blob: 734a0c0526e4a91ec5d47776d6ba2880ed84e30e [file] [log] [blame]
From 5300c730b0d6a6dfdbf92bc9db438f603e5d2a67 Mon Sep 17 00:00:00 2001
From: Geert Uytterhoeven <>
Date: Tue, 28 Mar 2017 11:13:44 +0200
Subject: [PATCH 126/286] serial: sh-sci: Fix hang in sci_reset()
When the .set_termios() callback resets the UART, it first waits (busy
loops) until all characters in the transmit FIFO have been transmitted,
to prevent a port configuration change from impacting these characters.
However, if the UART has dedicated RTS/CTS hardware flow control
enabled, these characters may have been stuck in the FIFO due to CTS not
being asserted by the remote side.
- When a new user opens the port, .set_termios() is called while
transmission is still disabled, leading to an infinite loop:
NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s!
- When an active user changes port configuration without waiting for
the draining of the transmit FIFO, this may also block indefinitely,
until CTS is asserted by the remote side.
This has been observed with SCIFA (on r8a7740/armadillo), and SCIFB and
HSCIF (on r8a7791/koelsch).
To fix this, remove the code that waits for the draining of the transmit
Signed-off-by: Geert Uytterhoeven <>
Signed-off-by: Greg Kroah-Hartman <>
(cherry picked from commit e37f712f760478a3bce8a68b8d85b5b0bf6642eb)
Signed-off-by: Simon Horman <>
drivers/tty/serial/sh-sci.c | 4 ----
1 file changed, 4 deletions(-)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -2159,10 +2159,6 @@ static void sci_reset(struct uart_port *
unsigned int status;
struct sci_port *s = to_sci_port(port);
- do {
- status = serial_port_in(port, SCxSR);
- } while (!(status & SCxSR_TEND(port)));
serial_port_out(port, SCSCR, 0x00); /* TE=0, RE=0, CKE1=0 */
reg = sci_getreg(port, SCFCR);