[PATCH v2 0/7] Fixes and improvements for RS485

[PATCH v2 0/7] Fixes and improvements for RS485

[Lino Sanfilippo]

The following series includes some fixes and improvements around RS485 in
the serial core and UART drivers:

Patch 1: Do not hold the port lock when setting rx-during-tx GPIO
Patch 2: Get rid of useless wrapper pl011_get_rs485_mode()
Patch 3: set missing supported flag for RX during TX GPIO
Patch 4: fix sanitizing check for RTS settings
Patch 5: make sure RS485 is cannot be enabled when it is not supported
Patch 6: imx: do not set RS485 enabled if it is not supported
Patch 7: omap: do not override settings for rs485 support

Changes in v2:
- add missing 'Fixes' tags as requested by Greg
- corrected a typo as pointed out by Hugo
- fix issue in imx driver in the serial core as suggested by Uwe
- partly rephrase some commit messages
- add patch 7

Lino Sanfilippo (7):
  serial: Do not hold the port lock when setting rx-during-tx GPIO
  serial: amba-pl011: get rid of useless wrapper pl011_get_rs485_mode()
  serial: core: set missing supported flag for RX during TX GPIO
  serial: core: fix sanitizing check for RTS settings
  serial: core: make sure RS485 cannot be enabled when it is not
    supported
  serial: core, imx: do not set RS485 enabled if it is not supported
  serial: omap: do not override settings for RS485 support

 drivers/tty/serial/amba-pl011.c  | 14 +---------
 drivers/tty/serial/imx.c         |  8 ------
 drivers/tty/serial/omap-serial.c |  8 +++---
 drivers/tty/serial/serial_core.c | 48 ++++++++++++++++++++++----------
 drivers/tty/serial/stm32-usart.c |  5 +---
 5 files changed, 39 insertions(+), 44 deletions(-)


base-commit: 94f6f0550c625fab1f373bb86a6669b45e9748b3
-- 
2.40.1

[PATCH v2 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 the
rs485_config() function by means of gpiod_set_value(). Since rs485_config()
is called with the port lock held, this can be an 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 setting the GPIO outside of the port lock in the serial
core and by using gpiod_set_value_cansleep() instead of gpiod_set_value().

Since now both the term and the rx-during-tx GPIO are set within the serial
core use a common function uart_set_rs485_gpios() to set both.

With moving it into the serial core setting the rx-during-tx GPIO is now
automatically done for all drivers that support such a GPIO.

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: 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 | 10 ++++++----
 drivers/tty/serial/stm32-usart.c |  5 +----
 3 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 13cb78340709..edb2ec6a5567 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1947,10 +1947,6 @@ 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 7bdc21d5e13b..ef0500be3553 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1391,14 +1391,16 @@ static void uart_sanitize_serial_rs485(struct uart_port *port, struct serial_rs4
 	memset(rs485->padding1, 0, sizeof(rs485->padding1));
 }
 
-static void uart_set_rs485_termination(struct uart_port *port,
-				       const struct serial_rs485 *rs485)
+static void uart_set_rs485_gpios(struct uart_port *port,
+				 const struct serial_rs485 *rs485)
 {
 	if (!(rs485->flags & SER_RS485_ENABLED))
 		return;
 
 	gpiod_set_value_cansleep(port->rs485_term_gpio,
 				 !!(rs485->flags & SER_RS485_TERMINATE_BUS));
+	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)
@@ -1407,7 +1409,7 @@ static int uart_rs485_config(struct uart_port *port)
 	int ret;
 
 	uart_sanitize_serial_rs485(port, rs485);
-	uart_set_rs485_termination(port, rs485);
+	uart_set_rs485_gpios(port, rs485);
 
 	ret = port->rs485_config(port, NULL, rs485);
 	if (ret)
@@ -1449,7 +1451,7 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
 	if (ret)
 		return ret;
 	uart_sanitize_serial_rs485(port, &rs485);
-	uart_set_rs485_termination(port, &rs485);
+	uart_set_rs485_gpios(port, &rs485);
 
 	spin_lock_irqsave(&port->lock, flags);
 	ret = port->rs485_config(port, &tty->termios, &rs485);
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 5e9cf0c48813..8eb13bf055f2 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -226,10 +226,7 @@ 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
+	if (!port->rs485_rx_during_tx_gpio)
 		rs485conf->flags |= SER_RS485_RX_DURING_TX;
 
 	if (rs485conf->flags & SER_RS485_ENABLED) {
-- 
2.40.1

[PATCH v2 2/7] serial: amba-pl011: get rid of useless wrapper pl011_get_rs485_mode()

[Lino Sanfilippo]

Due to earlier code changes function pl011_get_rs485_mode() is now merely
a wrapper for uart_get_rs485_mode() which does not add any further
functionality. So remove it and instead call uart_get_rs485_mode()
directly.

Reviewed-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---
 drivers/tty/serial/amba-pl011.c | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 3dc9b0fcab1c..70b44f3e9eb7 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -2716,18 +2716,6 @@ static int pl011_find_free_port(void)
 	return -EBUSY;
 }
 
-static int pl011_get_rs485_mode(struct uart_amba_port *uap)
-{
-	struct uart_port *port = &uap->port;
-	int ret;
-
-	ret = uart_get_rs485_mode(port);
-	if (ret)
-		return ret;
-
-	return 0;
-}
-
 static int pl011_setup_port(struct device *dev, struct uart_amba_port *uap,
 			    struct resource *mmiobase, int index)
 {
@@ -2748,7 +2736,7 @@ static int pl011_setup_port(struct device *dev, struct uart_amba_port *uap,
 	uap->port.flags = UPF_BOOT_AUTOCONF;
 	uap->port.line = index;
 
-	ret = pl011_get_rs485_mode(uap);
+	ret = uart_get_rs485_mode(&uap->port);
 	if (ret)
 		return ret;
 
-- 
2.40.1

Re: [PATCH v2 2/7] serial: amba-pl011: get rid of useless wrapper pl011_get_rs485_mode()

[Greg KH]

On Wed, Oct 11, 2023 at 07:38:24PM +0200, Lino Sanfilippo wrote:
> Due to earlier code changes function pl011_get_rs485_mode() is now merely
> a wrapper for uart_get_rs485_mode() which does not add any further
> functionality. So remove it and instead call uart_get_rs485_mode()
> directly.
> 
> Reviewed-by: Lukas Wunner <lukas@wunner.de>
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> ---
>  drivers/tty/serial/amba-pl011.c | 14 +-------------
>  1 file changed, 1 insertion(+), 13 deletions(-)

Why is patch 2/7 not cc: stable, when patches 3-7 are?  Either this
patch isn't needed in this series, and can go later (or to a different
branch), or it also needs to be marked for stable as the later patches
depend on it?

thanks,

greg k-h

Re: [PATCH v2 2/7] serial: amba-pl011: get rid of useless wrapper pl011_get_rs485_mode()

[Lino Sanfilippo]

Hi,

On 11.10.23 at 19:42, Greg KH wrote:
> On Wed, Oct 11, 2023 at 07:38:24PM +0200, Lino Sanfilippo wrote:
>> Due to earlier code changes function pl011_get_rs485_mode() is now merely
>> a wrapper for uart_get_rs485_mode() which does not add any further
>> functionality. So remove it and instead call uart_get_rs485_mode()
>> directly.
>>
>> Reviewed-by: Lukas Wunner <lukas@wunner.de>
>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>> ---
>>  drivers/tty/serial/amba-pl011.c | 14 +-------------
>>  1 file changed, 1 insertion(+), 13 deletions(-)
>
> Why is patch 2/7 not cc: stable, when patches 3-7 are?  Either this
> patch isn't needed in this series, and can go later (or to a different
> branch), or it also needs to be marked for stable as the later patches
> depend on it?
>

2/7 is really only a cleanup patch that does not provide a bugfix.
Should I remove it from this series?

Regards,
Lino

Re: [PATCH v2 2/7] serial: amba-pl011: get rid of useless wrapper pl011_get_rs485_mode()

[Greg KH]

On Wed, Oct 11, 2023 at 07:44:51PM +0200, Lino Sanfilippo wrote:
> 
> Hi,
> 
> On 11.10.23 at 19:42, Greg KH wrote:
> > On Wed, Oct 11, 2023 at 07:38:24PM +0200, Lino Sanfilippo wrote:
> >> Due to earlier code changes function pl011_get_rs485_mode() is now merely
> >> a wrapper for uart_get_rs485_mode() which does not add any further
> >> functionality. So remove it and instead call uart_get_rs485_mode()
> >> directly.
> >>
> >> Reviewed-by: Lukas Wunner <lukas@wunner.de>
> >> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> >> ---
> >>  drivers/tty/serial/amba-pl011.c | 14 +-------------
> >>  1 file changed, 1 insertion(+), 13 deletions(-)
> >
> > Why is patch 2/7 not cc: stable, when patches 3-7 are?  Either this
> > patch isn't needed in this series, and can go later (or to a different
> > branch), or it also needs to be marked for stable as the later patches
> > depend on it?
> >
> 
> 2/7 is really only a cleanup patch that does not provide a bugfix.
> Should I remove it from this series?

Please do, and send it later, or as part of a separate patch series
independant of this one.

thanks,

greg k-h

Re: [PATCH v2 2/7] serial: amba-pl011: get rid of useless wrapper pl011_get_rs485_mode()

[Lino Sanfilippo]

On 11.10.23 at 19:47, Greg KH wrote:
> On Wed, Oct 11, 2023 at 07:44:51PM +0200, Lino Sanfilippo wrote:
>>
>> Hi,
>>
>> On 11.10.23 at 19:42, Greg KH wrote:
>>> On Wed, Oct 11, 2023 at 07:38:24PM +0200, Lino Sanfilippo wrote:
>>>> Due to earlier code changes function pl011_get_rs485_mode() is now merely
>>>> a wrapper for uart_get_rs485_mode() which does not add any further
>>>> functionality. So remove it and instead call uart_get_rs485_mode()
>>>> directly.
>>>>
>>>> Reviewed-by: Lukas Wunner <lukas@wunner.de>
>>>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>>>> ---
>>>>  drivers/tty/serial/amba-pl011.c | 14 +-------------
>>>>  1 file changed, 1 insertion(+), 13 deletions(-)
>>>
>>> Why is patch 2/7 not cc: stable, when patches 3-7 are?  Either this
>>> patch isn't needed in this series, and can go later (or to a different
>>> branch), or it also needs to be marked for stable as the later patches
>>> depend on it?
>>>
>>
>> 2/7 is really only a cleanup patch that does not provide a bugfix.
>> Should I remove it from this series?
>
> Please do, and send it later, or as part of a separate patch series
> independant of this one.
>

Ok will do so.

BR,
Lino

[PATCH v2 3/7] 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")
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 ef0500be3553..697c36dc7ec8 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3622,6 +3622,8 @@ int uart_get_rs485_mode(struct uart_port *port)
 		port->rs485_rx_during_tx_gpio = NULL;
 		return dev_err_probe(dev, ret, "Cannot get rs485-rx-during-tx-gpios\n");
 	}
+	if (port->rs485_rx_during_tx_gpio)
+		port->rs485_supported.flags |= SER_RS485_RX_DURING_TX;
 
 	return 0;
 }
-- 
2.40.1

[PATCH v2 4/7] 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")
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 697c36dc7ec8..f4feebf8200f 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1370,19 +1370,27 @@ 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);
 
-- 
2.40.1

[PATCH v2 5/7] 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: stable@vger.kernel.org
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---
 drivers/tty/serial/serial_core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index f4feebf8200f..dca09877fabc 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1432,6 +1432,9 @@ static int uart_get_rs485_config(struct uart_port *port,
 	unsigned long flags;
 	struct serial_rs485 aux;
 
+	if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
+		return -ENOTTY;
+
 	spin_lock_irqsave(&port->lock, flags);
 	aux = port->rs485;
 	spin_unlock_irqrestore(&port->lock, flags);
@@ -1449,7 +1452,7 @@ 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)))
-- 
2.40.1

[PATCH v2 6/7] serial: core, imx: do not set RS485 enabled if it is not supported

[Lino Sanfilippo]

If the imx driver cannot support RS485 it sets the ports rs485_supported
structure to NULL. 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. Remove this check, too.

Fixes: 00d7a00e2a6f ("serial: imx: Fill in rs485_supported")
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         | 4 ----
 drivers/tty/serial/serial_core.c | 3 +++
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index edb2ec6a5567..c8c19bf8585d 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2332,10 +2332,6 @@ 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 dca09877fabc..95cec2343b35 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3576,6 +3576,9 @@ int uart_get_rs485_mode(struct uart_port *port)
 	int ret;
 	int rx_during_tx_gpio_flag;
 
+	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) {
-- 
2.40.1

[PATCH v2 7/7] serial: omap: do not override settings for RS485 support

[Lino Sanfilippo]

In serial_omap_rs485() RS485 support may be deactivated due to a missing
RTS GPIO. This is done by nullifying the ports rs485_supported struct.
After that however the serial_omap_rs485_supported struct is assigned to
the same structure unconditionally, which results in an unintended
reactivation of RS485 support.
Fix this by callling serial_omap_rs485() after the assignment of
rs485_supported.

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 | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index 0ead88c5a19a..4f7ee4392034 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1604,10 +1604,6 @@ 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;
@@ -1622,6 +1618,10 @@ 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);
-- 
2.40.1