[PATCH 5.10 0/2] Stable 5.10 backport of RS485 initial polarity fix

[PATCH 5.10 0/2] Stable 5.10 backport of RS485 initial polarity fix

[Dominique Martinet]

This is the backport of the RS485 polarity fixes discussed here:
https://lkml.kernel.org/r/20221010085305.GA32599@wunner.de

It fixes RS485 DE initially set wrong on driver init, blocking other
devices from transmitting on the bus.

Mizobuchi-san did the backport and tested on our imx-based platform, but
we do not have any hardware to test other drivers.


The commits also apply cleanly on 5.15, and for 5.19 the second commit
does (first one has already been picked up), but these have not been
tested so would require more checking.

Kernels older than 5.10 do not have this particular polarity inversion
problem and do not need this as far as I can see.
(there might be other problems this addresses that I am not aware of
though)


Thanks,


Lino Sanfilippo (1):
  serial: core: move RS485 configuration tasks from drivers into core

Lukas Wunner (1):
  serial: Deassert Transmit Enable on probe in driver-specific way

 drivers/tty/serial/8250/8250_omap.c |  3 ++
 drivers/tty/serial/8250/8250_pci.c  |  9 +----
 drivers/tty/serial/8250/8250_port.c | 12 +++---
 drivers/tty/serial/fsl_lpuart.c     |  7 ++--
 drivers/tty/serial/imx.c            |  8 +---
 drivers/tty/serial/serial_core.c    | 61 +++++++++++++++++++++++------
 6 files changed, 65 insertions(+), 35 deletions(-)

-- 
2.35.1

[PATCH 5.10 1/2] serial: core: move RS485 configuration tasks from drivers into core

[Dominique Martinet]

From: Lino Sanfilippo <LinoSanfilippo@gmx.de>

Several drivers that support setting the RS485 configuration via userspace
implement one or more of the following tasks:

- in case of an invalid RTS configuration (both RTS after send and RTS on
  send set or both unset) fall back to enable RTS on send and disable RTS
  after send

- nullify the padding field of the returned serial_rs485 struct

- copy the configuration into the uart port struct

- limit RTS delays to 100 ms

Move these tasks into the serial core to make them generic and to provide
a consistent behaviour among all drivers.

Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Link: https://lore.kernel.org/r/20220410104642.32195-2-LinoSanfilippo@gmx.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 0ed12afa5655512ee418047fb3546d229df20aa1 ]
Signed-off-by: Daisuke Mizobuchi <mizo@atmark-techno.com>
Signed-off-by: Dominique Martinet <dominique.martinet@atmark-techno.com>
---

This has been picked up as it makes the next patch easier to apply

 drivers/tty/serial/serial_core.c | 33 ++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index b578f7090b63..6cc909d44a81 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -42,6 +42,11 @@ static struct lock_class_key port_lock_key;
 
 #define HIGH_BITS_OFFSET	((sizeof(long)-sizeof(int))*8)
 
+/*
+ * Max time with active RTS before/after data is sent.
+ */
+#define RS485_MAX_RTS_DELAY	100 /* msecs */
+
 static void uart_change_speed(struct tty_struct *tty, struct uart_state *state,
 					struct ktermios *old_termios);
 static void uart_wait_until_sent(struct tty_struct *tty, int timeout);
@@ -1326,8 +1331,36 @@ static int uart_set_rs485_config(struct uart_port *port,
 	if (copy_from_user(&rs485, rs485_user, sizeof(*rs485_user)))
 		return -EFAULT;
 
+	/* pick sane settings if the user hasn't */
+	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;
+	}
+
+	if (rs485.delay_rts_before_send > RS485_MAX_RTS_DELAY) {
+		rs485.delay_rts_before_send = RS485_MAX_RTS_DELAY;
+		dev_warn_ratelimited(port->dev,
+			"%s (%d): RTS delay before sending clamped to %u ms\n",
+			port->name, port->line, rs485.delay_rts_before_send);
+	}
+
+	if (rs485.delay_rts_after_send > RS485_MAX_RTS_DELAY) {
+		rs485.delay_rts_after_send = RS485_MAX_RTS_DELAY;
+		dev_warn_ratelimited(port->dev,
+			"%s (%d): RTS delay after sending clamped to %u ms\n",
+			port->name, port->line, rs485.delay_rts_after_send);
+	}
+	/* Return clean padding area to userspace */
+	memset(rs485.padding, 0, sizeof(rs485.padding));
+
 	spin_lock_irqsave(&port->lock, flags);
 	ret = port->rs485_config(port, &rs485);
+	if (!ret)
+		port->rs485 = rs485;
 	spin_unlock_irqrestore(&port->lock, flags);
 	if (ret)
 		return ret;
-- 
2.35.1

[PATCH 5.10 2/2] serial: Deassert Transmit Enable on probe in driver-specific way

[Dominique Martinet]

From: Lukas Wunner <lukas@wunner.de>

When a UART port is newly registered, uart_configure_port() seeks to
deassert RS485 Transmit Enable by setting the RTS bit in port->mctrl.
However a number of UART drivers interpret a set RTS bit as *assertion*
instead of deassertion:  Affected drivers include those using
serial8250_em485_config() (except 8250_bcm2835aux.c) and some using
mctrl_gpio (e.g. imx.c).

Since the interpretation of the RTS bit is driver-specific, it is not
suitable as a means to centrally deassert Transmit Enable in the serial
core.  Instead, the serial core must call on drivers to deassert it in
their driver-specific way.  One way to achieve that is to call
->rs485_config().  It implicitly deasserts Transmit Enable.

So amend uart_configure_port() and uart_resume_port() to invoke
uart_rs485_config().  That allows removing calls to uart_rs485_config()
from drivers' ->probe() hooks and declaring the function static.

Skip any invocation of ->set_mctrl() if RS485 is enabled.  RS485 has no
hardware flow control, so the modem control lines are irrelevant and
need not be touched.  When leaving RS485 mode, reset the modem control
lines to the state stored in port->mctrl.  That way, UARTs which are
muxed between RS485 and RS232 transceivers drive the lines correctly
when switched to RS232.  (serial8250_do_startup() historically raises
the OUT1 modem signal because otherwise interrupts are not signaled on
ancient PC UARTs, but I believe that no longer applies to modern,
RS485-capable UARTs and is thus safe to be skipped.)

imx.c modifies port->mctrl whenever Transmit Enable is asserted and
deasserted.  Stop it from doing that so port->mctrl reflects the RS232
line state.

8250_omap.c deasserts Transmit Enable on ->runtime_resume() by calling
->set_mctrl().  Because that is now a no-op in RS485 mode, amend the
function to call serial8250_em485_stop_tx().

fsl_lpuart.c retrieves and applies the RS485 device tree properties
after registering the UART port.  Because applying now happens on
registration in uart_configure_port(), move retrieval of the properties
ahead of uart_add_one_port().

Link: https://lore.kernel.org/all/20220329085050.311408-1-matthias.schiffer@ew.tq-group.com/
Link: https://lore.kernel.org/all/8f538a8903795f22f9acc94a9a31b03c9c4ccacb.camel@ginzinger.com/
Fixes: d3b3404df318 ("serial: Fix incorrect rs485 polarity on uart open")
Cc: stable@vger.kernel.org # v4.14+
Reported-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Reported-by: Roosen Henri <Henri.Roosen@ginzinger.com>
Tested-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/2de36eba3fbe11278d5002e4e501afe0ceaca039.1663863805.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 7c7f9bc986e698873b489c371a08f206979d06b7 ]
Signed-off-by: Daisuke Mizobuchi <mizo@atmark-techno.com>
Signed-off-by: Dominique Martinet <dominique.martinet@atmark-techno.com>
---
 drivers/tty/serial/8250/8250_omap.c |  3 +++
 drivers/tty/serial/8250/8250_pci.c  |  9 +--------
 drivers/tty/serial/8250/8250_port.c | 12 +++++++-----
 drivers/tty/serial/fsl_lpuart.c     |  7 +++----
 drivers/tty/serial/imx.c            |  8 ++------
 drivers/tty/serial/serial_core.c    | 30 ++++++++++++++++-------------
 6 files changed, 33 insertions(+), 36 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 537bee8d2258..f3744ac805ec 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -342,6 +342,9 @@ static void omap8250_restore_regs(struct uart_8250_port *up)
 	omap8250_update_mdr1(up, priv);
 
 	up->port.ops->set_mctrl(&up->port, up->port.mctrl);
+
+	if (up->port.rs485.flags & SER_RS485_ENABLED)
+		serial8250_em485_stop_tx(up);
 }
 
 /*
diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index df10cc606582..b6656898699d 100644
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1531,7 +1531,6 @@ static int pci_fintek_init(struct pci_dev *dev)
 	resource_size_t bar_data[3];
 	u8 config_base;
 	struct serial_private *priv = pci_get_drvdata(dev);
-	struct uart_8250_port *port;
 
 	if (!(pci_resource_flags(dev, 5) & IORESOURCE_IO) ||
 			!(pci_resource_flags(dev, 4) & IORESOURCE_IO) ||
@@ -1578,13 +1577,7 @@ static int pci_fintek_init(struct pci_dev *dev)
 
 		pci_write_config_byte(dev, config_base + 0x06, dev->irq);
 
-		if (priv) {
-			/* re-apply RS232/485 mode when
-			 * pciserial_resume_ports()
-			 */
-			port = serial8250_get_port(priv->line[i]);
-			pci_fintek_rs485_config(&port->port, NULL);
-		} else {
+		if (!priv) {
 			/* First init without port data
 			 * force init to RS232 Mode
 			 */
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 9d60418e4adb..e6cadb23850a 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -592,7 +592,7 @@ EXPORT_SYMBOL_GPL(serial8250_rpm_put);
 static int serial8250_em485_init(struct uart_8250_port *p)
 {
 	if (p->em485)
-		return 0;
+		goto deassert_rts;
 
 	p->em485 = kmalloc(sizeof(struct uart_8250_em485), GFP_ATOMIC);
 	if (!p->em485)
@@ -608,7 +608,9 @@ static int serial8250_em485_init(struct uart_8250_port *p)
 	p->em485->active_timer = NULL;
 	p->em485->tx_stopped = true;
 
-	p->rs485_stop_tx(p);
+deassert_rts:
+	if (p->em485->tx_stopped)
+		p->rs485_stop_tx(p);
 
 	return 0;
 }
@@ -2030,6 +2032,9 @@ EXPORT_SYMBOL_GPL(serial8250_do_set_mctrl);
 
 static void serial8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
 {
+	if (port->rs485.flags & SER_RS485_ENABLED)
+		return;
+
 	if (port->set_mctrl)
 		port->set_mctrl(port, mctrl);
 	else
@@ -3159,9 +3164,6 @@ static void serial8250_config_port(struct uart_port *port, int flags)
 	if (flags & UART_CONFIG_TYPE)
 		autoconfig(up);
 
-	if (port->rs485.flags & SER_RS485_ENABLED)
-		port->rs485_config(port, &port->rs485);
-
 	/* if access method is AU, it is a 16550 with a quirk */
 	if (port->type == PORT_16550A && port->iotype == UPIO_AU)
 		up->bugs |= UART_BUG_NOMSR;
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index a2c4eab0b470..5ca61fa50efd 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -2667,10 +2667,6 @@ static int lpuart_probe(struct platform_device *pdev)
 	if (ret)
 		goto failed_irq_request;
 
-	ret = uart_add_one_port(&lpuart_reg, &sport->port);
-	if (ret)
-		goto failed_attach_port;
-
 	ret = uart_get_rs485_mode(&sport->port);
 	if (ret)
 		goto failed_get_rs485;
@@ -2683,6 +2679,9 @@ static int lpuart_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev, "driver doesn't support RTS delays\n");
 
 	sport->port.rs485_config(&sport->port, &sport->port.rs485);
+	ret = uart_add_one_port(&lpuart_reg, &sport->port);
+	if (ret)
+		goto failed_attach_port;
 
 	return 0;
 
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index bfbca711bbf9..cf3d53165776 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -398,8 +398,7 @@ static void imx_uart_rts_active(struct imx_port *sport, u32 *ucr2)
 {
 	*ucr2 &= ~(UCR2_CTSC | UCR2_CTS);
 
-	sport->port.mctrl |= TIOCM_RTS;
-	mctrl_gpio_set(sport->gpios, sport->port.mctrl);
+	mctrl_gpio_set(sport->gpios, sport->port.mctrl | TIOCM_RTS);
 }
 
 /* called with port.lock taken and irqs caller dependent */
@@ -408,8 +407,7 @@ static void imx_uart_rts_inactive(struct imx_port *sport, u32 *ucr2)
 	*ucr2 &= ~UCR2_CTSC;
 	*ucr2 |= UCR2_CTS;
 
-	sport->port.mctrl &= ~TIOCM_RTS;
-	mctrl_gpio_set(sport->gpios, sport->port.mctrl);
+	mctrl_gpio_set(sport->gpios, sport->port.mctrl & ~TIOCM_RTS);
 }
 
 static void start_hrtimer_ms(struct hrtimer *hrt, unsigned long msec)
@@ -2381,8 +2379,6 @@ static int imx_uart_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev,
 			"low-active RTS not possible when receiver is off, enabling receiver\n");
 
-	imx_uart_rs485_config(&sport->port, &sport->port.rs485);
-
 	/* Disable interrupts before requesting them */
 	ucr1 = imx_uart_readl(sport, UCR1);
 	ucr1 &= ~(UCR1_ADEN | UCR1_TRDYEN | UCR1_IDEN | UCR1_RRDYEN | UCR1_RTSDEN);
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 6cc909d44a81..605f928f0636 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -149,15 +149,10 @@ uart_update_mctrl(struct uart_port *port, unsigned int set, unsigned int clear)
 	unsigned long flags;
 	unsigned int old;
 
-	if (port->rs485.flags & SER_RS485_ENABLED) {
-		set &= ~TIOCM_RTS;
-		clear &= ~TIOCM_RTS;
-	}
-
 	spin_lock_irqsave(&port->lock, flags);
 	old = port->mctrl;
 	port->mctrl = (old & ~clear) | set;
-	if (old != port->mctrl)
+	if (old != port->mctrl && !(port->rs485.flags & SER_RS485_ENABLED))
 		port->ops->set_mctrl(port, port->mctrl);
 	spin_unlock_irqrestore(&port->lock, flags);
 }
@@ -1359,8 +1354,13 @@ static int uart_set_rs485_config(struct uart_port *port,
 
 	spin_lock_irqsave(&port->lock, flags);
 	ret = port->rs485_config(port, &rs485);
-	if (!ret)
+	if (!ret) {
 		port->rs485 = rs485;
+
+		/* Reset RTS and other mctrl lines when disabling RS485 */
+		if (!(rs485.flags & SER_RS485_ENABLED))
+			port->ops->set_mctrl(port, port->mctrl);
+	}
 	spin_unlock_irqrestore(&port->lock, flags);
 	if (ret)
 		return ret;
@@ -2335,7 +2335,8 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
 
 		uart_change_pm(state, UART_PM_STATE_ON);
 		spin_lock_irq(&uport->lock);
-		ops->set_mctrl(uport, 0);
+		if (!(uport->rs485.flags & SER_RS485_ENABLED))
+			ops->set_mctrl(uport, 0);
 		spin_unlock_irq(&uport->lock);
 		if (console_suspend_enabled || !uart_console(uport)) {
 			/* Protected by port mutex for now */
@@ -2346,7 +2347,10 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
 				if (tty)
 					uart_change_speed(tty, state, NULL);
 				spin_lock_irq(&uport->lock);
-				ops->set_mctrl(uport, uport->mctrl);
+				if (!(uport->rs485.flags & SER_RS485_ENABLED))
+					ops->set_mctrl(uport, uport->mctrl);
+				else
+					uport->rs485_config(uport, &uport->rs485);
 				ops->start_tx(uport);
 				spin_unlock_irq(&uport->lock);
 				tty_port_set_initialized(port, 1);
@@ -2444,10 +2448,10 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state,
 		 */
 		spin_lock_irqsave(&port->lock, flags);
 		port->mctrl &= TIOCM_DTR;
-		if (port->rs485.flags & SER_RS485_ENABLED &&
-		    !(port->rs485.flags & SER_RS485_RTS_AFTER_SEND))
-			port->mctrl |= TIOCM_RTS;
-		port->ops->set_mctrl(port, port->mctrl);
+		if (!(port->rs485.flags & SER_RS485_ENABLED))
+			port->ops->set_mctrl(port, port->mctrl);
+		else
+			port->rs485_config(port, &port->rs485);
 		spin_unlock_irqrestore(&port->lock, flags);
 
 		/*
-- 
2.35.1

Re: [PATCH 5.10 2/2] serial: Deassert Transmit Enable on probe in driver-specific way

[Dominique Martinet]

Dominique Martinet wrote on Mon, Oct 17, 2022 at 10:39:10AM +0900:
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> index a2c4eab0b470..5ca61fa50efd 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -2667,10 +2667,6 @@ static int lpuart_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto failed_irq_request;
>  
> -	ret = uart_add_one_port(&lpuart_reg, &sport->port);
> -	if (ret)
> -		goto failed_attach_port;
> -
>  	ret = uart_get_rs485_mode(&sport->port);
>  	if (ret)
>  		goto failed_get_rs485;
> @@ -2683,6 +2679,9 @@ static int lpuart_probe(struct platform_device *pdev)
>  		dev_err(&pdev->dev, "driver doesn't support RTS delays\n");
>  
>  	sport->port.rs485_config(&sport->port, &sport->port.rs485);

Ah, I've been quick on the review, sorry: this rs485_config() should
probably be removed.
(the similar uart_rs485_config() was removed in the upstream patch)

I'll send a v2 after this has gotten another review or when prompted,
sorry for the trouble.

> +	ret = uart_add_one_port(&lpuart_reg, &sport->port);
> +	if (ret)
> +		goto failed_attach_port;
>  
>  	return 0;
>  

Re: [PATCH 5.10 2/2] serial: Deassert Transmit Enable on probe in driver-specific way

[Greg Kroah-Hartman]

On Mon, Oct 17, 2022 at 10:57:56AM +0900, Dominique Martinet wrote:
> Dominique Martinet wrote on Mon, Oct 17, 2022 at 10:39:10AM +0900:
> > diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> > index a2c4eab0b470..5ca61fa50efd 100644
> > --- a/drivers/tty/serial/fsl_lpuart.c
> > +++ b/drivers/tty/serial/fsl_lpuart.c
> > @@ -2667,10 +2667,6 @@ static int lpuart_probe(struct platform_device *pdev)
> >  	if (ret)
> >  		goto failed_irq_request;
> >  
> > -	ret = uart_add_one_port(&lpuart_reg, &sport->port);
> > -	if (ret)
> > -		goto failed_attach_port;
> > -
> >  	ret = uart_get_rs485_mode(&sport->port);
> >  	if (ret)
> >  		goto failed_get_rs485;
> > @@ -2683,6 +2679,9 @@ static int lpuart_probe(struct platform_device *pdev)
> >  		dev_err(&pdev->dev, "driver doesn't support RTS delays\n");
> >  
> >  	sport->port.rs485_config(&sport->port, &sport->port.rs485);
> 
> Ah, I've been quick on the review, sorry: this rs485_config() should
> probably be removed.
> (the similar uart_rs485_config() was removed in the upstream patch)
> 
> I'll send a v2 after this has gotten another review or when prompted,
> sorry for the trouble.

Please fix up and resend a v2.

thanks,

greg k-h