1 files changed, 130 insertions, 0 deletions
diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
new file mode 100644
index 000000000000..64ccf053d32c
--- /dev/null
+++ b/drivers/cxl/mem.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2022 Intel Corporation. All rights reserved. */
+#include <linux/debugfs.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+
+#include "cxlmem.h"
+#include "cxlpci.h"
+
+/**
+ * DOC: cxl mem
+ *
+ * CXL memory endpoint devices and switches are CXL capable devices that are
+ * participating in CXL.mem protocol. Their functionality builds on top of the
+ * CXL.io protocol that allows enumerating and configuring components via
+ * standard PCI mechanisms.
+ *
+ * The cxl_mem driver owns kicking off the enumeration of this CXL.mem
+ * capability. With the detection of a CXL capable endpoint, the driver will
+ * walk up to find the platform specific port it is connected to, and determine
+ * if there are intervening switches in the path. If there are switches, a
+ * secondary action is to enumerate those (implemented in cxl_core). Finally the
+ * cxl_mem driver adds the device it is bound to as a CXL endpoint-port for use
+ * in higher level operations.
+ */
+
+static void enable_suspend(void *data)
+{
+	cxl_mem_active_dec();
+}
+
+static void remove_debugfs(void *dentry)
+{
+	debugfs_remove_recursive(dentry);
+}
+
+static int cxl_mem_dpa_show(struct seq_file *file, void *data)
+{
+	struct device *dev = file->private;
+	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+
+	cxl_dpa_debug(file, cxlmd->cxlds);
+
+	return 0;
+}
+
+static int cxl_mem_probe(struct device *dev)
+{
+	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+	struct cxl_port *parent_port;
+	struct cxl_dport *dport;
+	struct dentry *dentry;
+	int rc;
+
+	/*
+	 * Someone is trying to reattach this device after it lost its port
+	 * connection (an endpoint port previously registered by this memdev was
+	 * disabled). This racy check is ok because if the port is still gone,
+	 * no harm done, and if the port hierarchy comes back it will re-trigger
+	 * this probe. Port rescan and memdev detach work share the same
+	 * single-threaded workqueue.
+	 */
+	if (work_pending(&cxlmd->detach_work))
+		return -EBUSY;
+
+	dentry = cxl_debugfs_create_dir(dev_name(dev));
+	debugfs_create_devm_seqfile(dev, "dpamem", dentry, cxl_mem_dpa_show);
+	rc = devm_add_action_or_reset(dev, remove_debugfs, dentry);
+	if (rc)
+		return rc;
+
+	rc = devm_cxl_enumerate_ports(cxlmd);
+	if (rc)
+		return rc;
+
+	parent_port = cxl_mem_find_port(cxlmd, &dport);
+	if (!parent_port) {
+		dev_err(dev, "CXL port topology not found\n");
+		return -ENXIO;
+	}
+
+	device_lock(&parent_port->dev);
+	if (!parent_port->dev.driver) {
+		dev_err(dev, "CXL port topology %s not enabled\n",
+			dev_name(&parent_port->dev));
+		rc = -ENXIO;
+		goto unlock;
+	}
+
+	rc = devm_cxl_add_endpoint(cxlmd, dport);
+unlock:
+	device_unlock(&parent_port->dev);
+	put_device(&parent_port->dev);
+	if (rc)
+		return rc;
+
+	/*
+	 * The kernel may be operating out of CXL memory on this device,
+	 * there is no spec defined way to determine whether this device
+	 * preserves contents over suspend, and there is no simple way
+	 * to arrange for the suspend image to avoid CXL memory which
+	 * would setup a circular dependency between PCI resume and save
+	 * state restoration.
+	 *
+	 * TODO: support suspend when all the regions this device is
+	 * hosting are locked and covered by the system address map,
+	 * i.e. platform firmware owns restoring the HDM configuration
+	 * that it locked.
+	 */
+	cxl_mem_active_inc();
+	return devm_add_action_or_reset(dev, enable_suspend, NULL);
+}
+
+static struct cxl_driver cxl_mem_driver = {
+	.name = "cxl_mem",
+	.probe = cxl_mem_probe,
+	.id = CXL_DEVICE_MEMORY_EXPANDER,
+};
+
+module_cxl_driver(cxl_mem_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_IMPORT_NS(CXL);
+MODULE_ALIAS_CXL(CXL_DEVICE_MEMORY_EXPANDER);
+/*
+ * create_endpoint() wants to validate port driver attach immediately after
+ * endpoint registration.
+ */
+MODULE_SOFTDEP("pre: cxl_port");