linux-kernel - [PATCH LINUX v5 3/8] tty: xuartps: Don't consider circular buffer when enabling transmitter

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Message-ID: <1451126636-13699-4-git-send-email-soren.brinkmann@xilinx.com>
Date:	Sat, 26 Dec 2015 02:43:51 -0800
From:	Soren Brinkmann <soren.brinkmann@...inx.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>
CC:	Michal Simek <michal.simek@...inx.com>,
	<linux-serial@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	"Peter Hurley" <peter@...leysoftware.com>,
	Moritz Fischer <moritz.fischer@...us.com>,
	Soren Brinkmann <soren.brinkmann@...inx.com>
Subject: [PATCH LINUX v5 3/8] tty: xuartps: Don't consider circular buffer when enabling transmitter

Restarting the transmitter even if the circ buffer is empty may be
necessary to push out remaining data when the port is restarted after
being stopped.

Cc: Peter Hurley <peter@...leysoftware.com>
Signed-off-by: Soren Brinkmann <soren.brinkmann@...inx.com>
Reviewed-by: Peter Hurley <peter@...leysoftware.com>
---
v3:
 - changed this patch to not always enable the transmitter, but keep the
   check for uart_tx_stopped() in place, as suggested by Peter, whose
   explanation I also stole for the new commit message (thx)
---
 drivers/tty/serial/xilinx_uartps.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 2c98c357d9a0..6a7cd4e057ae 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -512,7 +512,7 @@ static void cdns_uart_start_tx(struct uart_port *port)
 {
 	unsigned int status, numbytes = port->fifosize;
 
-	if (uart_circ_empty(&port->state->xmit) || uart_tx_stopped(port))
+	if (uart_tx_stopped(port))
 		return;
 
 	/*
@@ -524,6 +524,9 @@ static void cdns_uart_start_tx(struct uart_port *port)
 	status |= CDNS_UART_CR_TX_EN;
 	writel(status, port->membase + CDNS_UART_CR_OFFSET);
 
+	if (uart_circ_empty(&port->state->xmit))
+		return;
+
 	while (numbytes-- && ((readl(port->membase + CDNS_UART_SR_OFFSET) &
 				CDNS_UART_SR_TXFULL)) != CDNS_UART_SR_TXFULL) {
 		/* Break if no more data available in the UART buffer */
-- 
2.6.3.3.g9bb996a

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