Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 9aba8d5b authored by Russell King's avatar Russell King
Browse files

SERIAL: core: add throttle/unthrottle callbacks for hardware assisted flow control 



Add two callbacks for hardware assisted flow control; we need to know
when the tty layers want us to stop and restart due to their buffer
levels.

Call a driver specific throttle/unthrottle function if and only if the
driver indicates that it is using an enabled hardware assisted flow
control method, otherwise fall back to the non-hardware assisted
methods.

Acked-by: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent dba05832

drivers/tty/serial/serial_core.c

+27 −4
Original line number Diff line number Diff line
@@ -610,27 +610,50 @@ static void uart_send_xchar(struct tty_struct *tty, char ch) 
static void uart_throttle(struct tty_struct *tty)

{

	struct uart_state *state = tty->driver_data;

	struct uart_port *port = state->uart_port;

	uint32_t mask = 0;



	if (I_IXOFF(tty))

		mask |= UPF_SOFT_FLOW;

	if (tty->termios.c_cflag & CRTSCTS)

		mask |= UPF_HARD_FLOW;



	if (port->flags & mask) {

		port->ops->throttle(port);

		mask &= ~port->flags;

	}



	if (mask & UPF_SOFT_FLOW)

		uart_send_xchar(tty, STOP_CHAR(tty));



	if (tty->termios.c_cflag & CRTSCTS)

		uart_clear_mctrl(state->uart_port, TIOCM_RTS);

	if (mask & UPF_HARD_FLOW)

		uart_clear_mctrl(port, TIOCM_RTS);

}



static void uart_unthrottle(struct tty_struct *tty)

{

	struct uart_state *state = tty->driver_data;

	struct uart_port *port = state->uart_port;

	uint32_t mask = 0;



	if (I_IXOFF(tty)) {

	if (I_IXOFF(tty))

		mask |= UPF_SOFT_FLOW;

	if (tty->termios.c_cflag & CRTSCTS)

		mask |= UPF_HARD_FLOW;



	if (port->flags & mask) {

		port->ops->unthrottle(port);

		mask &= ~port->flags;

	}



	if (mask & UPF_SOFT_FLOW) {

		if (port->x_char)

			port->x_char = 0;

		else

			uart_send_xchar(tty, START_CHAR(tty));

	}



	if (tty->termios.c_cflag & CRTSCTS)

	if (mask & UPF_HARD_FLOW)

		uart_set_mctrl(port, TIOCM_RTS);

}

include/linux/serial_core.h

+2 −0
Original line number Diff line number Diff line
@@ -46,6 +46,8 @@ struct uart_ops { 
	unsigned int	(*get_mctrl)(struct uart_port *);

	void		(*stop_tx)(struct uart_port *);

	void		(*start_tx)(struct uart_port *);

	void		(*throttle)(struct uart_port *);

	void		(*unthrottle)(struct uart_port *);

	void		(*send_xchar)(struct uart_port *, char ch);

	void		(*stop_rx)(struct uart_port *);

	void		(*enable_ms)(struct uart_port *);