Commit ad0c2748 authored by Marek Vasut's avatar Marek Vasut Committed by Greg Kroah-Hartman
Browse files

serial: stm32: Add RS485 RTS GPIO control again 



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.

Fixes: 7df5081c ("serial: stm32: Add RS485 RTS GPIO control")
Signed-off-by: default avatarMarek Vasut <marex@denx.de>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Manivannan Sadhasivam <mani@kernel.org>
Cc: Fabrice Gasnier <fabrice.gasnier@st.com>
Cc: linux-stm32@st-md-mailman.stormreply.com
Link: https://lore.kernel.org/r/20200831171045.205691-1-marex@denx.de


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 0fb9342d

drivers/tty/serial/stm32-usart.c

+25 −8
Original line number Diff line number Diff line
@@ -129,13 +129,9 @@ 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;

			mctrl_gpio_set(stm32_port->gpios,

					stm32_port->port.mctrl & ~TIOCM_RTS);

		} else {

			cr3 |= USART_CR3_DEP;

			rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;

			mctrl_gpio_set(stm32_port->gpios,

					stm32_port->port.mctrl | TIOCM_RTS);

		}



		writel_relaxed(cr3, port->membase + ofs->cr3);
@@ -541,17 +537,42 @@ static void stm32_disable_ms(struct uart_port *port) 
/* Transmit stop */

static void stm32_stop_tx(struct uart_port *port)

{

	struct stm32_port *stm32_port = to_stm32_port(port);

	struct serial_rs485 *rs485conf = &port->rs485;



	stm32_tx_interrupt_disable(port);



	if (rs485conf->flags & SER_RS485_ENABLED) {

		if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {

			mctrl_gpio_set(stm32_port->gpios,

					stm32_port->port.mctrl & ~TIOCM_RTS);

		} else {

			mctrl_gpio_set(stm32_port->gpios,

					stm32_port->port.mctrl | TIOCM_RTS);

		}

	}

}



/* There are probably characters waiting to be transmitted. */

static void stm32_start_tx(struct uart_port *port)

{

	struct stm32_port *stm32_port = to_stm32_port(port);

	struct serial_rs485 *rs485conf = &port->rs485;

	struct circ_buf *xmit = &port->state->xmit;



	if (uart_circ_empty(xmit))

		return;



	if (rs485conf->flags & SER_RS485_ENABLED) {

		if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {

			mctrl_gpio_set(stm32_port->gpios,

					stm32_port->port.mctrl | TIOCM_RTS);

		} else {

			mctrl_gpio_set(stm32_port->gpios,

					stm32_port->port.mctrl & ~TIOCM_RTS);

		}

	}



	stm32_transmit_chars(port);

}
@@ -851,13 +872,9 @@ 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;

			mctrl_gpio_set(stm32_port->gpios,

					stm32_port->port.mctrl & ~TIOCM_RTS);

		} else {

			cr3 |= USART_CR3_DEP;

			rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;

			mctrl_gpio_set(stm32_port->gpios,

					stm32_port->port.mctrl | TIOCM_RTS);

		}



	} else {