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From:   Heiko Stuebner <heiko@sntech.de>
To:     gregkh@linuxfoundation.org
Cc:     jslaby@suse.com, andriy.shevchenko@linux.intel.com,
        matwey.kornilov@gmail.com, linux-serial@vger.kernel.org,
        linux-kernel@vger.kernel.org, heiko@sntech.de,
        Giulio Benetti <giulio.benetti@micronovasrl.com>,
        Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Subject: [PATCH 1/7] serial: 8250: Make em485_rts_after_send() set mctrl according to rts state.
Date:   Wed, 18 Mar 2020 15:26:34 +0100
Message-Id: <20200318142640.982763-2-heiko@sntech.de>
In-Reply-To: <20200318142640.982763-1-heiko@sntech.de>
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From: Giulio Benetti <giulio.benetti@micronovasrl.com>

When rs485 enabled and RTS_AFTER_SEND set on startup, need to preserve
mctrl status, because later functions will call set_mctrl passing
port->mctrl=0 overriding rts status, resulting in rts pin in
transmission when idle.

Make mctrl reflect rts pin state.

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
---
 drivers/tty/serial/8250/8250_port.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 8407166610ce..67aa3a2a9afa 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -565,10 +565,13 @@ static inline void serial8250_em485_rts_after_send(struct uart_8250_port *p)
 {
 	unsigned char mcr = serial8250_in_MCR(p);
 
-	if (p->port.rs485.flags & SER_RS485_RTS_AFTER_SEND)
+	if (p->port.rs485.flags & SER_RS485_RTS_AFTER_SEND) {
 		mcr |= UART_MCR_RTS;
-	else
+		p->port.mctrl |= TIOCM_RTS;
+	} else {
 		mcr &= ~UART_MCR_RTS;
+		p->port.mctrl &= ~TIOCM_RTS;
+	}
 	serial8250_out_MCR(p, mcr);
 }
 
-- 
2.24.1