serial: 8250: introduce get_divisor() and set_divisor() hook

Add these two hooks so that they can be overridden with driver specific
implementations.
Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_core.c

@@ -1023,6 +1023,10 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
 			uart->port.get_mctrl = up->port.get_mctrl;
 		if (up->port.set_mctrl)
 			uart->port.set_mctrl = up->port.set_mctrl;
+		if (up->port.get_divisor)
+			uart->port.get_divisor = up->port.get_divisor;
+		if (up->port.set_divisor)
+			uart->port.set_divisor = up->port.set_divisor;
 		if (up->port.startup)
 			uart->port.startup = up->port.startup;
 		if (up->port.shutdown)

drivers/tty/serial/8250/8250_port.c

@@ -2498,7 +2498,7 @@ static unsigned int npcm_get_divisor(struct uart_8250_port *up,
 	return DIV_ROUND_CLOSEST(port->uartclk, 16 * baud + 2) - 2;
 }
 
-static unsigned int serial8250_get_divisor(struct uart_port *port,
+static unsigned int serial8250_do_get_divisor(struct uart_port *port,
 					      unsigned int baud,
 					      unsigned int *frac)
 {
@@ -2532,6 +2532,16 @@ static unsigned int serial8250_get_divisor(struct uart_port *port,
 	return quot;
 }
 
+static unsigned int serial8250_get_divisor(struct uart_port *port,
+					   unsigned int baud,
+					   unsigned int *frac)
+{
+	if (port->get_divisor)
+		return port->get_divisor(port, baud, frac);
+
+	return serial8250_do_get_divisor(port, baud, frac);
+}
+
 static unsigned char serial8250_compute_lcr(struct uart_8250_port *up,
 					    tcflag_t c_cflag)
 {
@@ -2570,7 +2580,7 @@ static unsigned char serial8250_compute_lcr(struct uart_8250_port *up,
 	return cval;
 }
 
-static void serial8250_set_divisor(struct uart_port *port, unsigned int baud,
+static void serial8250_do_set_divisor(struct uart_port *port, unsigned int baud,
 			    unsigned int quot, unsigned int quot_frac)
 {
 	struct uart_8250_port *up = up_to_u8250p(port);
@@ -2603,6 +2613,15 @@ static void serial8250_set_divisor(struct uart_port *port, unsigned int baud,
 	}
 }
 
+static void serial8250_set_divisor(struct uart_port *port, unsigned int baud,
+				   unsigned int quot, unsigned int quot_frac)
+{
+	if (port->set_divisor)
+		port->set_divisor(port, baud, quot, quot_frac);
+	else
+		serial8250_do_set_divisor(port, baud, quot, quot_frac);
+}
+
 static unsigned int serial8250_get_baud_rate(struct uart_port *port,
 					     struct ktermios *termios,
 					     struct ktermios *old)

include/linux/serial_core.h

@@ -127,6 +127,13 @@ struct uart_port {
 					     struct ktermios *);
 	unsigned int		(*get_mctrl)(struct uart_port *);
 	void			(*set_mctrl)(struct uart_port *, unsigned int);
+	unsigned int		(*get_divisor)(struct uart_port *,
+					       unsigned int baud,
+					       unsigned int *frac);
+	void			(*set_divisor)(struct uart_port *,
+					       unsigned int baud,
+					       unsigned int quot,
+					       unsigned int quot_frac);
 	int			(*startup)(struct uart_port *port);
 	void			(*shutdown)(struct uart_port *port);
 	void			(*throttle)(struct uart_port *port);