From: Lukas Wunner <lukas@xxxxxxxxx> 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@xxxxxxxxxxxxxxx/ Link: https://lore.kernel.org/all/8f538a8903795f22f9acc94a9a31b03c9c4ccacb.camel@xxxxxxxxxxxxx/ Fixes: d3b3404df318 ("serial: Fix incorrect rs485 polarity on uart open") Cc: stable@xxxxxxxxxxxxxxx # v4.14+ Reported-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx> Reported-by: Roosen Henri <Henri.Roosen@xxxxxxxxxxxxx> Tested-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx> Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> Link: https://lore.kernel.org/r/2de36eba3fbe11278d5002e4e501afe0ceaca039.1663863805.git.lukas@xxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 | 10 ++++------ drivers/tty/serial/imx.c | 8 ++------ drivers/tty/serial/serial_core.c | 36 ++++++++++++++++++++---------------- include/linux/serial_core.h | 1 - 7 files changed, 37 insertions(+), 42 deletions(-) --- 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 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); } /* --- 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_de 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_de 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 */ --- 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 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_mctr 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(struc 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; --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -2729,15 +2729,13 @@ static int lpuart_probe(struct platform_ 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_ 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; --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -380,8 +380,7 @@ static void imx_uart_rts_active(struct i { *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 *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 platfor 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); --- 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 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(s !!(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 * 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 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 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 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 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 * */ 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); /* --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -950,5 +950,4 @@ static inline int uart_handle_break(stru !((cflag) & CLOCAL)) int uart_get_rs485_mode(struct uart_port *port); -int uart_rs485_config(struct uart_port *port); #endif /* LINUX_SERIAL_CORE_H */
