diff --git a/drivers/ntb/hw/intel/ntb_hw_gen1.c b/drivers/ntb/hw/intel/ntb_hw_gen1.c
index 423f9b8fbbcf5e741dfc004d181188d16fcb9b26..3185efeab487ba6f93dc3d699b6abf68536e203b 100644
--- a/drivers/ntb/hw/intel/ntb_hw_gen1.c
+++ b/drivers/ntb/hw/intel/ntb_hw_gen1.c
@@ -1205,7 +1205,7 @@ int intel_ntb_peer_spad_write(struct ntb_dev *ntb, int pidx, int sidx,
 			       ndev->peer_reg->spad);
 }
 
-static u64 xeon_db_ioread(void __iomem *mmio)
+static u64 xeon_db_ioread(const void __iomem *mmio)
 {
 	return (u64)ioread16(mmio);
 }
diff --git a/drivers/ntb/hw/intel/ntb_hw_gen3.h b/drivers/ntb/hw/intel/ntb_hw_gen3.h
index 2bc5d83560455e33d3884f92ae31e543bc66c63f..dea93989942d5a5a30adb4b121162a467078c050 100644
--- a/drivers/ntb/hw/intel/ntb_hw_gen3.h
+++ b/drivers/ntb/hw/intel/ntb_hw_gen3.h
@@ -91,7 +91,7 @@
 #define GEN3_DB_TOTAL_SHIFT		33
 #define GEN3_SPAD_COUNT			16
 
-static inline u64 gen3_db_ioread(void __iomem *mmio)
+static inline u64 gen3_db_ioread(const void __iomem *mmio)
 {
 	return ioread64(mmio);
 }
diff --git a/drivers/ntb/hw/intel/ntb_hw_intel.h b/drivers/ntb/hw/intel/ntb_hw_intel.h
index d61fcd91714bbc0dd28a284275f8dde2d746c1cf..05e2335c9596b28f0c7bba8ada2c42d0675739b6 100644
--- a/drivers/ntb/hw/intel/ntb_hw_intel.h
+++ b/drivers/ntb/hw/intel/ntb_hw_intel.h
@@ -103,7 +103,7 @@ struct intel_ntb_dev;
 struct intel_ntb_reg {
 	int (*poll_link)(struct intel_ntb_dev *ndev);
 	int (*link_is_up)(struct intel_ntb_dev *ndev);
-	u64 (*db_ioread)(void __iomem *mmio);
+	u64 (*db_ioread)(const void __iomem *mmio);
 	void (*db_iowrite)(u64 db_bits, void __iomem *mmio);
 	unsigned long			ntb_ctl;
 	resource_size_t			db_size;