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From:   Sheng Long Wang <china_shenglong@163.com>
To:     johan@kernel.org, gregkh@linuxfoundation.org
Cc:     linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        jan.kiszka@siemens.com,
        Wang Sheng Long <shenglong.wang.ext@siemens.com>
Subject: [PATCH] usb-serial:cp210x: add CP210x support to software flow control
Date:   Fri, 24 Jul 2020 18:29:46 +0800
Message-Id: <20200724102946.15404-1-china_shenglong@163.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Wang Sheng Long <shenglong.wang.ext@siemens.com>

  The cp210x driver lacks soft-flow function,so need and
  this function.

Signed-off-by: Wang Sheng Long <shenglong.wang.ext@siemens.com>
---
 drivers/usb/serial/cp210x.c | 110 +++++++++++++++++++++++++++++++++---
 1 file changed, 103 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index e732949f65..ad5db0e2ae 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -380,6 +380,9 @@ static struct usb_serial_driver * const serial_drivers[] = {
 #define CP210X_PARTNUM_CP2102N_QFN20	0x22
 #define CP210X_PARTNUM_UNKNOWN	0xFF
 
+#define CP210X_VSTART  0x11
+#define CP210X_VSTOP   0x13
+
 /* CP210X_GET_COMM_STATUS returns these 0x13 bytes */
 struct cp210x_comm_status {
 	__le32   ulErrors;
@@ -391,6 +394,15 @@ struct cp210x_comm_status {
 	u8       bReserved;
 } __packed;
 
+struct cp210x_chars_respones{
+	u8       bEofchar;
+	u8       bErrochar;
+	u8       bBreakchar;
+	u8       bEventchar;
+	u8       bXonchar;
+	u8       bXoffchar;
+} __packed;
+
 /*
  * CP210X_PURGE - 16 bits passed in wValue of USB request.
  * SiLabs app note AN571 gives a strange description of the 4 bits:
@@ -624,6 +636,43 @@ static int cp210x_read_vendor_block(struct usb_serial *serial, u8 type, u16 val,
 	return result;
 }
 
+/*
+ * Read and Write Characrters Respones operate
+ * Register SET_CHARS/GET_CHATS
+ */
+static int cp210x_operate_chars_block(struct usb_serial_port *port, u8 req, u8 type,
+		void *buf, int bufsize)
+{
+	struct usb_serial *serial = port->serial;
+	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
+	void *dmabuf;
+	int result;
+
+	dmabuf = kmemdup(buf, bufsize, GFP_KERNEL);
+	if (!dmabuf)
+		return -ENOMEM;
+
+	result = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
+			req, type, 0, port_priv->bInterfaceNumber, dmabuf, bufsize,
+			USB_CTRL_SET_TIMEOUT);
+	if (result == bufsize) {
+		if (type == REQTYPE_DEVICE_TO_HOST)
+			memcpy(buf, dmabuf, bufsize);
+
+		result = 0;
+	} else {
+		dev_err(&port->dev, "failed get req 0x%x size %d status: %d\n",
+				req, bufsize, result);
+		if (result >= 0)
+			result = -EIO;
+
+	}
+
+	kfree(dmabuf);
+
+	return result;
+}
+
 /*
  * Writes any 16-bit CP210X_ register (req) whose value is passed
  * entirely in the wValue field of the USB request.
@@ -650,8 +699,8 @@ static int cp210x_write_u16_reg(struct usb_serial_port *port, u8 req, u16 val)
  * Writes a variable-sized block of CP210X_ registers, identified by req.
  * Data in buf must be in native USB byte order.
  */
-static int cp210x_write_reg_block(struct usb_serial_port *port, u8 req,
-		void *buf, int bufsize)
+static int cp210x_write_reg_block(struct usb_serial_port *port,
+				u8 req, void *buf, int bufsize)
 {
 	struct usb_serial *serial = port->serial;
 	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
@@ -1134,11 +1183,17 @@ static void cp210x_set_termios(struct tty_struct *tty,
 		struct usb_serial_port *port, struct ktermios *old_termios)
 {
 	struct device *dev = &port->dev;
-	unsigned int cflag, old_cflag;
+	struct cp210x_chars_respones CharsRes;
+	struct cp210x_flow_ctl flow_ctl;
+	unsigned int cflag, old_cflag, iflag;
 	u16 bits;
+	int result;
+	u32 ctl_hs;
+	u32 flow_repl;
 
 	cflag = tty->termios.c_cflag;
 	old_cflag = old_termios->c_cflag;
+	iflag = tty->termios.c_iflag;
 
 	if (tty->termios.c_ospeed != old_termios->c_ospeed)
 		cp210x_change_speed(tty, port, old_termios);
@@ -1212,10 +1267,6 @@ static void cp210x_set_termios(struct tty_struct *tty,
 	}
 
 	if ((cflag & CRTSCTS) != (old_cflag & CRTSCTS)) {
-		struct cp210x_flow_ctl flow_ctl;
-		u32 ctl_hs;
-		u32 flow_repl;
-
 		cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl,
 				sizeof(flow_ctl));
 		ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);
@@ -1252,6 +1303,51 @@ static void cp210x_set_termios(struct tty_struct *tty,
 				sizeof(flow_ctl));
 	}
 
+	/* Set Software  Flow  Control
+	 * Xon/Xoff code
+	 * Check the IXOFF/IXON status in the iflag component of the
+	 * termios structure.
+	 *
+	 */
+	if  ((iflag & IXOFF) || (iflag & IXON)) {
+		/*set vstart/vstop chars */
+		result = cp210x_operate_chars_block(port, CP210X_GET_CHARS,
+					  REQTYPE_DEVICE_TO_HOST, &CharsRes, sizeof(CharsRes));
+		dev_dbg(dev, "%s -  bXonchar=0x%x   bXoffchar=0x%x   \n",
+				__func__, CharsRes.bXonchar, CharsRes.bXoffchar);
+		if (result < 0) {
+			dev_err(dev, "Read Characrters Respones  failed "
+					"xon/xoff software flow control\n");
+			return;
+		}
+		CharsRes.bXonchar  = CP210X_VSTART;
+		CharsRes.bXoffchar = CP210X_VSTOP;
+		result = cp210x_operate_chars_block(port, CP210X_SET_CHARS,
+					 REQTYPE_HOST_TO_INTERFACE, &CharsRes, sizeof(CharsRes));
+		if (result < 0) {
+			memset(&CharsRes, 0, sizeof(CharsRes));
+			dev_err(dev, "Write Characrters Respones  failed"
+					"xon/xoff software flow control\n");
+			return;
+		}
+		/*Set  Rx/Tx Flow Contrl  Flag in ulFlowReplace*/
+		cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl, sizeof(flow_ctl));
+		flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
+		dev_dbg(dev, "%s - read ulControlHandshake=0x%08x, ulFlowReplace=0x%08x\n",
+				__func__, ctl_hs, flow_repl);
+		if (iflag & IXOFF)
+			flow_repl |= CP210X_SERIAL_AUTO_RECEIVE;
+		else
+			flow_repl &= ~CP210X_SERIAL_AUTO_RECEIVE;
+
+		if (iflag & IXON)
+			flow_repl |= CP210X_SERIAL_AUTO_TRANSMIT;
+		else
+			flow_repl &= ~CP210X_SERIAL_AUTO_TRANSMIT;
+
+		flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);
+		cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl, sizeof(flow_ctl));
+       }
 }
 
 static int cp210x_tiocmset(struct tty_struct *tty,
-- 
2.17.1