linux-kernel - Re: [PATCH v2 1/2] serial: core: introduce uart_port_tx

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Date: Thu, 01 Feb 2024 15:48:00 +0000
From: Emil Kronborg <emil.kronborg@...tonmail.com>
To: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
Cc: gregkh@...uxfoundation.org, linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] serial: core: introduce uart_port_tx_flags()

On Thu, Feb 01, 2024 at 11:55 +0100, Jiri Slaby (SUSE) wrote:
> And an enum with a flag: UART_TX_NOSTOP. To NOT call
> __port->ops->stop_tx() when the circular buffer is empty. mxs-uart needs
> this (see the next patch).
> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
> Cc: Emil Kronborg <emil.kronborg@...tonmail.com>
> ---
> 
> Notes:
>     [v2] fix/invert the condition
> 
>  include/linux/serial_core.h | 32 +++++++++++++++++++++++++++-----
>  1 file changed, 27 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> index 536b2581d3e2..55b1f3ba48ac 100644
> --- a/include/linux/serial_core.h
> +++ b/include/linux/serial_core.h
> @@ -748,8 +748,17 @@ struct uart_driver {
> 
>  void uart_write_wakeup(struct uart_port *port);
> 
> -#define __uart_port_tx(uport, ch, tx_ready, put_char, tx_done, for_test,      \
> -		for_post)						      \
> +/**
> + * enum UART_TX_FLAGS -- flags for uart_port_tx_flags()
> + *
> + * @UART_TX_NOSTOP: don't call port->ops->stop_tx() on empty buffer
> + */
> +enum UART_TX_FLAGS {
> +	UART_TX_NOSTOP = BIT(0),
> +};
> +
> +#define __uart_port_tx(uport, ch, flags, tx_ready, put_char, tx_done,	      \
> +		       for_test, for_post)				      \
>  ({									      \
>  	struct uart_port *__port = (uport);				      \
>  	struct circ_buf *xmit = &__port->state->xmit;			      \
> @@ -777,7 +786,7 @@ void uart_write_wakeup(struct uart_port *port);
>  	if (pending < WAKEUP_CHARS) {					      \
>  		uart_write_wakeup(__port);				      \
>  									      \
> -		if (pending == 0)					      \
> +		if (!((flags) & UART_TX_NOSTOP) && pending == 0)	      \
>  			__port->ops->stop_tx(__port);			      \
>  	}								      \
>  									      \
> @@ -812,7 +821,7 @@ void uart_write_wakeup(struct uart_port *port);
>   */
>  #define uart_port_tx_limited(port, ch, count, tx_ready, put_char, tx_done) ({ \
>  	unsigned int __count = (count);					      \
> -	__uart_port_tx(port, ch, tx_ready, put_char, tx_done, __count,	      \
> +	__uart_port_tx(port, ch, 0, tx_ready, put_char, tx_done, __count,     \
>  			__count--);					      \
>  })
> 
> @@ -826,8 +835,21 @@ void uart_write_wakeup(struct uart_port *port);
>   * See uart_port_tx_limited() for more details.
>   */
>  #define uart_port_tx(port, ch, tx_ready, put_char)			\
> -	__uart_port_tx(port, ch, tx_ready, put_char, ({}), true, ({}))
> +	__uart_port_tx(port, ch, 0, tx_ready, put_char, ({}), true, ({}))
> +
> 
> +/**
> + * uart_port_tx_flags -- transmit helper for uart_port with flags
> + * @port: uart port
> + * @ch: variable to store a character to be written to the HW
> + * @flags: %UART_TX_NOSTOP or similar
> + * @tx_ready: can HW accept more data function
> + * @put_char: function to write a character
> + *
> + * See uart_port_tx_limited() for more details.
> + */
> +#define uart_port_tx_flags(port, ch, flags, tx_ready, put_char)		\
> +	__uart_port_tx(port, ch, flags, tx_ready, put_char, ({}), true, ({}))
>  /*
>   * Baud rate helpers.
>   */
> --
> 2.43.0
> 

Tested on i.MX28 board.

Tested-by: Emil Kronborg <emil.kronborg@...tonmail.com>

-- 
Emil Kronborg