linux-kernel - [PATCH] tty: serial: fsl_lpuart: don't enable receiver/transmitter before rx/tx dma ready

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Date:   Mon, 28 Nov 2022 13:02:08 +0800
From:   Sherry Sun <sherry.sun@....com>
To:     gregkh@...uxfoundation.org, jirislaby@...nel.org
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-imx@....com
Subject: [PATCH] tty: serial: fsl_lpuart: don't enable receiver/transmitter before rx/tx dma ready

lpuart32_setup_watermark_enable() will configure the UART FIFO and
watermark, also enable the receiver and transmitter, this should be done
after the rx/tx dma steup ready.

Also add lpuart32_hw_disable() to make sure the receiver/transmitter and
interrupts are disabled during the dma steup.

Signed-off-by: Sherry Sun <sherry.sun@....com>
---
 drivers/tty/serial/fsl_lpuart.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 8918e08bb19e..bb12b328e224 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1682,6 +1682,16 @@ static int lpuart_startup(struct uart_port *port)
 	return 0;
 }
 
+static void lpuart32_hw_disable(struct lpuart_port *sport)
+{
+	unsigned long temp;
+
+	temp = lpuart32_read(&sport->port, UARTCTRL);
+	temp &= ~(UARTCTRL_RIE | UARTCTRL_ILIE | UARTCTRL_RE |
+		  UARTCTRL_TIE | UARTCTRL_TE);
+	lpuart32_write(&sport->port, temp, UARTCTRL);
+}
+
 static void lpuart32_configure(struct lpuart_port *sport)
 {
 	unsigned long temp;
@@ -1706,11 +1716,12 @@ static void lpuart32_hw_setup(struct lpuart_port *sport)
 
 	spin_lock_irqsave(&sport->port.lock, flags);
 
-	lpuart32_setup_watermark_enable(sport);
+	lpuart32_hw_disable(sport);
 
 	lpuart_rx_dma_startup(sport);
 	lpuart_tx_dma_startup(sport);
 
+	lpuart32_setup_watermark_enable(sport);
 	lpuart32_configure(sport);
 
 	spin_unlock_irqrestore(&sport->port.lock, flags);
-- 
2.17.1