From 3f6f5141142b68b62cd3acf96ee99fe6b0851925 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Mon, 16 Nov 2020 17:18:22 +0100
Subject: [PATCH] USB: serial: cp210x: clean up line-control handling

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 fd0c6db08058..2cacb039f40b 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -1389,9 +1389,11 @@ 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;
@@ -1402,74 +1404,53 @@ 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;
