diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index 9bbaad9f3d6326cdd113e48faa0d0e091bcde04c..efb44d5ab02156282f477fde76e8ca3bf4675f1b 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -499,7 +499,11 @@
 
 /* Bitfields in TISUBN */
 #define GEM_SUBNSINCR_OFFSET			0
-#define GEM_SUBNSINCR_SIZE			16
+#define GEM_SUBNSINCRL_OFFSET			24
+#define GEM_SUBNSINCRL_SIZE			8
+#define GEM_SUBNSINCRH_OFFSET			0
+#define GEM_SUBNSINCRH_SIZE			16
+#define GEM_SUBNSINCR_SIZE			24
 
 /* Bitfields in TI */
 #define GEM_NSINCR_OFFSET			0
diff --git a/drivers/net/ethernet/cadence/macb_ptp.c b/drivers/net/ethernet/cadence/macb_ptp.c
index a6dc47edc4cf6431066850770928640670e20bb1..8f912de44defcab99c4fc261249b79415f6b8c1f 100644
--- a/drivers/net/ethernet/cadence/macb_ptp.c
+++ b/drivers/net/ethernet/cadence/macb_ptp.c
@@ -115,7 +115,10 @@ static int gem_tsu_incr_set(struct macb *bp, struct tsu_incr *incr_spec)
 	 * to take effect.
 	 */
 	spin_lock_irqsave(&bp->tsu_clk_lock, flags);
-	gem_writel(bp, TISUBN, GEM_BF(SUBNSINCR, incr_spec->sub_ns));
+	/* RegBit[15:0] = Subns[23:8]; RegBit[31:24] = Subns[7:0] */
+	gem_writel(bp, TISUBN, GEM_BF(SUBNSINCRL, incr_spec->sub_ns) |
+		   GEM_BF(SUBNSINCRH, (incr_spec->sub_ns >>
+			  GEM_SUBNSINCRL_SIZE)));
 	gem_writel(bp, TI, GEM_BF(NSINCR, incr_spec->ns));
 	spin_unlock_irqrestore(&bp->tsu_clk_lock, flags);