1 files changed, 96 insertions, 0 deletions
diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
new file mode 100644
index 000000000000..c9a494d6976a
--- /dev/null
+++ b/drivers/cxl/core/pci.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2021 Intel Corporation. All rights reserved. */
+#include <linux/device.h>
+#include <linux/pci.h>
+#include <cxlpci.h>
+#include <cxl.h>
+#include "core.h"
+
+/**
+ * DOC: cxl core pci
+ *
+ * Compute Express Link protocols are layered on top of PCIe. CXL core provides
+ * a set of helpers for CXL interactions which occur via PCIe.
+ */
+
+struct cxl_walk_context {
+	struct pci_bus *bus;
+	struct cxl_port *port;
+	int type;
+	int error;
+	int count;
+};
+
+static int match_add_dports(struct pci_dev *pdev, void *data)
+{
+	struct cxl_walk_context *ctx = data;
+	struct cxl_port *port = ctx->port;
+	int type = pci_pcie_type(pdev);
+	struct cxl_register_map map;
+	struct cxl_dport *dport;
+	u32 lnkcap, port_num;
+	int rc;
+
+	if (pdev->bus != ctx->bus)
+		return 0;
+	if (!pci_is_pcie(pdev))
+		return 0;
+	if (type != ctx->type)
+		return 0;
+	if (pci_read_config_dword(pdev, pci_pcie_cap(pdev) + PCI_EXP_LNKCAP,
+				  &lnkcap))
+		return 0;
+
+	rc = cxl_find_regblock(pdev, CXL_REGLOC_RBI_COMPONENT, &map);
+	if (rc)
+		dev_dbg(&port->dev, "failed to find component registers\n");
+
+	port_num = FIELD_GET(PCI_EXP_LNKCAP_PN, lnkcap);
+	dport = devm_cxl_add_dport(port, &pdev->dev, port_num,
+				   cxl_regmap_to_base(pdev, &map));
+	if (IS_ERR(dport)) {
+		ctx->error = PTR_ERR(dport);
+		return PTR_ERR(dport);
+	}
+	ctx->count++;
+
+	dev_dbg(&port->dev, "add dport%d: %s\n", port_num, dev_name(&pdev->dev));
+
+	return 0;
+}
+
+/**
+ * devm_cxl_port_enumerate_dports - enumerate downstream ports of the upstream port
+ * @port: cxl_port whose ->uport is the upstream of dports to be enumerated
+ *
+ * Returns a positive number of dports enumerated or a negative error
+ * code.
+ */
+int devm_cxl_port_enumerate_dports(struct cxl_port *port)
+{
+	struct pci_bus *bus = cxl_port_to_pci_bus(port);
+	struct cxl_walk_context ctx;
+	int type;
+
+	if (!bus)
+		return -ENXIO;
+
+	if (pci_is_root_bus(bus))
+		type = PCI_EXP_TYPE_ROOT_PORT;
+	else
+		type = PCI_EXP_TYPE_DOWNSTREAM;
+
+	ctx = (struct cxl_walk_context) {
+		.port = port,
+		.bus = bus,
+		.type = type,
+	};
+	pci_walk_bus(bus, match_add_dports, &ctx);
+
+	if (ctx.count == 0)
+		return -ENODEV;
+	if (ctx.error)
+		return ctx.error;
+	return ctx.count;
+}
+EXPORT_SYMBOL_NS_GPL(devm_cxl_port_enumerate_dports, CXL);