diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
index 0cb31b7ad17b..f16f18e77578 100644
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -48,3 +48,73 @@ Description:
 		decode of CXL memory resources.  The 'Y' integer reflects the
 		hardware port unique-id used in the hardware decoder target
 		list.
+
+What:		/sys/bus/cxl/devices/decoderX.Y
+Date:		June, 2021
+KernelVersion:	v5.14
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		CXL decoder objects are enumerated from either a platform
+		firmware description, or a CXL HDM decoder register set in a
+		PCIe device (see CXL 2.0 section 8.2.5.12 CXL HDM Decoder
+		Capability Structure). The 'X' in decoderX.Y represents the
+		cxl_port container of this decoder, and 'Y' represents the
+		instance id of a given decoder resource.
+
+What:		/sys/bus/cxl/devices/decoderX.Y/{start,end}
+Date:		June, 2021
+KernelVersion:	v5.14
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		The 'start' and 'end' attributes together convey the physical
+		address base and last addressable byte of the decoder's decode
+		window. For decoders of devtype "cxl_decoder_root" the address
+		range is fixed. For decoders of devtype "cxl_decoder_switch" the
+		address is bounded by the decode range of the cxl_port ancestor
+		of the decoder's cxl_port, and dynamically updates based on the
+		active memory regions in that address space.
+
+What:		/sys/bus/cxl/devices/decoderX.Y/locked
+Date:		June, 2021
+KernelVersion:	v5.14
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		CXL HDM decoders have the capability to lock the configuration
+		until the next device reset. For decoders of devtype
+		"cxl_decoder_root" there is no standard facility to unlock them.
+		For decoders of devtype "cxl_decoder_switch" a secondary bus
+		reset, of the PCIe bridge that provides the bus for this
+		decoders uport, unlocks / resets the decoder.
+
+What:		/sys/bus/cxl/devices/decoderX.Y/target_list
+Date:		June, 2021
+KernelVersion:	v5.14
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		Display a comma separated list of the current decoder target
+		configuration. The list is ordered by the current configured
+		interleave order of the decoder's dport instances. Each entry in
+		the list is a dport id.
+
+What:		/sys/bus/cxl/devices/decoderX.Y/cap_{pmem,ram,type2,type3}
+Date:		June, 2021
+KernelVersion:	v5.14
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		When a CXL decoder is of devtype "cxl_decoder_root", it
+		represents a fixed memory window identified by platform
+		firmware. A fixed window may only support a subset of memory
+		types. The 'cap_*' attributes indicate whether persistent
+		memory, volatile memory, accelerator memory, and / or expander
+		memory may be mapped behind this decoder's memory window.
+
+What:		/sys/bus/cxl/devices/decoderX.Y/target_type
+Date:		June, 2021
+KernelVersion:	v5.14
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		When a CXL decoder is of devtype "cxl_decoder_switch", it can
+		optionally decode either accelerator memory (type-2) or expander
+		memory (type-3). The 'target_type' attribute indicates the
+		current setting which may dynamically change based on what
+		memory regions are activated in this decode hierarchy.
diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index ec324bf063b8..6f203ba7fc1d 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -70,6 +70,7 @@ static int add_host_bridge_uport(struct device *match, void *arg)
 	struct device *host = root_port->dev.parent;
 	struct acpi_pci_root *pci_root;
 	struct cxl_walk_context ctx;
+	struct cxl_decoder *cxld;
 	struct cxl_port *port;
 
 	if (!bridge)
@@ -94,7 +95,25 @@ static int add_host_bridge_uport(struct device *match, void *arg)
 
 	if (ctx.count == 0)
 		return -ENODEV;
-	return ctx.error;
+	if (ctx.error)
+		return ctx.error;
+
+	/* TODO: Scan CHBCR for HDM Decoder resources */
+
+	/*
+	 * In the single-port host-bridge case there are no HDM decoders
+	 * in the CHBCR and a 1:1 passthrough decode is implied.
+	 */
+	if (ctx.count == 1) {
+		cxld = devm_cxl_add_decoder(host, port, 1, 0, -2, 1, 0,
+					    CXL_DECODER_EXPANDER, 0);
+		if (IS_ERR(cxld))
+			return PTR_ERR(cxld);
+
+		dev_dbg(host, "add: %s\n", dev_name(&cxld->dev));
+	}
+
+	return 0;
 }
 
 static int add_host_bridge_dport(struct device *match, void *arg)
diff --git a/drivers/cxl/core.c b/drivers/cxl/core.c
index 4418b30cce4f..781efe51f186 100644
--- a/drivers/cxl/core.c
+++ b/drivers/cxl/core.c
@@ -33,6 +33,168 @@ static struct attribute_group cxl_base_attribute_group = {
 	.attrs = cxl_base_attributes,
 };
 
+static ssize_t start_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
+{
+	struct cxl_decoder *cxld = to_cxl_decoder(dev);
+
+	return sysfs_emit(buf, "%#llx\n", cxld->range.start);
+}
+static DEVICE_ATTR_RO(start);
+
+static ssize_t end_show(struct device *dev, struct device_attribute *attr,
+			char *buf)
+{
+	struct cxl_decoder *cxld = to_cxl_decoder(dev);
+
+	return sysfs_emit(buf, "%#llx\n", cxld->range.end);
+}
+static DEVICE_ATTR_RO(end);
+
+#define CXL_DECODER_FLAG_ATTR(name, flag)                            \
+static ssize_t name##_show(struct device *dev,                       \
+			   struct device_attribute *attr, char *buf) \
+{                                                                    \
+	struct cxl_decoder *cxld = to_cxl_decoder(dev);              \
+                                                                     \
+	return sysfs_emit(buf, "%s\n",                               \
+			  (cxld->flags & (flag)) ? "1" : "0");       \
+}                                                                    \
+static DEVICE_ATTR_RO(name)
+
+CXL_DECODER_FLAG_ATTR(cap_pmem, CXL_DECODER_F_PMEM);
+CXL_DECODER_FLAG_ATTR(cap_ram, CXL_DECODER_F_RAM);
+CXL_DECODER_FLAG_ATTR(cap_type2, CXL_DECODER_F_TYPE2);
+CXL_DECODER_FLAG_ATTR(cap_type3, CXL_DECODER_F_TYPE3);
+CXL_DECODER_FLAG_ATTR(locked, CXL_DECODER_F_LOCK);
+
+static ssize_t target_type_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct cxl_decoder *cxld = to_cxl_decoder(dev);
+
+	switch (cxld->target_type) {
+	case CXL_DECODER_ACCELERATOR:
+		return sysfs_emit(buf, "accelerator\n");
+	case CXL_DECODER_EXPANDER:
+		return sysfs_emit(buf, "expander\n");
+	}
+	return -ENXIO;
+}
+DEVICE_ATTR_RO(target_type);
+
+static ssize_t target_list_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct cxl_decoder *cxld = to_cxl_decoder(dev);
+	ssize_t offset = 0;
+	int i, rc = 0;
+
+	device_lock(dev);
+	for (i = 0; i < cxld->interleave_ways; i++) {
+		struct cxl_dport *dport = cxld->target[i];
+		struct cxl_dport *next = NULL;
+
+		if (!dport)
+			break;
+
+		if (i + 1 < cxld->interleave_ways)
+			next = cxld->target[i + 1];
+		rc = sysfs_emit_at(buf, offset, "%d%s", dport->port_id,
+				   next ? "," : "");
+		if (rc < 0)
+			break;
+		offset += rc;
+	}
+	device_unlock(dev);
+
+	if (rc < 0)
+		return rc;
+
+	rc = sysfs_emit_at(buf, offset, "\n");
+	if (rc < 0)
+		return rc;
+
+	return offset + rc;
+}
+DEVICE_ATTR_RO(target_list);
+
+static struct attribute *cxl_decoder_base_attrs[] = {
+	&dev_attr_start.attr,
+	&dev_attr_end.attr,
+	&dev_attr_locked.attr,
+	&dev_attr_target_list.attr,
+	NULL,
+};
+
+static struct attribute_group cxl_decoder_base_attribute_group = {
+	.attrs = cxl_decoder_base_attrs,
+};
+
+static struct attribute *cxl_decoder_root_attrs[] = {
+	&dev_attr_cap_pmem.attr,
+	&dev_attr_cap_ram.attr,
+	&dev_attr_cap_type2.attr,
+	&dev_attr_cap_type3.attr,
+	NULL,
+};
+
+static struct attribute_group cxl_decoder_root_attribute_group = {
+	.attrs = cxl_decoder_root_attrs,
+};
+
+static const struct attribute_group *cxl_decoder_root_attribute_groups[] = {
+	&cxl_decoder_root_attribute_group,
+	&cxl_decoder_base_attribute_group,
+	&cxl_base_attribute_group,
+	NULL,
+};
+
+static struct attribute *cxl_decoder_switch_attrs[] = {
+	&dev_attr_target_type.attr,
+	NULL,
+};
+
+static struct attribute_group cxl_decoder_switch_attribute_group = {
+	.attrs = cxl_decoder_switch_attrs,
+};
+
+static const struct attribute_group *cxl_decoder_switch_attribute_groups[] = {
+	&cxl_decoder_switch_attribute_group,
+	&cxl_decoder_base_attribute_group,
+	&cxl_base_attribute_group,
+	NULL,
+};
+
+static void cxl_decoder_release(struct device *dev)
+{
+	struct cxl_decoder *cxld = to_cxl_decoder(dev);
+	struct cxl_port *port = to_cxl_port(dev->parent);
+
+	ida_free(&port->decoder_ida, cxld->id);
+	kfree(cxld);
+}
+
+static const struct device_type cxl_decoder_switch_type = {
+	.name = "cxl_decoder_switch",
+	.release = cxl_decoder_release,
+	.groups = cxl_decoder_switch_attribute_groups,
+};
+
+static const struct device_type cxl_decoder_root_type = {
+	.name = "cxl_decoder_root",
+	.release = cxl_decoder_release,
+	.groups = cxl_decoder_root_attribute_groups,
+};
+
+struct cxl_decoder *to_cxl_decoder(struct device *dev)
+{
+	if (dev_WARN_ONCE(dev, dev->type->release != cxl_decoder_release,
+			  "not a cxl_decoder device\n"))
+		return NULL;
+	return container_of(dev, struct cxl_decoder, dev);
+}
+
 static void cxl_dport_release(struct cxl_dport *dport)
 {
 	put_device(dport->dport);
@@ -138,6 +300,7 @@ static struct cxl_port *cxl_port_alloc(struct device *uport,
 
 	port->uport = uport;
 	port->component_reg_phys = component_reg_phys;
+	ida_init(&port->decoder_ida);
 	INIT_LIST_HEAD(&port->dports);
 
 	device_initialize(dev);
@@ -262,6 +425,108 @@ int cxl_add_dport(struct cxl_port *port, struct device *dport_dev, int port_id,
 }
 EXPORT_SYMBOL_GPL(cxl_add_dport);
 
+static struct cxl_decoder *
+cxl_decoder_alloc(struct cxl_port *port, int nr_targets, resource_size_t base,
+		  resource_size_t len, int interleave_ways,
+		  int interleave_granularity, enum cxl_decoder_type type,
+		  unsigned long flags)
+{
+	struct cxl_decoder *cxld;
+	struct device *dev;
+	int rc = 0;
+
+	if (interleave_ways < 1)
+		return ERR_PTR(-EINVAL);
+
+	device_lock(&port->dev);
+	if (list_empty(&port->dports))
+		rc = -EINVAL;
+	device_unlock(&port->dev);
+	if (rc)
+		return ERR_PTR(rc);
+
+	cxld = kzalloc(struct_size(cxld, target, nr_targets), GFP_KERNEL);
+	if (!cxld)
+		return ERR_PTR(-ENOMEM);
+
+	rc = ida_alloc(&port->decoder_ida, GFP_KERNEL);
+	if (rc < 0)
+		goto err;
+
+	*cxld = (struct cxl_decoder) {
+		.id = rc,
+		.range = {
+			.start = base,
+			.end = base + len - 1,
+		},
+		.flags = flags,
+		.interleave_ways = interleave_ways,
+		.interleave_granularity = interleave_granularity,
+		.target_type = type,
+	};
+
+	/* handle implied target_list */
+	if (interleave_ways == 1)
+		cxld->target[0] =
+			list_first_entry(&port->dports, struct cxl_dport, list);
+	dev = &cxld->dev;
+	device_initialize(dev);
+	device_set_pm_not_required(dev);
+	dev->parent = &port->dev;
+	dev->bus = &cxl_bus_type;
+
+	/* root ports do not have a cxl_port_type parent */
+	if (port->dev.parent->type == &cxl_port_type)
+		dev->type = &cxl_decoder_switch_type;
+	else
+		dev->type = &cxl_decoder_root_type;
+
+	return cxld;
+err:
+	kfree(cxld);
+	return ERR_PTR(rc);
+}
+
+static void unregister_dev(void *dev)
+{
+	device_unregister(dev);
+}
+
+struct cxl_decoder *
+devm_cxl_add_decoder(struct device *host, struct cxl_port *port, int nr_targets,
+		     resource_size_t base, resource_size_t len,
+		     int interleave_ways, int interleave_granularity,
+		     enum cxl_decoder_type type, unsigned long flags)
+{
+	struct cxl_decoder *cxld;
+	struct device *dev;
+	int rc;
+
+	cxld = cxl_decoder_alloc(port, nr_targets, base, len, interleave_ways,
+				 interleave_granularity, type, flags);
+	if (IS_ERR(cxld))
+		return cxld;
+
+	dev = &cxld->dev;
+	rc = dev_set_name(dev, "decoder%d.%d", port->id, cxld->id);
+	if (rc)
+		goto err;
+
+	rc = device_add(dev);
+	if (rc)
+		goto err;
+
+	rc = devm_add_action_or_reset(host, unregister_dev, dev);
+	if (rc)
+		return ERR_PTR(rc);
+	return cxld;
+
+err:
+	put_device(dev);
+	return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_GPL(devm_cxl_add_decoder);
+
 /**
  * cxl_probe_component_regs() - Detect CXL Component register blocks
  * @dev: Host device of the @base mapping
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 0b89fcfe728a..f350c92d37d2 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -148,6 +148,44 @@ int cxl_map_device_regs(struct pci_dev *pdev,
 #define CXL_RESOURCE_NONE ((resource_size_t) -1)
 #define CXL_TARGET_STRLEN 20
 
+/*
+ * cxl_decoder flags that define the type of memory / devices this
+ * decoder supports as well as configuration lock status See "CXL 2.0
+ * 8.2.5.12.7 CXL HDM Decoder 0 Control Register" for details.
+ */
+#define CXL_DECODER_F_RAM   BIT(0)
+#define CXL_DECODER_F_PMEM  BIT(1)
+#define CXL_DECODER_F_TYPE2 BIT(2)
+#define CXL_DECODER_F_TYPE3 BIT(3)
+#define CXL_DECODER_F_LOCK  BIT(4)
+#define CXL_DECODER_F_MASK  GENMASK(4, 0)
+
+enum cxl_decoder_type {
+       CXL_DECODER_ACCELERATOR = 2,
+       CXL_DECODER_EXPANDER = 3,
+};
+
+/**
+ * struct cxl_decoder - CXL address range decode configuration
+ * @range: address range considered by this decoder
+ * @id: kernel device name id
+ * @interleave_ways: number of cxl_dports in this decode
+ * @interleave_granularity: data stride per dport
+ * @target_type: accelerator vs expander (type2 vs type3) selector
+ * @flags: memory type capabilities and locking
+ * @target: active ordered target list in current decoder configuration
+ */
+struct cxl_decoder {
+	struct device dev;
+	int id;
+	struct range range;
+	int interleave_ways;
+	int interleave_granularity;
+	enum cxl_decoder_type target_type;
+	unsigned long flags;
+	struct cxl_dport *target[];
+};
+
 /**
  * struct cxl_port - logical collection of upstream port devices and
  *		     downstream port devices to construct a CXL memory
@@ -156,6 +194,7 @@ int cxl_map_device_regs(struct pci_dev *pdev,
  * @uport: PCI or platform device implementing the upstream port capability
  * @id: id for port device-name
  * @dports: cxl_dport instances referenced by decoders
+ * @decoder_ida: allocator for decoder ids
  * @component_regs_phys: component register capability base address (optional)
  */
 struct cxl_port {
@@ -163,6 +202,7 @@ struct cxl_port {
 	struct device *uport;
 	int id;
 	struct list_head dports;
+	struct ida decoder_ida;
 	resource_size_t component_reg_phys;
 };
 
@@ -189,5 +229,13 @@ struct cxl_port *devm_cxl_add_port(struct device *host, struct device *uport,
 
 int cxl_add_dport(struct cxl_port *port, struct device *dport, int port_id,
 		  resource_size_t component_reg_phys);
+
+struct cxl_decoder *to_cxl_decoder(struct device *dev);
+struct cxl_decoder *
+devm_cxl_add_decoder(struct device *host, struct cxl_port *port, int nr_targets,
+		     resource_size_t base, resource_size_t len,
+		     int interleave_ways, int interleave_granularity,
+		     enum cxl_decoder_type type, unsigned long flags);
+
 extern struct bus_type cxl_bus_type;
 #endif /* __CXL_H__ */
