Index: head/sys/dev/uart/uart_tty.c
===================================================================
--- head/sys/dev/uart/uart_tty.c
+++ head/sys/dev/uart/uart_tty.c
@@ -53,6 +53,7 @@
 
 static cn_probe_t uart_cnprobe;
 static cn_init_t uart_cninit;
+static cn_init_t uart_cnresume;
 static cn_term_t uart_cnterm;
 static cn_getc_t uart_cngetc;
 static cn_putc_t uart_cnputc;
@@ -69,7 +70,10 @@
 static tsw_free_t uart_tty_free;
 static tsw_busy_t uart_tty_busy;
 
-CONSOLE_DRIVER(uart);
+CONSOLE_DRIVER(
+	uart,
+	.cn_resume = uart_cnresume,
+);
 
 static struct uart_devinfo uart_console;
 
@@ -112,6 +116,13 @@
 	di->type = UART_DEV_CONSOLE;
 	uart_add_sysdev(di);
 	uart_init(di);
+}
+
+static void
+uart_cnresume(struct consdev *cp)
+{
+
+	uart_init(cp->cn_arg);
 }
 
 static void
Index: head/sys/kern/kern_cons.c
===================================================================
--- head/sys/kern/kern_cons.c
+++ head/sys/kern/kern_cons.c
@@ -384,6 +384,19 @@
 	}
 }
 
+void
+cnresume()
+{
+	struct cn_device *cnd;
+	struct consdev *cn;
+
+	STAILQ_FOREACH(cnd, &cn_devlist, cnd_next) {
+		cn = cnd->cnd_cn;
+		if (cn->cn_ops->cn_resume != NULL)
+			cn->cn_ops->cn_resume(cn);
+	}
+}
+
 /*
  * Low level console routines.
  */
Index: head/sys/sys/cons.h
===================================================================
--- head/sys/sys/cons.h
+++ head/sys/sys/cons.h
@@ -66,6 +66,8 @@
 				/* grab console for exclusive kernel use */
 	cn_ungrab_t	*cn_ungrab;
 				/* ungrab console */
+	cn_init_t	*cn_resume;
+				/* set up console after sleep, optional */
 };
 
 struct consdev {
@@ -105,8 +107,9 @@
 	};								\
 	DATA_SET(cons_set, name)
 
-#define	CONSOLE_DRIVER(name)						\
+#define	CONSOLE_DRIVER(name, ...)					\
 	static const struct consdev_ops name##_consdev_ops = {		\
+		/* Mandatory methods. */				\
 		.cn_probe = name##_cnprobe,				\
 		.cn_init = name##_cninit,				\
 		.cn_term = name##_cnterm,				\
@@ -114,6 +117,8 @@
 		.cn_putc = name##_cnputc,				\
 		.cn_grab = name##_cngrab,				\
 		.cn_ungrab = name##_cnungrab,				\
+		/* Optional fields. */					\
+		__VA_ARGS__						\
 	};								\
 	CONSOLE_DEVICE(name##_consdev, name##_consdev_ops, NULL)
 
@@ -126,6 +131,7 @@
 void	cnselect(struct consdev *);
 void	cngrab(void);
 void	cnungrab(void);
+void	cnresume(void);
 int	cncheckc(void);
 int	cngetc(void);
 void	cngets(char *, size_t, int);
Index: head/sys/x86/acpica/acpi_wakeup.c
===================================================================
--- head/sys/x86/acpica/acpi_wakeup.c
+++ head/sys/x86/acpica/acpi_wakeup.c
@@ -46,6 +46,7 @@
 #include <sys/memrange.h>
 #include <sys/smp.h>
 #include <sys/systm.h>
+#include <sys/cons.h>
 
 #include <vm/vm.h>
 #include <vm/pmap.h>
@@ -296,6 +297,12 @@
 		for (;;)
 			ia32_pause();
 	} else {
+		/*
+		 * Re-initialize console hardware as soon as possibe.
+		 * No console output (e.g. printf) is allowed before
+		 * this point.
+		 */
+		cnresume();
 #ifdef __amd64__
 		fpuresume(susppcbs[0]->sp_fpususpend);
 #else