[PATCH 2/6] tty: serial: fsl_lpuart: set receive watermark for imx8qxp platform

[Sherry Sun]

Since imx8qxp RX FIFO depth is 64 datawords, it will be better to set
the rx watermark as 31, which means when the number of datawords in the
receive FIFO(>= 32) is greater than the watermark, an interrupt or a DMA
request is generated.
Also keep the console rx watermark as 1 to make sure it responsive.

Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
---
 drivers/tty/serial/fsl_lpuart.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index e4aa161e61bf..868c2783d2c7 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -321,7 +321,7 @@ static struct lpuart_soc_data imx8qxp_data = {
 	.devtype = IMX8QXP_LPUART,
 	.iotype = UPIO_MEM32,
 	.reg_off = IMX_REG_OFF,
-	.rx_watermark = 1,
+	.rx_watermark = 31,
 };
 static struct lpuart_soc_data imxrt1050_data = {
 	.devtype = IMXRT1050_LPUART,
@@ -1527,6 +1527,8 @@ static void lpuart_setup_watermark(struct lpuart_port *sport)
 		writeb(UARTSFIFO_RXUF, sport->port.membase + UARTSFIFO);
 	}
 
+	if (uart_console(&sport->port))
+		sport->rx_watermark = 1;
 	writeb(0, sport->port.membase + UARTTWFIFO);
 	writeb(sport->rx_watermark, sport->port.membase + UARTRWFIFO);
 
@@ -1563,6 +1565,8 @@ static void lpuart32_setup_watermark(struct lpuart_port *sport)
 	lpuart32_write(&sport->port, val, UARTFIFO);
 
 	/* set the watermark */
+	if (uart_console(&sport->port))
+		sport->rx_watermark = 1;
 	val = (sport->rx_watermark << UARTWATER_RXWATER_OFF) |
 	      (0x0 << UARTWATER_TXWATER_OFF);
 	lpuart32_write(&sport->port, val, UARTWATER);
-- 
2.17.1