linux-kernel - Re: [PATCH 12/18] tty: serial: samsung: use TIOCSER_TEMT for tx

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Message-ID: <CAPLW+4knt2P5yEJMRJsKydGUaa8RSMLxdVy-Kjq=bkGw9tA8Kg@mail.gmail.com>
Date: Tue, 16 Jan 2024 12:46:57 -0600
From: Sam Protsenko <semen.protsenko@...aro.org>
To: Tudor Ambarus <tudor.ambarus@...aro.org>
Cc: krzysztof.kozlowski@...aro.org, alim.akhtar@...sung.com, 
	gregkh@...uxfoundation.org, jirislaby@...nel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org, 
	andre.draszik@...aro.org, peter.griffin@...aro.org, kernel-team@...roid.com, 
	willmcvicker@...gle.com
Subject: Re: [PATCH 12/18] tty: serial: samsung: use TIOCSER_TEMT for tx_empty()

On Wed, Jan 10, 2024 at 4:24 AM Tudor Ambarus <tudor.ambarus@...aroorg> wrote:
>
> The core expects for tx_empty() either TIOCSER_TEMT when the tx is
> empty or 0 otherwise. Respect the core and use TIOCSER_TEMT.
>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
> ---
>  drivers/tty/serial/samsung_tty.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> index f2413da14b1d..46fba70f3d77 100644
> --- a/drivers/tty/serial/samsung_tty.c
> +++ b/drivers/tty/serial/samsung_tty.c
> @@ -990,11 +990,10 @@ static unsigned int s3c24xx_serial_tx_empty(struct uart_port *port)
>         if (ufcon & S3C2410_UFCON_FIFOMODE) {
>                 if ((ufstat & info->tx_fifomask) || (ufstat & info->tx_fifofull))
>                         return 0;
> -
> -               return 1;
> +               return TIOCSER_TEMT;
>         }
>
> -       return s3c24xx_serial_txempty_nofifo(port);
> +       return s3c24xx_serial_txempty_nofifo(port) ? TIOCSER_TEMT : 0;

And because s3c24xx_serial_txempty_nofifo() might actually return 0x4,
and at least uart_get_lsr_info() tries to clear exactly 0x1 bit, this
brings functional change, which I think is in fact a fix. So a
"Fixed:" tag is needed here.

>  }
>
>  /* no modem control lines */
> --
> 2.43.0.472.g3155946c3a-goog
>
>