diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index ff6ea869fcc9..1bec38385a71 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -1421,6 +1421,20 @@ static int decoder_populate_targets(struct cxl_switch_decoder *cxlsd,
 	return rc;
 }
 
+static struct cxl_dport *cxl_hb_modulo(struct cxl_root_decoder *cxlrd, int pos)
+{
+	struct cxl_switch_decoder *cxlsd = &cxlrd->cxlsd;
+	struct cxl_decoder *cxld = &cxlsd->cxld;
+	int iw;
+
+	iw = cxld->interleave_ways;
+	if (dev_WARN_ONCE(&cxld->dev, iw != cxlsd->nr_targets,
+			  "misconfigured root decoder\n"))
+		return NULL;
+
+	return cxlrd->cxlsd.target[pos % iw];
+}
+
 static struct lock_class_key cxl_decoder_key;
 
 /**
@@ -1510,6 +1524,8 @@ struct cxl_root_decoder *cxl_root_decoder_alloc(struct cxl_port *port,
 		return ERR_PTR(rc);
 	}
 
+	cxlrd->calc_hb = cxl_hb_modulo;
+
 	cxld = &cxlsd->cxld;
 	cxld->dev.type = &cxl_decoder_root_type;
 	/*
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 5e84aa2d09e2..8f39cfb0d972 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -322,11 +322,13 @@ struct cxl_switch_decoder {
  * struct cxl_root_decoder - Static platform CXL address decoder
  * @res: host / parent resource for region allocations
  * @region_id: region id for next region provisioning event
+ * @calc_hb: which host bridge covers the n'th position by granularity
  * @cxlsd: base cxl switch decoder
  */
 struct cxl_root_decoder {
 	struct resource *res;
 	atomic_t region_id;
+	struct cxl_dport *(*calc_hb)(struct cxl_root_decoder *cxlrd, int pos);
 	struct cxl_switch_decoder cxlsd;
 };