serial: omap: Disallow RS-485 if rts-gpio is not specified

The serial-omap driver requires an rts-gpio for RS-485 to work.
Historically it has allowed enabling RS-485 even if no rts-gpio was
specified in the device tree.

That doesn't make any sense, so disable RS-485 on probe if rts-gpio is
missing and disallow user space from enabling it.

Three NULL pointer checks for up->rts_gpiod can be dropped as a result,
simplifying the driver slightly.

Cc: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/f191dcca0d8ea03598c463fc0d3fba8941ff2275.1662888075.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index c87d85b901a7d167ae1cabd98673de8cec8011d2..9c4fd0985f3d618c64cda35de884670e10e1d12e 100644 (file)
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -300,8 +300,7 @@ static void serial_omap_stop_tx(struct uart_port *port)
                        serial_out(up, UART_OMAP_SCR, up->scr);
                        res = (port->rs485.flags & SER_RS485_RTS_AFTER_SEND) ?
                                1 : 0;
-                       if (up->rts_gpiod &&
-                           gpiod_get_value(up->rts_gpiod) != res) {
+                       if (gpiod_get_value(up->rts_gpiod) != res) {
                                if (port->rs485.delay_rts_after_send > 0)
                                        mdelay(
                                        port->rs485.delay_rts_after_send);
@@ -397,7 +396,7 @@ static void serial_omap_start_tx(struct uart_port *port)
 
                /* if rts not already enabled */
                res = (port->rs485.flags & SER_RS485_RTS_ON_SEND) ? 1 : 0;
-               if (up->rts_gpiod && gpiod_get_value(up->rts_gpiod) != res) {
+               if (gpiod_get_value(up->rts_gpiod) != res) {
                        gpiod_set_value(up->rts_gpiod, res);
                        if (port->rs485.delay_rts_before_send > 0)
                                mdelay(port->rs485.delay_rts_before_send);
@@ -1336,13 +1335,11 @@ serial_omap_config_rs485(struct uart_port *port, struct ktermios *termios,
        up->ier = 0;
        serial_out(up, UART_IER, 0);
 
-       if (up->rts_gpiod) {
-               /* enable / disable rts */
-               val = (rs485->flags & SER_RS485_ENABLED) ?
-                       SER_RS485_RTS_AFTER_SEND : SER_RS485_RTS_ON_SEND;
-               val = (rs485->flags & val) ? 1 : 0;
-               gpiod_set_value(up->rts_gpiod, val);
-       }
+       /* enable / disable rts */
+       val = (rs485->flags & SER_RS485_ENABLED) ?
+             SER_RS485_RTS_AFTER_SEND : SER_RS485_RTS_ON_SEND;
+       val = (rs485->flags & val) ? 1 : 0;
+       gpiod_set_value(up->rts_gpiod, val);
 
        /* Enable interrupts */
        up->ier = mode;
@@ -1547,11 +1544,13 @@ static int serial_omap_probe_rs485(struct uart_omap_port *up,
                ret = PTR_ERR(up->rts_gpiod);
                if (ret == -EPROBE_DEFER)
                        return ret;
-               /*
-                * FIXME: the code historically ignored any other error than
-                * -EPROBE_DEFER and just went on without GPIO.
-                */
+
                up->rts_gpiod = NULL;
+               up->port.rs485_supported = (const struct serial_rs485) { };
+               if (rs485conf->flags & SER_RS485_ENABLED) {
+                       dev_err(dev, "disabling RS-485 (rts-gpio missing in device tree)\n");
+                       memset(rs485conf, 0, sizeof(*rs485conf));
+               }
        } else {
                gpiod_set_consumer_name(up->rts_gpiod, "omap-serial");
        }