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From:   Philippe Schenker <philippe.schenker@toradex.com>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>
CC:     Max Krummenacher <max.krummenacher@toradex.com>,
        Jiri Slaby <jslaby@suse.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Fugang Duan <fugang.duan@nxp.com>,
        Stefan Agner <stefan@agner.ch>,
        "linux-imx@nxp.com" <linux-imx@nxp.com>,
        Andrey Smirnov <andrew.smirnov@gmail.com>,
        Philippe Schenker <philippe.schenker@toradex.com>
Subject: [PATCH v1 3/3] tty: serial: lpuart: Add RS485 support for 32-bit uart
 flavour
Thread-Topic: [PATCH v1 3/3] tty: serial: lpuart: Add RS485 support for 32-bit
 uart flavour
Thread-Index: AQHVhDUIydsEsSxrwEmSYx3VY636Fw==
Date:   Wed, 16 Oct 2019 15:18:59 +0000
Message-ID: <20191016151845.15859-3-philippe.schenker@toradex.com>
References: <20191016151845.15859-1-philippe.schenker@toradex.com>
In-Reply-To: <20191016151845.15859-1-philippe.schenker@toradex.com>
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This commits adds RS485 support for LPUART hardware that uses 32-bit
registers. These are typically found in i.MX8 processors.

Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>

---

 drivers/tty/serial/fsl_lpuart.c | 65 ++++++++++++++++++++++++++++++++-
 1 file changed, 63 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuar=
t.c
index 346b4a070ce9..22df5f8f48b6 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1280,6 +1280,57 @@ static int lpuart_config_rs485(struct uart_port *por=
t,
 	return 0;
 }
=20
+static int lpuart32_config_rs485(struct uart_port *port,
+			struct serial_rs485 *rs485)
+{
+	struct lpuart_port *sport =3D container_of(port,
+			struct lpuart_port, port);
+
+	unsigned long modem =3D lpuart32_read(&sport->port, UARTMODIR)
+				& ~(UARTMODEM_TXRTSPOL | UARTMODEM_TXRTSE);
+	lpuart32_write(&sport->port, modem, UARTMODIR);
+
+	/* clear unsupported configurations */
+	rs485->delay_rts_before_send =3D 0;
+	rs485->delay_rts_after_send =3D 0;
+	rs485->flags &=3D ~SER_RS485_RX_DURING_TX;
+
+	if (rs485->flags & SER_RS485_ENABLED) {
+		/* Enable auto RS-485 RTS mode */
+		modem |=3D UARTMODEM_TXRTSE;
+
+		/*
+		 * RTS needs to be logic HIGH either during transer _or_ after
+		 * transfer, other variants are not supported by the hardware.
+		 */
+
+		if (!(rs485->flags & (SER_RS485_RTS_ON_SEND |
+				SER_RS485_RTS_AFTER_SEND)))
+			rs485->flags |=3D SER_RS485_RTS_ON_SEND;
+
+		if (rs485->flags & SER_RS485_RTS_ON_SEND &&
+				rs485->flags & SER_RS485_RTS_AFTER_SEND)
+			rs485->flags &=3D ~SER_RS485_RTS_AFTER_SEND;
+
+		/*
+		 * The hardware defaults to RTS logic HIGH while transfer.
+		 * Switch polarity in case RTS shall be logic HIGH
+		 * after transfer.
+		 * Note: UART is assumed to be active high.
+		 */
+		if (rs485->flags & SER_RS485_RTS_ON_SEND)
+			modem &=3D ~UARTMODEM_TXRTSPOL;
+		else if (rs485->flags & SER_RS485_RTS_AFTER_SEND)
+			modem |=3D UARTMODEM_TXRTSPOL;
+	}
+
+	/* Store the new configuration */
+	sport->port.rs485 =3D *rs485;
+
+	lpuart32_write(&sport->port, modem, UARTMODIR);
+	return 0;
+}
+
 static unsigned int lpuart_get_mctrl(struct uart_port *port)
 {
 	unsigned int temp =3D 0;
@@ -1878,6 +1929,13 @@ lpuart32_set_termios(struct uart_port *port, struct =
ktermios *termios,
 		ctrl |=3D UARTCTRL_M;
 	}
=20
+	/*
+	 * When auto RS-485 RTS mode is enabled,
+	 * hardware flow control need to be disabled.
+	 */
+	if (sport->port.rs485.flags & SER_RS485_ENABLED)
+		termios->c_cflag &=3D ~CRTSCTS;
+
 	if (termios->c_cflag & CRTSCTS) {
 		modem |=3D (UARTMODIR_RXRTSE | UARTMODIR_TXCTSE);
 	} else {
@@ -2405,7 +2463,10 @@ static int lpuart_probe(struct platform_device *pdev=
)
 		sport->port.ops =3D &lpuart_pops;
 	sport->port.flags =3D UPF_BOOT_AUTOCONF;
=20
-	sport->port.rs485_config =3D lpuart_config_rs485;
+	if (lpuart_is_32(sport))
+		sport->port.rs485_config =3D lpuart32_config_rs485;
+	else
+		sport->port.rs485_config =3D lpuart_config_rs485;
=20
 	sport->ipg_clk =3D devm_clk_get(&pdev->dev, "ipg");
 	if (IS_ERR(sport->ipg_clk)) {
@@ -2459,7 +2520,7 @@ static int lpuart_probe(struct platform_device *pdev)
 	    sport->port.rs485.delay_rts_after_send)
 		dev_err(&pdev->dev, "driver doesn't support RTS delays\n");
=20
-	lpuart_config_rs485(&sport->port, &sport->port.rs485);
+	sport->port.rs485_config(&sport->port, &sport->port.rs485);
=20
 	sport->dma_tx_chan =3D dma_request_slave_channel(sport->port.dev, "tx");
 	if (!sport->dma_tx_chan)
--=20
2.23.0