linux-kernel - [PATCH 7/8] serial: 8250: Make em485_rts_after_send() set mctrl according to rts state.

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Message-Id: <20180601124021.102970-8-giulio.benetti@micronovasrl.com>
Date:   Fri,  1 Jun 2018 14:40:20 +0200
From:   Giulio Benetti <giulio.benetti@...ronovasrl.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jiri Slaby <jslaby@...e.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>,
        Matthias Brugger <mbrugger@...e.com>,
        Allen Pais <allen.lkml@...il.com>, Sean Young <sean@...s.org>,
        Ed Blake <ed.blake@...drel.com>,
        Stefan Potyra <Stefan.Potyra@...ktrobit.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Joshua Scott <joshua.scott@...iedtelesis.co.nz>,
        Vignesh R <vigneshr@...com>,
        Rolf Evers-Fischer <rolf.evers.fischer@...iv.com>,
        Aaron Sierra <asierra@...-inc.com>,
        Rafael Gago <rafael.gago@...il.com>,
        Joel Stanley <joel@....id.au>,
        Sean Wang <sean.wang@...iatek.com>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Giulio Benetti <giulio.benetti@...ronovasrl.com>
Subject: [PATCH 7/8] serial: 8250: Make em485_rts_after_send() set mctrl according to rts state.

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@...ronovasrl.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 e14badbbf181..8432445c80e5 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -562,10 +562,13 @@ 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);
 }
 
-- 
2.17.0