[PATCH 5.19 083/717] serial: stm32: Deassert Transmit Enable on ->rs485_config()

Greg Kroah-Hartman
2022-10-22T10:46:10Z

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.1662886616.git.lukas@wunner.de
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
@@ -62,6 +62,53 @@ 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)
{
@@ -145,6 +192,12 @@ 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;
}

@@ -460,42 +513,6 @@ 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);
@@ -738,17 +755,6 @@ 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);