diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index 35e64f65b164..c8e2840cda15 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -1533,6 +1533,18 @@ static const struct mtk_iommu_plat_data mt8183_data = {
 	.larbid_remap = {{0}, {4}, {5}, {6}, {7}, {2}, {3}, {1}},
 };
 
+static const unsigned int mt8186_larb_region_msk[MT8192_MULTI_REGION_NR_MAX][MTK_LARB_NR_MAX] = {
+	[0] = {~0, ~0, ~0},			/* Region0: all ports for larb0/1/2 */
+	[1] = {0, 0, 0, 0, ~0, 0, 0, ~0},	/* Region1: larb4/7 */
+	[2] = {0, 0, 0, 0, 0, 0, 0, 0,		/* Region2: larb8/9/11/13/16/17/19/20 */
+	       ~0, ~0, 0, ~0, 0, ~(u32)(BIT(9) | BIT(10)), 0, 0,
+						/* larb13: the other ports except port9/10 */
+	       ~0, ~0, 0, ~0, ~0},
+	[3] = {0},
+	[4] = {[13] = BIT(9) | BIT(10)},	/* larb13 port9/10 */
+	[5] = {[14] = ~0},			/* larb14 */
+};
+
 static const struct mtk_iommu_plat_data mt8186_data_mm = {
 	.m4u_plat       = M4U_MT8186,
 	.flags          = HAS_BCLK | HAS_SUB_COMM_2BITS | OUT_ORDER_WR_EN |
@@ -1545,6 +1557,7 @@ static const struct mtk_iommu_plat_data mt8186_data_mm = {
 	.banks_enable   = {true},
 	.iova_region    = mt8192_multi_dom,
 	.iova_region_nr = ARRAY_SIZE(mt8192_multi_dom),
+	.iova_region_larb_msk = mt8186_larb_region_msk,
 };
 
 static const unsigned int mt8192_larb_region_msk[MT8192_MULTI_REGION_NR_MAX][MTK_LARB_NR_MAX] = {