linux-kernel - [PATCH] tty: serial: fsl_lpuart: fix the wrong return value in lpuart32_get

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Date:   Thu, 29 Jul 2021 16:31:09 +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: fix the wrong return value in lpuart32_get_mctrl

Patch e60c2991f18b make the lpuart32_get_mctrl always return 0, actually
this will break the functions of device which use flow control such as
Bluetooth.
For lpuart32 plaform, the hardware can handle the CTS automatically.
So we should set TIOCM_CTS active. Also need to set CAR and DSR active.

Fixes: e60c2991f18b ("serial: fsl_lpuart: remove RTSCTS handling from get_mctrl()")

Patch has been tested on lpuart32 platforms such as imx8qm and imx8ulp.

Signed-off-by: Sherry Sun <sherry.sun@....com>
---
 drivers/tty/serial/fsl_lpuart.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 508128ddfa01..f0e5da77ed6d 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1415,7 +1415,7 @@ static unsigned int lpuart_get_mctrl(struct uart_port *port)
 
 static unsigned int lpuart32_get_mctrl(struct uart_port *port)
 {
-	unsigned int mctrl = 0;
+	unsigned int mctrl = TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
 	u32 reg;
 
 	reg = lpuart32_read(port, UARTCTRL);
-- 
2.17.1