[PATCH v20 02/22] cxl/port: Arrange for always synchronous endpoint attach

alejandro.lucero-palau
2025-11-10T15:37:25Z

From: Dan Williams <dan.j.williams@intel.com>

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.

MODULE_SOFTDEP() is not sufficient for this purpose, but a hard link-time
dependency is reliable.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/cxl/mem.c | 38 --------------------------------------
drivers/cxl/port.c | 41 +++++++++++++++++++++++++++++++++++++++++
drivers/cxl/private.h | 7 ++++++-
3 files changed, 47 insertions(+), 39 deletions(-)

diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
index fa5d901ee817..01a8e808196e 100644
--- a/drivers/cxl/mem.c
+++ b/drivers/cxl/mem.c
@@ -46,44 +46,6 @@ 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;
diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
index 51c8f2f84717..ef65d983e1c8 100644
--- a/drivers/cxl/port.c
+++ b/drivers/cxl/port.c
@@ -6,6 +6,7 @@

#include "cxlmem.h"
#include "cxlpci.h"
+#include "private.h"

/**
* DOC: cxl port
@@ -156,10 +157,50 @@ 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_NS_GPL(devm_cxl_add_endpoint, "CXL");
+
static int __init cxl_port_init(void)
{
return cxl_driver_register(&cxl_port_driver);
diff --git a/drivers/cxl/private.h b/drivers/cxl/private.h
index 50c2ac57afb5..f8d1ff64f534 100644
--- a/drivers/cxl/private.h
+++ b/drivers/cxl/private.h
@@ -1,10 +1,15 @@
/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright(c) 2025 Intel Corporation. */

-/* Private interfaces betwen common drivers ("cxl_mem") and the cxl_core */
+/*
+ * Private interfaces betwen common drivers ("cxl_mem", "cxl_port") and
+ * the cxl_core.
+ */

#ifndef __CXL_PRIVATE_H__
#define __CXL_PRIVATE_H__
struct cxl_memdev *cxl_memdev_alloc(struct cxl_dev_state *cxlds);
int devm_cxl_memdev_add_or_reset(struct device *host, struct cxl_memdev *cxlmd);
+int devm_cxl_add_endpoint(struct device *host, struct cxl_memdev *cxlmd,
+ struct cxl_dport *parent_dport);
#endif /* __CXL_PRIVATE_H__ */
--
2.34.1