diff mbox series

[4.19,144/245] serial: uartps: Wait for tx_empty in console setup

Message ID 20200929105953.992070373@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg KH Sept. 29, 2020, 10:59 a.m. UTC 
From: Raviteja Narayanam <raviteja.narayanam@xilinx.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@xilinx.com>
Reviewed-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Link: https://lore.kernel.org/r/1586413563-29125-2-git-send-email-raviteja.narayanam@xilinx.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/xilinx_uartps.c | 8 ++++++++
 1 file changed, 8 insertions(+)

Comments

Pavel Machek Sept. 30, 2020, 8:07 p.m. UTC | #1 
Hi!

> From: Raviteja Narayanam <raviteja.narayanam@xilinx.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.

> @@ -1246,6 +1247,13 @@ 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();
> +

So this is spinning for half a second. Could we use msleep(1) instead
of cpu_relax or something like that?

Best regards,
									Pavel
diff mbox series

Patch

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 31950a38f0fb7..23f9b0cdff086 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1236,6 +1236,7 @@  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 (!port->membase) {
 		pr_debug("console on " CDNS_UART_TTY_NAME "%i not present\n",
@@ -1246,6 +1247,13 @@  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);
 }