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Subject[PATCH 5.15 046/171] serial: pl011: Fix incorrect rs485 RTS polarity on set_mctrl
Date
From: Jochen Mades <jochen@mades.net>

commit 62f676ff7898f6c1bd26ce014564773a3dc00601 upstream.

Commit 8d479237727c ("serial: amba-pl011: add RS485 support") sought to
keep RTS deasserted on set_mctrl if rs485 is enabled. However it did so
only if deasserted RTS polarity is high. Fix it in case it's low.

Fixes: 8d479237727c ("serial: amba-pl011: add RS485 support")
Cc: stable@vger.kernel.org # v5.15+
Cc: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Jochen Mades <jochen@mades.net>
[lukas: copyedit commit message, add stable designation]
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/85fa3323ba8c307943969b7343e23f34c3e652ba.1642909284.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/serial/amba-pl011.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1615,8 +1615,12 @@ static void pl011_set_mctrl(struct uart_
container_of(port, struct uart_amba_port, port);
unsigned int cr;

- if (port->rs485.flags & SER_RS485_ENABLED)
- mctrl &= ~TIOCM_RTS;
+ if (port->rs485.flags & SER_RS485_ENABLED) {
+ if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
+ mctrl &= ~TIOCM_RTS;
+ else
+ mctrl |= TIOCM_RTS;
+ }

cr = pl011_read(uap, REG_CR);


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