tty: xuartps: Add support for setting modem control signals

Add support for setting the state of the DTR and RTS signals.

Acked-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 21 insertions, 1 deletions

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 200c1af2141b..542bab37e502 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -133,6 +133,15 @@ MODULE_PARM_DESC(rx_timeout, "Rx timeout, 1-255");
 #define CDNS_UART_IXR_BRK       0x80000000
 
 /*
+ * Modem Control register:
+ * The read/write Modem Control register controls the interface with the modem
+ * or data set, or a peripheral device emulating a modem.
+ */
+#define CDNS_UART_MODEMCR_FCM   0x00000020 /* Automatic flow control mode */
+#define CDNS_UART_MODEMCR_RTS   0x00000002 /* Request to send output control */
+#define CDNS_UART_MODEMCR_DTR   0x00000001 /* Data Terminal Ready */
+
+/*
  * Channel Status Register:
  * The channel status register (CSR) is provided to enable the control logic
  * to monitor the status of bits in the channel interrupt status register,
@@ -915,7 +924,18 @@ static unsigned int cdns_uart_get_mctrl(struct uart_port *port)
 
 static void cdns_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
 {
-        /* N/A */
+        u32 val;
+
+        val = cdns_uart_readl(CDNS_UART_MODEMCR_OFFSET);
+
+        val &= ~(CDNS_UART_MODEMCR_RTS | CDNS_UART_MODEMCR_DTR);
+
+        if (mctrl & TIOCM_RTS)
+                val |= CDNS_UART_MODEMCR_RTS;
+        if (mctrl & TIOCM_DTR)
+                val |= CDNS_UART_MODEMCR_DTR;
+
+        cdns_uart_writel(val, CDNS_UART_MODEMCR_OFFSET);
 }
 
 #ifdef CONFIG_CONSOLE_POLL