From 582e9a24fc139adabb1dc951620870806bfc1583 Mon Sep 17 00:00:00 2001 From: Harald Seiler Date: Wed, 19 Jan 2022 15:52:03 +0100 Subject: [PATCH] tty: serial: imx: Add fast path when rs485 delays are 0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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. Reviewed-by: Uwe Kleine-König Signed-off-by: Harald Seiler Link: https://lore.kernel.org/r/20220119145204.238767-1-hws@denx.de Signed-off-by: Greg Kroah-Hartman --- 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 d8034f1666861..0b467ce8d737a 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 */ } 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 */ } if (sport->tx_state == WAIT_AFTER_SEND -- 2.30.2