linux-kernel - Re: [PATCH AUTOSEL 4.4 42/64] serial: uartps: Wait for tx

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Message-ID: <CA+G9fYsi87yT-bEdpQ+7ca5gH_QcWHmticMSxKuCSt+SLrWj-A@mail.gmail.com>
Date:   Tue, 29 Sep 2020 01:46:59 +0530
From:   Naresh Kamboju <naresh.kamboju@...aro.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     open list <linux-kernel@...r.kernel.org>,
        linux- stable <stable@...r.kernel.org>,
        Raviteja Narayanam <raviteja.narayanam@...inx.com>,
        Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-serial@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH AUTOSEL 4.4 42/64] serial: uartps: Wait for tx_empty in
 console setup

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

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@...aro.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
>

-- 
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