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: Daisuke Mizobuchi <mizo@atmark-techno.com>
Signed-off-by: Dominique Martinet <dominique.martinet@atmark-techno.com>
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 537bee8d2258abe60c312608d0b2eadd93a39e22..f3744ac805ecb44b99da9ab157ce7d56523ac60b 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 df10cc606582b121a7cf436d63126b120c5ed756..b6656898699d10f5dd01e86e60cf341f9f3a9a8f 100644 (file)
--- 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 71d143c00248824740d97b2375bdf3098c65b74f..8b3756e4bb05c0bd50b90ef8a4fd4078d15cae08 100644 (file)
--- 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
@@ -3161,9 +3166,6 @@ 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 269d1e3a025d224fb97b2e900bde118aeb00e7d1..43aca5a2ef0f2b54780a1281e8eca9f3be013269 100644 (file)
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -2669,10 +2669,6 @@ 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;
@@ -2684,7 +2680,9 @@ static int lpuart_probe(struct platform_device *pdev)
            sport->port.rs485.delay_rts_after_send)
                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 bfbca711bbf9bf4ce99e249a3fca751eb4c7d730..cf3d531657762ed4940f3d46a32ac8e7c9119bd7 100644 (file)
--- 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 6cc909d44a8108c9bb0451b2d3c6b18456b93d95..605f928f0636a774fb00d80202bf0090b512dcef 100644 (file)
--- 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);
 
                /*