The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
Possible dependencies:
adafbbf6895e ("serial: stm32: Deassert Transmit Enable on ->rs485_config()")
d7c76716169d ("serial: stm32: Use TC interrupt to deassert GPIO RTS in RS485 mode")
3bcea529b295 ("serial: stm32: Factor out GPIO RTS toggling into separate function")
037b91ec7729 ("serial: stm32: fix software flow control transfer")
2a3bcfe03725 ("serial: stm32: fix flow control transfer in DMA mode")
33bb2f6ac308 ("serial: stm32: rework RX over DMA")
cc58d0a3f0a4 ("serial: stm32: re-introduce an irq flag condition in usart_receive_chars")
2aa1bbb21f26 ("serial: stm32: add FIFO threshold configuration")
cea37afd28f1 ("serial: stm32: defer sysrq processing")
e359b4411c28 ("serial: stm32: fix threaded interrupt handling")
3d530017bef1 ("serial: stm32: update wakeup IRQ management")
3db1d52466dc ("serial: stm32: fix tx_empty condition")
12761869f0ef ("serial: stm32: fix wake-up flag handling")
ad7676812437 ("serial: stm32: fix a deadlock condition with wakeup event")
25a8e7611da5 ("serial: stm32: fix TX and RX FIFO thresholds")
f4518a8a75f5 ("serial: stm32: fix startup by enabling usart for reception")
87fd0741d6dc ("serial: stm32: fix probe and remove order for dma")
a99163e9e708 ("Merge tag 'devicetree-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From adafbbf6895eb0ce41a313c6ee68870ab9aa93cd Mon Sep 17 00:00:00 2001
From: Lukas Wunner <lukas@xxxxxxxxx>
Date: Sun, 11 Sep 2022 11:02:03 +0200
Subject: [PATCH] serial: stm32: Deassert Transmit Enable on ->rs485_config()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
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>
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 0b18615b2ca4..c48f225eba86 100644
--- 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 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);
