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    SubjectRe: [PATCH] tty/serial: atmel_serial: BUG: stop DMA from transmitting in stop_tx
    On Mon, Jan 02, 2017 at 03:16:46PM +0100, Richard Genoud wrote:
    > 2017-01-02 12:13 GMT+01:00 Nicolas Ferre <nicolas.ferre@atmel.com>:
    > > Le 13/12/2016 à 17:27, Richard Genoud a écrit :
    > >> If we don't disable the transmitter in atmel_stop_tx, the DMA buffer
    > >> continues to send data until it is emptied.
    > >> This cause problems with the flow control (CTS is asserted and data are
    > >> still sent).
    > >>
    > >> So, disabling the transmitter in atmel_stop_tx is a sane thing to do.
    > >>
    > >> Tested on at91sam9g35-cm(DMA)
    > >> Tested for regressions on sama5d2-xplained(Fifo) and at91sam9g20ek(PDC)
    > >>
    > >> Cc: <stable@vger.kernel.org> (beware, this won't apply before 4.3)
    > >> Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
    > >
    > > Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
    > >
    > >> ---
    > >> drivers/tty/serial/atmel_serial.c | 11 +++++++++++
    > >> 1 file changed, 11 insertions(+)
    > >>
    > >> NB: this is not for the 4.10 merge window, I'm just sending it now to
    > >> have some comments if someone is againts it.
    > >>
    > >> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
    > >> index 168b10cad47b..f9d42de5ab2d 100644
    > >> --- a/drivers/tty/serial/atmel_serial.c
    > >> +++ b/drivers/tty/serial/atmel_serial.c
    > >> @@ -481,6 +481,14 @@ static void atmel_stop_tx(struct uart_port *port)
    > >> /* disable PDC transmit */
    > >> atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_TXTDIS);
    > >> }
    > >> +
    > >> + /*
    > >> + * Disable the transmitter.
    > >> + * This is mandatory when DMA is used, otherwise the DMA buffer
    > >> + * is fully transmitted.
    > >> + */
    > >> + atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS);
    > >> +
    > >> /* Disable interrupts */
    > >> atmel_uart_writel(port, ATMEL_US_IDR, atmel_port->tx_done_mask);
    > >>
    > >> @@ -513,6 +521,9 @@ static void atmel_start_tx(struct uart_port *port)
    > >>
    > >> /* Enable interrupts */
    > >> atmel_uart_writel(port, ATMEL_US_IER, atmel_port->tx_done_mask);
    > >> +
    > >> + /* re-enable the transmitter */
    > >> + atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN);
    > >> }
    > >>
    > >> /*
    > >>
    > >
    > >
    > > --
    > > Nicolas Ferre
    >
    > Greg, could you also take this patch in your tree ?

    Yup!

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