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@xxxxxxx>
Cc: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Cc: Manivannan Sadhasivam <mani@xxxxxxxxxx>
Cc: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
