From e37f712f760478a3bce8a68b8d85b5b0bf6642eb Mon Sep 17 00:00:00 2001 From: Geert Uytterhoeven Date: Tue, 28 Mar 2017 11:13:44 +0200 Subject: [PATCH] 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 FIFO. Signed-off-by: Geert Uytterhoeven Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/sh-sci.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index 1df5746..446a23b 100644 --- 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 *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); -- 2.7.4