From: Aaron Sierra <asie...@xes-inc.com>
[ Upstream commit 0ab84da2e076948c49d36197ee7d254125c53eab ]
The upper four bits of the XR17V35x fractional divisor register (DLD)
control general chip function (RS-485 direction pin polarity, multidrop
mode, XON/XOFF parity check, and fast IR mode). Don't allow these bits
to be clobbered when setting the baudrate.
Signed-off-by: Aaron Sierra <asie...@xes-inc.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.le...@verizon.com>
---
drivers/tty/serial/8250/8250_port.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/8250/8250_port.c
b/drivers/tty/serial/8250/8250_port.c
index 1ef31e3ee4a1..f6e4373a8850 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2526,8 +2526,11 @@ static void serial8250_set_divisor(struct uart_port
*port, unsigned int baud,
serial_dl_write(up, quot);
/* XR17V35x UARTs have an extra fractional divisor register (DLD) */
- if (up->port.type == PORT_XR17V35X)
+ if (up->port.type == PORT_XR17V35X) {
+ /* Preserve bits not related to baudrate; DLD[7:4]. */
+ quot_frac |= serial_port_in(port, 0x2) & 0xf0;
serial_port_out(port, 0x2, quot_frac);
+ }
}
static unsigned int serial8250_get_baud_rate(struct uart_port *port,
--
2.11.0
