linux-kernel - Re: [PATCH] tty: serial: fsl_lpuart: flush RX and TX FIFO when lpuart shutdown

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Message-ID: <Z31MKgrQEsMAc3aR@lizhi-Precision-Tower-5810>
Date: Tue, 7 Jan 2025 10:45:46 -0500
From: Frank Li <Frank.li@....com>
To: Sherry Sun <sherry.sun@....com>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	imx@...ts.linux.dev
Subject: Re: [PATCH] tty: serial: fsl_lpuart: flush RX and TX FIFO when
 lpuart shutdown

On Tue, Jan 07, 2025 at 03:48:34PM +0800, Sherry Sun wrote:
> Need to flush UART RX and TX FIFO when lpuart is shutting down to make
> sure restore a clean data transfer environment.

why not flush it at open()?

Frank

>
> Signed-off-by: Sherry Sun <sherry.sun@....com>
> ---
>  drivers/tty/serial/fsl_lpuart.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> index 7cb1e36fdaab..c91b9d9818cd 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -1965,6 +1965,11 @@ static void lpuart32_shutdown(struct uart_port *port)
>  			UARTCTRL_TIE | UARTCTRL_TCIE | UARTCTRL_RIE | UARTCTRL_SBK);
>  	lpuart32_write(port, temp, UARTCTRL);
>
> +	/* flush Rx/Tx FIFO */
> +	temp = lpuart32_read(port, UARTFIFO);
> +	temp |= UARTFIFO_TXFLUSH | UARTFIFO_RXFLUSH;
> +	lpuart32_write(port, temp, UARTFIFO);
> +
>  	uart_port_unlock_irqrestore(port, flags);
>
>  	lpuart_dma_shutdown(sport);
> --
> 2.34.1
>