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: Alan Cox <alan@linux.intel.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index bc2065d..bd10bbd 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -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;
        }
 

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 3c43022..0005138 100644 (file)
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -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))