From 8d5b305484e8a3216eeb700ed6c6de870306adbd Mon Sep 17 00:00:00 2001 From: Lukas Wunner Date: Fri, 27 Mar 2020 15:38:16 +0100 Subject: [PATCH] serial: 8250: Optimize irq enable after console write Commit 7f9803072ff6 ("serial: 8250: Support console on software emulated rs485 ports") amended serial8250_console_write() with rs485 support, but positioned the invocation of ->rs485_stop_tx() after re-enablement of interrupts. The irq handler and ->console_write() are serialized with the port spinlock, so no problem there, but due to the rs485 delay, the irq handler may unnecessarily spin for a while. Avoid that by moving ->rs485_stop_tx() before re-enablement of interrupts, which also mirrors the order at the beginning of serial8250_console_write(). Signed-off-by: Lukas Wunner Link: https://lore.kernel.org/r/019839cb1f61b01210b6ff9ac9f9079ca77f8411.1585319447.git.lukas@wunner.de Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_port.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index a1d3aef3c406..f77bf820b7a3 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -3268,7 +3268,6 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, * and restore the IER */ wait_for_xmitr(up, BOTH_EMPTY); - serial_port_out(port, UART_IER, ier); if (em485) { mdelay(port->rs485.delay_rts_after_send); @@ -3276,6 +3275,8 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, up->rs485_stop_tx(up); } + serial_port_out(port, UART_IER, ier); + /* * The receive handling will happen properly because the * receive ready bit will still be set; it is not cleared