Commit 5951b850 authored by Johan Hovold's avatar Johan Hovold
Browse files

USB: serial: cp210x: suppress modem-control errors 



The CP210X_SET_MHS request cannot be used to control RTS when hardware
flow control (auto-RTS) is enabled and instead returns an error which is
currently logged as:

	cp210x ttyUSB0: failed set request 0x7 status: -32

when opening and closing a port (and on TIOCMSET requests).

Add a crtscts flag to keep track of the hardware flow-control setting
and use it to suppress any request to change RTS when auto-RTS is
enabled.

Note that RTS is still deasserted when disabling the UART as part of
close.

Reported-by: default avatarPho Tran <pho.tran@silabs.com>
Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
parent fea7372c

drivers/usb/serial/cp210x.c

+30 −3
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/usb/serial.h>

#include <linux/gpio/driver.h>

#include <linux/bitops.h>

#include <linux/mutex.h>



#define DRIVER_DESC "Silicon Labs CP210x RS232 serial adaptor driver"
@@ -265,6 +266,9 @@ struct cp210x_port_private { 
	bool			event_mode;

	enum cp210x_event_state event_state;

	u8			lsr;



	struct mutex		mutex;

	bool			crtscts;

};



static struct usb_serial_driver cp210x_device = {
@@ -1117,6 +1121,7 @@ static bool cp210x_termios_change(const struct ktermios *a, const struct ktermio 
static void cp210x_set_flow_control(struct tty_struct *tty,

		struct usb_serial_port *port, struct ktermios *old_termios)

{

	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);

	struct cp210x_special_chars chars;

	struct cp210x_flow_ctl flow_ctl;

	u32 flow_repl;
@@ -1143,10 +1148,12 @@ static void cp210x_set_flow_control(struct tty_struct *tty, 
			return;

	}



	mutex_lock(&port_priv->mutex);



	ret = cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl,

			sizeof(flow_ctl));

	if (ret)

		return;

		goto out_unlock;



	ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);

	flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
@@ -1161,10 +1168,12 @@ static void cp210x_set_flow_control(struct tty_struct *tty, 
		ctl_hs |= CP210X_SERIAL_CTS_HANDSHAKE;

		flow_repl &= ~CP210X_SERIAL_RTS_MASK;

		flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_FLOW_CTL);

		port_priv->crtscts = true;

	} else {

		ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE;

		flow_repl &= ~CP210X_SERIAL_RTS_MASK;

		flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_ACTIVE);

		port_priv->crtscts = false;

	}



	if (I_IXOFF(tty))
@@ -1188,6 +1197,8 @@ static void cp210x_set_flow_control(struct tty_struct *tty, 


	cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl,

			sizeof(flow_ctl));

out_unlock:

	mutex_unlock(&port_priv->mutex);

}



static void cp210x_set_termios(struct tty_struct *tty,
@@ -1272,7 +1283,9 @@ static int cp210x_tiocmset(struct tty_struct *tty, 
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);

	u16 control = 0;

	int ret;



	if (set & TIOCM_RTS) {

		control |= CONTROL_RTS;
@@ -1291,9 +1304,22 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port, 
		control |= CONTROL_WRITE_DTR;

	}



	mutex_lock(&port_priv->mutex);



	/*

	 * 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.

	 */

	if (port_priv->crtscts)

		control &= ~CONTROL_WRITE_RTS;



	dev_dbg(&port->dev, "%s - control = 0x%.4x\n", __func__, control);



	return cp210x_write_u16_reg(port, CP210X_SET_MHS, control);

	ret = cp210x_write_u16_reg(port, CP210X_SET_MHS, control);



	mutex_unlock(&port_priv->mutex);



	return ret;

}



static void cp210x_dtr_rts(struct usb_serial_port *port, int on)
@@ -1770,6 +1796,7 @@ static int cp210x_port_probe(struct usb_serial_port *port) 
		return -ENOMEM;



	port_priv->bInterfaceNumber = cp210x_interface_num(serial);

	mutex_init(&port_priv->mutex);



	usb_set_serial_port_data(port, port_priv);