Hi Ian,
On Fri, Jul 14, 2017 at 1:31 PM, Ian Jamison <ian.dev@xxxxxxxxxx> wrote:
> Function imx_transmit_buffer starts a TX DMA if DMA is enabled, since
> commit 91a1a909f921 ("serial: imx: Support sw flow control in DMA mode").
> It also carries on and attempts to write the same TX buffer using PIO.
> This results in TX data corruption and double-incrementing xmit->tail
> with the knock-on effect of tail passing head and a page of garbage
> being sent out.
>
> This seems to be triggered mostly when using RS485 half duplex on SMP
> systems, but is probably not limited to just those.
>
> Tested locally on an i.MX6Q with an RS485 half duplex transceiver on
> UART3, and also by Clemens Gruber.
>
> Tested-by: Clemens Gruber <clemens.gruber@xxxxxxxxxxxx>
> Signed-off-by: Ian Jamison <ian.dev@xxxxxxxxxx>
Thanks for fixing the long standing bug!
Reviewed-by: Fabio Estevam <fabio.estevam@xxxxxxx>
> ---
> drivers/tty/serial/imx.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 9e3162bf3bd1..f6c37ce457c1 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -464,7 +464,7 @@ static inline void imx_transmit_buffer(struct imx_port *sport)
> }
> }
>
> - while (!uart_circ_empty(xmit) &&
> + while (!uart_circ_empty(xmit) && !sport->dma_is_txing &&
> !(readl(sport->port.membase + uts_reg(sport)) & UTS_TXFULL)) {
> /* send xmit->buf[xmit->tail]
> * out the port here */
> --
> 2.13.2
>
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