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

Ports which are handling h/w flow control in hardware must not have
their RTS state altered depending on the tty's hardware-stopped state.
Avoid this additional logic when setting the termios state.

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 16:41:10 +01:00
parent 2cbacafd7a
commit dba05832cb
2 changed files with 9 additions and 0 deletions
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7
drivers/tty/serial/serial_core.c
View File

@ -1255,6 +1255,13 @@ static void uart_set_termios(struct tty_struct *tty,
uart_set_mctrl(uport, mask);
}
/*
* If the port is doing h/w assisted flow control, do nothing.
* We assume that tty->hw_stopped has never been set.
*/
if (uport->flags & UPF_HARD_FLOW)
return;
/* Handle turning off CRTSCTS */
if ((old_termios->c_cflag & CRTSCTS) && !(cflag & CRTSCTS)) {
spin_lock_irqsave(&uport->lock, flags);

2
include/linux/serial_core.h
View File

@ -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 h/w flow control (iow, auto-RTS *not* auto-CTS) */
#define UPF_HARD_FLOW ((__force upf_t) (1 << 21))
/* 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))