linux-kernel - [PATCH AUTOSEL 4.14 086/127] serial: uartps: Wait for tx

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Date:   Thu, 17 Sep 2020 22:11:39 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Raviteja Narayanam <raviteja.narayanam@...inx.com>,
        Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>, linux-serial@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH AUTOSEL 4.14 086/127] serial: uartps: Wait for tx_empty in console setup

From: Raviteja Narayanam <raviteja.narayanam@...inx.com>

[ Upstream commit 42e11948ddf68b9f799cad8c0ddeab0a39da33e8 ]

On some platforms, the log is corrupted while console is being
registered. It is observed that when set_termios is called, there
are still some bytes in the FIFO to be transmitted.

So, wait for tx_empty inside cdns_uart_console_setup before calling
set_termios.

Signed-off-by: Raviteja Narayanam <raviteja.narayanam@...inx.com>
Reviewed-by: Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
Link: https://lore.kernel.org/r/1586413563-29125-2-git-send-email-raviteja.narayanam@xilinx.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/tty/serial/xilinx_uartps.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 81657f09761cd..00a740b8ad273 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1282,6 +1282,7 @@ static int cdns_uart_console_setup(struct console *co, char *options)
 	int bits = 8;
 	int parity = 'n';
 	int flow = 'n';
+	unsigned long time_out;
 
 	if (co->index < 0 || co->index >= CDNS_UART_NR_PORTS)
 		return -EINVAL;
@@ -1295,6 +1296,13 @@ static int cdns_uart_console_setup(struct console *co, char *options)
 	if (options)
 		uart_parse_options(options, &baud, &parity, &bits, &flow);
 
+	/* Wait for tx_empty before setting up the console */
+	time_out = jiffies + usecs_to_jiffies(TX_TIMEOUT);
+
+	while (time_before(jiffies, time_out) &&
+	       cdns_uart_tx_empty(port) != TIOCSER_TEMT)
+		cpu_relax();
+
 	return uart_set_options(port, co, baud, parity, bits, flow);
 }
 
-- 
2.25.1