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tty: serial: fsl_lpuart: reduce RX watermark to 0 on LS1028A

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[ Upstream commit a82c3df955 ]

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@digi.com/
Fixes: 9ad9df8447 ("tty: serial: fsl_lpuart: Fix the wrong RXWATER setting for rx dma case")
Cc: stable <stable@kernel.org>
Signed-off-by: Robert Hodaszi <robert.hodaszi@digi.com>
Message-ID: <20230609121334.1878626-1-robert.hodaszi@digi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Robert Hodaszi 2023-06-09 14:13:34 +02:00 committed by Greg Kroah-Hartman
parent 17732fed85
commit c4465bff4d
1 changed files with 1 additions and 1 deletions
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2
drivers/tty/serial/fsl_lpuart.c
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@ -302,7 +302,7 @@ static const struct lpuart_soc_data ls1021a_data = {
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 = {