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

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_ker...@gmail.com>
---
 drivers/usb/serial/f81534.c | 84 ++++++++++++++++++++++++++++++++++++---------
 1 file changed, 68 insertions(+), 16 deletions(-)

diff --git a/drivers/usb/serial/f81534.c b/drivers/usb/serial/f81534.c
index cb8214860192..76c676ef5f0d 100644
--- a/drivers/usb/serial/f81534.c
+++ b/drivers/usb/serial/f81534.c
@@ -45,6 +45,7 @@
 #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
@@ -61,7 +62,7 @@
 
 /* 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
@@ -100,7 +101,6 @@
 #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)
@@ -110,6 +110,22 @@
 #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_CLK_1_846_MHZ           BIT(0)
+#define F81534_CLK_18_46_MHZ           (BIT(0) | BIT(1))
+#define F81534_CLK_24_MHZ              (BIT(0) | BIT(2))
+#define F81534_CLK_14_77_MHZ           (BIT(0) | BIT(1) | BIT(2))
+
 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) },
@@ -133,6 +149,7 @@ 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;
@@ -464,13 +481,51 @@ 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_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 idx;
        u8 value;
+       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};
+
+       do {
+               for (idx = 0; idx < ARRAY_SIZE(baudrate_table); ++idx) {
+                       if (baudrate <= baudrate_table[idx] &&
+                                       baudrate_table[idx] % baudrate == 0)
+                               break;
+               }
+
+               /* Found acceptable baud rate */
+               if (idx != ARRAY_SIZE(baudrate_table))
+                       break;
+
+               if (baudrate == old_baudrate &&
+                               old_baudrate != F81534_DEFAULT_BAUD_RATE)
+                       old_baudrate = F81534_DEFAULT_BAUD_RATE;
+
+               dev_warn(&port->dev,
+                               "baudrate: %d not supported, change to: %d\n",
+                               baudrate, old_baudrate);
+
+               baudrate = old_baudrate;
+               tty_encode_baud_rate(tty, baudrate, baudrate);
+
+       } while (1);
+
+       port_priv->baud_base = baudrate_table[idx];
+       status = f81534_set_port_register(port, F81534_CLOCK_REG,
+                       clock_table[idx]);
+       if (status) {
+               dev_err(&port->dev, "CLOCK_REG setting failed\n");
+               return status;
+       }
 
        if (baudrate <= 1200)
                value = F81534_1X_RXTRIGGER;    /* 128 FIFO & TL: 1x */
@@ -486,7 +541,7 @@ 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);
@@ -495,7 +550,7 @@ 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, baudrate_table[idx]);
 
        mutex_lock(&port_priv->lcr_mutex);
 
@@ -745,6 +800,7 @@ 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);
@@ -784,18 +840,14 @@ 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);
@@ -951,7 +1003,7 @@ 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;
-- 
2.7.4

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