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

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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: Alan Cox <alan@linux.intel.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2012-04-17 17:23:14 +01:00
parent dba05832cb
commit 9aba8d5b01
2 changed files with 29 additions and 4 deletions
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31
drivers/tty/serial/serial_core.c
View File

@ -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);
}

2
include/linux/serial_core.h
View File

@ -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 *);