[PATCH AUTOSEL for 4.9 14/24] serial: 8250: Preserve DLD[7:4] for PORT_XR17V35X

[alexander . levin]

From: Aaron Sierra 

[ 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 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Sasha Levin 
---
 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

[PATCH AUTOSEL for 4.9 14/24] serial: 8250: Preserve DLD[7:4] for PORT_XR17V35X

[alexander . levin]

From: Aaron Sierra 

[ 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 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Sasha Levin 
---
 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