From: Lukas Wunner lukas@wunner.de
commit adafbbf6895eb0ce41a313c6ee68870ab9aa93cd upstream.
The STM32 USART can control RS-485 Transmit Enable in hardware. Since commit 7df5081cbf5e ("serial: stm32: Add RS485 RTS GPIO control"), it can alternatively be controlled in software. That was done to allow RS-485 even if the RTS pin is unavailable because it's pinmuxed to a different function.
However the commit neglected to deassert Transmit Enable upon invocation of the ->rs485_config() callback. Fix it.
Avoid forward declarations by moving stm32_usart_tx_empty(), stm32_usart_rs485_rts_enable() and stm32_usart_rs485_rts_disable() further up in the driver.
Fixes: 7df5081cbf5e ("serial: stm32: Add RS485 RTS GPIO control") Cc: stable@vger.kernel.org # v5.9+ Cc: Marek Vasut marex@denx.de Reviewed-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com Signed-off-by: Lukas Wunner lukas@wunner.de Link: https://lore.kernel.org/r/6059eab35dba394468335ef640df8b0050fd9dbd.166288661... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/stm32-usart.c | 100 ++++++++++++++++++++------------------- 1 file changed, 53 insertions(+), 47 deletions(-)
--- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -131,6 +131,53 @@ static void stm32_usart_clr_bits(struct writel_relaxed(val, port->membase + reg); }
+static unsigned int stm32_usart_tx_empty(struct uart_port *port) +{ + struct stm32_port *stm32_port = to_stm32_port(port); + const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; + + if (readl_relaxed(port->membase + ofs->isr) & USART_SR_TC) + return TIOCSER_TEMT; + + return 0; +} + +static void stm32_usart_rs485_rts_enable(struct uart_port *port) +{ + struct stm32_port *stm32_port = to_stm32_port(port); + struct serial_rs485 *rs485conf = &port->rs485; + + if (stm32_port->hw_flow_control || + !(rs485conf->flags & SER_RS485_ENABLED)) + return; + + 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); + } +} + +static void stm32_usart_rs485_rts_disable(struct uart_port *port) +{ + struct stm32_port *stm32_port = to_stm32_port(port); + struct serial_rs485 *rs485conf = &port->rs485; + + if (stm32_port->hw_flow_control || + !(rs485conf->flags & SER_RS485_ENABLED)) + return; + + 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); + } +} + static void stm32_usart_config_reg_rs485(u32 *cr1, u32 *cr3, u32 delay_ADE, u32 delay_DDE, u32 baud) { @@ -214,6 +261,12 @@ static int stm32_usart_config_rs485(stru
stm32_usart_set_bits(port, ofs->cr1, BIT(cfg->uart_enable_bit));
+ /* Adjust RTS polarity in case it's driven in software */ + if (stm32_usart_tx_empty(port)) + stm32_usart_rs485_rts_disable(port); + else + stm32_usart_rs485_rts_enable(port); + return 0; }
@@ -529,42 +582,6 @@ static void stm32_usart_tc_interrupt_dis stm32_usart_clr_bits(port, ofs->cr1, USART_CR1_TCIE); }
-static void stm32_usart_rs485_rts_enable(struct uart_port *port) -{ - struct stm32_port *stm32_port = to_stm32_port(port); - struct serial_rs485 *rs485conf = &port->rs485; - - if (stm32_port->hw_flow_control || - !(rs485conf->flags & SER_RS485_ENABLED)) - return; - - 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); - } -} - -static void stm32_usart_rs485_rts_disable(struct uart_port *port) -{ - struct stm32_port *stm32_port = to_stm32_port(port); - struct serial_rs485 *rs485conf = &port->rs485; - - if (stm32_port->hw_flow_control || - !(rs485conf->flags & SER_RS485_ENABLED)) - return; - - 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); - } -} - static void stm32_usart_transmit_chars_pio(struct uart_port *port) { struct stm32_port *stm32_port = to_stm32_port(port); @@ -807,17 +824,6 @@ static irqreturn_t stm32_usart_threaded_ return IRQ_HANDLED; }
-static unsigned int stm32_usart_tx_empty(struct uart_port *port) -{ - struct stm32_port *stm32_port = to_stm32_port(port); - const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; - - if (readl_relaxed(port->membase + ofs->isr) & USART_SR_TC) - return TIOCSER_TEMT; - - return 0; -} - static void stm32_usart_set_mctrl(struct uart_port *port, unsigned int mctrl) { struct stm32_port *stm32_port = to_stm32_port(port);