[PATCH v7 1/7] serial: Do not hold the port lock when setting rx-during-tx GPIO

[PATCH v7 1/7] serial: Do not hold the port lock when setting rx-during-tx GPIO

[Lino Sanfilippo]

Both the imx and stm32 driver set the rx-during-tx GPIO in rs485_config().
Since this function is called with the port lock held, this can be a
problem in case that setting the GPIO line can sleep (e.g. if a GPIO
expander is used which is connected via SPI or I2C).

Avoid this issue by moving the GPIO setting outside of the port lock into
the serial core and thus making it a generic feature.

Also with commit c54d48543689 ("serial: stm32: Add support for rs485
RX_DURING_TX output GPIO") the SER_RS485_RX_DURING_TX flag is only set if a
rx-during-tx GPIO is _not_ available, which is wrong. Fix this, too.

Furthermore reset old GPIO settings in case that changing the RS485
configuration failed.

Fixes: c54d48543689 ("serial: stm32: Add support for rs485 RX_DURING_TX output GPIO")
Fixes: ca530cfa968c ("serial: imx: Add support for RS485 RX_DURING_TX output GPIO")
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---
 drivers/tty/serial/imx.c         |  4 ----
 drivers/tty/serial/serial_core.c | 26 ++++++++++++++++++++++++--
 drivers/tty/serial/stm32-usart.c |  8 ++------
 3 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 708b9852a575..9cffeb23112b 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1943,10 +1943,6 @@ static int imx_uart_rs485_config(struct uart_port *port, struct ktermios *termio
 	    rs485conf->flags & SER_RS485_RX_DURING_TX)
 		imx_uart_start_rx(port);
 
-	if (port->rs485_rx_during_tx_gpio)
-		gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
-					 !!(rs485conf->flags & SER_RS485_RX_DURING_TX));
-
 	return 0;
 }
 
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index f1348a509552..d155131f221d 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1402,6 +1402,16 @@ static void uart_set_rs485_termination(struct uart_port *port,
 				 !!(rs485->flags & SER_RS485_TERMINATE_BUS));
 }
 
+static void uart_set_rs485_rx_during_tx(struct uart_port *port,
+					const struct serial_rs485 *rs485)
+{
+	if (!(rs485->flags & SER_RS485_ENABLED))
+		return;
+
+	gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
+				 !!(rs485->flags & SER_RS485_RX_DURING_TX));
+}
+
 static int uart_rs485_config(struct uart_port *port)
 {
 	struct serial_rs485 *rs485 = &port->rs485;
@@ -1413,12 +1423,17 @@ static int uart_rs485_config(struct uart_port *port)
 
 	uart_sanitize_serial_rs485(port, rs485);
 	uart_set_rs485_termination(port, rs485);
+	uart_set_rs485_rx_during_tx(port, rs485);
 
 	uart_port_lock_irqsave(port, &flags);
 	ret = port->rs485_config(port, NULL, rs485);
 	uart_port_unlock_irqrestore(port, flags);
-	if (ret)
+	if (ret) {
 		memset(rs485, 0, sizeof(*rs485));
+		/* unset GPIOs */
+		gpiod_set_value_cansleep(port->rs485_term_gpio, 0);
+		gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio, 0);
+	}
 
 	return ret;
 }
@@ -1457,6 +1472,7 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
 		return ret;
 	uart_sanitize_serial_rs485(port, &rs485);
 	uart_set_rs485_termination(port, &rs485);
+	uart_set_rs485_rx_during_tx(port, &rs485);
 
 	uart_port_lock_irqsave(port, &flags);
 	ret = port->rs485_config(port, &tty->termios, &rs485);
@@ -1468,8 +1484,14 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
 			port->ops->set_mctrl(port, port->mctrl);
 	}
 	uart_port_unlock_irqrestore(port, flags);
-	if (ret)
+	if (ret) {
+		/* restore old GPIO settings */
+		gpiod_set_value_cansleep(port->rs485_term_gpio,
+			!!(port->rs485.flags & SER_RS485_TERMINATE_BUS));
+		gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
+			!!(port->rs485.flags & SER_RS485_RX_DURING_TX));
 		return ret;
+	}
 
 	if (copy_to_user(rs485_user, &port->rs485, sizeof(port->rs485)))
 		return -EFAULT;
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 3048620315d6..fc7fd40bca98 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -226,12 +226,6 @@ static int stm32_usart_config_rs485(struct uart_port *port, struct ktermios *ter
 
 	stm32_usart_clr_bits(port, ofs->cr1, BIT(cfg->uart_enable_bit));
 
-	if (port->rs485_rx_during_tx_gpio)
-		gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
-					 !!(rs485conf->flags & SER_RS485_RX_DURING_TX));
-	else
-		rs485conf->flags |= SER_RS485_RX_DURING_TX;
-
 	if (rs485conf->flags & SER_RS485_ENABLED) {
 		cr1 = readl_relaxed(port->membase + ofs->cr1);
 		cr3 = readl_relaxed(port->membase + ofs->cr3);
@@ -256,6 +250,8 @@ static int stm32_usart_config_rs485(struct uart_port *port, struct ktermios *ter
 
 		writel_relaxed(cr3, port->membase + ofs->cr3);
 		writel_relaxed(cr1, port->membase + ofs->cr1);
+
+		rs485conf->flags |= SER_RS485_RX_DURING_TX;
 	} else {
 		stm32_usart_clr_bits(port, ofs->cr3,
 				     USART_CR3_DEM | USART_CR3_DEP);
-- 
2.43.0

Re: [PATCH v7 1/7] serial: Do not hold the port lock when setting rx-during-tx GPIO

[Ilpo Järvinen]

On Wed, 3 Jan 2024, Lino Sanfilippo wrote:

> Both the imx and stm32 driver set the rx-during-tx GPIO in rs485_config().
> Since this function is called with the port lock held, this can be a
> problem in case that setting the GPIO line can sleep (e.g. if a GPIO
> expander is used which is connected via SPI or I2C).
> 
> Avoid this issue by moving the GPIO setting outside of the port lock into
> the serial core and thus making it a generic feature.
> 
> Also with commit c54d48543689 ("serial: stm32: Add support for rs485
> RX_DURING_TX output GPIO") the SER_RS485_RX_DURING_TX flag is only set if a
> rx-during-tx GPIO is _not_ available, which is wrong. Fix this, too.

This doesn't explain why it's wrong and I could figure it out myself 
either.

> Furthermore reset old GPIO settings in case that changing the RS485
> configuration failed.
> 
> Fixes: c54d48543689 ("serial: stm32: Add support for rs485 RX_DURING_TX output GPIO")
> Fixes: ca530cfa968c ("serial: imx: Add support for RS485 RX_DURING_TX output GPIO")
> Cc: Shawn Guo <shawnguo@kernel.org>
> Cc: Sascha Hauer <s.hauer@pengutronix.de>
> Cc: stable@vger.kernel.org
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> ---
>  drivers/tty/serial/imx.c         |  4 ----
>  drivers/tty/serial/serial_core.c | 26 ++++++++++++++++++++++++--
>  drivers/tty/serial/stm32-usart.c |  8 ++------
>  3 files changed, 26 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 708b9852a575..9cffeb23112b 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -1943,10 +1943,6 @@ static int imx_uart_rs485_config(struct uart_port *port, struct ktermios *termio
>  	    rs485conf->flags & SER_RS485_RX_DURING_TX)
>  		imx_uart_start_rx(port);
>  
> -	if (port->rs485_rx_during_tx_gpio)
> -		gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
> -					 !!(rs485conf->flags & SER_RS485_RX_DURING_TX));
> -
>  	return 0;
>  }
>  
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index f1348a509552..d155131f221d 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -1402,6 +1402,16 @@ static void uart_set_rs485_termination(struct uart_port *port,
>  				 !!(rs485->flags & SER_RS485_TERMINATE_BUS));
>  }
>  
> +static void uart_set_rs485_rx_during_tx(struct uart_port *port,
> +					const struct serial_rs485 *rs485)
> +{
> +	if (!(rs485->flags & SER_RS485_ENABLED))
> +		return;
> +
> +	gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
> +				 !!(rs485->flags & SER_RS485_RX_DURING_TX));
> +}
> +
>  static int uart_rs485_config(struct uart_port *port)
>  {
>  	struct serial_rs485 *rs485 = &port->rs485;
> @@ -1413,12 +1423,17 @@ static int uart_rs485_config(struct uart_port *port)
>  
>  	uart_sanitize_serial_rs485(port, rs485);
>  	uart_set_rs485_termination(port, rs485);
> +	uart_set_rs485_rx_during_tx(port, rs485);
>  
>  	uart_port_lock_irqsave(port, &flags);
>  	ret = port->rs485_config(port, NULL, rs485);
>  	uart_port_unlock_irqrestore(port, flags);
> -	if (ret)
> +	if (ret) {
>  		memset(rs485, 0, sizeof(*rs485));
> +		/* unset GPIOs */
> +		gpiod_set_value_cansleep(port->rs485_term_gpio, 0);
> +		gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio, 0);
> +	}
>  
>  	return ret;
>  }
> @@ -1457,6 +1472,7 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
>  		return ret;
>  	uart_sanitize_serial_rs485(port, &rs485);
>  	uart_set_rs485_termination(port, &rs485);
> +	uart_set_rs485_rx_during_tx(port, &rs485);
>  
>  	uart_port_lock_irqsave(port, &flags);
>  	ret = port->rs485_config(port, &tty->termios, &rs485);
> @@ -1468,8 +1484,14 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
>  			port->ops->set_mctrl(port, port->mctrl);
>  	}
>  	uart_port_unlock_irqrestore(port, flags);
> -	if (ret)
> +	if (ret) {
> +		/* restore old GPIO settings */
> +		gpiod_set_value_cansleep(port->rs485_term_gpio,
> +			!!(port->rs485.flags & SER_RS485_TERMINATE_BUS));
> +		gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
> +			!!(port->rs485.flags & SER_RS485_RX_DURING_TX));
>  		return ret;
> +	}
>  
>  	if (copy_to_user(rs485_user, &port->rs485, sizeof(port->rs485)))
>  		return -EFAULT;
> diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
> index 3048620315d6..fc7fd40bca98 100644
> --- a/drivers/tty/serial/stm32-usart.c
> +++ b/drivers/tty/serial/stm32-usart.c
> @@ -226,12 +226,6 @@ static int stm32_usart_config_rs485(struct uart_port *port, struct ktermios *ter
>  
>  	stm32_usart_clr_bits(port, ofs->cr1, BIT(cfg->uart_enable_bit));
>  
> -	if (port->rs485_rx_during_tx_gpio)
> -		gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
> -					 !!(rs485conf->flags & SER_RS485_RX_DURING_TX));
> -	else
> -		rs485conf->flags |= SER_RS485_RX_DURING_TX;
> -
>  	if (rs485conf->flags & SER_RS485_ENABLED) {
>  		cr1 = readl_relaxed(port->membase + ofs->cr1);
>  		cr3 = readl_relaxed(port->membase + ofs->cr3);
> @@ -256,6 +250,8 @@ static int stm32_usart_config_rs485(struct uart_port *port, struct ktermios *ter
>  
>  		writel_relaxed(cr3, port->membase + ofs->cr3);
>  		writel_relaxed(cr1, port->membase + ofs->cr1);
> +
> +		rs485conf->flags |= SER_RS485_RX_DURING_TX;

Is it really intentional to force this on even if user requests it not to 
be enabled (and after GPIO set value code used the value user provided)?

Other than that, this change looks fine.

-- 
 i.

Re: [PATCH v7 1/7] serial: Do not hold the port lock when setting rx-during-tx GPIO

[Lino Sanfilippo]

On 03.01.24 at 12:10, Ilpo Järvinen wrote:
> On Wed, 3 Jan 2024, Lino Sanfilippo wrote:
>

>> Also with commit c54d48543689 ("serial: stm32: Add support for rs485
>> RX_DURING_TX output GPIO") the SER_RS485_RX_DURING_TX flag is only set if a
>> rx-during-tx GPIO is _not_ available, which is wrong. Fix this, too.
>
> This doesn't explain why it's wrong and I could figure it out myself
> either.
>

Ugh, you are right. I confused some things here. This part of the patch is completely
wrong and the concerning code was correct as it was before. I will correct this patch
for v8.


Thanks,
Lino

[PATCH v7 2/7] serial: core: set missing supported flag for RX during TX GPIO

[Lino Sanfilippo]

If the RS485 feature RX-during-TX is supported by means of a GPIO set the
according supported flag. Otherwise setting this feature from userspace may
not be possible, since in uart_sanitize_serial_rs485() the passed RS485
configuration is matched against the supported features and unsupported
settings are thereby removed and thus take no effect.

Cc: stable@vger.kernel.org
Fixes: 163f080eb717 ("serial: core: Add option to output RS485 RX_DURING_TX state via GPIO")
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---
 drivers/tty/serial/serial_core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index d155131f221d..1204102d7162 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3642,6 +3642,8 @@ int uart_get_rs485_mode(struct uart_port *port)
 	if (IS_ERR(desc))
 		return dev_err_probe(dev, PTR_ERR(desc), "Cannot get rs485-rx-during-tx-gpios\n");
 	port->rs485_rx_during_tx_gpio = desc;
+	if (port->rs485_rx_during_tx_gpio)
+		port->rs485_supported.flags |= SER_RS485_RX_DURING_TX;
 
 	return 0;
 }
-- 
2.43.0

[PATCH v7 3/7] serial: core: fix sanitizing check for RTS settings

[Lino Sanfilippo]

Among other things uart_sanitize_serial_rs485() tests the sanity of the RTS
settings in a RS485 configuration that has been passed by userspace.
If RTS-on-send and RTS-after-send are both set or unset the configuration
is adjusted and RTS-after-send is disabled and RTS-on-send enabled.

This however makes only sense if both RTS modes are actually supported by
the driver.

With commit be2e2cb1d281 ("serial: Sanitize rs485_struct") the code does
take the driver support into account but only checks if one of both RTS
modes are supported. This may lead to the errorneous result of RTS-on-send
being set even if only RTS-after-send is supported.

Fix this by changing the implemented logic: First clear all unsupported
flags in the RS485 configuration, then adjust an invalid RTS setting by
taking into account which RTS mode is supported.

Cc: stable@vger.kernel.org
Fixes: be2e2cb1d281 ("serial: Sanitize rs485_struct")
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---
 drivers/tty/serial/serial_core.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 1204102d7162..f67fb6a04983 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1371,19 +1371,27 @@ static void uart_sanitize_serial_rs485(struct uart_port *port, struct serial_rs4
 		return;
 	}
 
+	rs485->flags &= supported_flags;
+
 	/* Pick sane settings if the user hasn't */
-	if ((supported_flags & (SER_RS485_RTS_ON_SEND|SER_RS485_RTS_AFTER_SEND)) &&
-	    !(rs485->flags & SER_RS485_RTS_ON_SEND) ==
+	if (!(rs485->flags & SER_RS485_RTS_ON_SEND) ==
 	    !(rs485->flags & SER_RS485_RTS_AFTER_SEND)) {
-		dev_warn_ratelimited(port->dev,
-			"%s (%d): invalid RTS setting, using RTS_ON_SEND instead\n",
-			port->name, port->line);
-		rs485->flags |= SER_RS485_RTS_ON_SEND;
-		rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
-		supported_flags |= SER_RS485_RTS_ON_SEND|SER_RS485_RTS_AFTER_SEND;
-	}
+		if (supported_flags & SER_RS485_RTS_ON_SEND) {
+			rs485->flags |= SER_RS485_RTS_ON_SEND;
+			rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
 
-	rs485->flags &= supported_flags;
+			dev_warn_ratelimited(port->dev,
+				"%s (%d): invalid RTS setting, using RTS_ON_SEND instead\n",
+				port->name, port->line);
+		} else {
+			rs485->flags |= SER_RS485_RTS_AFTER_SEND;
+			rs485->flags &= ~SER_RS485_RTS_ON_SEND;
+
+			dev_warn_ratelimited(port->dev,
+				"%s (%d): invalid RTS setting, using RTS_AFTER_SEND instead\n",
+				port->name, port->line);
+		}
+	}
 
 	uart_sanitize_serial_rs485_delays(port, rs485);
 
-- 
2.43.0

[PATCH v7 4/7] serial: core: make sure RS485 cannot be enabled when it is not supported

[Lino Sanfilippo]

Some uart drivers specify a rs485_config() function and then decide later
to disable RS485 support for some reason (e.g. imx and ar933).

In these cases userspace may be able to activate RS485 via TIOCSRS485
nevertheless, since in uart_set_rs485_config() an existing rs485_config()
function indicates that RS485 is supported.

Make sure that this is not longer possible by checking the uarts
rs485_supported.flags instead and bailing out if SER_RS485_ENABLED is not
set.

Furthermore instead of returning an empty structure return -ENOTTY if the
RS485 configuration is requested via TIOCGRS485 but RS485 is not supported.
This has a small impact on userspace visibility but it is consistent with
the -ENOTTY error for TIOCGRS485.

Fixes: e849145e1fdd ("serial: ar933x: Fill in rs485_supported")
Fixes: 55e18c6b6d42 ("serial: imx: Remove serial_rs485 sanitization")
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: stable@vger.kernel.org
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---
 drivers/tty/serial/serial_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index f67fb6a04983..28bcbc686c67 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1469,7 +1469,7 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
 	int ret;
 	unsigned long flags;
 
-	if (!port->rs485_config)
+	if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
 		return -ENOTTY;
 
 	if (copy_from_user(&rs485, rs485_user, sizeof(*rs485_user)))
-- 
2.43.0

[PATCH v7 5/7] serial: core, imx: do not set RS485 enabled if it is not supported

[Lino Sanfilippo]

If the imx driver cannot support RS485 it nullifies the ports
rs485_supported structure. But it still calls uart_get_rs485_mode() which
may set the RS485_ENABLED flag nevertheless.

This may lead to an attempt to configure RS485 even if it is not supported
when the flag is evaluated in uart_configure_port() at port startup.

Avoid this by bailing out of uart_get_rs485_mode() if the RS485_ENABLED
flag is not supported by the caller.

With this fix a check for RTS availability is now obsolete in the imx
driver, since it can not evaluate to true any more. So remove this check.

Furthermore the explicit nullifcation of rs485_supported is not needed,
since the memory has already been set to zeros at allocation. So remove
this, too.

Fixes: 00d7a00e2a6f ("serial: imx: Fill in rs485_supported")
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: stable@vger.kernel.org
Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---
 drivers/tty/serial/imx.c         | 7 -------
 drivers/tty/serial/serial_core.c | 3 +++
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 9cffeb23112b..198ce7e7bc8b 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2206,7 +2206,6 @@ static enum hrtimer_restart imx_trigger_stop_tx(struct hrtimer *t)
 	return HRTIMER_NORESTART;
 }
 
-static const struct serial_rs485 imx_no_rs485 = {};	/* No RS485 if no RTS */
 static const struct serial_rs485 imx_rs485_supported = {
 	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND |
 		 SER_RS485_RX_DURING_TX,
@@ -2290,8 +2289,6 @@ static int imx_uart_probe(struct platform_device *pdev)
 	/* RTS is required to control the RS485 transmitter */
 	if (sport->have_rtscts || sport->have_rtsgpio)
 		sport->port.rs485_supported = imx_rs485_supported;
-	else
-		sport->port.rs485_supported = imx_no_rs485;
 	sport->port.flags = UPF_BOOT_AUTOCONF;
 	timer_setup(&sport->timer, imx_uart_timeout, 0);
 
@@ -2328,10 +2325,6 @@ static int imx_uart_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	if (sport->port.rs485.flags & SER_RS485_ENABLED &&
-	    (!sport->have_rtscts && !sport->have_rtsgpio))
-		dev_err(&pdev->dev, "no RTS control, disabling rs485\n");
-
 	/*
 	 * If using the i.MX UART RTS/CTS control then the RTS (CTS_B)
 	 * signal cannot be set low during transmission in case the
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 28bcbc686c67..93e4e1693601 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3600,6 +3600,9 @@ int uart_get_rs485_mode(struct uart_port *port)
 	u32 rs485_delay[2];
 	int ret;
 
+	if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
+		return 0;
+
 	ret = device_property_read_u32_array(dev, "rs485-rts-delay",
 					     rs485_delay, 2);
 	if (!ret) {
-- 
2.43.0

Re: [PATCH v7 5/7] serial: core, imx: do not set RS485 enabled if it is not supported

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 3124 bytes --]

On Wed, 3 Jan 2024, Lino Sanfilippo wrote:

> If the imx driver cannot support RS485 it nullifies the ports
> rs485_supported structure. But it still calls uart_get_rs485_mode() which
> may set the RS485_ENABLED flag nevertheless.
> 
> This may lead to an attempt to configure RS485 even if it is not supported
> when the flag is evaluated in uart_configure_port() at port startup.
> 
> Avoid this by bailing out of uart_get_rs485_mode() if the RS485_ENABLED
> flag is not supported by the caller.
> 
> With this fix a check for RTS availability is now obsolete in the imx
> driver, since it can not evaluate to true any more. So remove this check.
> 
> Furthermore the explicit nullifcation of rs485_supported is not needed,
> since the memory has already been set to zeros at allocation. So remove
> this, too.
> 
> Fixes: 00d7a00e2a6f ("serial: imx: Fill in rs485_supported")
> Cc: Shawn Guo <shawnguo@kernel.org>
> Cc: Sascha Hauer <s.hauer@pengutronix.de>
> Cc: stable@vger.kernel.org
> Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> ---
>  drivers/tty/serial/imx.c         | 7 -------
>  drivers/tty/serial/serial_core.c | 3 +++
>  2 files changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 9cffeb23112b..198ce7e7bc8b 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -2206,7 +2206,6 @@ static enum hrtimer_restart imx_trigger_stop_tx(struct hrtimer *t)
>  	return HRTIMER_NORESTART;
>  }
>  
> -static const struct serial_rs485 imx_no_rs485 = {};	/* No RS485 if no RTS */
>  static const struct serial_rs485 imx_rs485_supported = {
>  	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND |
>  		 SER_RS485_RX_DURING_TX,
> @@ -2290,8 +2289,6 @@ static int imx_uart_probe(struct platform_device *pdev)
>  	/* RTS is required to control the RS485 transmitter */
>  	if (sport->have_rtscts || sport->have_rtsgpio)
>  		sport->port.rs485_supported = imx_rs485_supported;
> -	else
> -		sport->port.rs485_supported = imx_no_rs485;
>  	sport->port.flags = UPF_BOOT_AUTOCONF;
>  	timer_setup(&sport->timer, imx_uart_timeout, 0);
>  
> @@ -2328,10 +2325,6 @@ static int imx_uart_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> -	if (sport->port.rs485.flags & SER_RS485_ENABLED &&
> -	    (!sport->have_rtscts && !sport->have_rtsgpio))
> -		dev_err(&pdev->dev, "no RTS control, disabling rs485\n");
> -
>  	/*
>  	 * If using the i.MX UART RTS/CTS control then the RTS (CTS_B)
>  	 * signal cannot be set low during transmission in case the
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 28bcbc686c67..93e4e1693601 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -3600,6 +3600,9 @@ int uart_get_rs485_mode(struct uart_port *port)
>  	u32 rs485_delay[2];
>  	int ret;
>  
> +	if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
> +		return 0;
> +

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

-- 
 i.

[PATCH v7 6/7] serial: omap: do not override settings for RS485 support

[Lino Sanfilippo]

The drivers RS485 support is deactivated if there is no RTS GPIO available.
This is done by nullifying the ports rs485_supported struct. After that
however the settings in serial_omap_rs485_supported are assigned to the
same structure unconditionally, which results in an unintended reactivation
of RS485 support.

Fix this by moving the assignment to the beginning of
serial_omap_probe_rs485() and thus before uart_get_rs485_mode() gets
called.

Also replace the assignment of rs485_config() to have the complete RS485
setup in one function.

Fixes: e2752ae3cfc9 ("serial: omap: Disallow RS-485 if rts-gpio is not specified")
Cc: stable@vger.kernel.org
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---
 drivers/tty/serial/omap-serial.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index ad4c1c5d0a7f..f4c6ff806465 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1483,6 +1483,13 @@ static struct omap_uart_port_info *of_get_uart_port_info(struct device *dev)
 	return omap_up_info;
 }
 
+static const struct serial_rs485 serial_omap_rs485_supported = {
+	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND |
+		 SER_RS485_RX_DURING_TX,
+	.delay_rts_before_send = 1,
+	.delay_rts_after_send = 1,
+};
+
 static int serial_omap_probe_rs485(struct uart_omap_port *up,
 				   struct device *dev)
 {
@@ -1497,6 +1504,9 @@ static int serial_omap_probe_rs485(struct uart_omap_port *up,
 	if (!np)
 		return 0;
 
+	up->port.rs485_config = serial_omap_config_rs485;
+	up->port.rs485_supported = serial_omap_rs485_supported;
+
 	ret = uart_get_rs485_mode(&up->port);
 	if (ret)
 		return ret;
@@ -1531,13 +1541,6 @@ static int serial_omap_probe_rs485(struct uart_omap_port *up,
 	return 0;
 }
 
-static const struct serial_rs485 serial_omap_rs485_supported = {
-	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND |
-		 SER_RS485_RX_DURING_TX,
-	.delay_rts_before_send = 1,
-	.delay_rts_after_send = 1,
-};
-
 static int serial_omap_probe(struct platform_device *pdev)
 {
 	struct omap_uart_port_info *omap_up_info = dev_get_platdata(&pdev->dev);
@@ -1604,17 +1607,11 @@ static int serial_omap_probe(struct platform_device *pdev)
 		dev_info(up->port.dev, "no wakeirq for uart%d\n",
 			 up->port.line);
 
-	ret = serial_omap_probe_rs485(up, &pdev->dev);
-	if (ret < 0)
-		goto err_rs485;
-
 	sprintf(up->name, "OMAP UART%d", up->port.line);
 	up->port.mapbase = mem->start;
 	up->port.membase = base;
 	up->port.flags = omap_up_info->flags;
 	up->port.uartclk = omap_up_info->uartclk;
-	up->port.rs485_config = serial_omap_config_rs485;
-	up->port.rs485_supported = serial_omap_rs485_supported;
 	if (!up->port.uartclk) {
 		up->port.uartclk = DEFAULT_CLK_SPEED;
 		dev_warn(&pdev->dev,
@@ -1622,6 +1619,10 @@ static int serial_omap_probe(struct platform_device *pdev)
 			 DEFAULT_CLK_SPEED);
 	}
 
+	ret = serial_omap_probe_rs485(up, &pdev->dev);
+	if (ret < 0)
+		goto err_rs485;
+
 	up->latency = PM_QOS_CPU_LATENCY_DEFAULT_VALUE;
 	up->calc_latency = PM_QOS_CPU_LATENCY_DEFAULT_VALUE;
 	cpu_latency_qos_add_request(&up->pm_qos_request, up->latency);
-- 
2.43.0

Re: [PATCH v7 6/7] serial: omap: do not override settings for RS485 support

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 4205 bytes --]

On Wed, 3 Jan 2024, Lino Sanfilippo wrote:

> The drivers RS485 support is deactivated if there is no RTS GPIO available.
> This is done by nullifying the ports rs485_supported struct. After that
> however the settings in serial_omap_rs485_supported are assigned to the
> same structure unconditionally, which results in an unintended reactivation
> of RS485 support.
> 
> Fix this by moving the assignment to the beginning of
> serial_omap_probe_rs485() and thus before uart_get_rs485_mode() gets
> called.

This doesn't seem to accurately reflect what the problem is (which you 
correctly described in the paragraph above this). The problem doesn't seem 
to have anything to do with the placement of uart_get_rs485_mode() call 
but the if (IS_ERR(up->rts_gpiod)) block that clears rs485_supported?

A future work item that came to my mind while reviewing this: I suppose 
uart_disable_rs485_support() could be added into core which memsets  
rs485_supported and rs485 to zero so this driver could just call it.

> Also replace the assignment of rs485_config() to have the complete RS485
> setup in one function.
> 
> Fixes: e2752ae3cfc9 ("serial: omap: Disallow RS-485 if rts-gpio is not specified")
> Cc: stable@vger.kernel.org
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> ---
>  drivers/tty/serial/omap-serial.c | 27 ++++++++++++++-------------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
> index ad4c1c5d0a7f..f4c6ff806465 100644
> --- a/drivers/tty/serial/omap-serial.c
> +++ b/drivers/tty/serial/omap-serial.c
> @@ -1483,6 +1483,13 @@ static struct omap_uart_port_info *of_get_uart_port_info(struct device *dev)
>  	return omap_up_info;
>  }
>  
> +static const struct serial_rs485 serial_omap_rs485_supported = {
> +	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND |
> +		 SER_RS485_RX_DURING_TX,
> +	.delay_rts_before_send = 1,
> +	.delay_rts_after_send = 1,
> +};
> +
>  static int serial_omap_probe_rs485(struct uart_omap_port *up,
>  				   struct device *dev)
>  {
> @@ -1497,6 +1504,9 @@ static int serial_omap_probe_rs485(struct uart_omap_port *up,
>  	if (!np)
>  		return 0;
>  
> +	up->port.rs485_config = serial_omap_config_rs485;
> +	up->port.rs485_supported = serial_omap_rs485_supported;
> +
>  	ret = uart_get_rs485_mode(&up->port);
>  	if (ret)
>  		return ret;
> @@ -1531,13 +1541,6 @@ static int serial_omap_probe_rs485(struct uart_omap_port *up,
>  	return 0;
>  }
>  
> -static const struct serial_rs485 serial_omap_rs485_supported = {
> -	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND |
> -		 SER_RS485_RX_DURING_TX,
> -	.delay_rts_before_send = 1,
> -	.delay_rts_after_send = 1,
> -};
> -
>  static int serial_omap_probe(struct platform_device *pdev)
>  {
>  	struct omap_uart_port_info *omap_up_info = dev_get_platdata(&pdev->dev);
> @@ -1604,17 +1607,11 @@ static int serial_omap_probe(struct platform_device *pdev)
>  		dev_info(up->port.dev, "no wakeirq for uart%d\n",
>  			 up->port.line);
>  
> -	ret = serial_omap_probe_rs485(up, &pdev->dev);
> -	if (ret < 0)
> -		goto err_rs485;
> -
>  	sprintf(up->name, "OMAP UART%d", up->port.line);
>  	up->port.mapbase = mem->start;
>  	up->port.membase = base;
>  	up->port.flags = omap_up_info->flags;
>  	up->port.uartclk = omap_up_info->uartclk;
> -	up->port.rs485_config = serial_omap_config_rs485;
> -	up->port.rs485_supported = serial_omap_rs485_supported;
>  	if (!up->port.uartclk) {
>  		up->port.uartclk = DEFAULT_CLK_SPEED;
>  		dev_warn(&pdev->dev,
> @@ -1622,6 +1619,10 @@ static int serial_omap_probe(struct platform_device *pdev)
>  			 DEFAULT_CLK_SPEED);
>  	}
>  
> +	ret = serial_omap_probe_rs485(up, &pdev->dev);
> +	if (ret < 0)
> +		goto err_rs485;
> +
>  	up->latency = PM_QOS_CPU_LATENCY_DEFAULT_VALUE;
>  	up->calc_latency = PM_QOS_CPU_LATENCY_DEFAULT_VALUE;
>  	cpu_latency_qos_add_request(&up->pm_qos_request, up->latency);

Moving of serial_omap_probe_rs485() later in serial_omap_probe() doesn't 
seem anymore required but I guess it doesn't hurt either.

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

-- 
 i.

Re: [PATCH v7 6/7] serial: omap: do not override settings for RS485 support

[Lino Sanfilippo]

On 03.01.24 at 12:36, Ilpo Järvinen wrote:
> On Wed, 3 Jan 2024, Lino Sanfilippo wrote:
>
>> The drivers RS485 support is deactivated if there is no RTS GPIO available.
>> This is done by nullifying the ports rs485_supported struct. After that
>> however the settings in serial_omap_rs485_supported are assigned to the
>> same structure unconditionally, which results in an unintended reactivation
>> of RS485 support.
>>
>> Fix this by moving the assignment to the beginning of
>> serial_omap_probe_rs485() and thus before uart_get_rs485_mode() gets
>> called.
>
> This doesn't seem to accurately reflect what the problem is (which you
> correctly described in the paragraph above this). The problem doesn't seem
> to have anything to do with the placement of uart_get_rs485_mode() call
> but the if (IS_ERR(up->rts_gpiod)) block that clears rs485_supported?
>

Right, this should be "...Fix this by moving the assignment to the beginning of
serial_omap_probe_rs485() and thus before the check for the RTS GPIO."
I will correct this.


> A future work item that came to my mind while reviewing this: I suppose
> uart_disable_rs485_support() could be added into core which memsets
> rs485_supported and rs485 to zero so this driver could just call it.
>

Yes, and the ar933x driver could use that as well.


Regards,
Lino

[PATCH v7 7/7] serial: 8250_exar: Set missing rs485_supported flag

[Lino Sanfilippo]

The UART supports an auto-RTS mode in which the RTS pin is automatically
activated during transmission. So mark this mode as being supported even
if RTS is not controlled by the driver but the UART.

Also the serial core expects now at least one of both modes rts-on-send or
rts-after-send to be supported. This is since during sanitization
unsupported flags are deleted from a RS485 configuration set by userspace.
However if the configuration ends up with both flags unset, the core prints
a warning since it considers such a configuration invalid (see
uart_sanitize_serial_rs485()).

Cc: stable@vger.kernel.org
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---
 drivers/tty/serial/8250/8250_exar.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c
index 6085d356ad86..23366f868ae3 100644
--- a/drivers/tty/serial/8250/8250_exar.c
+++ b/drivers/tty/serial/8250/8250_exar.c
@@ -480,7 +480,7 @@ static int sealevel_rs485_config(struct uart_port *port, struct ktermios *termio
 }
 
 static const struct serial_rs485 generic_rs485_supported = {
-	.flags = SER_RS485_ENABLED,
+	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND,
 };
 
 static const struct exar8250_platform exar8250_default_platform = {
@@ -524,7 +524,8 @@ static int iot2040_rs485_config(struct uart_port *port, struct ktermios *termios
 }
 
 static const struct serial_rs485 iot2040_rs485_supported = {
-	.flags = SER_RS485_ENABLED | SER_RS485_RX_DURING_TX | SER_RS485_TERMINATE_BUS,
+	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND |
+		 SER_RS485_RX_DURING_TX | SER_RS485_TERMINATE_BUS,
 };
 
 static const struct property_entry iot2040_gpio_properties[] = {
-- 
2.43.0