This is a note to let you know that I've just added the patch titled
serial: stm32: Deassert Transmit Enable on ->rs485_config()
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
serial-stm32-deassert-transmit-enable-on-rs485_confi.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit edf11620c93fc1a9a7b3dbbdb5eccb8e45608c79
Author: Lukas Wunner <lukas@xxxxxxxxx>
Date: Sun Sep 11 11:02:03 2022 +0200
serial: stm32: Deassert Transmit Enable on ->rs485_config()
[ Upstream commit adafbbf6895eb0ce41a313c6ee68870ab9aa93cd ]
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@xxxxxxxxxxxxxxx # v5.9+
Cc: Marek Vasut <marex@xxxxxxx>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
Link: https://lore.kernel.org/r/6059eab35dba394468335ef640df8b0050fd9dbd.1662886616.git.lukas@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 4a4108ef23e8..c2daf8c151e6 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -61,6 +61,53 @@ 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)
{
@@ -149,6 +196,12 @@ static int stm32_usart_config_rs485(struct uart_port *port,
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;
}
@@ -436,42 +489,6 @@ 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);
@@ -689,17 +706,6 @@ 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);
