diff --git a/sys/dev/uart/uart.h b/sys/dev/uart/uart.h
index 5eae06ceba6f..213f8eca457c 100644
--- a/sys/dev/uart/uart.h
+++ b/sys/dev/uart/uart.h
@@ -1,125 +1,135 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause
  *
  * Copyright (c) 2003 Marcel Moolenaar
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef _DEV_UART_H_
 #define _DEV_UART_H_
 
 /*
  * Bus access structure. This structure holds the minimum information needed
  * to access the UART. The rclk field, although not important to actually
  * access the UART, is important for baudrate programming, delay loops and
  * other timing related computations.
  */
 struct uart_bas {
 	bus_space_tag_t bst;
 	bus_space_handle_t bsh;
 	u_int	chan;
 	u_int	rclk;
 	u_int	regshft;
 	u_int	regiowidth;
 	u_int	busy_detect;
 };
 
 #define	uart_regofs(bas, reg)		((reg) << (bas)->regshft)
 #define	uart_regiowidth(bas)		((bas)->regiowidth)
 
 static inline uint32_t
 uart_getreg(struct uart_bas *bas, int reg)
 {
 	uint32_t ret;
 
 	switch (uart_regiowidth(bas)) {
+#if !defined(__i386__)
+	case 8:
+		ret = bus_space_read_8(bas->bst, bas->bsh, uart_regofs(bas, reg));
+		break;
+#endif
 	case 4:
 		ret = bus_space_read_4(bas->bst, bas->bsh, uart_regofs(bas, reg));
 		break;
 	case 2:
 		ret = bus_space_read_2(bas->bst, bas->bsh, uart_regofs(bas, reg));
 		break;
 	default:
 		ret = bus_space_read_1(bas->bst, bas->bsh, uart_regofs(bas, reg));
 		break;
 	}
 
 	return (ret);
 }
 
 static inline void
-uart_setreg(struct uart_bas *bas, int reg, int value)
+uart_setreg(struct uart_bas *bas, int reg, uint32_t value)
 {
 
 	switch (uart_regiowidth(bas)) {
+#if !defined(__i386__)
+	case 8:
+		bus_space_write_8(bas->bst, bas->bsh, uart_regofs(bas, reg), value);
+		break;
+#endif
 	case 4:
 		bus_space_write_4(bas->bst, bas->bsh, uart_regofs(bas, reg), value);
 		break;
 	case 2:
 		bus_space_write_2(bas->bst, bas->bsh, uart_regofs(bas, reg), value);
 		break;
 	default:
 		bus_space_write_1(bas->bst, bas->bsh, uart_regofs(bas, reg), value);
 		break;
 	}
 }
 
 /*
  * XXX we don't know the length of the bus space address range in use by
  * the UART. Since barriers don't use the length field currently, we put
  * a zero there for now.
  */
 #define uart_barrier(bas)		\
 	bus_space_barrier((bas)->bst, (bas)->bsh, 0, 0,		\
 	    BUS_SPACE_BARRIER_READ|BUS_SPACE_BARRIER_WRITE)
 
 /*
  * UART device classes.
  */
 struct uart_class;
 
 extern struct uart_class uart_ns8250_class __attribute__((weak));
 extern struct uart_class uart_quicc_class __attribute__((weak));
 extern struct uart_class uart_z8530_class __attribute__((weak));
 
 /*
  * Device flags.
  */
 #define	UART_FLAGS_CONSOLE(f)		((f) & 0x10)
 #define	UART_FLAGS_DBGPORT(f)		((f) & 0x80)
 #define	UART_FLAGS_FCR_RX_LOW(f)	((f) & 0x100)
 #define	UART_FLAGS_FCR_RX_MEDL(f)	((f) & 0x200)
 #define	UART_FLAGS_FCR_RX_MEDH(f)	((f) & 0x400)
 #define	UART_FLAGS_FCR_RX_HIGH(f)	((f) & 0x800)
 
 /*
  * Data parity values (magical numbers related to ns8250).
  */
 #define	UART_PARITY_NONE		0
 #define	UART_PARITY_ODD			1
 #define	UART_PARITY_EVEN		3
 #define	UART_PARITY_MARK		5
 #define	UART_PARITY_SPACE		7
 
 #endif /* _DEV_UART_H_ */