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 | 136 +++++++++++++++++++++++++++++++++
 drivers/cxl/core/region.c      |  21 +++--
 drivers/cxl/cxl.h              |   5 ++
 4 files changed, 159 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..4a8cf8322cf0 100644
--- a/drivers/cxl/core/pmem_region.c
+++ b/drivers/cxl/core/pmem_region.c
@@ -287,3 +287,139 @@ 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;
+	bool dport_matched = false;
+
+	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 (int i = 0; i < cxlrd->cxlsd.nr_targets; i++) {
+		if (dport == cxlrd->cxlsd.target[i]) {
+			dport_matched = true;
+			break;
+		}
+	}
+
+	if (!dport_matched)
+		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_endpoint_decoder_by_port() - find a cxl root decoder on cxl bus
+ * @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_region *cxlr;
+	struct cxl_memdev *cxlmd;
+	struct cxl_nvdimm *cxl_nvd;
+	struct cxl_endpoint_decoder *cxled;
+	struct cxl_pmem_region_params *params;
+
+	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 9a86d1c467b2..1b39f7028ca1 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 8c76c4a981bf..088841a3e238 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -792,6 +792,7 @@ 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);
@@ -933,6 +934,7 @@ 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)
 {
@@ -942,6 +944,9 @@ 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

On Fri,  9 Jan 2026 18:14:36 +0530
Neeraj Kumar <s.neeraj@samsung.com> wrote:

> 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>
Hi Neeraj,

Just a few minor things.

Jonathan

> diff --git a/drivers/cxl/core/pmem_region.c b/drivers/cxl/core/pmem_region.c
> index 53d3d81e9676..4a8cf8322cf0 100644
> --- a/drivers/cxl/core/pmem_region.c
> +++ b/drivers/cxl/core/pmem_region.c
> @@ -287,3 +287,139 @@ 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;
> +	bool dport_matched = false;
> +
> +	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;
> +
There is a fairly standard way to check if a loop matched without
needing a boolean. Just check if the exit condition was reached.

drop declaration of i out of here.
> +	for (int i = 0; i < cxlrd->cxlsd.nr_targets; i++) {
> +		if (dport == cxlrd->cxlsd.target[i]) {
> +			dport_matched = true;
No need for this.
> +			break;
> +		}
> +	}
> +
> +	if (!dport_matched)
	if (i == cxlrd->cxlsd.nr_targets)
		return 0;

> +		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);
> +}

> +void create_pmem_region(struct nvdimm *nvdimm)
> +{
> +	struct cxl_region *cxlr;
> +	struct cxl_memdev *cxlmd;
> +	struct cxl_nvdimm *cxl_nvd;
> +	struct cxl_endpoint_decoder *cxled;
> +	struct cxl_pmem_region_params *params;

CXL tends to be reverse xmas tree and good to stick to local style.

> +
> +	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");

On 15/01/26 06:28PM, Jonathan Cameron wrote:
>On Fri,  9 Jan 2026 18:14:36 +0530
>Neeraj Kumar <s.neeraj@samsung.com> wrote:
>
>> 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>
>Hi Neeraj,
>
>Just a few minor things.
>
>Jonathan
>
>> diff --git a/drivers/cxl/core/pmem_region.c b/drivers/cxl/core/pmem_region.c
>> index 53d3d81e9676..4a8cf8322cf0 100644
>> --- a/drivers/cxl/core/pmem_region.c
>> +++ b/drivers/cxl/core/pmem_region.c
>> @@ -287,3 +287,139 @@ 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;
>> +	bool dport_matched = false;
>> +
>> +	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;
>> +
>There is a fairly standard way to check if a loop matched without
>needing a boolean. Just check if the exit condition was reached.
>
>drop declaration of i out of here.
>> +	for (int i = 0; i < cxlrd->cxlsd.nr_targets; i++) {
>> +		if (dport == cxlrd->cxlsd.target[i]) {
>> +			dport_matched = true;
>No need for this.
>> +			break;
>> +		}
>> +	}
>> +
>> +	if (!dport_matched)
>	if (i == cxlrd->cxlsd.nr_targets)
>		return 0;

Thanks for your suggestion. I have fixed it accordingly in V6.

>
>> +		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);
>> +}
>
>> +void create_pmem_region(struct nvdimm *nvdimm)
>> +{
>> +	struct cxl_region *cxlr;
>> +	struct cxl_memdev *cxlmd;
>> +	struct cxl_nvdimm *cxl_nvd;
>> +	struct cxl_endpoint_decoder *cxled;
>> +	struct cxl_pmem_region_params *params;
>
>CXL tends to be reverse xmas tree and good to stick to local style.

Changed them in reverse xmas tree style.


Regards,
Neeraj