This is a note to let you know that I've just added the patch titled
tty: serial: fsl_lpuart: Clear the error flags by writing 1 for lpuart32 platforms
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tty-serial-fsl_lpuart-clear-the-error-flags-by-writing-1-for-lpuart32-platforms.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 282069845af388b08d622ad192b831dcd0549c62 Mon Sep 17 00:00:00 2001
From: Sherry Sun <sherry.sun@xxxxxxx>
Date: Tue, 1 Aug 2023 10:23:04 +0800
Subject: tty: serial: fsl_lpuart: Clear the error flags by writing 1 for lpuart32 platforms
From: Sherry Sun <sherry.sun@xxxxxxx>
commit 282069845af388b08d622ad192b831dcd0549c62 upstream.
Do not read the data register to clear the error flags for lpuart32
platforms, the additional read may cause the receive FIFO underflow
since the DMA has already read the data register.
Actually all lpuart32 platforms support write 1 to clear those error
bits, let's use this method to better clear the error flags.
Fixes: 42b68768e51b ("serial: fsl_lpuart: DMA support for 32-bit variant")
Cc: stable <stable@xxxxxxxxxx>
Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
Link: https://lore.kernel.org/r/20230801022304.24251-1-sherry.sun@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/fsl_lpuart.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1107,8 +1107,8 @@ static void lpuart_copy_rx_to_tty(struct
unsigned long sr = lpuart32_read(&sport->port, UARTSTAT);
if (sr & (UARTSTAT_PE | UARTSTAT_FE)) {
- /* Read DR to clear the error flags */
- lpuart32_read(&sport->port, UARTDATA);
+ /* Clear the error flags */
+ lpuart32_write(&sport->port, sr, UARTSTAT);
if (sr & UARTSTAT_PE)
sport->port.icount.parity++;
Patches currently in stable-queue which might be from sherry.sun@xxxxxxx are
queue-5.15/tty-serial-fsl_lpuart-clear-the-error-flags-by-writing-1-for-lpuart32-platforms.patch
queue-5.15/tty-serial-fsl_lpuart-make-rx_watermark-configurable.patch
