From 2411fd94ceaa6e11326e95d6ebf876cbfed28d23 Mon Sep 17 00:00:00 2001
From: Sherry Sun <sherry.sun@nxp.com>
Date: Thu, 23 Feb 2023 17:39:41 +0800
Subject: [PATCH] tty: serial: fsl_lpuart: skip waiting for transmission complete when UARTCTRL_SBK is asserted
Git-commit: 2411fd94ceaa6e11326e95d6ebf876cbfed28d23
Patch-mainline: v6.3-rc3
References: git-fixes
According to LPUART RM, Transmission Complete Flag becomes 0 if queuing
a break character by writing 1 to CTRL[SBK], so here need to skip
waiting for transmission complete when UARTCTRL_SBK is asserted,
otherwise the kernel may stuck here.
And actually set_termios() adds transmission completion waiting to avoid
data loss or data breakage when changing the baud rate, but we don't
need to worry about this when queuing break characters.
Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Cc: stable <stable@kernel.org>
Link: https://lore.kernel.org/r/20230223093941.31790-1-sherry.sun@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/tty/serial/fsl_lpuart.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index e945f41b93d4..f9e164abf920 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -2240,9 +2240,15 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios,
/* update the per-port timeout */
uart_update_timeout(port, termios->c_cflag, baud);
- /* wait transmit engin complete */
- lpuart32_write(&sport->port, 0, UARTMODIR);
- lpuart32_wait_bit_set(&sport->port, UARTSTAT, UARTSTAT_TC);
+ /*
+ * LPUART Transmission Complete Flag may never be set while queuing a break
+ * character, so skip waiting for transmission complete when UARTCTRL_SBK is
+ * asserted.
+ */
+ if (!(old_ctrl & UARTCTRL_SBK)) {
+ lpuart32_write(&sport->port, 0, UARTMODIR);
+ lpuart32_wait_bit_set(&sport->port, UARTSTAT, UARTSTAT_TC);
+ }
/* disable transmit and receive */
lpuart32_write(&sport->port, old_ctrl & ~(UARTCTRL_TE | UARTCTRL_RE),
--
2.35.3