linux-kernel - [PATCH] USB: otg: Fix error 32 when enable hardware flow control.

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Date:   Mon, 11 Jan 2021 04:55:22 +0000
From:   Pho Tran <Pho.Tran@...abs.com>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        Hung Nguyen <Hung.Nguyen@...abs.com>,
        Tung Pham <Tung.Pham@...abs.com>
Subject: [PATCH] USB: otg: Fix error 32 when enable hardware flow control.

When hardware flow control is enabled,
don't allow host send MHS command to cp210x.

Signed-off-by: Pho Tran<pho.tran@...abs.com>
---
 drivers/usb/serial/cp210x.c | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index fbb10dfc56e3..f231cecdaf7d 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -1204,6 +1204,7 @@ static int cp210x_tiocmset(struct tty_struct *tty,
 		unsigned int set, unsigned int clear)
 {
 	struct usb_serial_port *port = tty->driver_data;
+
 	return cp210x_tiocmset_port(port, set, clear);
 }
 
@@ -1211,6 +1212,11 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port,
 		unsigned int set, unsigned int clear)
 {
 	u16 control = 0;
+	struct cp210x_flow_ctl flow_ctl;
+	u32 ctl_hs = 0;
+	u32 flow_repl = 0;
+	bool auto_dtr = false;
+	bool auto_rts = false;
 
 	if (set & TIOCM_RTS) {
 		control |= CONTROL_RTS;
@@ -1230,6 +1236,30 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port,
 	}
 
 	dev_dbg(&port->dev, "%s - control = 0x%.4x\n", __func__, control);
+	/*
+	 *	Don't send MHS command if device in hardware flowcontrol mode
+	 */
+	cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl,
+				sizeof(flow_ctl));
+	ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);
+	flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
+
+	if (CP210X_SERIAL_DTR_SHIFT(CP210X_SERIAL_DTR_FLOW_CTL)
+		== (ctl_hs & CP210X_SERIAL_DTR_MASK))
+		auto_dtr = true;
+	else
+		auto_dtr = false;
+
+	if (CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_FLOW_CTL)
+		== (flow_repl & CP210X_SERIAL_RTS_MASK))
+		auto_rts = true;
+	else
+		auto_rts = false;
+
+	if (auto_dtr || auto_rts) {
+		dev_dbg(&port->dev, "Don't set MHS when while device in flow control mode\n");
+		return 0;
+	}
 
 	return cp210x_write_u16_reg(port, CP210X_SET_MHS, control);
 }
@@ -1256,7 +1286,7 @@ static int cp210x_tiocmget(struct tty_struct *tty)
 		|((control & CONTROL_RTS) ? TIOCM_RTS : 0)
 		|((control & CONTROL_CTS) ? TIOCM_CTS : 0)
 		|((control & CONTROL_DSR) ? TIOCM_DSR : 0)
-		|((control & CONTROL_RING)? TIOCM_RI  : 0)
+		|((control & CONTROL_RING) ? TIOCM_RI  : 0)
 		|((control & CONTROL_DCD) ? TIOCM_CD  : 0);
 
 	dev_dbg(&port->dev, "%s - control = 0x%.2x\n", __func__, control);
-- 
2.17.1