On 11/19/2015 03:02 PM, Soren Brinkmann wrote:
> start_tx must start transmitting characters. Regardless of the state of
> the circular buffer, always enable the transmitter hardware.
Why?
Does cdns_uart_stop_tx() actually stop the transmitter so that
data remains in the transmitter?
> Signed-off-by: Soren Brinkmann <soren.brinkmann@xxxxxxxxxx>
> ---
> drivers/tty/serial/xilinx_uartps.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
> index 2c98c357d9a0..df6778d17949 100644
> --- a/drivers/tty/serial/xilinx_uartps.c
> +++ b/drivers/tty/serial/xilinx_uartps.c
> @@ -512,9 +512,6 @@ static void cdns_uart_start_tx(struct uart_port *port)
> {
> unsigned int status, numbytes = port->fifosize;
>
> - if (uart_circ_empty(&port->state->xmit) || uart_tx_stopped(port))
> - return;
The test for tx stopped needs to remain; otherwise, transmission will
restart even if the tty has been stopped (for example by userspace
or IXON software flow control).
Regards,
Peter Hurley
> -
> /*
> * Set the TX enable bit and clear the TX disable bit to enable the
> * transmitter.
> @@ -524,6 +521,9 @@ static void cdns_uart_start_tx(struct uart_port *port)
> status |= CDNS_UART_CR_TX_EN;
> writel(status, port->membase + CDNS_UART_CR_OFFSET);
>
> + if (uart_circ_empty(&port->state->xmit) || uart_tx_stopped(port))
> + return;
> +
> while (numbytes-- && ((readl(port->membase + CDNS_UART_SR_OFFSET) &
> CDNS_UART_SR_TXFULL)) != CDNS_UART_SR_TXFULL) {
> /* Break if no more data available in the UART buffer */
>
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