diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
index 5ada6d9543d3..0b672248d126 100644
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -190,3 +190,19 @@ Description:
 		found to support CDAT data.  If it is present and the length of
 		the data is 0 reading the CDAT data failed.  Otherwise the CDAT
 		data is reported.
+
+
+What:		/sys/bus/cxl/devices/decoderX.Y/mode
+Date:		May, 2022
+KernelVersion:	v5.20
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		(RO) When a CXL decoder is of devtype "cxl_decoder_endpoint" it
+		translates from a host physical address range, to a device local
+		address range. Device-local address ranges are further split
+		into a 'ram' (volatile memory) range and 'pmem' (persistent
+		memory) range. The 'mode' attribute emits one of 'ram', 'pmem',
+		'mixed', or 'none'. The 'mixed' indication is for error cases
+		when a decoder straddles the volatile/persistent partition
+		boundary, and 'none' indicates the decoder is not actively
+		decoding, or no DPA allocation policy has been set.
diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index 47e3af440b3d..c2cff5783fda 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -226,6 +226,16 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
 	cxled->dpa_res = res;
 	cxled->skip = skipped;
 
+	if (resource_contains(&cxlds->pmem_res, res))
+		cxled->mode = CXL_DECODER_PMEM;
+	else if (resource_contains(&cxlds->ram_res, res))
+		cxled->mode = CXL_DECODER_RAM;
+	else {
+		dev_dbg(dev, "decoder%d.%d: %pr mixed\n", port->id,
+			cxled->cxld.id, cxled->dpa_res);
+		cxled->mode = CXL_DECODER_MIXED;
+	}
+
 	return 0;
 }
 
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 2cfa870428c2..9a312f2e2d35 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -172,6 +172,25 @@ static ssize_t target_list_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(target_list);
 
+static ssize_t mode_show(struct device *dev, struct device_attribute *attr,
+			 char *buf)
+{
+	struct cxl_endpoint_decoder *cxled = to_cxl_endpoint_decoder(dev);
+
+	switch (cxled->mode) {
+	case CXL_DECODER_RAM:
+		return sysfs_emit(buf, "ram\n");
+	case CXL_DECODER_PMEM:
+		return sysfs_emit(buf, "pmem\n");
+	case CXL_DECODER_NONE:
+		return sysfs_emit(buf, "none\n");
+	case CXL_DECODER_MIXED:
+	default:
+		return sysfs_emit(buf, "mixed\n");
+	}
+}
+static DEVICE_ATTR_RO(mode);
+
 static struct attribute *cxl_decoder_base_attrs[] = {
 	&dev_attr_start.attr,
 	&dev_attr_size.attr,
@@ -222,6 +241,7 @@ static const struct attribute_group *cxl_decoder_switch_attribute_groups[] = {
 
 static struct attribute *cxl_decoder_endpoint_attrs[] = {
 	&dev_attr_target_type.attr,
+	&dev_attr_mode.attr,
 	NULL,
 };
 
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 5fe8b59a0b18..afaa76f065f9 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -241,16 +241,25 @@ struct cxl_decoder {
 	unsigned long flags;
 };
 
+enum cxl_decoder_mode {
+	CXL_DECODER_NONE,
+	CXL_DECODER_RAM,
+	CXL_DECODER_PMEM,
+	CXL_DECODER_MIXED,
+};
+
 /**
  * struct cxl_endpoint_decoder - Endpoint  / SPA to DPA decoder
  * @cxld: base cxl_decoder_object
  * @dpa_res: actively claimed DPA span of this decoder
  * @skip: offset into @dpa_res where @cxld.hpa_range maps
+ * @mode: which memory type / access-mode-partition this decoder targets
  */
 struct cxl_endpoint_decoder {
 	struct cxl_decoder cxld;
 	struct resource *dpa_res;
 	resource_size_t skip;
+	enum cxl_decoder_mode mode;
 };
 
 /**