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Commit 2cbacafd authored by Russell King's avatar Russell King
Browse files

SERIAL: core: add hardware assisted s/w flow control support 



Ports which are capable of handling s/w flow control in hardware to
know when the s/w flow control termios settings are changed.  Add a
flag to allow the low level serial drivers to indicate that they
support this, and these changes should be propagated to them.

Acked-by: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent dec94e70

drivers/tty/serial/serial_core.c

+14 −2
Original line number Diff line number Diff line
@@ -1213,7 +1213,19 @@ static void uart_set_termios(struct tty_struct *tty, 
	struct uart_port *uport = state->uart_port;

	unsigned long flags;

	unsigned int cflag = tty->termios.c_cflag;

	unsigned int iflag_mask = IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK;

	bool sw_changed = false;



	/*

	 * Drivers doing software flow control also need to know

	 * about changes to these input settings.

	 */

	if (uport->flags & UPF_SOFT_FLOW) {

		iflag_mask |= IXANY|IXON|IXOFF;

		sw_changed =

		   tty->termios.c_cc[VSTART] != old_termios->c_cc[VSTART] ||

		   tty->termios.c_cc[VSTOP] != old_termios->c_cc[VSTOP];

	}



	/*

	 * These are the bits that are used to setup various
@@ -1221,11 +1233,11 @@ static void uart_set_termios(struct tty_struct *tty, 
	 * bits in c_cflag; c_[io]speed will always be set

	 * appropriately by set_termios() in tty_ioctl.c

	 */

#define RELEVANT_IFLAG(iflag)	((iflag) & (IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK))

	if ((cflag ^ old_termios->c_cflag) == 0 &&

	    tty->termios.c_ospeed == old_termios->c_ospeed &&

	    tty->termios.c_ispeed == old_termios->c_ispeed &&

	    RELEVANT_IFLAG(tty->termios.c_iflag ^ old_termios->c_iflag) == 0) {

	    ((tty->termios.c_iflag ^ old_termios->c_iflag) & iflag_mask) == 0 &&

	    !sw_changed) {

		return;

	}

include/linux/serial_core.h

+2 −0
Original line number Diff line number Diff line
@@ -163,6 +163,8 @@ struct uart_port { 
#define UPF_BUGGY_UART		((__force upf_t) (1 << 14))

#define UPF_NO_TXEN_TEST	((__force upf_t) (1 << 15))

#define UPF_MAGIC_MULTIPLIER	((__force upf_t) (1 << 16))

/* Port has hardware-assisted s/w flow control */

#define UPF_SOFT_FLOW		((__force upf_t) (1 << 22))

#define UPF_CONS_FLOW		((__force upf_t) (1 << 23))

#define UPF_SHARE_IRQ		((__force upf_t) (1 << 24))

#define UPF_EXAR_EFR		((__force upf_t) (1 << 25))