linux-kernel - [PATCH 3/6] cxl/port: Arrange for always synchronous endpoint attach

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Message-ID: <20251204022136.2573521-4-dan.j.williams@intel.com>
Date: Wed,  3 Dec 2025 18:21:33 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: dave.jiang@...el.com
Cc: linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Smita.KoralahalliChannabasappa@....com,
	alison.schofield@...el.com,
	terry.bowman@....com,
	alejandro.lucero-palau@....com,
	linux-pci@...r.kernel.org,
	Jonathan.Cameron@...wei.com,
	Alejandro Lucero <alucerop@....com>
Subject: [PATCH 3/6] cxl/port: Arrange for always synchronous endpoint attach

Make it so that upon return from devm_cxl_add_endpoint() that
cxl_mem_probe() can assume that the endpoint has had a chance to complete
cxl_port_probe().  I.e. cxl_port module loading has completed prior to
device registration.

Delete the MODULE_SOFTDEP() as it is not sufficient for this purpose, but a
hard link-time dependency is reliable. Specifically MODULE_SOFTDEP() does
not guarantee that the module loading has completed prior to the completion
of the current module's init.

Cc: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
Cc: Alejandro Lucero <alucerop@....com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 drivers/cxl/cxl.h  |  2 ++
 drivers/cxl/mem.c  | 43 -------------------------------------------
 drivers/cxl/port.c | 40 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 43 deletions(-)

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index ba17fa86d249..c796c3db36e0 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -780,6 +780,8 @@ struct cxl_port *devm_cxl_add_port(struct device *host,
 				   struct cxl_dport *parent_dport);
 struct cxl_root *devm_cxl_add_root(struct device *host,
 				   const struct cxl_root_ops *ops);
+int devm_cxl_add_endpoint(struct device *host, struct cxl_memdev *cxlmd,
+			  struct cxl_dport *parent_dport);
 struct cxl_root *find_cxl_root(struct cxl_port *port);
 
 DEFINE_FREE(put_cxl_root, struct cxl_root *, if (_T) put_device(&_T->port.dev))
diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
index 55883797ab2d..d62931526fd4 100644
--- a/drivers/cxl/mem.c
+++ b/drivers/cxl/mem.c
@@ -45,44 +45,6 @@ static int cxl_mem_dpa_show(struct seq_file *file, void *data)
 	return 0;
 }
 
-static int devm_cxl_add_endpoint(struct device *host, struct cxl_memdev *cxlmd,
-				 struct cxl_dport *parent_dport)
-{
-	struct cxl_port *parent_port = parent_dport->port;
-	struct cxl_port *endpoint, *iter, *down;
-	int rc;
-
-	/*
-	 * Now that the path to the root is established record all the
-	 * intervening ports in the chain.
-	 */
-	for (iter = parent_port, down = NULL; !is_cxl_root(iter);
-	     down = iter, iter = to_cxl_port(iter->dev.parent)) {
-		struct cxl_ep *ep;
-
-		ep = cxl_ep_load(iter, cxlmd);
-		ep->next = down;
-	}
-
-	/* Note: endpoint port component registers are derived from @cxlds */
-	endpoint = devm_cxl_add_port(host, &cxlmd->dev, CXL_RESOURCE_NONE,
-				     parent_dport);
-	if (IS_ERR(endpoint))
-		return PTR_ERR(endpoint);
-
-	rc = cxl_endpoint_autoremove(cxlmd, endpoint);
-	if (rc)
-		return rc;
-
-	if (!endpoint->dev.driver) {
-		dev_err(&cxlmd->dev, "%s failed probe\n",
-			dev_name(&endpoint->dev));
-		return -ENXIO;
-	}
-
-	return 0;
-}
-
 static int cxl_debugfs_poison_inject(void *data, u64 dpa)
 {
 	struct cxl_memdev *cxlmd = data;
@@ -275,8 +237,3 @@ MODULE_DESCRIPTION("CXL: Memory Expansion");
 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");
diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
index 51c8f2f84717..7937e7e53797 100644
--- a/drivers/cxl/port.c
+++ b/drivers/cxl/port.c
@@ -156,10 +156,50 @@ static struct cxl_driver cxl_port_driver = {
 	.probe = cxl_port_probe,
 	.id = CXL_DEVICE_PORT,
 	.drv = {
+		.probe_type = PROBE_FORCE_SYNCHRONOUS,
 		.dev_groups = cxl_port_attribute_groups,
 	},
 };
 
+int devm_cxl_add_endpoint(struct device *host, struct cxl_memdev *cxlmd,
+			  struct cxl_dport *parent_dport)
+{
+	struct cxl_port *parent_port = parent_dport->port;
+	struct cxl_port *endpoint, *iter, *down;
+	int rc;
+
+	/*
+	 * Now that the path to the root is established record all the
+	 * intervening ports in the chain.
+	 */
+	for (iter = parent_port, down = NULL; !is_cxl_root(iter);
+	     down = iter, iter = to_cxl_port(iter->dev.parent)) {
+		struct cxl_ep *ep;
+
+		ep = cxl_ep_load(iter, cxlmd);
+		ep->next = down;
+	}
+
+	/* Note: endpoint port component registers are derived from @cxlds */
+	endpoint = devm_cxl_add_port(host, &cxlmd->dev, CXL_RESOURCE_NONE,
+				     parent_dport);
+	if (IS_ERR(endpoint))
+		return PTR_ERR(endpoint);
+
+	rc = cxl_endpoint_autoremove(cxlmd, endpoint);
+	if (rc)
+		return rc;
+
+	if (!endpoint->dev.driver) {
+		dev_err(&cxlmd->dev, "%s failed probe\n",
+			dev_name(&endpoint->dev));
+		return -ENXIO;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_FOR_MODULES(devm_cxl_add_endpoint, "cxl_mem");
+
 static int __init cxl_port_init(void)
 {
 	return cxl_driver_register(&cxl_port_driver);
-- 
2.51.1