Index: com.c
===================================================================
RCS file: /cvs/src/sys/dev/ic/com.c,v
retrieving revision 1.158
diff -u -p -r1.158 com.c
--- com.c	14 Sep 2014 14:17:24 -0000	1.158
+++ com.c	5 Jan 2016 23:36:27 -0000
@@ -79,6 +79,7 @@
 #endif
 
 #include <machine/bus.h>
+#include <machine/cpufunc.h>
 #if !defined(__sparc__) || defined(__sparc64__)
 #include <machine/intr.h>
 #endif
@@ -146,6 +147,32 @@ void   com_kgdb_putc(void *, int);
 #define	DEVUNIT(x)	(minor(x) & 0x7f)
 #define	DEVCUA(x)	(minor(x) & 0x80)
 
+void
+disp_reg(char *identifier, bus_space_tag_t iot, bus_space_handle_t ioh)
+{
+	int	i;
+	unsigned char	reg[16];
+	unsigned char	lcr;
+
+	disable_intr();
+
+	lcr = bus_space_read_1(iot, ioh, com_lcr);
+
+	bus_space_write_1(iot, ioh, com_lcr, lcr | LCR_DLAB);
+	for (i = 0; i < 8; i++) reg[i + 8] = bus_space_read_1(iot, ioh, i);
+
+	bus_space_write_1(iot, ioh, com_lcr, lcr);
+	for (i = 1; i < 8; i++) reg[i] = bus_space_read_1(iot, ioh, i);
+
+	reg[0] = 0xff;
+
+	enable_intr();
+
+	printf("%s: ", identifier);
+	for (i = 0; i < 16; i++) printf("%02x ", reg[i]);
+	printf("\n");
+}
+
 int
 comspeed(long freq, long speed)
 {
@@ -431,6 +458,7 @@ comopen(dev_t dev, int flag, int mode, s
 #endif
 		}
 #endif
+disp_reg("comopen", iot, ioh);
 	} else if (ISSET(tp->t_state, TS_XCLUDE) && suser(p, 0) != 0)
 		return EBUSY;
 	else
@@ -681,6 +709,7 @@ com_resume(struct com_softc *sc)
 #endif
 	}
 #endif
+disp_reg("com_resume", iot, ioh);
 }
 
 void
@@ -981,6 +1010,7 @@ comparam(struct tty *tp, struct termios 
 		bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
 	}
 
+disp_reg("comparam", iot, ioh);
 	/* Just to be sure... */
 	comstart(tp);
 	return 0;
@@ -1403,6 +1433,7 @@ cominit(bus_space_tag_t iot, bus_space_h
 	    FIFO_ENABLE | FIFO_RCV_RST | FIFO_XMT_RST | FIFO_TRIGGER_1);
 	stat = bus_space_read_1(iot, ioh, com_iir);
 	splx(s);
+disp_reg("cominit", iot, ioh);
 }
 
 #ifdef COM_CONSOLE