[PATCH 0/6] USB: serial: cp210x: clean up termios handling

[PATCH 0/6] USB: serial: cp210x: clean up termios handling

[Johan Hovold]

Unlike other drivers cp210x have been retrieving the current terminal
settings from the device on open and reflecting those in termios.
    
Due to how set_termios() was implemented this saved a few control
requests on open but has instead caused problems like broken flow
control and has required adding workarounds for swapped line-control in
cp2108 and line-speed initialisation on cp2104.

This unusual implementation also complicates adding new features for no
good reason.

Rip out the corresponding code and the above mentioned workarounds and
instead initialise the terminal settings unconditionally on open.

Johan


Johan Hovold (6):
  USB: serial: cp210x: return early on unchanged termios
  USB: serial: cp210x: clean up line-control handling
  USB: serial: cp210x: set terminal settings on open
  USB: serial: cp210x: drop flow-control debugging
  USB: serial: cp210x: refactor flow-control handling
  USB: serial: cp210x: clean up dts_rts

 drivers/usb/serial/cp210x.c | 499 ++++++++----------------------------
 1 file changed, 104 insertions(+), 395 deletions(-)

-- 
2.26.2

[PATCH 1/6] USB: serial: cp210x: return early on unchanged termios

[Johan Hovold]

Return early from set_termios() in case no relevant terminal settings
have changed.

This avoids testing each parameter in turn and specifically allows the
line-control handling to be cleaned up further.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/cp210x.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index d0c05aa8a0d6..f1fd109d97d5 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -1352,6 +1352,15 @@ static void cp210x_disable_event_mode(struct usb_serial_port *port)
 	port_priv->event_mode = false;
 }
 
+static bool cp210x_termios_change(const struct ktermios *a, const struct ktermios *b)
+{
+	bool iflag_change;
+
+	iflag_change = ((a->c_iflag ^ b->c_iflag) & INPCK);
+
+	return tty_termios_hw_change(a, b) || iflag_change;
+}
+
 static void cp210x_set_termios(struct tty_struct *tty,
 		struct usb_serial_port *port, struct ktermios *old_termios)
 {
@@ -1359,6 +1368,9 @@ static void cp210x_set_termios(struct tty_struct *tty,
 	unsigned int cflag, old_cflag;
 	u16 bits;
 
+	if (!cp210x_termios_change(&tty->termios, old_termios))
+		return;
+
 	cflag = tty->termios.c_cflag;
 	old_cflag = old_termios->c_cflag;
 
-- 
2.26.2

[PATCH 2/6] USB: serial: cp210x: clean up line-control handling

[Johan Hovold]

Update the line-control settings in one request unconditionally instead
of setting the word-length, parity and stop-bit settings separately.

This avoids multiple requests when several settings are changed even if
this scheme could potentially also be used to detect unsupported device
settings. Since all device types but CP2101 appears to support all
settings, let's handle that one specifically and also report back the
unsupported settings properly through termios by clearing the
corresponding bits.

Also drop the related unnecessary debug printks.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/cp210x.c | 101 +++++++++++++++---------------------
 1 file changed, 41 insertions(+), 60 deletions(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index f1fd109d97d5..ad134e517849 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -1364,9 +1364,11 @@ static bool cp210x_termios_change(const struct ktermios *a, const struct ktermio
 static void cp210x_set_termios(struct tty_struct *tty,
 		struct usb_serial_port *port, struct ktermios *old_termios)
 {
+	struct cp210x_serial_private *priv = usb_get_serial_data(port->serial);
 	struct device *dev = &port->dev;
 	unsigned int cflag, old_cflag;
 	u16 bits;
+	int ret;
 
 	if (!cp210x_termios_change(&tty->termios, old_termios))
 		return;
@@ -1377,74 +1379,53 @@ static void cp210x_set_termios(struct tty_struct *tty,
 	if (tty->termios.c_ospeed != old_termios->c_ospeed)
 		cp210x_change_speed(tty, port, old_termios);
 
-	/* If the number of data bits is to be updated */
-	if ((cflag & CSIZE) != (old_cflag & CSIZE)) {
-		cp210x_get_line_ctl(port, &bits);
-		bits &= ~BITS_DATA_MASK;
-		switch (cflag & CSIZE) {
-		case CS5:
-			bits |= BITS_DATA_5;
-			dev_dbg(dev, "%s - data bits = 5\n", __func__);
-			break;
-		case CS6:
-			bits |= BITS_DATA_6;
-			dev_dbg(dev, "%s - data bits = 6\n", __func__);
-			break;
-		case CS7:
-			bits |= BITS_DATA_7;
-			dev_dbg(dev, "%s - data bits = 7\n", __func__);
-			break;
-		case CS8:
-		default:
-			bits |= BITS_DATA_8;
-			dev_dbg(dev, "%s - data bits = 8\n", __func__);
-			break;
-		}
-		if (cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits))
-			dev_dbg(dev, "Number of data bits requested not supported by device\n");
+	/* CP2101 only supports CS8, 1 stop bit and non-stick parity. */
+	if (priv->partnum == CP210X_PARTNUM_CP2101) {
+		tty->termios.c_cflag &= ~(CSIZE | CSTOPB | CMSPAR);
+		tty->termios.c_cflag |= CS8;
 	}
 
-	if ((cflag     & (PARENB|PARODD|CMSPAR)) !=
-	    (old_cflag & (PARENB|PARODD|CMSPAR))) {
-		cp210x_get_line_ctl(port, &bits);
-		bits &= ~BITS_PARITY_MASK;
-		if (cflag & PARENB) {
-			if (cflag & CMSPAR) {
-				if (cflag & PARODD) {
-					bits |= BITS_PARITY_MARK;
-					dev_dbg(dev, "%s - parity = MARK\n", __func__);
-				} else {
-					bits |= BITS_PARITY_SPACE;
-					dev_dbg(dev, "%s - parity = SPACE\n", __func__);
-				}
-			} else {
-				if (cflag & PARODD) {
-					bits |= BITS_PARITY_ODD;
-					dev_dbg(dev, "%s - parity = ODD\n", __func__);
-				} else {
-					bits |= BITS_PARITY_EVEN;
-					dev_dbg(dev, "%s - parity = EVEN\n", __func__);
-				}
-			}
-		}
-		if (cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits))
-			dev_dbg(dev, "Parity mode not supported by device\n");
+	bits = 0;
+
+	switch (C_CSIZE(tty)) {
+	case CS5:
+		bits |= BITS_DATA_5;
+		break;
+	case CS6:
+		bits |= BITS_DATA_6;
+		break;
+	case CS7:
+		bits |= BITS_DATA_7;
+		break;
+	case CS8:
+	default:
+		bits |= BITS_DATA_8;
+		break;
 	}
 
-	if ((cflag & CSTOPB) != (old_cflag & CSTOPB)) {
-		cp210x_get_line_ctl(port, &bits);
-		bits &= ~BITS_STOP_MASK;
-		if (cflag & CSTOPB) {
-			bits |= BITS_STOP_2;
-			dev_dbg(dev, "%s - stop bits = 2\n", __func__);
+	if (C_PARENB(tty)) {
+		if (C_CMSPAR(tty)) {
+			if (C_PARODD(tty))
+				bits |= BITS_PARITY_MARK;
+			else
+				bits |= BITS_PARITY_SPACE;
 		} else {
-			bits |= BITS_STOP_1;
-			dev_dbg(dev, "%s - stop bits = 1\n", __func__);
+			if (C_PARODD(tty))
+				bits |= BITS_PARITY_ODD;
+			else
+				bits |= BITS_PARITY_EVEN;
 		}
-		if (cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits))
-			dev_dbg(dev, "Number of stop bits requested not supported by device\n");
 	}
 
+	if (C_CSTOPB(tty))
+		bits |= BITS_STOP_2;
+	else
+		bits |= BITS_STOP_1;
+
+	ret = cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
+	if (ret)
+		dev_err(&port->dev, "failed to set line control: %d\n", ret);
+
 	if ((cflag & CRTSCTS) != (old_cflag & CRTSCTS)) {
 		struct cp210x_flow_ctl flow_ctl;
 		u32 ctl_hs;
-- 
2.26.2

[PATCH 3/6] USB: serial: cp210x: set terminal settings on open

[Johan Hovold]

Unlike other drivers cp210x have been retrieving the current terminal
settings from the device on open and reflecting those in termios.

Due to how set_termios() used to be implemented, this saved a few
control requests on open but has instead caused problems like broken
flow control and has required adding workarounds for swapped
line-control in cp2108 and line-speed initialisation on cp2104.

This unusual implementation also complicates adding new features for no
good reason.

Rip out the corresponding code and the above mentioned workarounds and
instead initialise the terminal settings unconditionally on open.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/cp210x.c | 289 +-----------------------------------
 1 file changed, 6 insertions(+), 283 deletions(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index ad134e517849..bb9c3d7ccaee 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -31,9 +31,6 @@
  */
 static int cp210x_open(struct tty_struct *tty, struct usb_serial_port *);
 static void cp210x_close(struct usb_serial_port *);
-static void cp210x_get_termios(struct tty_struct *, struct usb_serial_port *);
-static void cp210x_get_termios_port(struct usb_serial_port *port,
-	tcflag_t *cflagp, unsigned int *baudp);
 static void cp210x_change_speed(struct tty_struct *, struct usb_serial_port *,
 							struct ktermios *);
 static void cp210x_set_termios(struct tty_struct *, struct usb_serial_port *,
@@ -267,7 +264,6 @@ enum cp210x_event_state {
 
 struct cp210x_port_private {
 	u8			bInterfaceNumber;
-	bool			has_swapped_line_ctl;
 	bool			event_mode;
 	enum cp210x_event_state event_state;
 	u8 lsr;
@@ -593,46 +589,6 @@ static int cp210x_read_reg_block(struct usb_serial_port *port, u8 req,
 	return result;
 }
 
-/*
- * Reads any 32-bit CP210X_ register identified by req.
- */
-static int cp210x_read_u32_reg(struct usb_serial_port *port, u8 req, u32 *val)
-{
-	__le32 le32_val;
-	int err;
-
-	err = cp210x_read_reg_block(port, req, &le32_val, sizeof(le32_val));
-	if (err) {
-		/*
-		 * FIXME Some callers don't bother to check for error,
-		 * at least give them consistent junk until they are fixed
-		 */
-		*val = 0;
-		return err;
-	}
-
-	*val = le32_to_cpu(le32_val);
-
-	return 0;
-}
-
-/*
- * Reads any 16-bit CP210X_ register identified by req.
- */
-static int cp210x_read_u16_reg(struct usb_serial_port *port, u8 req, u16 *val)
-{
-	__le16 le16_val;
-	int err;
-
-	err = cp210x_read_reg_block(port, req, &le16_val, sizeof(le16_val));
-	if (err)
-		return err;
-
-	*val = le16_to_cpu(le16_val);
-
-	return 0;
-}
-
 /*
  * Reads any 8-bit CP210X_ register identified by req.
  */
@@ -780,59 +736,6 @@ static int cp210x_write_vendor_block(struct usb_serial *serial, u8 type,
 }
 #endif
 
-/*
- * Detect CP2108 GET_LINE_CTL bug and activate workaround.
- * Write a known good value 0x800, read it back.
- * If it comes back swapped the bug is detected.
- * Preserve the original register value.
- */
-static int cp210x_detect_swapped_line_ctl(struct usb_serial_port *port)
-{
-	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
-	u16 line_ctl_save;
-	u16 line_ctl_test;
-	int err;
-
-	err = cp210x_read_u16_reg(port, CP210X_GET_LINE_CTL, &line_ctl_save);
-	if (err)
-		return err;
-
-	err = cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, 0x800);
-	if (err)
-		return err;
-
-	err = cp210x_read_u16_reg(port, CP210X_GET_LINE_CTL, &line_ctl_test);
-	if (err)
-		return err;
-
-	if (line_ctl_test == 8) {
-		port_priv->has_swapped_line_ctl = true;
-		line_ctl_save = swab16(line_ctl_save);
-	}
-
-	return cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, line_ctl_save);
-}
-
-/*
- * Must always be called instead of cp210x_read_u16_reg(CP210X_GET_LINE_CTL)
- * to workaround cp2108 bug and get correct value.
- */
-static int cp210x_get_line_ctl(struct usb_serial_port *port, u16 *ctl)
-{
-	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
-	int err;
-
-	err = cp210x_read_u16_reg(port, CP210X_GET_LINE_CTL, ctl);
-	if (err)
-		return err;
-
-	/* Workaround swapped bytes in 16-bit value from CP210X_GET_LINE_CTL */
-	if (port_priv->has_swapped_line_ctl)
-		*ctl = swab16(*ctl);
-
-	return 0;
-}
-
 static int cp210x_open(struct tty_struct *tty, struct usb_serial_port *port)
 {
 	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
@@ -844,16 +747,8 @@ static int cp210x_open(struct tty_struct *tty, struct usb_serial_port *port)
 		return result;
 	}
 
-	/* Configure the termios structure */
-	cp210x_get_termios(tty, port);
-
-	if (tty) {
-		/* The baud rate must be initialised on cp2104 */
-		cp210x_change_speed(tty, port, NULL);
-
-		if (I_INPCK(tty))
-			cp210x_enable_event_mode(port);
-	}
+	if (tty)
+		cp210x_set_termios(tty, port, NULL);
 
 	result = usb_serial_generic_open(tty, port);
 	if (result)
@@ -1032,167 +927,6 @@ static bool cp210x_tx_empty(struct usb_serial_port *port)
 	return !count;
 }
 
-/*
- * cp210x_get_termios
- * Reads the baud rate, data bits, parity, stop bits and flow control mode
- * from the device, corrects any unsupported values, and configures the
- * termios structure to reflect the state of the device
- */
-static void cp210x_get_termios(struct tty_struct *tty,
-	struct usb_serial_port *port)
-{
-	unsigned int baud;
-
-	if (tty) {
-		cp210x_get_termios_port(tty->driver_data,
-			&tty->termios.c_cflag, &baud);
-		tty_encode_baud_rate(tty, baud, baud);
-	} else {
-		tcflag_t cflag;
-		cflag = 0;
-		cp210x_get_termios_port(port, &cflag, &baud);
-	}
-}
-
-/*
- * cp210x_get_termios_port
- * This is the heart of cp210x_get_termios which always uses a &usb_serial_port.
- */
-static void cp210x_get_termios_port(struct usb_serial_port *port,
-	tcflag_t *cflagp, unsigned int *baudp)
-{
-	struct device *dev = &port->dev;
-	tcflag_t cflag;
-	struct cp210x_flow_ctl flow_ctl;
-	u32 baud;
-	u16 bits;
-	u32 ctl_hs;
-	u32 flow_repl;
-
-	cp210x_read_u32_reg(port, CP210X_GET_BAUDRATE, &baud);
-
-	dev_dbg(dev, "%s - baud rate = %d\n", __func__, baud);
-	*baudp = baud;
-
-	cflag = *cflagp;
-
-	cp210x_get_line_ctl(port, &bits);
-	cflag &= ~CSIZE;
-	switch (bits & BITS_DATA_MASK) {
-	case BITS_DATA_5:
-		dev_dbg(dev, "%s - data bits = 5\n", __func__);
-		cflag |= CS5;
-		break;
-	case BITS_DATA_6:
-		dev_dbg(dev, "%s - data bits = 6\n", __func__);
-		cflag |= CS6;
-		break;
-	case BITS_DATA_7:
-		dev_dbg(dev, "%s - data bits = 7\n", __func__);
-		cflag |= CS7;
-		break;
-	case BITS_DATA_8:
-		dev_dbg(dev, "%s - data bits = 8\n", __func__);
-		cflag |= CS8;
-		break;
-	case BITS_DATA_9:
-		dev_dbg(dev, "%s - data bits = 9 (not supported, using 8 data bits)\n", __func__);
-		cflag |= CS8;
-		bits &= ~BITS_DATA_MASK;
-		bits |= BITS_DATA_8;
-		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
-		break;
-	default:
-		dev_dbg(dev, "%s - Unknown number of data bits, using 8\n", __func__);
-		cflag |= CS8;
-		bits &= ~BITS_DATA_MASK;
-		bits |= BITS_DATA_8;
-		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
-		break;
-	}
-
-	switch (bits & BITS_PARITY_MASK) {
-	case BITS_PARITY_NONE:
-		dev_dbg(dev, "%s - parity = NONE\n", __func__);
-		cflag &= ~PARENB;
-		break;
-	case BITS_PARITY_ODD:
-		dev_dbg(dev, "%s - parity = ODD\n", __func__);
-		cflag |= (PARENB|PARODD);
-		break;
-	case BITS_PARITY_EVEN:
-		dev_dbg(dev, "%s - parity = EVEN\n", __func__);
-		cflag &= ~PARODD;
-		cflag |= PARENB;
-		break;
-	case BITS_PARITY_MARK:
-		dev_dbg(dev, "%s - parity = MARK\n", __func__);
-		cflag |= (PARENB|PARODD|CMSPAR);
-		break;
-	case BITS_PARITY_SPACE:
-		dev_dbg(dev, "%s - parity = SPACE\n", __func__);
-		cflag &= ~PARODD;
-		cflag |= (PARENB|CMSPAR);
-		break;
-	default:
-		dev_dbg(dev, "%s - Unknown parity mode, disabling parity\n", __func__);
-		cflag &= ~PARENB;
-		bits &= ~BITS_PARITY_MASK;
-		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
-		break;
-	}
-
-	cflag &= ~CSTOPB;
-	switch (bits & BITS_STOP_MASK) {
-	case BITS_STOP_1:
-		dev_dbg(dev, "%s - stop bits = 1\n", __func__);
-		break;
-	case BITS_STOP_1_5:
-		dev_dbg(dev, "%s - stop bits = 1.5 (not supported, using 1 stop bit)\n", __func__);
-		bits &= ~BITS_STOP_MASK;
-		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
-		break;
-	case BITS_STOP_2:
-		dev_dbg(dev, "%s - stop bits = 2\n", __func__);
-		cflag |= CSTOPB;
-		break;
-	default:
-		dev_dbg(dev, "%s - Unknown number of stop bits, using 1 stop bit\n", __func__);
-		bits &= ~BITS_STOP_MASK;
-		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
-		break;
-	}
-
-	cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl,
-			sizeof(flow_ctl));
-	ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);
-	if (ctl_hs & CP210X_SERIAL_CTS_HANDSHAKE) {
-		dev_dbg(dev, "%s - flow control = CRTSCTS\n", __func__);
-		/*
-		 * When the port is closed, the CP210x hardware disables
-		 * auto-RTS and RTS is deasserted but it leaves auto-CTS when
-		 * in hardware flow control mode. When re-opening the port, if
-		 * auto-CTS is enabled on the cp210x, then auto-RTS must be
-		 * re-enabled in the driver.
-		 */
-		flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
-		flow_repl &= ~CP210X_SERIAL_RTS_MASK;
-		flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_FLOW_CTL);
-		flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);
-		cp210x_write_reg_block(port,
-				CP210X_SET_FLOW,
-				&flow_ctl,
-				sizeof(flow_ctl));
-
-		cflag |= CRTSCTS;
-	} else {
-		dev_dbg(dev, "%s - flow control = NONE\n", __func__);
-		cflag &= ~CRTSCTS;
-	}
-
-	*cflagp = cflag;
-}
-
 struct cp210x_rate {
 	speed_t rate;
 	speed_t high;
@@ -1366,17 +1100,13 @@ static void cp210x_set_termios(struct tty_struct *tty,
 {
 	struct cp210x_serial_private *priv = usb_get_serial_data(port->serial);
 	struct device *dev = &port->dev;
-	unsigned int cflag, old_cflag;
 	u16 bits;
 	int ret;
 
-	if (!cp210x_termios_change(&tty->termios, old_termios))
+	if (old_termios && !cp210x_termios_change(&tty->termios, old_termios))
 		return;
 
-	cflag = tty->termios.c_cflag;
-	old_cflag = old_termios->c_cflag;
-
-	if (tty->termios.c_ospeed != old_termios->c_ospeed)
+	if (!old_termios || tty->termios.c_ospeed != old_termios->c_ospeed)
 		cp210x_change_speed(tty, port, old_termios);
 
 	/* CP2101 only supports CS8, 1 stop bit and non-stick parity. */
@@ -1426,7 +1156,7 @@ static void cp210x_set_termios(struct tty_struct *tty,
 	if (ret)
 		dev_err(&port->dev, "failed to set line control: %d\n", ret);
 
-	if ((cflag & CRTSCTS) != (old_cflag & CRTSCTS)) {
+	if (!old_termios || C_CRTSCTS(tty) != (old_termios->c_cflag & CRTSCTS)) {
 		struct cp210x_flow_ctl flow_ctl;
 		u32 ctl_hs;
 		u32 flow_repl;
@@ -1443,7 +1173,7 @@ static void cp210x_set_termios(struct tty_struct *tty,
 		ctl_hs &= ~CP210X_SERIAL_DSR_SENSITIVITY;
 		ctl_hs &= ~CP210X_SERIAL_DTR_MASK;
 		ctl_hs |= CP210X_SERIAL_DTR_SHIFT(CP210X_SERIAL_DTR_ACTIVE);
-		if (cflag & CRTSCTS) {
+		if (C_CRTSCTS(tty)) {
 			ctl_hs |= CP210X_SERIAL_CTS_HANDSHAKE;
 
 			flow_repl &= ~CP210X_SERIAL_RTS_MASK;
@@ -1979,7 +1709,6 @@ static int cp210x_port_probe(struct usb_serial_port *port)
 {
 	struct usb_serial *serial = port->serial;
 	struct cp210x_port_private *port_priv;
-	int ret;
 
 	port_priv = kzalloc(sizeof(*port_priv), GFP_KERNEL);
 	if (!port_priv)
@@ -1989,12 +1718,6 @@ static int cp210x_port_probe(struct usb_serial_port *port)
 
 	usb_set_serial_port_data(port, port_priv);
 
-	ret = cp210x_detect_swapped_line_ctl(port);
-	if (ret) {
-		kfree(port_priv);
-		return ret;
-	}
-
 	return 0;
 }
 
-- 
2.26.2

[PATCH 4/6] USB: serial: cp210x: drop flow-control debugging

[Johan Hovold]

Drop some unnecessary flow-control debugging.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/cp210x.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index bb9c3d7ccaee..04d2b15ceded 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -1165,8 +1165,6 @@ static void cp210x_set_termios(struct tty_struct *tty,
 				sizeof(flow_ctl));
 		ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);
 		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);
 
 		ctl_hs &= ~CP210X_SERIAL_DSR_HANDSHAKE;
 		ctl_hs &= ~CP210X_SERIAL_DCD_HANDSHAKE;
@@ -1179,17 +1177,15 @@ static void cp210x_set_termios(struct tty_struct *tty,
 			flow_repl &= ~CP210X_SERIAL_RTS_MASK;
 			flow_repl |= CP210X_SERIAL_RTS_SHIFT(
 					CP210X_SERIAL_RTS_FLOW_CTL);
-			dev_dbg(dev, "%s - flow control = CRTSCTS\n", __func__);
 		} else {
 			ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE;
 
 			flow_repl &= ~CP210X_SERIAL_RTS_MASK;
 			flow_repl |= CP210X_SERIAL_RTS_SHIFT(
 					CP210X_SERIAL_RTS_ACTIVE);
-			dev_dbg(dev, "%s - flow control = NONE\n", __func__);
 		}
 
-		dev_dbg(dev, "%s - write ulControlHandshake=0x%08x, ulFlowReplace=0x%08x\n",
+		dev_dbg(dev, "%s - ulControlHandshake=0x%08x, ulFlowReplace=0x%08x\n",
 				__func__, ctl_hs, flow_repl);
 		flow_ctl.ulControlHandshake = cpu_to_le32(ctl_hs);
 		flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);
-- 
2.26.2

[PATCH 5/6] USB: serial: cp210x: refactor flow-control handling

[Johan Hovold]

Add a helper function to be used to configure flow control.

The flow-control code was the last caller that relied on the
memset-on-failure behaviour of cp210x_read_reg_block(), which we can now
drop in favour of bailing out on errors when retrieving the flow-control
settings.

This should also simplify adding support for software flow control.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/cp210x.c | 97 ++++++++++++++++++-------------------
 1 file changed, 47 insertions(+), 50 deletions(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index 04d2b15ceded..c77fd09b91ce 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -555,14 +555,8 @@ static int cp210x_read_reg_block(struct usb_serial_port *port, u8 req,
 	int result;
 
 	dmabuf = kmalloc(bufsize, GFP_KERNEL);
-	if (!dmabuf) {
-		/*
-		 * FIXME Some callers don't bother to check for error,
-		 * at least give them consistent junk until they are fixed
-		 */
-		memset(buf, 0, bufsize);
+	if (!dmabuf)
 		return -ENOMEM;
-	}
 
 	result = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
 			req, REQTYPE_INTERFACE_TO_HOST, 0,
@@ -576,12 +570,6 @@ static int cp210x_read_reg_block(struct usb_serial_port *port, u8 req,
 				req, bufsize, result);
 		if (result >= 0)
 			result = -EIO;
-
-		/*
-		 * FIXME Some callers don't bother to check for error,
-		 * at least give them consistent junk until they are fixed
-		 */
-		memset(buf, 0, bufsize);
 	}
 
 	kfree(dmabuf);
@@ -1095,11 +1083,55 @@ static bool cp210x_termios_change(const struct ktermios *a, const struct ktermio
 	return tty_termios_hw_change(a, b) || iflag_change;
 }
 
+static void cp210x_set_flow_control(struct tty_struct *tty,
+		struct usb_serial_port *port, struct ktermios *old_termios)
+{
+	struct cp210x_flow_ctl flow_ctl;
+	u32 flow_repl;
+	u32 ctl_hs;
+	int ret;
+
+	if (old_termios && C_CRTSCTS(tty) == (old_termios->c_cflag & CRTSCTS))
+		return;
+
+	ret = cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl,
+			sizeof(flow_ctl));
+	if (ret)
+		return;
+
+	ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);
+	flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
+
+	ctl_hs &= ~CP210X_SERIAL_DSR_HANDSHAKE;
+	ctl_hs &= ~CP210X_SERIAL_DCD_HANDSHAKE;
+	ctl_hs &= ~CP210X_SERIAL_DSR_SENSITIVITY;
+	ctl_hs &= ~CP210X_SERIAL_DTR_MASK;
+	ctl_hs |= CP210X_SERIAL_DTR_SHIFT(CP210X_SERIAL_DTR_ACTIVE);
+
+	if (C_CRTSCTS(tty)) {
+		ctl_hs |= CP210X_SERIAL_CTS_HANDSHAKE;
+		flow_repl &= ~CP210X_SERIAL_RTS_MASK;
+		flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_FLOW_CTL);
+	} else {
+		ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE;
+		flow_repl &= ~CP210X_SERIAL_RTS_MASK;
+		flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_ACTIVE);
+	}
+
+	dev_dbg(&port->dev, "%s - ulControlHandshake=0x%08x, ulFlowReplace=0x%08x\n",
+			__func__, ctl_hs, flow_repl);
+
+	flow_ctl.ulControlHandshake = cpu_to_le32(ctl_hs);
+	flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);
+
+	cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl,
+			sizeof(flow_ctl));
+}
+
 static void cp210x_set_termios(struct tty_struct *tty,
 		struct usb_serial_port *port, struct ktermios *old_termios)
 {
 	struct cp210x_serial_private *priv = usb_get_serial_data(port->serial);
-	struct device *dev = &port->dev;
 	u16 bits;
 	int ret;
 
@@ -1156,42 +1188,7 @@ static void cp210x_set_termios(struct tty_struct *tty,
 	if (ret)
 		dev_err(&port->dev, "failed to set line control: %d\n", ret);
 
-	if (!old_termios || C_CRTSCTS(tty) != (old_termios->c_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);
-		flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
-
-		ctl_hs &= ~CP210X_SERIAL_DSR_HANDSHAKE;
-		ctl_hs &= ~CP210X_SERIAL_DCD_HANDSHAKE;
-		ctl_hs &= ~CP210X_SERIAL_DSR_SENSITIVITY;
-		ctl_hs &= ~CP210X_SERIAL_DTR_MASK;
-		ctl_hs |= CP210X_SERIAL_DTR_SHIFT(CP210X_SERIAL_DTR_ACTIVE);
-		if (C_CRTSCTS(tty)) {
-			ctl_hs |= CP210X_SERIAL_CTS_HANDSHAKE;
-
-			flow_repl &= ~CP210X_SERIAL_RTS_MASK;
-			flow_repl |= CP210X_SERIAL_RTS_SHIFT(
-					CP210X_SERIAL_RTS_FLOW_CTL);
-		} else {
-			ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE;
-
-			flow_repl &= ~CP210X_SERIAL_RTS_MASK;
-			flow_repl |= CP210X_SERIAL_RTS_SHIFT(
-					CP210X_SERIAL_RTS_ACTIVE);
-		}
-
-		dev_dbg(dev, "%s - ulControlHandshake=0x%08x, ulFlowReplace=0x%08x\n",
-				__func__, ctl_hs, flow_repl);
-		flow_ctl.ulControlHandshake = cpu_to_le32(ctl_hs);
-		flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);
-		cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl,
-				sizeof(flow_ctl));
-	}
+	cp210x_set_flow_control(tty, port, old_termios);
 
 	/*
 	 * Enable event-insertion mode only if input parity checking is
-- 
2.26.2

[PATCH 6/6] USB: serial: cp210x: clean up dts_rts

[Johan Hovold]

Clean up dtr_rts by renaming the port parameter and adding missing
whitespace.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/cp210x.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index c77fd09b91ce..fbb10dfc56e3 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -46,7 +46,7 @@ static void cp210x_disconnect(struct usb_serial *);
 static void cp210x_release(struct usb_serial *);
 static int cp210x_port_probe(struct usb_serial_port *);
 static int cp210x_port_remove(struct usb_serial_port *);
-static void cp210x_dtr_rts(struct usb_serial_port *p, int on);
+static void cp210x_dtr_rts(struct usb_serial_port *port, int on);
 static void cp210x_process_read_urb(struct urb *urb);
 static void cp210x_enable_event_mode(struct usb_serial_port *port);
 static void cp210x_disable_event_mode(struct usb_serial_port *port);
@@ -1234,12 +1234,12 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port,
 	return cp210x_write_u16_reg(port, CP210X_SET_MHS, control);
 }
 
-static void cp210x_dtr_rts(struct usb_serial_port *p, int on)
+static void cp210x_dtr_rts(struct usb_serial_port *port, int on)
 {
 	if (on)
-		cp210x_tiocmset_port(p, TIOCM_DTR|TIOCM_RTS, 0);
+		cp210x_tiocmset_port(port, TIOCM_DTR | TIOCM_RTS, 0);
 	else
-		cp210x_tiocmset_port(p, 0, TIOCM_DTR|TIOCM_RTS);
+		cp210x_tiocmset_port(port, 0, TIOCM_DTR | TIOCM_RTS);
 }
 
 static int cp210x_tiocmget(struct tty_struct *tty)
-- 
2.26.2

Re: [PATCH 0/6] USB: serial: cp210x: clean up termios handling

[Johan Hovold]

On Mon, Nov 16, 2020 at 05:18:20PM +0100, Johan Hovold wrote:
> Unlike other drivers cp210x have been retrieving the current terminal
> settings from the device on open and reflecting those in termios.
>     
> Due to how set_termios() was implemented this saved a few control
> requests on open but has instead caused problems like broken flow
> control and has required adding workarounds for swapped line-control in
> cp2108 and line-speed initialisation on cp2104.
> 
> This unusual implementation also complicates adding new features for no
> good reason.
> 
> Rip out the corresponding code and the above mentioned workarounds and
> instead initialise the terminal settings unconditionally on open.

> Johan Hovold (6):
>   USB: serial: cp210x: return early on unchanged termios
>   USB: serial: cp210x: clean up line-control handling
>   USB: serial: cp210x: set terminal settings on open
>   USB: serial: cp210x: drop flow-control debugging
>   USB: serial: cp210x: refactor flow-control handling
>   USB: serial: cp210x: clean up dts_rts
> 
>  drivers/usb/serial/cp210x.c | 499 ++++++++----------------------------
>  1 file changed, 104 insertions(+), 395 deletions(-)

I have applied this series for -next now.

Johan