Commit 8d5b3054 authored Mar 27, 2020 by Lukas Wunner Committed by Greg Kroah-Hartman Mar 27, 2020

serial: 8250: Optimize irq enable after console write



Commit 7f980307 ("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 <lukas@wunner.de>
Link: https://lore.kernel.org/r/019839cb1f61b01210b6ff9ac9f9079ca77f8411.1585319447.git.lukas@wunner.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 4e36f94e

drivers/tty/serial/8250/8250_port.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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

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