Commit adafbbf6 authored by Lukas Wunner's avatar Lukas Wunner Committed by Greg Kroah-Hartman
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serial: stm32: Deassert Transmit Enable on ->rs485_config() 



The STM32 USART can control RS-485 Transmit Enable in hardware.  Since
commit 7df5081c ("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: 7df5081c ("serial: stm32: Add RS485 RTS GPIO control")
Cc: stable@vger.kernel.org # v5.9+
Cc: Marek Vasut <marex@denx.de>
Reviewed-by: default avatarIlpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: default avatarLukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/6059eab35dba394468335ef640df8b0050fd9dbd.1662886616.git.lukas@wunner.de


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3a939433

drivers/tty/serial/stm32-usart.c

+53 −47
Original line number Diff line number Diff line
@@ -131,6 +131,53 @@ static void stm32_usart_clr_bits(struct uart_port *port, u32 reg, u32 bits) 
	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(struct uart_port *port, struct ktermios *ter 


	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_disable(struct uart_port *port) 
	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_interrupt(int irq, void *ptr) 
	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);