linux-kernel - [PATCH] tty: serial: fsl_lpuart: flush RX and TX FIFO when lpuart shutdown

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Message-Id: <20250107074834.3115230-1-sherry.sun@nxp.com>
Date: Tue,  7 Jan 2025 15:48:34 +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,
	imx@...ts.linux.dev
Subject: [PATCH] tty: serial: fsl_lpuart: flush RX and TX FIFO when lpuart shutdown

Need to flush UART RX and TX FIFO when lpuart is shutting down to make
sure restore a clean data transfer environment.

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

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 7cb1e36fdaab..c91b9d9818cd 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1965,6 +1965,11 @@ static void lpuart32_shutdown(struct uart_port *port)
 			UARTCTRL_TIE | UARTCTRL_TCIE | UARTCTRL_RIE | UARTCTRL_SBK);
 	lpuart32_write(port, temp, UARTCTRL);
 
+	/* flush Rx/Tx FIFO */
+	temp = lpuart32_read(port, UARTFIFO);
+	temp |= UARTFIFO_TXFLUSH | UARTFIFO_RXFLUSH;
+	lpuart32_write(port, temp, UARTFIFO);
+
 	uart_port_unlock_irqrestore(port, flags);
 
 	lpuart_dma_shutdown(sport);
-- 
2.34.1