[v2,tty-next,2/2] serial: 8250: Optimize irq enable after console write

Message ID 019839cb1f61b01210b6ff9ac9f9079ca77f8411.1585319447.git.lukas@wunner.de
State New
Headers show
  • Untitled series #39260
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Commit Message

Lukas Wunner March 27, 2020, 2:38 p.m.
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 <lukas@wunner.de>
 fix hash of referenced commit

 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) {
@@ -3276,6 +3275,8 @@  void serial8250_console_write(struct uart_8250_port *up, const char *s,
+	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