@@ -63,6 +63,7 @@
#define CH341_REG_DIVISOR 0x13
#define CH341_REG_LCR 0x18
#define CH341_REG_LCR2 0x25
+#define CH341_REG_FLOW_CTL 0x27
#define CH341_NBREAK_BITS 0x01
@@ -77,6 +78,9 @@
#define CH341_LCR_CS6 0x01
#define CH341_LCR_CS5 0x00
+#define CH341_FLOW_CTL_NONE 0x000
+#define CH341_FLOW_CTL_RTSCTS 0x101
+
#define CH341_QUIRK_LIMITED_PRESCALER BIT(0)
#define CH341_QUIRK_SIMULATE_BREAK BIT(1)
@@ -478,6 +482,41 @@ static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
return r;
}
+static void ch341_set_flow_control(struct tty_struct *tty,
+ struct usb_serial_port *port,
+ const struct ktermios *old_termios)
+{
+ int r;
+
+ if (old_termios &&
+ C_CRTSCTS(tty) == (old_termios->c_cflag & CRTSCTS))
+ return;
+
+ if (C_CRTSCTS(tty)) {
+ r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG,
+ CH341_REG_FLOW_CTL |
+ ((u16)CH341_REG_FLOW_CTL << 8),
+ CH341_FLOW_CTL_RTSCTS);
+ if (r < 0) {
+ dev_err(&port->dev,
+ "%s - failed to enable flow control: %d\n",
+ __func__, r);
+ tty->termios.c_cflag &= ~CRTSCTS;
+ }
+ } else {
+ r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG,
+ CH341_REG_FLOW_CTL |
+ ((u16)CH341_REG_FLOW_CTL << 8),
+ CH341_FLOW_CTL_NONE);
+ if (r < 0) {
+ dev_err(&port->dev,
+ "%s - failed to disable flow control: %d\n",
+ __func__, r);
+ tty->termios.c_cflag |= CRTSCTS;
+ }
+ }
+}
+
/* Old_termios contains the original termios settings and
* tty->termios contains the new setting to be used.
*/
@@ -546,6 +585,8 @@ static void ch341_set_termios(struct tty_struct *tty,
spin_unlock_irqrestore(&priv->lock, flags);
ch341_set_handshake(port->serial->dev, priv->mcr);
+
+ ch341_set_flow_control(tty, port, old_termios);
}
/*
This adds support for enabling and disabling RTS/CTS hardware flow control. Tested using a CH340E in combination with a CP2102. Fixes part of the following bug report: Link: https://bugzilla.kernel.org/show_bug.cgi?id=197109 Signed-off-by: Lode Willems <me@lodewillems.com> --- drivers/usb/serial/ch341.c | 41 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+)