ARM: 5933/1: amba-pl011: support hardware flow control

Enable/disable automatic hardware flow control as requested by the
termios.  The controller does not allow us to control the RTS line when
auto-RTS is enabled, so we enable auto-RTS only if the kernel has not
disabled RTS.

Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/serial/amba-pl011.c b/drivers/serial/amba-pl011.c
index ef7adc8135dd..ce6c35333ff7 100644
--- a/drivers/serial/amba-pl011.c
+++ b/drivers/serial/amba-pl011.c
@@ -71,6 +71,7 @@ struct uart_amba_port {
         unsigned int            im;     /* interrupt mask */
         unsigned int            old_status;
         unsigned int            ifls;   /* vendor-specific */
+        bool                    autorts;
 };
 
 /* There is by now at least one vendor with differing details, so handle it */
@@ -308,6 +309,11 @@ static void pl011_set_mctrl(struct uart_port *port, unsigned int mctrl)
         TIOCMBIT(TIOCM_OUT1, UART011_CR_OUT1);
         TIOCMBIT(TIOCM_OUT2, UART011_CR_OUT2);
         TIOCMBIT(TIOCM_LOOP, UART011_CR_LBE);
+
+        if (uap->autorts) {
+                /* We need to disable auto-RTS if we want to turn RTS off */
+                TIOCMBIT(TIOCM_RTS, UART011_CR_RTSEN);
+        }
 #undef TIOCMBIT
 
         writew(cr, uap->port.membase + UART011_CR);
@@ -437,6 +443,7 @@ static void pl011_shutdown(struct uart_port *port)
         /*
          * disable the port
          */
+        uap->autorts = false;
         writew(UART01x_CR_UARTEN | UART011_CR_TXE, uap->port.membase + UART011_CR);
 
         /*
@@ -456,6 +463,7 @@ static void
 pl011_set_termios(struct uart_port *port, struct ktermios *termios,
                      struct ktermios *old)
 {
+        struct uart_amba_port *uap = (struct uart_amba_port *)port;
         unsigned int lcr_h, old_cr;
         unsigned long flags;
         unsigned int baud, quot;
@@ -532,6 +540,17 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios,
         old_cr = readw(port->membase + UART011_CR);
         writew(0, port->membase + UART011_CR);
 
+        if (termios->c_cflag & CRTSCTS) {
+                if (old_cr & UART011_CR_RTS)
+                        old_cr |= UART011_CR_RTSEN;
+
+                old_cr |= UART011_CR_CTSEN;
+                uap->autorts = true;
+        } else {
+                old_cr &= ~(UART011_CR_CTSEN | UART011_CR_RTSEN);
+                uap->autorts = false;
+        }
+
         /* Set baud rate */
         writew(quot & 0x3f, port->membase + UART011_FBRD);
         writew(quot >> 6, port->membase + UART011_IBRD);