Re: [PATCH] serial: mxs-auart: wait for DMA buffer to flush before shutdown

[Hector Palacios <hector.palacios@digi.com>]

On 10/01/2013 06:18 PM, Hector Palacios wrote:
> The shutdown function was not waiting for the DMA buffer to flush
> before disabling the AUART. This lead to many bytes not being
> transferred (specially at low baudrates), as they were still in the
> DMA buffer when the AUART was shutdown.
> This patch also adds the check for the BUSY flag.
>
> Signed-off-by: Hector Palacios <hector.palacios@digi.com>
>
> https://jira.digi.com/browse/DEL-616
> ---
>   drivers/tty/serial/mxs-auart.c | 16 +++++++++++++++-
>   1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
> index f85b8e6..0d8b2ca 100644
> --- a/drivers/tty/serial/mxs-auart.c
> +++ b/drivers/tty/serial/mxs-auart.c
> @@ -750,12 +750,26 @@ static int mxs_auart_startup(struct uart_port *u)
>   	return 0;
>   }
>
> +static unsigned int mxs_auart_tx_empty(struct uart_port *u);
> +
>   static void mxs_auart_shutdown(struct uart_port *u)
>   {
>   	struct mxs_auart_port *s = to_auart_port(u);
> +	unsigned int to;
> +
> +	if (auart_dma_enabled(s)) {
> +		/* Wait enough time to flush DMA buffer completely */
> +		to = u->timeout * UART_XMIT_SIZE / u->fifosize;
> +		while (!mxs_auart_tx_empty(u) && to--)
> +			mdelay(1);
>
> -	if (auart_dma_enabled(s))
>   		mxs_auart_dma_exit(s);
> +	}
> +
> +	/* Wait for transmitter to become empty ... */
> +	to = u->timeout;
> +	while ((readl(port->membase + AUART_STAT) & AUART_STAT_BUSY) && to--)

Just noticed a bug. It should be u->membase. I'll fix it in V2.


Best regards,
--
Hector Palacios