Commit cf00ead0 authored by Johan Hovold's avatar Johan Hovold
Browse files

USB: serial: cp210x: fix RTS handling 



Clearing TIOCM_RTS should always deassert RTS and setting the same bit
should enable auto-RTS if hardware flow control is enabled.

This allows user space to throttle input directly at the source also
when hardware-assisted flow control is enabled and makes dtr_rts()
always deassert both lines during close (when HUPCL is set).

Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
parent 6b667274

drivers/usb/serial/cp210x.c

+40 −7
Original line number Diff line number Diff line
@@ -1166,7 +1166,10 @@ static void cp210x_set_flow_control(struct tty_struct *tty, 
	if (C_CRTSCTS(tty)) {

		ctl_hs |= CP210X_SERIAL_CTS_HANDSHAKE;

		flow_repl &= ~CP210X_SERIAL_RTS_MASK;

		if (port_priv->rts)

			flow_repl |= CP210X_SERIAL_RTS_FLOW_CTL;

		else

			flow_repl |= CP210X_SERIAL_RTS_INACTIVE;

		port_priv->crtscts = true;

	} else {

		ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE;
@@ -1286,6 +1289,8 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port, 
		unsigned int set, unsigned int clear)

{

	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);

	struct cp210x_flow_ctl flow_ctl;

	u32 ctl_hs, flow_repl;

	u16 control = 0;

	int ret;
@@ -1313,16 +1318,44 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port, 
	}



	/*

	 * SET_MHS cannot be used to control RTS when auto-RTS is enabled.

	 * Note that RTS is still deasserted when disabling the UART on close.

	 * Use SET_FLOW to set DTR and enable/disable auto-RTS when hardware

	 * flow control is enabled.

	 */

	if (port_priv->crtscts)

		control &= ~CONTROL_WRITE_RTS;

	if (port_priv->crtscts && control & CONTROL_WRITE_RTS) {

		ret = cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl,

				sizeof(flow_ctl));

		if (ret)

			goto out_unlock;



		ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);

		flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);



		ctl_hs &= ~CP210X_SERIAL_DTR_MASK;

		if (port_priv->dtr)

			ctl_hs |= CP210X_SERIAL_DTR_ACTIVE;

		else

			ctl_hs |= CP210X_SERIAL_DTR_INACTIVE;



		flow_repl &= ~CP210X_SERIAL_RTS_MASK;

		if (port_priv->rts)

			flow_repl |= CP210X_SERIAL_RTS_FLOW_CTL;

		else

			flow_repl |= CP210X_SERIAL_RTS_INACTIVE;



		flow_ctl.ulControlHandshake = cpu_to_le32(ctl_hs);

		flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);



		dev_dbg(&port->dev, "%s - ctrl = 0x%02x, flow = 0x%02x\n",

				__func__, ctl_hs, flow_repl);



		ret = cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl,

				sizeof(flow_ctl));

	} else {

		dev_dbg(&port->dev, "%s - control = 0x%04x\n", __func__, control);



		ret = cp210x_write_u16_reg(port, CP210X_SET_MHS, control);



	}

out_unlock:

	mutex_unlock(&port_priv->mutex);



	return ret;