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serial: stm32: Add RS485 RTS GPIO control again

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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: 7df5081cbf ("serial: stm32: Add RS485 RTS GPIO control")
Signed-off-by: Marek 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Marek Vasut 2020-08-31 19:10:45 +02:00 committed by Greg Kroah-Hartman
parent 0fb9342d06
commit ad0c274805
1 changed files with 25 additions and 8 deletions
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33
drivers/tty/serial/stm32-usart.c
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@ -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 {