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Date:      Mon, 1 May 2017 19:47:10 +0000 (UTC)
From:      Alexander Motin <mav@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r317659 - head/sys/dev/uart
Message-ID:  <201705011947.v41JlAIv031962@repo.freebsd.org>
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Author: mav
Date: Mon May  1 19:47:10 2017
New Revision: 317659
URL: https://svnweb.freebsd.org/changeset/base/317659

Log:
  Make some UART consoles to not spin wait for data to be sent.
  
  At least with Tx FIFO enabled it shows me ~10% reduction of verbose boot
  time with serial console at 115200 baud.
  
  Reviewed by:	marcel
  MFC after:	2 weeks

Modified:
  head/sys/dev/uart/uart_dev_lpc.c
  head/sys/dev/uart/uart_dev_ns8250.c

Modified: head/sys/dev/uart/uart_dev_lpc.c
==============================================================================
--- head/sys/dev/uart/uart_dev_lpc.c	Mon May  1 19:34:15 2017	(r317658)
+++ head/sys/dev/uart/uart_dev_lpc.c	Mon May  1 19:47:10 2017	(r317659)
@@ -345,9 +345,6 @@ lpc_ns8250_putc(struct uart_bas *bas, in
 		DELAY(4);
 	uart_setreg(bas, REG_DATA, c);
 	uart_barrier(bas);
-	limit = 250000;
-	while ((uart_getreg(bas, REG_LSR) & LSR_TEMT) == 0 && --limit)
-		DELAY(4);
 }
 
 static int
@@ -890,8 +887,13 @@ lpc_ns8250_bus_transmit(struct uart_soft
 
 	bas = &sc->sc_bas;
 	uart_lock(sc->sc_hwmtx);
-	while ((uart_getreg(bas, REG_LSR) & LSR_THRE) == 0)
-		;
+	if (sc->sc_txdatasz > 1) {
+		if ((uart_getreg(bas, REG_LSR) & LSR_TEMT) == 0)
+			ns8250_drain(bas, UART_DRAIN_TRANSMITTER);
+	} else {
+		while ((uart_getreg(bas, REG_LSR) & LSR_THRE) == 0)
+			DELAY(4);
+	}
 	for (i = 0; i < sc->sc_txdatasz; i++) {
 		uart_setreg(bas, REG_DATA, sc->sc_txbuf[i]);
 		uart_barrier(bas);

Modified: head/sys/dev/uart/uart_dev_ns8250.c
==============================================================================
--- head/sys/dev/uart/uart_dev_ns8250.c	Mon May  1 19:34:15 2017	(r317658)
+++ head/sys/dev/uart/uart_dev_ns8250.c	Mon May  1 19:47:10 2017	(r317659)
@@ -315,7 +315,7 @@ ns8250_init(struct uart_bas *bas, int ba
 	/* Disable the FIFO (if present). */
 	val = 0;
 #ifdef CPU_XBURST
-	val = FCR_UART_ON;
+	val |= FCR_UART_ON;
 #endif
 	uart_setreg(bas, REG_FCR, val);
 	uart_barrier(bas);
@@ -346,9 +346,6 @@ ns8250_putc(struct uart_bas *bas, int c)
 		DELAY(4);
 	uart_setreg(bas, REG_DATA, c);
 	uart_barrier(bas);
-	limit = 250000;
-	while ((uart_getreg(bas, REG_LSR) & LSR_TEMT) == 0 && --limit)
-		DELAY(4);
 }
 
 static int
@@ -999,8 +996,13 @@ ns8250_bus_transmit(struct uart_softc *s
 
 	bas = &sc->sc_bas;
 	uart_lock(sc->sc_hwmtx);
-	while ((uart_getreg(bas, REG_LSR) & LSR_THRE) == 0)
-		;
+	if (sc->sc_txdatasz > 1) {
+		if ((uart_getreg(bas, REG_LSR) & LSR_TEMT) == 0)
+			ns8250_drain(bas, UART_DRAIN_TRANSMITTER);
+	} else {
+		while ((uart_getreg(bas, REG_LSR) & LSR_THRE) == 0)
+			DELAY(4);
+	}
 	for (i = 0; i < sc->sc_txdatasz; i++) {
 		uart_setreg(bas, REG_DATA, sc->sc_txbuf[i]);
 		uart_barrier(bas);

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