cxl_decoder *cxld;
	struct cxl_dport *dport;
	struct cxl_port *port;

	if (!bridge)
		return 0;

	dport = find_dport_by_dev(root_port, match);
	if (!dport) {
		dev_dbg(host, "host bridge expected and not found\n");
		return 0;
	}

	port = devm_cxl_add_port(host, match, dport->component_reg_phys,
				 root_port);
	if (IS_ERR(port))
		return PTR_ERR(port);
	dev_dbg(host, "%s: add: %s\n", dev_name(match), dev_name(&port->dev));

	/*
	 * Note that this lookup already succeeded in
	 * to_cxl_host_bridge(), so no need to check for failure here
	 */
	pci_root = acpi_pci_find_root(bridge->handle);
	ctx = (struct cxl_walk_context){
		.dev = host,
		.root = pci_root->bus,
		.port = port,
	};
	pci_walk_bus(pci_root->bus, match_add_root_ports, &ctx);

	if (ctx.count == 0)
		return -ENODEV;
	if (ctx.error)
		return ctx.error;
	if (ctx.count > 1)
		return 0;

	/* TODO: Scan CHBCR for HDM Decoder resources */

	/*
	 * Per the CXL specification (8.2.5.12 CXL HDM Decoder Capability
	 * Structure) single ported host-bridges need not publish a decoder
	 * capability when a passthrough decode can be assumed, i.e. all
	 * transactions that the uport sees are claimed and passed to the single
	 * dport. Disable the range until the first CXL region is enumerated /
	 * activated.
	 */
	cxld = cxl_decoder_alloc(port, 1);
	if (IS_ERR(cxld))
		return PTR_ERR(cxld);

	cxld->interleave_ways = 1;
	cxld->interleave_granularity = PAGE_SIZE;
	cxld->target_type = CXL_DECODER_EXPANDER;
	cxld->range = (struct range) {
		.start = 0,
		.end = -1,
	};

	device_lock(&port->dev);
	dport = list_first_entry(&port->dports, typeof(*dport), list);
	device_unlock(&port->dev);

	single_port_map[0] = dport->port_id;

	rc = cxl_decoder_add(cxld, single_port_map);
	if (rc)
		put_device(&cxld->dev);
	else
		rc = cxl_decoder_autoremove(host, cxld);

	if (rc == 0)
		dev_dbg(host, "add: %s\n", dev_name(&cxld->dev));
	return rc;
}