serial: sc16is7xx: announce support for SER_RS485_RTS_ON_SEND

commit 068d35a upstream.

When specifying flag SER_RS485_RTS_ON_SEND in RS485 configuration,
we get the following warning after commit 4afeced ("serial: core:
fix sanitizing check for RTS settings"):

    invalid RTS setting, using RTS_AFTER_SEND instead

This results in SER_RS485_RTS_AFTER_SEND being set and the
driver always write to the register field SC16IS7XX_EFCR_RTS_INVERT_BIT,
which breaks some hardware using these chips.

The hardware supports both RTS_ON_SEND and RTS_AFTER_SEND modes, so fix
this by announcing support for RTS_ON_SEND.

Signed-off-by: Hugo Villeneuve <[email protected]>
Suggested-by: Konstantin Pugin <[email protected]>
Link: https://lore.kernel.org/lkml/[email protected]
Reviewed-by: Andy Shevchenko <[email protected]>
Tested-by: Hugo Villeneuve <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: hvilleneuvedoo

drivers/tty/serial/sc16is7xx.c

@@ -1478,7 +1478,7 @@ static int sc16is7xx_setup_mctrl_ports(struct sc16is7xx_port *s,
 }
 
 static const struct serial_rs485 sc16is7xx_rs485_supported = {
-	.flags = SER_RS485_ENABLED | SER_RS485_RTS_AFTER_SEND,
+	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND,
 	.delay_rts_before_send = 1,
 	.delay_rts_after_send = 1,	/* Not supported but keep returning -EINVAL */
 };