diff --git a/arch/arm/src/stm32f0l0g0/stm32_serial_v2.c b/arch/arm/src/stm32f0l0g0/stm32_serial_v2.c
index d4ea002914..c0a5abca7e 100644
--- a/arch/arm/src/stm32f0l0g0/stm32_serial_v2.c
+++ b/arch/arm/src/stm32f0l0g0/stm32_serial_v2.c
@@ -496,18 +496,6 @@ static inline void up_serialout(struct up_dev_s *priv,
   putreg32(value, priv->usartbase + offset);
 }
 
-/****************************************************************************
- * Name: up_serialmod
- ****************************************************************************/
-
-static inline void up_serialmod(struct up_dev_s *priv, int offset,
-                                uint32_t clrbits, uint32_t setbits)
-{
-  uint32_t addr = priv->usartbase + offset;
-  uint32_t regval = (getreg32(addr) & ~clrbits) | setbits;
-  putreg32(regval, addr);
-}
-
 /****************************************************************************
  * Name: up_setusartint
  ****************************************************************************/
diff --git a/arch/arm/src/stm32h7/stm32_serial.c b/arch/arm/src/stm32h7/stm32_serial.c
index 7cc366e764..8f1d1b82a3 100644
--- a/arch/arm/src/stm32h7/stm32_serial.c
+++ b/arch/arm/src/stm32h7/stm32_serial.c
@@ -1535,18 +1535,6 @@ static inline void up_serialout(struct up_dev_s *priv, int offset,
   putreg32(value, priv->usartbase + offset);
 }
 
-/****************************************************************************
- * Name: up_serialmod
- ****************************************************************************/
-
-static inline void up_serialmod(struct up_dev_s *priv, int offset,
-                                uint32_t clrbits, uint32_t setbits)
-{
-  uint32_t addr = priv->usartbase + offset;
-  uint32_t regval = (getreg32(addr) & ~clrbits) | setbits;
-  putreg32(regval, addr);
-}
-
 /****************************************************************************
  * Name: up_setusartint
  ****************************************************************************/