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USB: serial: cp210x: add minimun baud rate for CP2105 SCI

PATCH New Johan Hovold 1 participant 1 message Feb 7, 2019 USB

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Johan Hovold

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PATCH v2 1/1 USB: serial: cp210x: add minimun baud rate for CP2105 SCI

Quoted 4 lines · Johanna Abrahamsson

From: Johanna Abrahamsson <[email protected]>

This patch adds minimum baud rate to the cp210x driver.

Quoted 8 lines

According to the datasheet for CP2105, the SCI supports 2400 as the lowest baud rate. As this is not heeded in the current code, an error message 'failed set req 0x1e size 4 status: -32' when trying to set a lower baud rate such as 300.
The other cp210x models to date supports a minimum baud rate of 300.

Signed-off-by Johanna Abrahamsson <[email protected]>

---

Thanks for the update.

Now applied with a few minor tweaks:

Quoted 16 lines
 drivers/usb/serial/cp210x.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)
drivers/usb/serial/cp210x.c +1 -0
index 260c875dd263..ceff735e961c 100644
@@ -245,6 +245,7 @@ struct cp210x_serial_private {
 	u8			gpio_input;
 #endif
 	u8			partnum;
+	speed_t			min_speed;
 	speed_t			max_speed;
 	bool			use_actual_rate;
 };

drivers/usb/serial/cp210x.c static speed_t cp210x_get_actual_rate(struct usb_serial *serial, speed_t baud) · line 1081

Quoted 4 lines
drivers/usb/serial/cp210x.c +0 -1
@@ -1078,8 +1079,6 @@ static speed_t cp210x_get_actual_rate(struct usb_serial *serial, speed_t baud)
 	unsigned int prescale = 1;
 	unsigned int div;
 
-	baud = clamp(baud, 300u, priv->max_speed);

priv is now unused in this function and thus triggered a compilation warning. I dropped priv along with the serial pointer.

drivers/usb/serial/cp210x.c static void cp210x_change_speed(struct tty_struct *tty, · line 1124

Quoted 10 lines
drivers/usb/serial/cp210x.c +1 -2
-
 	if (baud <= 365)
 		prescale = 4;
 

@@ -1122,7 +1121,7 @@ static void cp210x_change_speed(struct tty_struct *tty,
 	struct cp210x_serial_private *priv = usb_get_serial_data(serial);
 	u32 baud;
 
-	baud = tty->termios.c_ospeed;
+	baud = clamp(tty->termios.c_ospeed, priv->min_speed, priv->max_speed);

I moved this clamp after the comment since this construct now makes sure we honour max_speed.

Quoted 12 lines
drivers/usb/serial/cp210x.c +0 -2
 	/*
 	 * This maps the requested rate to the actual rate, a valid rate on

@@ -1134,8 +1133,6 @@ static void cp210x_change_speed(struct tty_struct *tty,
 		baud = cp210x_get_actual_rate(serial, baud);
 	else if (baud < 1000000)
 		baud = cp210x_get_an205_rate(baud);
-	else if (baud > priv->max_speed)
-		baud = priv->max_speed;
 
 	dev_dbg(&port->dev, "%s - setting baud rate to %u\n", __func__, baud);
 	if (cp210x_write_u32_reg(port, CP210X_SET_BAUDRATE, baud)) {

drivers/usb/serial/cp210x.c static void cp210x_init_max_speed(struct usb_serial *serial) · line 1797

Quoted 4 lines
drivers/usb/serial/cp210x.c +1 -0
@@ -1797,28 +1794,35 @@ static void cp210x_init_max_speed(struct usb_serial *serial)
 {
 	struct cp210x_serial_private *priv = usb_get_serial_data(serial);
 	bool use_actual_rate = false;
+	speed_t min;

And I initialised min to 300 here which allows most initialisations below to be removed.

Quoted 38 lines
drivers/usb/serial/cp210x.c +7 -0
 	speed_t max;
 
 	switch (priv->partnum) {
 	case CP210X_PARTNUM_CP2101:
+		min = 300;
 		max = 921600;
 		break;
 	case CP210X_PARTNUM_CP2102:
 	case CP210X_PARTNUM_CP2103:
+		min = 300;
 		max = 1000000;
 		break;
 	case CP210X_PARTNUM_CP2104:
 		use_actual_rate = true;
+		min = 300;
 		max = 2000000;
 		break;
 	case CP210X_PARTNUM_CP2108:
+		min = 300;
 		max = 2000000;
 		break;
 	case CP210X_PARTNUM_CP2105:
 		if (cp210x_interface_num(serial) == 0) {
 			use_actual_rate = true;
+			min = 300;
 			max = 2000000;	/* ECI */
 		} else {
+			min = 2400;
 			max = 921600;	/* SCI */
 		}
 		break;

@@ -1826,13 +1830,16 @@ static void cp210x_init_max_speed(struct usb_serial *serial)
 	case CP210X_PARTNUM_CP2102N_QFN24:
 	case CP210X_PARTNUM_CP2102N_QFN20:
 		use_actual_rate = true;
+		min = 300;
 		max = 3000000;
 		break;

drivers/usb/serial/cp210x.c static void cp210x_init_max_speed(struct usb_serial *serial) · line 1845

Quoted 10 lines
drivers/usb/serial/cp210x.c +2 -0
 	default:
+		min = 300;
 		max = 2000000;
 		break;
 	}
 
+	priv->min_speed = min;
 	priv->max_speed = max;
 	priv->use_actual_rate = use_actual_rate;
 }

Thanks,
Johan