diff --git a/sys/alpha/alpha/busdma_machdep.c b/sys/alpha/alpha/busdma_machdep.c
index 44971671d682..0dc361cf422f 100644
--- a/sys/alpha/alpha/busdma_machdep.c
+++ b/sys/alpha/alpha/busdma_machdep.c
@@ -229,11 +229,11 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
 	if (parent != NULL) {
 		newtag->lowaddr = MIN(parent->lowaddr, newtag->lowaddr);
 		newtag->highaddr = MAX(parent->highaddr, newtag->highaddr);
-		/*
-		 * XXX Not really correct??? Probably need to honor boundary
-		 *     all the way up the inheritence chain.
-		 */
-		newtag->boundary = MAX(parent->boundary, newtag->boundary);
+		if (newtag->boundary == 0)
+			newtag->boundary = parent->boundary;
+		else if (parent->boundary != 0)
+			newtag->boundary = MIN(parent->boundary,
+					       newtag->boundary);
 		if (newtag->filter == NULL) {
 			/*
 			 * Short circuit looking at our parent directly
diff --git a/sys/amd64/amd64/busdma_machdep.c b/sys/amd64/amd64/busdma_machdep.c
index 8ea33e965ede..c10bad3ea092 100644
--- a/sys/amd64/amd64/busdma_machdep.c
+++ b/sys/amd64/amd64/busdma_machdep.c
@@ -248,11 +248,11 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
 	if (parent != NULL) {
 		newtag->lowaddr = MIN(parent->lowaddr, newtag->lowaddr);
 		newtag->highaddr = MAX(parent->highaddr, newtag->highaddr);
-		/*
-		 * XXX Not really correct??? Probably need to honor boundary
-		 *     all the way up the inheritence chain.
-		 */
-		newtag->boundary = MAX(parent->boundary, newtag->boundary);
+		if (newtag->boundary == 0)
+			newtag->boundary = parent->boundary;
+		else if (parent->boundary != 0)
+			newtag->boundary = MIN(parent->boundary,
+					       newtag->boundary);
 		if (newtag->filter == NULL) {
 			/*
 			 * Short circuit looking at our parent directly
diff --git a/sys/arm/arm/busdma_machdep.c b/sys/arm/arm/busdma_machdep.c
index 117e808fdffe..2a97646bd306 100644
--- a/sys/arm/arm/busdma_machdep.c
+++ b/sys/arm/arm/busdma_machdep.c
@@ -207,12 +207,11 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
         if (parent != NULL) {
                 newtag->lowaddr = min(parent->lowaddr, newtag->lowaddr);
                 newtag->highaddr = max(parent->highaddr, newtag->highaddr);
-		
-                /*
-                 * XXX Not really correct??? Probably need to honor boundary
-                 *     all the way up the inheritence chain.
-                 */
-                newtag->boundary = max(parent->boundary, newtag->boundary);
+		if (newtag->boundary == 0)
+			newtag->boundary = parent->boundary;
+		else if (parent->boundary != 0)
+                	newtag->boundary = min(parent->boundary,
+					       newtag->boundary);
                 if (newtag->filter == NULL) {
                         /*
                          * Short circuit looking at our parent directly
diff --git a/sys/i386/i386/busdma_machdep.c b/sys/i386/i386/busdma_machdep.c
index 8ea33e965ede..c10bad3ea092 100644
--- a/sys/i386/i386/busdma_machdep.c
+++ b/sys/i386/i386/busdma_machdep.c
@@ -248,11 +248,11 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
 	if (parent != NULL) {
 		newtag->lowaddr = MIN(parent->lowaddr, newtag->lowaddr);
 		newtag->highaddr = MAX(parent->highaddr, newtag->highaddr);
-		/*
-		 * XXX Not really correct??? Probably need to honor boundary
-		 *     all the way up the inheritence chain.
-		 */
-		newtag->boundary = MAX(parent->boundary, newtag->boundary);
+		if (newtag->boundary == 0)
+			newtag->boundary = parent->boundary;
+		else if (parent->boundary != 0)
+			newtag->boundary = MIN(parent->boundary,
+					       newtag->boundary);
 		if (newtag->filter == NULL) {
 			/*
 			 * Short circuit looking at our parent directly
diff --git a/sys/ia64/ia64/busdma_machdep.c b/sys/ia64/ia64/busdma_machdep.c
index 517aef9f54af..2c190853fc1b 100644
--- a/sys/ia64/ia64/busdma_machdep.c
+++ b/sys/ia64/ia64/busdma_machdep.c
@@ -247,11 +247,11 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
 	if (parent != NULL) {
 		newtag->lowaddr = MIN(parent->lowaddr, newtag->lowaddr);
 		newtag->highaddr = MAX(parent->highaddr, newtag->highaddr);
-		/*
-		 * XXX Not really correct??? Probably need to honor boundary
-		 *     all the way up the inheritence chain.
-		 */
-		newtag->boundary = MAX(parent->boundary, newtag->boundary);
+		if (newtag->boundary == 0)
+			newtag->boundary = parent->boundary;
+		else if (parent->boundary != 0)
+			newtag->boundary = MIN(parent->boundary,
+					       newtag->boundary);
 		if (newtag->filter == NULL) {
 			/*
 			 * Short circuit looking at our parent directly
diff --git a/sys/powerpc/powerpc/busdma_machdep.c b/sys/powerpc/powerpc/busdma_machdep.c
index a97c5355052b..f058f5fd1542 100644
--- a/sys/powerpc/powerpc/busdma_machdep.c
+++ b/sys/powerpc/powerpc/busdma_machdep.c
@@ -167,12 +167,11 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
         if (parent != NULL) {
                 newtag->lowaddr = min(parent->lowaddr, newtag->lowaddr);
                 newtag->highaddr = max(parent->highaddr, newtag->highaddr);
-		
-                /*
-                 * XXX Not really correct??? Probably need to honor boundary
-                 *     all the way up the inheritence chain.
-                 */
-                newtag->boundary = max(parent->boundary, newtag->boundary);
+		if (newtag->boundary == 0)
+			newtag->boundary = parent->boundary;
+		else if (parent->boundary != 0)
+                	newtag->boundary = MIN(parent->boundary,
+					       newtag->boundary);
                 if (newtag->filter == NULL) {
                         /*
                          * Short circuit looking at our parent directly
diff --git a/sys/sparc64/sparc64/bus_machdep.c b/sys/sparc64/sparc64/bus_machdep.c
index d1cdac86157f..47f41839cd63 100644
--- a/sys/sparc64/sparc64/bus_machdep.c
+++ b/sys/sparc64/sparc64/bus_machdep.c
@@ -255,12 +255,11 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
 		    newtag->dt_lowaddr);
 		newtag->dt_highaddr = ulmax(parent->dt_highaddr,
 		    newtag->dt_highaddr);
-		/*
-		 * XXX Not really correct??? Probably need to honor boundary
-		 *     all the way up the inheritence chain.
-		 */
-		newtag->dt_boundary = ulmin(parent->dt_boundary,
-		    newtag->dt_boundary);
+                if (newtag->dt_boundary == 0)
+                        newtag->dt_boundary = parent->dt_boundary;
+                else if (parent->dt_boundary != 0)            
+			newtag->dt_boundary = ulmin(parent->dt_boundary,
+			    newtag->dt_boundary);
 		atomic_add_int(&parent->dt_ref_count, 1);
 	}