This is a note to let you know that I've just added the patch titled
tty: serial: fsl_lpuart: reduce RX watermark to 0 on LS1028A
to the 6.3-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-reduce-rx-watermark-to-0-on-ls1028a.patch
and it can be found in the queue-6.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a82c3df955f8c1c726e4976527aa6ae924a67dd9 Mon Sep 17 00:00:00 2001
From: Robert Hodaszi <robert.hodaszi@xxxxxxxx>
Date: Fri, 9 Jun 2023 14:13:34 +0200
Subject: tty: serial: fsl_lpuart: reduce RX watermark to 0 on LS1028A
From: Robert Hodaszi <robert.hodaszi@xxxxxxxx>
commit a82c3df955f8c1c726e4976527aa6ae924a67dd9 upstream.
LS1028A is using DMA with LPUART. Having RX watermark set to 1, means
DMA transactions are started only after receiving the second character.
On other platforms with newer LPUART IP, Receiver Idle Empty function
initiates the DMA request after the receiver is idling for 4 characters.
But this feature is missing on LS1028A, which is causing a 1-character
delay in the RX direction on this platform.
Set RX watermark to 0 to initiate RX DMA after each character.
Link: https://lore.kernel.org/linux-serial/20230607103459.1222426-1-robert.hodaszi@xxxxxxxx/
Fixes: 9ad9df844754 ("tty: serial: fsl_lpuart: Fix the wrong RXWATER setting for rx dma case")
Cc: stable <stable@xxxxxxxxxx>
Signed-off-by: Robert Hodaszi <robert.hodaszi@xxxxxxxx>
Message-ID: <20230609121334.1878626-1-robert.hodaszi@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/fsl_lpuart.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -310,7 +310,7 @@ static const struct lpuart_soc_data ls10
static const struct lpuart_soc_data ls1028a_data = {
.devtype = LS1028A_LPUART,
.iotype = UPIO_MEM32,
- .rx_watermark = 1,
+ .rx_watermark = 0,
};
static struct lpuart_soc_data imx7ulp_data = {
Patches currently in stable-queue which might be from robert.hodaszi@xxxxxxxx are
queue-6.3/tty-serial-fsl_lpuart-reduce-rx-watermark-to-0-on-ls1028a.patch
