From: Aaron Sierra asierra@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 asierra@xes-inc.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin alexander.levin@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,