From: Marek Vasut <marex@denx.de>
To: linux-serial@vger.kernel.org
Cc: Marek Vasut <marex@denx.de>,
Andy Shevchenko <andy.shevchenko@gmail.com>,
Manivannan Sadhasivam <mani@kernel.org>,
Fabrice Gasnier <fabrice.gasnier@st.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: [PATCH] tty: serial: Add RS485 RTS GPIO control
Date: Fri, 24 Jul 2020 12:14:18 +0200 [thread overview]
Message-ID: <20200724101418.146234-1-marex@denx.de> (raw)
While the STM32 does support RS485 drive-enable control within the
UART IP itself, some systems have the drive-enable line connected
to a pin which cannot be pinmuxed as RTS. Add support for toggling
the RTS GPIO line using the modem control GPIOs to provide at least
some sort of emulation.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Manivannan Sadhasivam <mani@kernel.org>
Cc: Fabrice Gasnier <fabrice.gasnier@st.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/serial/stm32-usart.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index d1c5e536a167..22c8477571ce 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -34,6 +34,7 @@
#include "serial_mctrl_gpio.h"
#include "stm32-usart.h"
+static void stm32_set_mctrl(struct uart_port *port, unsigned int mctrl);
static void stm32_stop_tx(struct uart_port *port);
static void stm32_transmit_chars(struct uart_port *port);
@@ -129,9 +130,13 @@ static int stm32_config_rs485(struct uart_port *port,
if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {
cr3 &= ~USART_CR3_DEP;
rs485conf->flags &= ~SER_RS485_RTS_AFTER_SEND;
+ stm32_set_mctrl(port,
+ stm32_port->port.mctrl & ~TIOCM_RTS);
} else {
cr3 |= USART_CR3_DEP;
rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;
+ stm32_set_mctrl(port,
+ stm32_port->port.mctrl | TIOCM_RTS);
}
writel_relaxed(cr3, port->membase + ofs->cr3);
@@ -847,9 +852,13 @@ static void stm32_set_termios(struct uart_port *port, struct ktermios *termios,
if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {
cr3 &= ~USART_CR3_DEP;
rs485conf->flags &= ~SER_RS485_RTS_AFTER_SEND;
+ stm32_set_mctrl(port,
+ stm32_port->port.mctrl & ~TIOCM_RTS);
} else {
cr3 |= USART_CR3_DEP;
rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;
+ stm32_set_mctrl(port,
+ stm32_port->port.mctrl | TIOCM_RTS);
}
} else {
--
2.27.0
next reply other threads:[~2020-07-24 10:14 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-24 10:14 Marek Vasut [this message]
2020-07-24 14:08 ` [PATCH] tty: serial: Add RS485 RTS GPIO control Fabrice Gasnier
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