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SubjectRe: [PATCH] serial: uartps: Wait for tx_empty in console setup
On 2020-04-07 18:53, Raviteja Narayanam wrote:
> 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>
> ---
> drivers/tty/serial/xilinx_uartps.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/tty/serial/xilinx_uartps.c
> b/drivers/tty/serial/xilinx_uartps.c
> index 6b26f76..23468ff 100644
> --- a/drivers/tty/serial/xilinx_uartps.c
> +++ b/drivers/tty/serial/xilinx_uartps.c
> @@ -1260,6 +1260,8 @@ static int cdns_uart_console_setup(struct
> console *co, char *options)
> int bits = 8;
> int parity = 'n';
> int flow = 'n';
> + unsigned long time_out = jiffies + usecs_to_jiffies(TX_TIMEOUT);
> + int status;
>
> if (!port->membase) {
> pr_debug("console on " CDNS_UART_TTY_NAME "%i not present\n",
> @@ -1270,6 +1272,14 @@ 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 */
> + while (time_before(jiffies, time_out)) {
> + status = cdns_uart_tx_empty(port);
> + if (status == TIOCSER_TEMT)
> + break;
> + cpu_relax();
> + }
> +
> return uart_set_options(port, co, baud, parity, bits, flow);
> }
> #endif /* CONFIG_SERIAL_XILINX_PS_UART_CONSOLE */

You could do without the status variable. You could even combine the
while and if conditions.

And while you're at it, you might as well also rewrite the lines
1236-1238 to also use cdns_uart_tx_empty() for clarity.

Maarten

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