From ad0c2748059fff13e8295ae91f51073d6c0311b7 Mon Sep 17 00:00:00 2001 From: Marek Vasut Date: Mon, 31 Aug 2020 19:10:45 +0200 Subject: [PATCH] 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: 7df5081cbf5e ("serial: stm32: Add RS485 RTS GPIO control") Signed-off-by: Marek Vasut Cc: Alexandre Torgue Cc: Andy Shevchenko Cc: Manivannan Sadhasivam Cc: Fabrice Gasnier 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 --- drivers/tty/serial/stm32-usart.c | 33 +++++++++++++++++++++++++-------- 1 file changed, 25 insertions(+), 8 deletions(-) diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index ba503dd..ee6c776 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -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 { -- 2.7.4