[PATCH V6 17/18] cxl/pmem_region: Create pmem region using information parsed from LSA

Neeraj Kumar
2026-01-23T11:31:52Z

create_pmem_region() creates CXL region based on region information
parsed from the Label Storage Area (LSA). This routine requires cxl
endpoint decoder and root decoder. Add cxl_find_root_decoder_by_port()
and cxl_find_free_ep_decoder() to find the root decoder and a free
endpoint decoder respectively.

Signed-off-by: Neeraj Kumar <s.neeraj@samsung.com>
---
drivers/cxl/core/core.h | 5 ++
drivers/cxl/core/pmem_region.c | 133 +++++++++++++++++++++++++++++++++
drivers/cxl/core/region.c | 21 ++++--
drivers/cxl/cxl.h | 5 ++
4 files changed, 156 insertions(+), 8 deletions(-)

diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
index 5ae693269771..8421ea0ef834 100644
--- a/drivers/cxl/core/core.h
+++ b/drivers/cxl/core/core.h
@@ -46,6 +46,7 @@ struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
struct cxl_pmem_region_params *pmem_params,
struct cxl_endpoint_decoder *cxled);
struct cxl_region *to_cxl_region(struct device *dev);
+bool is_free_decoder(struct device *dev);

#else
static inline u64 cxl_dpa_to_hpa(struct cxl_region *cxlr,
@@ -87,6 +88,10 @@ static inline struct cxl_region *to_cxl_region(struct device *dev)
{
return NULL;
}
+static inline bool is_free_decoder(struct device *dev)
+{
+ return false;
+}
#define CXL_REGION_ATTR(x) NULL
#define CXL_REGION_TYPE(x) NULL
#define SET_CXL_REGION_ATTR(x)
diff --git a/drivers/cxl/core/pmem_region.c b/drivers/cxl/core/pmem_region.c
index 53d3d81e9676..cdee2788fad8 100644
--- a/drivers/cxl/core/pmem_region.c
+++ b/drivers/cxl/core/pmem_region.c
@@ -287,3 +287,136 @@ int devm_cxl_add_pmem_region(struct cxl_region *cxlr)
cxlr->cxl_nvb = NULL;
return rc;
}
+
+static int match_root_decoder_by_dport(struct device *dev, const void *data)
+{
+ const struct cxl_port *ep_port = data;
+ struct cxl_root_decoder *cxlrd;
+ struct cxl_port *root_port;
+ struct cxl_decoder *cxld;
+ struct cxl_dport *dport;
+ int i;
+
+ if (!is_root_decoder(dev))
+ return 0;
+
+ cxld = to_cxl_decoder(dev);
+ if (!(cxld->flags & CXL_DECODER_F_PMEM))
+ return 0;
+
+ cxlrd = to_cxl_root_decoder(dev);
+
+ root_port = cxlrd_to_port(cxlrd);
+ dport = cxl_find_dport_by_dev(root_port, ep_port->host_bridge);
+ if (!dport)
+ return 0;
+
+ for (i = 0; i < cxlrd->cxlsd.nr_targets; i++)
+ if (dport == cxlrd->cxlsd.target[i])
+ break;
+
+ if (i == cxlrd->cxlsd.nr_targets)
+ return 0;
+
+ return is_root_decoder(dev);
+}
+
+/**
+ * cxl_find_root_decoder_by_port() - find a cxl root decoder on cxl bus
+ * @port: any descendant port in CXL port topology
+ * @cxled: endpoint decoder
+ *
+ * Caller of this function must call put_device() when done as a device ref
+ * is taken via device_find_child()
+ */
+static struct cxl_root_decoder *
+cxl_find_root_decoder_by_port(struct cxl_port *port,
+ struct cxl_endpoint_decoder *cxled)
+{
+ struct cxl_root *cxl_root __free(put_cxl_root) = find_cxl_root(port);
+ struct cxl_port *ep_port = cxled_to_port(cxled);
+ struct device *dev;
+
+ if (!cxl_root)
+ return NULL;
+
+ dev = device_find_child(&cxl_root->port.dev, ep_port,
+ match_root_decoder_by_dport);
+ if (!dev)
+ return NULL;
+
+ return to_cxl_root_decoder(dev);
+}
+
+static int match_free_ep_decoder(struct device *dev, const void *data)
+{
+ if (!is_endpoint_decoder(dev))
+ return 0;
+
+ return is_free_decoder(dev);
+}
+
+/**
+ * cxl_find_free_ep_decoder() - find a cxl endpoint decoder using cxl port
+ * @port: any descendant port in CXL port topology
+ *
+ * Caller of this function must call put_device() when done as a device ref
+ * is taken via device_find_child()
+ */
+static struct cxl_decoder *cxl_find_free_ep_decoder(struct cxl_port *port)
+{
+ struct device *dev;
+
+ dev = device_find_child(&port->dev, NULL, match_free_ep_decoder);
+ if (!dev)
+ return NULL;
+
+ return to_cxl_decoder(dev);
+}
+
+void create_pmem_region(struct nvdimm *nvdimm)
+{
+ struct cxl_pmem_region_params *params;
+ struct cxl_endpoint_decoder *cxled;
+ struct cxl_nvdimm *cxl_nvd;
+ struct cxl_memdev *cxlmd;
+ struct cxl_region *cxlr;
+
+ if (!nvdimm_has_cxl_region(nvdimm))
+ return;
+
+ lockdep_assert_held(&cxl_rwsem.region);
+ cxl_nvd = nvdimm_provider_data(nvdimm);
+ params = nvdimm_get_cxl_region_param(nvdimm);
+ cxlmd = cxl_nvd->cxlmd;
+
+ /* TODO: Region creation support only for interleave way == 1 */
+ if (!(params->nlabel == 1)) {
+ dev_dbg(&cxlmd->dev,
+ "Region Creation is not supported with iw > 1\n");
+ return;
+ }
+
+ struct cxl_decoder *cxld __free(put_cxl_decoder) =
+ cxl_find_free_ep_decoder(cxlmd->endpoint);
+ if (!cxld) {
+ dev_err(&cxlmd->dev, "CXL endpoint decoder not found\n");
+ return;
+ }
+
+ cxled = to_cxl_endpoint_decoder(&cxld->dev);
+
+ struct cxl_root_decoder *cxlrd __free(put_cxl_root_decoder) =
+ cxl_find_root_decoder_by_port(cxlmd->endpoint, cxled);
+ if (!cxlrd) {
+ dev_err(&cxlmd->dev, "CXL root decoder not found\n");
+ return;
+ }
+
+ cxlr = cxl_create_region(cxlrd, CXL_PARTMODE_PMEM,
+ atomic_read(&cxlrd->region_id),
+ params, cxled);
+ if (IS_ERR(cxlr))
+ dev_warn(&cxlmd->dev, "Region Creation failed\n");
+}
+EXPORT_SYMBOL_NS_GPL(create_pmem_region, "CXL");
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index f9b3dd6cee50..37b88641b818 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -838,25 +838,22 @@ static int check_commit_order(struct device *dev, void *data)
return 0;
}

-static int match_free_decoder(struct device *dev, const void *data)
+bool is_free_decoder(struct device *dev)
{
struct cxl_port *port = to_cxl_port(dev->parent);
struct cxl_decoder *cxld;
int rc;

- if (!is_switch_decoder(dev))
- return 0;
-
cxld = to_cxl_decoder(dev);

if (cxld->id != port->commit_end + 1)
- return 0;
+ return false;

if (cxld->region) {
dev_dbg(dev->parent,
"next decoder to commit (%s) is already reserved (%s)\n",
dev_name(dev), dev_name(&cxld->region->dev));
- return 0;
+ return false;
}

rc = device_for_each_child_reverse_from(dev->parent, dev, NULL,
@@ -865,9 +862,17 @@ static int match_free_decoder(struct device *dev, const void *data)
dev_dbg(dev->parent,
"unable to allocate %s due to out of order shutdown\n",
dev_name(dev));
- return 0;
+ return false;
}
- return 1;
+ return true;
+}
+
+static int match_free_decoder(struct device *dev, const void *data)
+{
+ if (!is_switch_decoder(dev))
+ return 0;
+
+ return is_free_decoder(dev);
}

static bool spa_maps_hpa(const struct cxl_region_params *p,
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 32a8296a833a..1fc3e6260a00 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -794,6 +794,7 @@ 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))
DEFINE_FREE(put_cxl_port, struct cxl_port *, if (!IS_ERR_OR_NULL(_T)) put_device(&_T->dev))
DEFINE_FREE(put_cxl_root_decoder, struct cxl_root_decoder *, if (!IS_ERR_OR_NULL(_T)) put_device(&_T->cxlsd.cxld.dev))
+DEFINE_FREE(put_cxl_decoder, struct cxl_decoder *, if (!IS_ERR_OR_NULL(_T)) put_device(&_T->dev))
DEFINE_FREE(put_cxl_region, struct cxl_region *, if (!IS_ERR_OR_NULL(_T)) put_device(&_T->dev))

int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd);
@@ -935,6 +936,7 @@ static inline int cxl_region_discovery(struct cxl_memdev *cxlmd)
#ifdef CONFIG_CXL_PMEM_REGION
bool is_cxl_pmem_region(struct device *dev);
struct cxl_pmem_region *to_cxl_pmem_region(struct device *dev);
+void create_pmem_region(struct nvdimm *nvdimm);
#else
static inline bool is_cxl_pmem_region(struct device *dev)
{
@@ -944,6 +946,9 @@ static inline struct cxl_pmem_region *to_cxl_pmem_region(struct device *dev)
{
return NULL;
}
+static inline void create_pmem_region(struct nvdimm *nvdimm)
+{
+}
#endif

void cxl_endpoint_parse_cdat(struct cxl_port *port);
--
2.34.1