greybus: uart: Handle CRTSCTS flag in termios

Handle the CRTSCTS flag in set_termios, so that auto
flow control can be turned off. For this, add a new flag
in the line coding request specifically for this purpose.
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Axel Haslam <ahaslam@baylibre.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/greybus_protocols.h

@@ -1304,6 +1304,9 @@ struct gb_uart_set_line_coding_request {
 #define GB_SERIAL_SPACE_PARITY			4
 
 	__u8	data_bits;
+
+	__u8	flow_control;
+#define GB_SERIAL_AUTO_RTSCTS_EN		0x1
 } __packed;
 
 /* output control lines */

drivers/staging/greybus/uart.c

@@ -39,6 +39,7 @@ struct gb_tty_line_coding {
 	__u8	format;
 	__u8	parity;
 	__u8	data_bits;
+	__u8	flow_control;
 };
 
 struct gb_tty {
@@ -375,9 +376,9 @@ static void gb_tty_set_termios(struct tty_struct *tty,
 
 	if (C_BAUD(tty) == B0) {
 		newline.rate = gb_tty->line_coding.rate;
-		newctrl &= ~GB_UART_CTRL_DTR;
+		newctrl &= ~(GB_UART_CTRL_DTR | GB_UART_CTRL_RTS);
 	} else if (termios_old && (termios_old->c_cflag & CBAUD) == B0) {
-		newctrl |= GB_UART_CTRL_DTR;
+		newctrl |= (GB_UART_CTRL_DTR | GB_UART_CTRL_RTS);
 	}
 
 	if (newctrl != gb_tty->ctrlout) {
@@ -385,6 +386,11 @@ static void gb_tty_set_termios(struct tty_struct *tty,
 		send_control(gb_tty, newctrl);
 	}
 
+	if (C_CRTSCTS(tty) && C_BAUD(tty) != B0)
+		newline.flow_control |= GB_SERIAL_AUTO_RTSCTS_EN;
+	else
+		newline.flow_control &= ~GB_SERIAL_AUTO_RTSCTS_EN;
+
 	if (memcmp(&gb_tty->line_coding, &newline, sizeof(newline))) {
 		memcpy(&gb_tty->line_coding, &newline, sizeof(newline));
 		send_line_coding(gb_tty);