Re: [PATCH 2/2] serial: sh-sci: Terminate TX DMA during buffer flushing

[Eugeniu Rosca <erosca@de.adit-jv.com>]

On Mon, Jun 24, 2019 at 02:35:40PM +0200, Geert Uytterhoeven wrote:
[..]
> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
> index d4504daff99263f5..d18c680aa64b3427 100644
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -1656,11 +1656,18 @@ static void sci_free_dma(struct uart_port *port)
>  
>  static void sci_flush_buffer(struct uart_port *port)
>  {
> +	struct sci_port *s = to_sci_port(port);
> +
>  	/*
>  	 * In uart_flush_buffer(), the xmit circular buffer has just been
> -	 * cleared, so we have to reset tx_dma_len accordingly.
> +	 * cleared, so we have to reset tx_dma_len accordingly, and stop any
> +	 * pending transfers
>  	 */
> -	to_sci_port(port)->tx_dma_len = 0;
> +	s->tx_dma_len = 0;
> +	if (s->chan_tx) {
> +		dmaengine_terminate_async(s->chan_tx);
> +		s->cookie_tx = -EINVAL;
> +	}

I am seeing a similar solution being employed by other tty/serial
drivers [1]. One major difference is that those drivers make use of
dmaengine_terminate_all(). Since the latter is deprecated starting
with commit [2], the API choice looks reasonable to me.

Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>

[1] git grep -W "static void.*flush_buffer" -- drivers/tty/serial/ | grep dmaengine_terminate
drivers/tty/serial/fsl_lpuart.c-		dmaengine_terminate_all(sport->dma_tx_chan);
drivers/tty/serial/imx.c-	dmaengine_terminate_all(sport->dma_chan_tx);
drivers/tty/serial/serial-tegra.c-		dmaengine_terminate_all(tup->tx_dma_chan);

[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b36f09c3c441a6
    ("dmaengine: Add transfer termination synchronization support")

-- 
Best Regards,
Eugeniu.