linux-kernel - [PATCH] serial: sprd: Add loopback function support

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Date:   Wed, 21 Aug 2019 20:39:09 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     gregkh@...uxfoundation.org, jslaby@...e.com
Cc:     orsonzhai@...il.com, zhang.lyra@...il.com, cixi.geng@...soc.com,
        lanqing.liu@...soc.com, baolin.wang@...aro.org,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] serial: sprd: Add loopback function support

Add loopback function support for Spreadtrum serial controller.

Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
---
 drivers/tty/serial/sprd_serial.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
index 73d71a4..85fc57c 100644
--- a/drivers/tty/serial/sprd_serial.c
+++ b/drivers/tty/serial/sprd_serial.c
@@ -79,6 +79,7 @@
 /* control register 1 */
 #define SPRD_CTL1		0x001C
 #define SPRD_DMA_EN		BIT(15)
+#define SPRD_LOOPBACK_EN	BIT(14)
 #define RX_HW_FLOW_CTL_THLD	BIT(6)
 #define RX_HW_FLOW_CTL_EN	BIT(7)
 #define TX_HW_FLOW_CTL_EN	BIT(8)
@@ -164,7 +165,14 @@ static unsigned int sprd_get_mctrl(struct uart_port *port)
 
 static void sprd_set_mctrl(struct uart_port *port, unsigned int mctrl)
 {
-	/* nothing to do */
+	u32 val = serial_in(port, SPRD_CTL1);
+
+	if (mctrl & TIOCM_LOOP)
+		val |= SPRD_LOOPBACK_EN;
+	else
+		val &= ~SPRD_LOOPBACK_EN;
+
+	serial_out(port, SPRD_CTL1, val);
 }
 
 static void sprd_stop_rx(struct uart_port *port)
-- 
1.7.9.5