[PATCH v2 3/6] cxl/port: Arrange for always synchronous endpoint attach

Dan Williams
2025-12-16T00:55:34Z

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@amd.com>
Cc: Alejandro Lucero <alucerop@amd.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Ben Cheatham <benjamin.cheatham@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Tested-by: Alejandro Lucero <alucerop@amd.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.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