USB: serial: f81534: add high baud rate support

The F81532/534 had 4 clocksource 1.846/18.46/14.77/24MHz and baud rates
can be up to 1.5Mbits with 24MHz.

This device may generate data overrun when baud rate setting to 921600bps
or higher with old UART trigger level setting (8x14=112) with full
loading. We'll change trigger level from 8x14=112 to 8x8=64 to avoid data
overrun.

Also the read/write of EP0 will be affected by this patch. The worst case
of responding time is 20s when all serial port are full loading and trying
to access EP0, so we change EP0 timeout from 10 to 20s.

F81532/534 Clock register (offset +08h)

Bit0:	UART Enable (always on)
Bit2-1:	Clock source selector
			00: 1.846MHz.
			01: 18.46MHz.
			10: 24MHz.
			11: 14.77MHz.

Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@gmail.com>
[ johan: only use GENMASK() for masks ]
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/f81534.c

@@ -41,6 +41,7 @@
 #define F81534_MODEM_CONTROL_REG	(0x04 + F81534_UART_BASE_ADDRESS)
 #define F81534_LINE_STATUS_REG		(0x05 + F81534_UART_BASE_ADDRESS)
 #define F81534_MODEM_STATUS_REG		(0x06 + F81534_UART_BASE_ADDRESS)
+#define F81534_CLOCK_REG		(0x08 + F81534_UART_BASE_ADDRESS)
 #define F81534_CONFIG1_REG		(0x09 + F81534_UART_BASE_ADDRESS)
 
 #define F81534_DEF_CONF_ADDRESS_START	0x3000
@@ -57,7 +58,7 @@
 
 /* Default URB timeout for USB operations */
 #define F81534_USB_MAX_RETRY		10
-#define F81534_USB_TIMEOUT		1000
+#define F81534_USB_TIMEOUT		2000
 #define F81534_SET_GET_REGISTER		0xA0
 
 #define F81534_NUM_PORT			4
@@ -96,7 +97,6 @@
 #define F81534_CMD_READ			0x03
 
 #define F81534_DEFAULT_BAUD_RATE	9600
-#define F81534_MAX_BAUDRATE		115200
 
 #define F81534_PORT_CONF_DISABLE_PORT	BIT(3)
 #define F81534_PORT_CONF_NOT_EXIST_PORT	BIT(7)
@@ -106,6 +106,24 @@
 #define F81534_1X_RXTRIGGER		0xc3
 #define F81534_8X_RXTRIGGER		0xcf
 
+/*
+ * F81532/534 Clock registers (offset +08h)
+ *
+ * Bit0:	UART Enable (always on)
+ * Bit2-1:	Clock source selector
+ *			00: 1.846MHz.
+ *			01: 18.46MHz.
+ *			10: 24MHz.
+ *			11: 14.77MHz.
+ */
+
+#define F81534_UART_EN			BIT(0)
+#define F81534_CLK_1_846_MHZ		0
+#define F81534_CLK_18_46_MHZ		BIT(1)
+#define F81534_CLK_24_MHZ		BIT(2)
+#define F81534_CLK_14_77_MHZ		(BIT(1) | BIT(2))
+#define F81534_CLK_MASK			GENMASK(2, 1)
+
 static const struct usb_device_id f81534_id_table[] = {
 	{ USB_DEVICE(FINTEK_VENDOR_ID_1, FINTEK_DEVICE_ID) },
 	{ USB_DEVICE(FINTEK_VENDOR_ID_2, FINTEK_DEVICE_ID) },
@@ -129,12 +147,18 @@ struct f81534_port_private {
 	struct usb_serial_port *port;
 	unsigned long tx_empty;
 	spinlock_t msr_lock;
+	u32 baud_base;
 	u8 shadow_mcr;
 	u8 shadow_lcr;
 	u8 shadow_msr;
+	u8 shadow_clk;
 	u8 phy_num;
 };
 
+static u32 const baudrate_table[] = { 115200, 921600, 1152000, 1500000 };
+static u8 const clock_table[] = { F81534_CLK_1_846_MHZ, F81534_CLK_14_77_MHZ,
+				F81534_CLK_18_46_MHZ, F81534_CLK_24_MHZ };
+
 static int f81534_logic_to_phy_port(struct usb_serial *serial,
 					struct usb_serial_port *port)
 {
@@ -460,13 +484,52 @@ static u32 f81534_calc_baud_divisor(u32 baudrate, u32 clockrate)
 	return DIV_ROUND_CLOSEST(clockrate, baudrate);
 }
 
-static int f81534_set_port_config(struct usb_serial_port *port, u32 baudrate,
-					u8 lcr)
+static int f81534_find_clk(u32 baudrate)
+{
+	int idx;
+
+	for (idx = 0; idx < ARRAY_SIZE(baudrate_table); ++idx) {
+		if (baudrate <= baudrate_table[idx] &&
+				baudrate_table[idx] % baudrate == 0)
+			return idx;
+	}
+
+	return -EINVAL;
+}
+
+static int f81534_set_port_config(struct usb_serial_port *port,
+		struct tty_struct *tty, u32 baudrate, u32 old_baudrate, u8 lcr)
 {
 	struct f81534_port_private *port_priv = usb_get_serial_port_data(port);
 	u32 divisor;
 	int status;
+	int i;
+	int idx;
 	u8 value;
+	u32 baud_list[] = {baudrate, old_baudrate, F81534_DEFAULT_BAUD_RATE};
+
+	for (i = 0; i < ARRAY_SIZE(baud_list); ++i) {
+		idx = f81534_find_clk(baud_list[i]);
+		if (idx >= 0) {
+			baudrate = baud_list[i];
+			tty_encode_baud_rate(tty, baudrate, baudrate);
+			break;
+		}
+	}
+
+	if (idx < 0)
+		return -EINVAL;
+
+	port_priv->baud_base = baudrate_table[idx];
+	port_priv->shadow_clk &= ~F81534_CLK_MASK;
+	port_priv->shadow_clk |= clock_table[idx];
+
+	status = f81534_set_port_register(port, F81534_CLOCK_REG,
+			port_priv->shadow_clk);
+	if (status) {
+		dev_err(&port->dev, "CLOCK_REG setting failed\n");
+		return status;
+	}
 
 	if (baudrate <= 1200)
 		value = F81534_1X_RXTRIGGER;	/* 128 FIFO & TL: 1x */
@@ -482,7 +545,7 @@ static int f81534_set_port_config(struct usb_serial_port *port, u32 baudrate,
 	if (baudrate <= 1200)
 		value = UART_FCR_TRIGGER_1 | UART_FCR_ENABLE_FIFO; /* TL: 1 */
 	else
-		value = UART_FCR_R_TRIG_11 | UART_FCR_ENABLE_FIFO; /* TL: 14 */
+		value = UART_FCR_TRIGGER_8 | UART_FCR_ENABLE_FIFO; /* TL: 8 */
 
 	status = f81534_set_port_register(port, F81534_FIFO_CONTROL_REG,
 						value);
@@ -491,7 +554,7 @@ static int f81534_set_port_config(struct usb_serial_port *port, u32 baudrate,
 		return status;
 	}
 
-	divisor = f81534_calc_baud_divisor(baudrate, F81534_MAX_BAUDRATE);
+	divisor = f81534_calc_baud_divisor(baudrate, port_priv->baud_base);
 
 	mutex_lock(&port_priv->lcr_mutex);
 
@@ -741,6 +804,7 @@ static void f81534_set_termios(struct tty_struct *tty,
 	u8 new_lcr = 0;
 	int status;
 	u32 baud;
+	u32 old_baud;
 
 	if (C_BAUD(tty) == B0)
 		f81534_update_mctrl(port, 0, TIOCM_DTR | TIOCM_RTS);
@@ -780,18 +844,14 @@ static void f81534_set_termios(struct tty_struct *tty,
 	if (!baud)
 		return;
 
-	if (baud > F81534_MAX_BAUDRATE) {
-		if (old_termios)
-			baud = tty_termios_baud_rate(old_termios);
-		else
-			baud = F81534_DEFAULT_BAUD_RATE;
-
-		tty_encode_baud_rate(tty, baud, baud);
-	}
+	if (old_termios)
+		old_baud = tty_termios_baud_rate(old_termios);
+	else
+		old_baud = F81534_DEFAULT_BAUD_RATE;
 
 	dev_dbg(&port->dev, "%s: baud: %d\n", __func__, baud);
 
-	status = f81534_set_port_config(port, baud, new_lcr);
+	status = f81534_set_port_config(port, tty, baud, old_baud, new_lcr);
 	if (status < 0) {
 		dev_err(&port->dev, "%s: set port config failed: %d\n",
 				__func__, status);
@@ -947,7 +1007,7 @@ static int f81534_get_serial_info(struct usb_serial_port *port,
 	tmp.type = PORT_16550A;
 	tmp.port = port->port_number;
 	tmp.line = port->minor;
-	tmp.baud_base = F81534_MAX_BAUDRATE;
+	tmp.baud_base = port_priv->baud_base;
 
 	if (copy_to_user(retinfo, &tmp, sizeof(*retinfo)))
 		return -EFAULT;
@@ -1221,6 +1281,7 @@ static int f81534_port_probe(struct usb_serial_port *port)
 	if (!port_priv)
 		return -ENOMEM;
 
+	port_priv->shadow_clk = F81534_UART_EN;
 	spin_lock_init(&port_priv->msr_lock);
 	mutex_init(&port_priv->mcr_mutex);
 	mutex_init(&port_priv->lcr_mutex);