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	6 Jan 2016 02:46:41 -0000
@@ -106,6 +106,7 @@
 cdev_decl(com);
 
 static u_char tiocm_xxx2mcr(int);
+static void write_lcr(bus_space_tag_t, bus_space_handle_t, u_int8_t);
 
 void	compwroff(struct com_softc *);
 void	cominit(bus_space_tag_t, bus_space_handle_t, int, int);
@@ -146,6 +147,21 @@ void   com_kgdb_putc(void *, int);
 #define	DEVUNIT(x)	(minor(x) & 0x7f)
 #define	DEVCUA(x)	(minor(x) & 0x80)
 
+static void
+write_lcr(bus_space_tag_t iot, bus_space_handle_t ioh, u_int8_t lcr)
+{
+	int i;
+
+	/* there is a buggy UART which sometimes fails to
+	 * write LCR register, so retry it */
+	for (i = 0; i < 1000; i++) {
+		bus_space_write_1(iot, ioh, com_lcr, lcr);
+		if (bus_space_read_1(iot, ioh, com_lcr) == lcr) break;
+	}
+
+	if (i) printf("write_lcr: failed to set lcr %d\n", i);
+}
+
 int
 comspeed(long freq, long speed)
 {
@@ -342,11 +358,11 @@ comopen(dev_t dev, int flag, int mode, s
 			switch (sc->sc_uarttype) {
 			case COM_UART_ST16650:
 			case COM_UART_ST16650V2:
-				bus_space_write_1(iot, ioh, com_lcr, LCR_EFR);
+				write_lcr(iot, ioh, LCR_EFR);
 				bus_space_write_1(iot, ioh, com_efr, EFR_ECB);
 				bus_space_write_1(iot, ioh, com_ier, 0);
 				bus_space_write_1(iot, ioh, com_efr, 0);
-				bus_space_write_1(iot, ioh, com_lcr, 0);
+				write_lcr(iot, ioh, 0);
 				break;
 			case COM_UART_TI16750:
 				bus_space_write_1(iot, ioh, com_ier, 0);
@@ -370,8 +386,7 @@ comopen(dev_t dev, int flag, int mode, s
 			if (sc->sc_uarttype == COM_UART_TI16750) {
 				fifo |= FIFO_ENABLE_64BYTE;
 				lcr = bus_space_read_1(iot, ioh, com_lcr);
-				bus_space_write_1(iot, ioh, com_lcr,
-				    lcr | LCR_DLAB);
+				write_lcr(iot, ioh, lcr | LCR_DLAB);
 			}
 
 			/*
@@ -397,7 +412,7 @@ comopen(dev_t dev, int flag, int mode, s
 					break;
 			}
 			if (sc->sc_uarttype == COM_UART_TI16750)
-				bus_space_write_1(iot, ioh, com_lcr, lcr);
+				write_lcr(iot, ioh, lcr);
 		}
 
 		/* Flush any pending I/O. */
@@ -531,7 +546,7 @@ compwroff(struct com_softc *sc)
 	struct tty *tp = sc->sc_tty;
 
 	CLR(sc->sc_lcr, LCR_SBREAK);
-	bus_space_write_1(iot, ioh, com_lcr, sc->sc_lcr);
+	write_lcr(iot, ioh, sc->sc_lcr);
 	bus_space_write_1(iot, ioh, com_ier, 0);
 	if (ISSET(tp->t_cflag, HUPCL) &&
 	    !ISSET(sc->sc_swflags, COM_SW_SOFTCAR)) {
@@ -555,10 +570,10 @@ compwroff(struct com_softc *sc)
 		switch (sc->sc_uarttype) {
 		case COM_UART_ST16650:
 		case COM_UART_ST16650V2:
-			bus_space_write_1(iot, ioh, com_lcr, LCR_EFR);
+			write_lcr(iot, ioh, LCR_EFR);
 			bus_space_write_1(iot, ioh, com_efr, EFR_ECB);
 			bus_space_write_1(iot, ioh, com_ier, IER_SLEEP);
-			bus_space_write_1(iot, ioh, com_lcr, 0);
+			write_lcr(iot, ioh, 0);
 			break;
 		case COM_UART_TI16750:
 			bus_space_write_1(iot, ioh, com_ier, IER_SLEEP);
@@ -599,11 +614,11 @@ com_resume(struct com_softc *sc)
 		switch (sc->sc_uarttype) {
 		case COM_UART_ST16650:
 		case COM_UART_ST16650V2:
-			bus_space_write_1(iot, ioh, com_lcr, LCR_EFR);
+			write_lcr(iot, ioh, LCR_EFR);
 			bus_space_write_1(iot, ioh, com_efr, EFR_ECB);
 			bus_space_write_1(iot, ioh, com_ier, 0);
 			bus_space_write_1(iot, ioh, com_efr, 0);
-			bus_space_write_1(iot, ioh, com_lcr, 0);
+			write_lcr(iot, ioh, 0);
 			break;
 		case COM_UART_TI16750:
 			bus_space_write_1(iot, ioh, com_ier, 0);
@@ -617,12 +632,12 @@ com_resume(struct com_softc *sc)
 	ospeed = comspeed(sc->sc_frequency, tp->t_ospeed);
 
 	if (ospeed != 0) {
-		bus_space_write_1(iot, ioh, com_lcr, sc->sc_lcr | LCR_DLAB);
+		write_lcr(iot, ioh, sc->sc_lcr | LCR_DLAB);
 		bus_space_write_1(iot, ioh, com_dlbl, ospeed);
 		bus_space_write_1(iot, ioh, com_dlbh, ospeed >> 8);
-		bus_space_write_1(iot, ioh, com_lcr, sc->sc_lcr);
+		write_lcr(iot, ioh, sc->sc_lcr);
 	} else {
-		bus_space_write_1(iot, ioh, com_lcr, sc->sc_lcr);
+		write_lcr(iot, ioh, sc->sc_lcr);
 	}
 
 	if (ISSET(sc->sc_hwflags, COM_HW_FIFO)) {
@@ -638,8 +653,7 @@ com_resume(struct com_softc *sc)
 		if (sc->sc_uarttype == COM_UART_TI16750) {
 			fifo |= FIFO_ENABLE_64BYTE;
 			lcr = bus_space_read_1(iot, ioh, com_lcr);
-			bus_space_write_1(iot, ioh, com_lcr,
-			    lcr | LCR_DLAB);
+			write_lcr(iot, ioh, lcr | LCR_DLAB);
 		}
 
 		/*
@@ -665,7 +679,7 @@ com_resume(struct com_softc *sc)
 				break;
 		}
 		if (sc->sc_uarttype == COM_UART_TI16750)
-			bus_space_write_1(iot, ioh, com_lcr, lcr);
+			write_lcr(iot, ioh, lcr);
 	}
 
 	/* You turn me on, baby! */
@@ -751,11 +765,11 @@ comioctl(dev_t dev, u_long cmd, caddr_t 
 	switch (cmd) {
 	case TIOCSBRK:
 		SET(sc->sc_lcr, LCR_SBREAK);
-		bus_space_write_1(iot, ioh, com_lcr, sc->sc_lcr);
+		write_lcr(iot, ioh, sc->sc_lcr);
 		break;
 	case TIOCCBRK:
 		CLR(sc->sc_lcr, LCR_SBREAK);
-		bus_space_write_1(iot, ioh, com_lcr, sc->sc_lcr);
+		write_lcr(iot, ioh, sc->sc_lcr);
 		break;
 	case TIOCSDTR:
 		SET(sc->sc_mcr, sc->sc_dtr);
@@ -921,30 +935,29 @@ comparam(struct tty *tp, struct termios 
 				}
 			}
 
-			bus_space_write_1(iot, ioh, com_lcr, lcr | LCR_DLAB);
+			write_lcr(iot, ioh, lcr | LCR_DLAB);
 			bus_space_write_1(iot, ioh, com_dlbl, ospeed);
 			bus_space_write_1(iot, ioh, com_dlbh, ospeed >> 8);
-			bus_space_write_1(iot, ioh, com_lcr, lcr);
+			write_lcr(iot, ioh, lcr);
 			SET(sc->sc_mcr, MCR_DTR);
 			bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
 		} else
-			bus_space_write_1(iot, ioh, com_lcr, lcr);
+			write_lcr(iot, ioh, lcr);
 
 		if (ISSET(sc->sc_hwflags, COM_HW_FIFO)) {
 			if (sc->sc_uarttype == COM_UART_TI16750) {
-				bus_space_write_1(iot, ioh, com_lcr,
-				    lcr | LCR_DLAB);
+				write_lcr(iot, ioh, lcr | LCR_DLAB);
 				bus_space_write_1(iot, ioh, com_fifo,
 				    FIFO_ENABLE | FIFO_ENABLE_64BYTE |
 				    (t->c_ispeed <= 1200 ? FIFO_TRIGGER_1 : FIFO_TRIGGER_8));
-				bus_space_write_1(iot, ioh, com_lcr, lcr);
+				write_lcr(iot, ioh, lcr);
 			} else
 				bus_space_write_1(iot, ioh, com_fifo,
 				    FIFO_ENABLE |
 				    (t->c_ispeed <= 1200 ? FIFO_TRIGGER_1 : FIFO_TRIGGER_8));
 		}
 	} else
-		bus_space_write_1(iot, ioh, com_lcr, lcr);
+		write_lcr(iot, ioh, lcr);
 
 	/* When not using CRTSCTS, RTS follows DTR. */
 	if (!ISSET(t->c_cflag, CRTSCTS)) {
@@ -1387,11 +1400,11 @@ cominit(bus_space_tag_t iot, bus_space_h
 	int s = splhigh();
 	u_char stat;
 
-	bus_space_write_1(iot, ioh, com_lcr, LCR_DLAB);
+	write_lcr(iot, ioh, LCR_DLAB);
 	rate = comspeed(frequency, rate); /* XXX not comdefaultrate? */
 	bus_space_write_1(iot, ioh, com_dlbl, rate);
 	bus_space_write_1(iot, ioh, com_dlbh, rate >> 8);
-	bus_space_write_1(iot, ioh, com_lcr, LCR_8BITS);
+	write_lcr(iot, ioh, LCR_8BITS);
 	bus_space_write_1(iot, ioh, com_mcr, MCR_DTR | MCR_RTS);
 #ifdef COM_PXA2X0
 	/* XXX */
@@ -1606,9 +1619,9 @@ com_attach_subr(struct com_softc *sc)
 	 * Probe for all known forms of UART.
 	 */
 	lcr = bus_space_read_1(iot, ioh, com_lcr);
-	bus_space_write_1(iot, ioh, com_lcr, LCR_EFR);
+	write_lcr(iot, ioh, LCR_EFR);
 	bus_space_write_1(iot, ioh, com_efr, 0);
-	bus_space_write_1(iot, ioh, com_lcr, 0);
+	write_lcr(iot, ioh, 0);
 
 	bus_space_write_1(iot, ioh, com_fifo, FIFO_ENABLE);
 	delay(100);
@@ -1633,14 +1646,14 @@ com_attach_subr(struct com_softc *sc)
 		}
 
 	if (sc->sc_uarttype == COM_UART_16550A) { /* Probe for ST16650s */
-		bus_space_write_1(iot, ioh, com_lcr, lcr | LCR_DLAB);
+		write_lcr(iot, ioh, lcr | LCR_DLAB);
 		if (bus_space_read_1(iot, ioh, com_efr) == 0) {
 			bus_space_write_1(iot, ioh, com_efr, EFR_CTS);
 			if (bus_space_read_1(iot, ioh, com_efr) != 0)
 				sc->sc_uarttype = COM_UART_ST16650;
 			bus_space_write_1(iot, ioh, com_efr, 0);
 		} else {
-			bus_space_write_1(iot, ioh, com_lcr, LCR_EFR);
+			write_lcr(iot, ioh, LCR_EFR);
 			if (bus_space_read_1(iot, ioh, com_efr) == 0)
 				sc->sc_uarttype = COM_UART_ST16650V2;
 		}
@@ -1651,7 +1664,7 @@ com_attach_subr(struct com_softc *sc)
 		u_int8_t dlbl, dlbh;
 
 		/* Enable latch access and get the current values. */
-		bus_space_write_1(iot, ioh, com_lcr, lcr | LCR_DLAB);
+		write_lcr(iot, ioh, lcr | LCR_DLAB);
 		dlbl = bus_space_read_1(iot, ioh, com_dlbl);
 		dlbh = bus_space_read_1(iot, ioh, com_dlbh);
 
@@ -1671,12 +1684,12 @@ com_attach_subr(struct com_softc *sc)
 #endif
 
 	if (sc->sc_uarttype == COM_UART_16550A) { /* Probe for TI16750s */
-		bus_space_write_1(iot, ioh, com_lcr, lcr | LCR_DLAB);
+		write_lcr(iot, ioh, lcr | LCR_DLAB);
 		bus_space_write_1(iot, ioh, com_fifo,
 		    FIFO_ENABLE | FIFO_ENABLE_64BYTE);
 		if ((bus_space_read_1(iot, ioh, com_iir) >> 5) == 7) {
 #if 0
-			bus_space_write_1(iot, ioh, com_lcr, 0);
+			write_lcr(iot, ioh, 0);
 			if ((bus_space_read_1(iot, ioh, com_iir) >> 5) == 6)
 #endif
 				sc->sc_uarttype = COM_UART_TI16750;
@@ -1685,7 +1698,7 @@ com_attach_subr(struct com_softc *sc)
 	}
 
 	/* Reset the LCR (latch access is probably enabled). */
-	bus_space_write_1(iot, ioh, com_lcr, lcr);
+	write_lcr(iot, ioh, lcr);
 	if (sc->sc_uarttype == COM_UART_16450) { /* Probe for 8250 */
 		u_int8_t scr0, scr1, scr2;
 
@@ -1856,10 +1869,10 @@ com_fifo_probe(struct com_softc *sc)
 		ier |= IER_EUART;
 #endif
 	bus_space_write_1(iot, ioh, com_ier, ier);
-	bus_space_write_1(iot, ioh, com_lcr, LCR_DLAB);
+	write_lcr(iot, ioh, LCR_DLAB);
 	bus_space_write_1(iot, ioh, com_dlbl, 3);
 	bus_space_write_1(iot, ioh, com_dlbh, 0);
-	bus_space_write_1(iot, ioh, com_lcr, LCR_PNONE | LCR_8BITS);
+	write_lcr(iot, ioh, LCR_PNONE | LCR_8BITS);
 	bus_space_write_1(iot, ioh, com_mcr, MCR_LOOPBACK);
 
 	fifo = FIFO_ENABLE | FIFO_RCV_RST | FIFO_XMT_RST;