serial: Deassert Transmit Enable on probe in driver-specific way

commit 7c7f9bc986e698873b489c371a08f206979d06b7 upstream.

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>

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index f7fbef83583c8c004a4910317db897eeccfb714b..38ee3e42251af0e6cb64b73f354fc4c306f0592f 100644 (file)
--- 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 6f66dc2ebacc7acec27131b2b9f19b1dae24b350..b260c5579e1b99d6eec5582b212b1cd348cd0a80 100644 (file)
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1627,7 +1627,6 @@ 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) ||
@@ -1674,13 +1673,7 @@ 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]);
-                       uart_rs485_config(&port->port);
-               } 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 39b35a61958c04e43e1862b84f9ff7829324cbf5..7e92536aea594465984bbff6d7aa1eb9dee3500b 100644 (file)
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -600,7 +600,7 @@ 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)
@@ -616,7 +616,9 @@ 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;
 }
@@ -2042,6 +2044,9 @@ 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
@@ -3187,9 +3192,6 @@ 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)
-               uart_rs485_config(port);
-
        /* 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 fbc4b071b3309e0d479bb31c880e1d41486ea15c..6eb3d6c62458357687f312a664a6bc8ad7ebaf24 100644 (file)
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -2729,15 +2729,13 @@ static int lpuart_probe(struct platform_device *pdev)
        if (ret)
                goto failed_reset;
 
-       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;
 
-       uart_rs485_config(&sport->port);
+       ret = uart_add_one_port(&lpuart_reg, &sport->port);
+       if (ret)
+               goto failed_attach_port;
 
        ret = devm_request_irq(&pdev->dev, sport->port.irq, handler, 0,
                                DRIVER_NAME, sport);
@@ -2747,9 +2745,9 @@ static int lpuart_probe(struct platform_device *pdev)
        return 0;
 
 failed_irq_request:
-failed_get_rs485:
        uart_remove_one_port(&lpuart_reg, &sport->port);
 failed_attach_port:
+failed_get_rs485:
 failed_reset:
        lpuart_disable_clks(sport);
        return ret;

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 522445a8f666e5b09a7f2931c820d849d7162ff3..278b4033a3ccedb6201214584453f2064f6354ce 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -380,8 +380,7 @@ 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 */
@@ -390,8 +389,7 @@ 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)
@@ -2347,8 +2345,6 @@ 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");
 
-       uart_rs485_config(&sport->port);
-
        /* 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 12c87cd201a7659e958258629f99214eacd01b94..74b2784b8b5df506f7a894b8247310e8fb01cf1e 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -158,15 +158,10 @@ 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);
 }
@@ -1391,7 +1386,7 @@ static void uart_set_rs485_termination(struct uart_port *port,
                                 !!(rs485->flags & SER_RS485_TERMINATE_BUS));
 }
 
-int uart_rs485_config(struct uart_port *port)
+static int uart_rs485_config(struct uart_port *port)
 {
        struct serial_rs485 *rs485 = &port->rs485;
        int ret;
@@ -1405,7 +1400,6 @@ int uart_rs485_config(struct uart_port *port)
 
        return ret;
 }
-EXPORT_SYMBOL_GPL(uart_rs485_config);
 
 static int uart_get_rs485_config(struct uart_port *port,
                         struct serial_rs485 __user *rs485)
@@ -1444,8 +1438,13 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
 
        spin_lock_irqsave(&port->lock, flags);
        ret = port->rs485_config(port, &tty->termios, &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;
@@ -2352,7 +2351,8 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
 
                spin_lock_irq(&uport->lock);
                ops->stop_tx(uport);
-               ops->set_mctrl(uport, 0);
+               if (!(uport->rs485.flags & SER_RS485_ENABLED))
+                       ops->set_mctrl(uport, 0);
                /* save mctrl so it can be restored on resume */
                mctrl = uport->mctrl;
                uport->mctrl = 0;
@@ -2440,7 +2440,8 @@ 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 */
@@ -2451,7 +2452,10 @@ 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
+                                       uart_rs485_config(uport);
                                ops->start_tx(uport);
                                spin_unlock_irq(&uport->lock);
                                tty_port_set_initialized(port, 1);
@@ -2558,10 +2562,10 @@ 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
+                       uart_rs485_config(port);
                spin_unlock_irqrestore(&port->lock, flags);
 
                /*

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 1eaea9fe44d8e519bdcea9a2f87ff7feedc1d518..8290b66363727503ac82063ac8dca5149dc35d73 100644 (file)
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -950,5 +950,4 @@ static inline int uart_handle_break(struct uart_port *port)
                                         !((cflag) & CLOCAL))
 
 int uart_get_rs485_mode(struct uart_port *port);
-int uart_rs485_config(struct uart_port *port);
 #endif /* LINUX_SERIAL_CORE_H */