On Wed, Jan 19, 2022 at 03:52:03PM +0100, Harald Seiler wrote:
> Right now, even when `delay_rts_before_send` and `delay_rts_after_send`
> are 0, the hrtimer is triggered (with timeout 0) which can introduce a
> few 100us of additional overhead on slower i.MX platforms.
>
> Implement a fast path when the delays are 0, where the RTS signal is
> toggled immediately instead of going through an hrtimer. This fast path
> behaves identical to the code before delay support was implemented.
>
> Signed-off-by: Harald Seiler <hws@xxxxxxx>
> ---
> drivers/tty/serial/imx.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index df8a0c8b8b29..67bbbb69229d 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -455,9 +455,14 @@ static void imx_uart_stop_tx(struct uart_port *port)
> if (port->rs485.flags & SER_RS485_ENABLED) {
> if (sport->tx_state == SEND) {
> sport->tx_state = WAIT_AFTER_SEND;
> - start_hrtimer_ms(&sport->trigger_stop_tx,
> +
> + if (port->rs485.delay_rts_after_send > 0) {
> + start_hrtimer_ms(&sport->trigger_stop_tx,
> port->rs485.delay_rts_after_send);
> - return;
> + return;
> + }
> +
> + /* continue without any delay */
Is it right to keep the assignment sport->tx_state = WAIT_AFTER_SEND ?
> }
>
> if (sport->tx_state == WAIT_AFTER_RTS ||
> @@ -698,9 +703,14 @@ static void imx_uart_start_tx(struct uart_port *port)
> imx_uart_stop_rx(port);
>
> sport->tx_state = WAIT_AFTER_RTS;
> - start_hrtimer_ms(&sport->trigger_start_tx,
> +
> + if (port->rs485.delay_rts_before_send > 0) {
> + start_hrtimer_ms(&sport->trigger_start_tx,
> port->rs485.delay_rts_before_send);
> - return;
> + return;
> + }
> +
> + /* continue without any delay */
Here similar question here about sport->tx_state = WAIT_AFTER_RTS;
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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