Re: [PATCH AUTOSEL 4.4 42/64] serial: uartps: Wait for tx_empty in console setup

Naresh Kamboju
2020-09-28T20:17:16Z

On Fri, 18 Sep 2020 at 07:51, Sasha Levin <sashal@kernel.org> wrote:
>
> 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>

stable rc branch 4.4 arm64 build broken.

../drivers/tty/serial/xilinx_uartps.c: In function ‘cdns_uart_console_setup’:
../drivers/tty/serial/xilinx_uartps.c:1170:40: error: ‘TX_TIMEOUT’
undeclared (first use in this function)
1170 | time_out = jiffies + usecs_to_jiffies(TX_TIMEOUT);
^~~~~~~~~~
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.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 06efcef1b4953..5b4469098888a 100644
> --- a/drivers/tty/serial/xilinx_uartps.c
> +++ b/drivers/tty/serial/xilinx_uartps.c
> @@ -1152,6 +1152,7 @@ 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;
> @@ -1165,6 +1166,13 @@ 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
>

--
Linaro LKFT