serial: core, imx: do not set RS485 enabled if it is not supported

commit 74eab89b26ac433ad857292f4707b43c1a8f0209 upstream.

If the imx driver cannot support RS485 it nullifies the ports
rs485_supported structure. 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. So remove this check.

Furthermore the explicit nullifcation of rs485_supported is not needed,
since the memory has already been set to zeros at allocation. So remove
this, too.

Fixes: 00d7a00e2a6f ("serial: imx: Fill in rs485_supported")
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc:  <stable@vger.kernel.org>
Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240103061818.564-6-l.sanfilippo@kunbus.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 13cb783..230660c 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2214,7 +2214,6 @@ static enum hrtimer_restart imx_trigger_stop_tx(struct hrtimer *t)
        return HRTIMER_NORESTART;
 }
 
-static const struct serial_rs485 imx_no_rs485 = {};    /* No RS485 if no RTS */
 static const struct serial_rs485 imx_rs485_supported = {
        .flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND |
                 SER_RS485_RX_DURING_TX,
@@ -2298,8 +2297,6 @@ static int imx_uart_probe(struct platform_device *pdev)
        /* RTS is required to control the RS485 transmitter */
        if (sport->have_rtscts || sport->have_rtsgpio)
                sport->port.rs485_supported = imx_rs485_supported;
-       else
-               sport->port.rs485_supported = imx_no_rs485;
        sport->port.flags = UPF_BOOT_AUTOCONF;
        timer_setup(&sport->timer, imx_uart_timeout, 0);
 
@@ -2336,10 +2333,6 @@ 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 50e1b26..18b49b1 100644 (file)
--- 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) {