serial: sirf: add serial loopback function support

Signed-off-by: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 21 insertions, 1 deletions

diff --git a/drivers/tty/serial/sirfsoc_uart.c b/drivers/tty/serial/sirfsoc_uart.c
index a5007216338d..0e4379939703 100644
--- a/drivers/tty/serial/sirfsoc_uart.c
+++ b/drivers/tty/serial/sirfsoc_uart.c
@@ -108,6 +108,26 @@ static void sirfsoc_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
         unsigned int val = assert ? SIRFUART_AFC_CTRL_RX_THD : 0x0;
         unsigned int current_val;
 
+        if (mctrl & TIOCM_LOOP) {
+                if (sirfport->uart_reg->uart_type == SIRF_REAL_UART)
+                        wr_regl(port, ureg->sirfsoc_line_ctrl,
+                                rd_regl(port, ureg->sirfsoc_line_ctrl) |
+                                SIRFUART_LOOP_BACK);
+                else
+                        wr_regl(port, ureg->sirfsoc_mode1,
+                                rd_regl(port, ureg->sirfsoc_mode1) |
+                                SIRFSOC_USP_LOOP_BACK_CTRL);
+        } else {
+                if (sirfport->uart_reg->uart_type == SIRF_REAL_UART)
+                        wr_regl(port, ureg->sirfsoc_line_ctrl,
+                                rd_regl(port, ureg->sirfsoc_line_ctrl) &
+                                ~SIRFUART_LOOP_BACK);
+                else
+                        wr_regl(port, ureg->sirfsoc_mode1,
+                                rd_regl(port, ureg->sirfsoc_mode1) &
+                                ~SIRFSOC_USP_LOOP_BACK_CTRL);
+        }
+
         if (!sirfport->hw_flow_ctrl || !sirfport->ms_enabled)
                 return;
         if (sirfport->uart_reg->uart_type == SIRF_REAL_UART) {
diff --git a/drivers/tty/serial/sirfsoc_uart.h b/drivers/tty/serial/sirfsoc_uart.h
index b49c23a94ee8..3ab3141e1aae 100644
--- a/drivers/tty/serial/sirfsoc_uart.h
+++ b/drivers/tty/serial/sirfsoc_uart.h
@@ -322,7 +322,7 @@ struct sirfsoc_uart_register sirfsoc_uart = {
 #define SIRFSOC_USP_RX_CLK_DIVISOR_OFFSET       24
 #define SIRFSOC_USP_ASYNC_DIV2_MASK             0x3f
 #define SIRFSOC_USP_ASYNC_DIV2_OFFSET           16
-
+#define SIRFSOC_USP_LOOP_BACK_CTRL              BIT(2)
 /* USP-UART Common */
 #define SIRFSOC_UART_RX_TIMEOUT(br, to) (((br) * (((to) + 999) / 1000)) / 1000)
 #define SIRFUART_RECV_TIMEOUT_VALUE(x)  \