diff --git a/arch/arm/src/sama5/sam_lowputc.c b/arch/arm/src/sama5/sam_lowputc.c
index 6931c6ceed0..2685335ca25 100644
--- a/arch/arm/src/sama5/sam_lowputc.c
+++ b/arch/arm/src/sama5/sam_lowputc.c
@@ -149,10 +149,10 @@
 #  undef HAVE_UART_CONSOLE
 #endif
 
-/* The UART/USART modules are driven by the main clock (MCK). */
+/* The UART/USART modules are driven by the peripheral clock (MCK or MCK2). */
 
-#define SAM_USART_CLOCK  BOARD_MCK_FREQUENCY  /* Frequency of the main clock */
-#define SAM_MR_USCLKS    UART_MR_USCLKS_MCK   /* Source = Main clock */
+#define SAM_USART_CLOCK  BOARD_USART_FREQUENCY /* Frequency of the USART clock */
+#define SAM_MR_USCLKS    UART_MR_USCLKS_MCK    /* Source = Main clock */
 
 /* Select USART parameters for the selected console */
 
diff --git a/arch/arm/src/sama5/sam_serial.c b/arch/arm/src/sama5/sam_serial.c
index 8dcc05bdb26..479caf5b0c3 100644
--- a/arch/arm/src/sama5/sam_serial.c
+++ b/arch/arm/src/sama5/sam_serial.c
@@ -382,10 +382,10 @@
 #  define USART4_ASSIGNED      1
 #endif
 
-/* The UART/USART modules are driven by the main clock (MCK). */
+/* The UART/USART modules are driven by the peripheral clock (MCK or MCK2). */
 
-#define SAM_USART_CLOCK  BOARD_MCK_FREQUENCY  /* Frequency of the main clock */
-#define SAM_MR_USCLKS    UART_MR_USCLKS_MCK   /* Source = Main clock */
+#define SAM_USART_CLOCK  BOARD_USART_FREQUENCY /* Frequency of the USART clock */
+#define SAM_MR_USCLKS    UART_MR_USCLKS_MCK    /* Source = Main clock */
 
 /****************************************************************************
  * Private Types
diff --git a/configs/sama5d3-xplained/include/board_384mhz.h b/configs/sama5d3-xplained/include/board_384mhz.h
index 75b41677746..f9d38fba3e1 100644
--- a/configs/sama5d3-xplained/include/board_384mhz.h
+++ b/configs/sama5d3-xplained/include/board_384mhz.h
@@ -167,6 +167,12 @@
 #define BOARD_MCK_FREQUENCY        (128000000) /* MCK:     PLLACK / 2 / 1 / 3 */
 #define BOARD_ADCCLK_FREQUENCY     (8000000)   /* ADCCLK:  MCK / ((7+1)*2) */
 
+/* On some SAMA5's, the clocking to peripherals may be divided down from MCK,
+ * but not for the SAMA5D3.
+ */
+
+#define BOARD_USART_FREQUENCY      BOARD_MCK_FREQUENCY
+
 /* HSMCI clocking
  *
  * Multimedia Card Interface clock (MCCK or MCI_CK) is Master Clock (MCK)
diff --git a/configs/sama5d3-xplained/include/board_396mhz.h b/configs/sama5d3-xplained/include/board_396mhz.h
index a16190a0bda..7293956a50e 100644
--- a/configs/sama5d3-xplained/include/board_396mhz.h
+++ b/configs/sama5d3-xplained/include/board_396mhz.h
@@ -125,6 +125,12 @@
 #define BOARD_MCK_FREQUENCY        (132000000) /* MCK:     PLLACK / 2 / 1 / 3 */
 #define BOARD_ADCCLK_FREQUENCY     (8250000)   /* ADCCLK:  MCK / ((7+1)*2) */
 
+/* On some SAMA5's, the clocking to peripherals may be divided down from MCK,
+ * but not for the SAMA5D3.
+ */
+
+#define BOARD_USART_FREQUENCY      BOARD_MCK_FREQUENCY
+
 #if defined(CONFIG_SAMA5_EHCI) || defined(CONFIG_SAMA5_OHCI) || \
     defined(CONFIG_SAMA5_UDPHS)
 
diff --git a/configs/sama5d3-xplained/include/board_528mhz.h b/configs/sama5d3-xplained/include/board_528mhz.h
index ff1b88ca68c..dc857bee4b1 100644
--- a/configs/sama5d3-xplained/include/board_528mhz.h
+++ b/configs/sama5d3-xplained/include/board_528mhz.h
@@ -124,6 +124,12 @@
 #define BOARD_MCK_FREQUENCY        (132000000) /* MCK:     PLLACK / 1 / 1 / 4 */
 #define BOARD_ADCCLK_FREQUENCY     (8250000)   /* ADCCLK:  MCK / ((7+1)*2) */
 
+/* On some SAMA5's, the clocking to peripherals may be divided down from MCK,
+ * but not for the SAMA5D3.
+ */
+
+#define BOARD_USART_FREQUENCY      BOARD_MCK_FREQUENCY
+
 #if defined(CONFIG_SAMA5_EHCI) || defined(CONFIG_SAMA5_OHCI) || \
     defined(CONFIG_SAMA5_UDPHS)
 
diff --git a/configs/sama5d3-xplained/include/board_sdram.h b/configs/sama5d3-xplained/include/board_sdram.h
index 61d25155b5b..4f2e5f971f1 100644
--- a/configs/sama5d3-xplained/include/board_sdram.h
+++ b/configs/sama5d3-xplained/include/board_sdram.h
@@ -63,6 +63,12 @@
 #define BOARD_PCK_FREQUENCY        (sam_pck_frequency(BOARD_MAINOSC_FREQUENCY))
 #define BOARD_MCK_FREQUENCY        (sam_mck_frequency(BOARD_MAINOSC_FREQUENCY))
 
+/* On some SAMA5's, the clocking to peripherals may be divided down from MCK,
+ * but not for the SAMA5D3.
+ */
+
+#define BOARD_USART_FREQUENCY      BOARD_MCK_FREQUENCY
+
 #if defined(CONFIG_SAMA5_EHCI) || defined(CONFIG_SAMA5_OHCI) || \
     defined(CONFIG_SAMA5_UDPHS)
 
diff --git a/configs/sama5d3x-ek/include/board_384mhz.h b/configs/sama5d3x-ek/include/board_384mhz.h
index 3dee820444a..528ff509a33 100644
--- a/configs/sama5d3x-ek/include/board_384mhz.h
+++ b/configs/sama5d3x-ek/include/board_384mhz.h
@@ -167,6 +167,12 @@
 #define BOARD_MCK_FREQUENCY        (128000000) /* MCK:     PLLACK / 2 / 1 / 3 */
 #define BOARD_ADCCLK_FREQUENCY     (8000000)   /* ADCCLK:  MCK / ((7+1)*2) */
 
+/* On some SAMA5's, the clocking to peripherals may be divided down from MCK,
+ * but not for the SAMA5D3.
+ */
+
+#define BOARD_USART_FREQUENCY      BOARD_MCK_FREQUENCY
+
 /* HSMCI clocking
  *
  * Multimedia Card Interface clock (MCCK or MCI_CK) is Master Clock (MCK)
diff --git a/configs/sama5d3x-ek/include/board_396mhz.h b/configs/sama5d3x-ek/include/board_396mhz.h
index 707ffd87838..ef850fda8fa 100644
--- a/configs/sama5d3x-ek/include/board_396mhz.h
+++ b/configs/sama5d3x-ek/include/board_396mhz.h
@@ -125,6 +125,12 @@
 #define BOARD_MCK_FREQUENCY        (132000000) /* MCK:     PLLACK / 2 / 1 / 3 */
 #define BOARD_ADCCLK_FREQUENCY     (8250000)   /* ADCCLK:  MCK / ((7+1)*2) */
 
+/* On some SAMA5's, the clocking to peripherals may be divided down from MCK,
+ * but not for the SAMA5D3.
+ */
+
+#define BOARD_USART_FREQUENCY      BOARD_MCK_FREQUENCY
+
 #if defined(CONFIG_SAMA5_EHCI) || defined(CONFIG_SAMA5_OHCI) || \
     defined(CONFIG_SAMA5_UDPHS)
 
diff --git a/configs/sama5d3x-ek/include/board_528mhz.h b/configs/sama5d3x-ek/include/board_528mhz.h
index 4f79ecd4a64..0b2744030d8 100644
--- a/configs/sama5d3x-ek/include/board_528mhz.h
+++ b/configs/sama5d3x-ek/include/board_528mhz.h
@@ -124,6 +124,11 @@
 #define BOARD_MCK_FREQUENCY        (132000000) /* MCK:     PLLACK / 1 / 1 / 4 */
 #define BOARD_ADCCLK_FREQUENCY     (8250000)   /* ADCCLK:  MCK / ((7+1)*2) */
 
+/* On some SAMA5's, the clocking to peripherals may be divided down from MCK,
+ * but not for the SAMA5D3.
+ */
+
+#define BOARD_USART_FREQUENCY      BOARD_MCK_FREQUENCY
 #if defined(CONFIG_SAMA5_EHCI) || defined(CONFIG_SAMA5_OHCI) || \
     defined(CONFIG_SAMA5_UDPHS)
 
diff --git a/configs/sama5d3x-ek/include/board_sdram.h b/configs/sama5d3x-ek/include/board_sdram.h
index f7e8b8015a8..9e4b6046904 100644
--- a/configs/sama5d3x-ek/include/board_sdram.h
+++ b/configs/sama5d3x-ek/include/board_sdram.h
@@ -63,6 +63,12 @@
 #define BOARD_PCK_FREQUENCY        (sam_pck_frequency(BOARD_MAINOSC_FREQUENCY))
 #define BOARD_MCK_FREQUENCY        (sam_mck_frequency(BOARD_MAINOSC_FREQUENCY))
 
+/* On some SAMA5's, the clocking to peripherals may be divided down from MCK,
+ * but not for the SAMA5D3.
+ */
+
+#define BOARD_USART_FREQUENCY      BOARD_MCK_FREQUENCY
+
 #if defined(CONFIG_SAMA5_EHCI) || defined(CONFIG_SAMA5_OHCI) || \
     defined(CONFIG_SAMA5_UDPHS)
 
diff --git a/configs/sama5d4-ek/include/board_384mhz.h b/configs/sama5d4-ek/include/board_384mhz.h
index 878c82222ac..fc2d4e4bc1f 100644
--- a/configs/sama5d4-ek/include/board_384mhz.h
+++ b/configs/sama5d4-ek/include/board_384mhz.h
@@ -165,6 +165,13 @@
 #define BOARD_MCK_FREQUENCY        (128000000) /* MCK:     PLLACK / 2 / 1 / 3 */
 #define BOARD_ADCCLK_FREQUENCY     (8000000)   /* ADCCLK:  MCK / ((7+1)*2) */
 
+/* Clocking to certain peripherals may be MCK/2.
+ *
+ * REVISIT:  I am not sure why this is.  Perhaps because of H32MXDIV?
+ */
+
+#define BOARD_USART_FREQUENCY      (BOARD_MCK_FREQUENCY >> 1)
+
 /* HSMCI clocking
  *
  * Multimedia Card Interface clock (MCCK or MCI_CK) is Master Clock (MCK)
diff --git a/configs/sama5d4-ek/include/board_396mhz.h b/configs/sama5d4-ek/include/board_396mhz.h
index a20527403d6..11af935ed3a 100644
--- a/configs/sama5d4-ek/include/board_396mhz.h
+++ b/configs/sama5d4-ek/include/board_396mhz.h
@@ -123,6 +123,13 @@
 #define BOARD_MCK_FREQUENCY        (132000000) /* MCK:     PLLACK / 2 / 1 / 3 */
 #define BOARD_ADCCLK_FREQUENCY     (8250000)   /* ADCCLK:  MCK / ((7+1)*2) */
 
+/* Clocking to certain peripherals may be MCK/2.
+ *
+ * REVISIT:  I am not sure why this is.  Perhaps because of H32MXDIV?
+ */
+
+#define BOARD_USART_FREQUENCY      (BOARD_MCK_FREQUENCY >> 1)
+
 #if defined(CONFIG_SAMA5_EHCI) || defined(CONFIG_SAMA5_OHCI) || \
     defined(CONFIG_SAMA5_UDPHS)
 
diff --git a/configs/sama5d4-ek/include/board_528mhz.h b/configs/sama5d4-ek/include/board_528mhz.h
index 446a480ab23..aa6a336e85d 100644
--- a/configs/sama5d4-ek/include/board_528mhz.h
+++ b/configs/sama5d4-ek/include/board_528mhz.h
@@ -122,6 +122,13 @@
 #define BOARD_MCK_FREQUENCY        (132000000) /* MCK:     PLLACK / 1 / 1 / 4 */
 #define BOARD_ADCCLK_FREQUENCY     (8250000)   /* ADCCLK:  MCK / ((7+1)*2) */
 
+/* Clocking to certain peripherals may be MCK/2.
+ *
+ * REVISIT:  I am not sure why this is.  Perhaps because of H32MXDIV?
+ */
+
+#define BOARD_USART_FREQUENCY      (BOARD_MCK_FREQUENCY >> 1)
+
 #if defined(CONFIG_SAMA5_EHCI) || defined(CONFIG_SAMA5_OHCI) || \
     defined(CONFIG_SAMA5_UDPHS)
 
diff --git a/configs/sama5d4-ek/include/board_sdram.h b/configs/sama5d4-ek/include/board_sdram.h
index 338c0381817..5b113d17eed 100644
--- a/configs/sama5d4-ek/include/board_sdram.h
+++ b/configs/sama5d4-ek/include/board_sdram.h
@@ -63,6 +63,13 @@
 #define BOARD_PCK_FREQUENCY        (sam_pck_frequency(BOARD_MAINOSC_FREQUENCY))
 #define BOARD_MCK_FREQUENCY        (sam_mck_frequency(BOARD_MAINOSC_FREQUENCY))
 
+/* Clocking to certain peripherals may be MCK/2.
+ *
+ * REVISIT:  I am not sure why this is.  Perhaps because of H32MXDIV?
+ */
+
+#define BOARD_USART_FREQUENCY      (BOARD_MCK_FREQUENCY >> 1)
+
 #if defined(CONFIG_SAMA5_EHCI) || defined(CONFIG_SAMA5_OHCI) || \
     defined(CONFIG_SAMA5_UDPHS)