The F81232 had 4 clocksource 1.846/18.46/14.77/24MHz and baud rates
can be up to 1.5Mbits with 24MHz.

F81232 Clock registers (106h)

Bit1-0:     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/f81232.c | 105 +++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 94 insertions(+), 11 deletions(-)

diff --git a/drivers/usb/serial/f81232.c b/drivers/usb/serial/f81232.c
index 46836041c50e..bdd7f337cd5f 100644
--- a/drivers/usb/serial/f81232.c
+++ b/drivers/usb/serial/f81232.c
@@ -28,7 +28,8 @@ static const struct usb_device_id id_table[] = {
 MODULE_DEVICE_TABLE(usb, id_table);
 
 /* Maximum baudrate for F81232 */
-#define F81232_MAX_BAUDRATE            115200
+#define F81232_MAX_BAUDRATE            1500000
+#define F81232_DEF_BAUDRATE            9600
 
 /* USB Control EP parameter */
 #define F81232_REGISTER_REQUEST                0xa0
@@ -44,18 +45,42 @@ MODULE_DEVICE_TABLE(usb, id_table);
 #define LINE_STATUS_REGISTER           (0x05 + SERIAL_BASE_ADDRESS)
 #define MODEM_STATUS_REGISTER          (0x06 + SERIAL_BASE_ADDRESS)
 
+/*
+ * F81232 Clock registers (106h)
+ *
+ * Bit1-0:     Clock source selector
+ *                     00: 1.846MHz.
+ *                     01: 18.46MHz.
+ *                     10: 24MHz.
+ *                     11: 14.77MHz.
+ */
+#define F81232_CLK_REGISTER            0x106
+#define F81232_CLK_1_846_MHZ           0
+#define F81232_CLK_18_46_MHZ           BIT(0)
+#define F81232_CLK_24_MHZ              BIT(1)
+#define F81232_CLK_14_77_MHZ           (BIT(1) | BIT(0))
+#define F81232_CLK_MASK                        GENMASK(1, 0)
+
 struct f81232_private {
        struct mutex lock;
        u8 modem_control;
        u8 modem_status;
+       speed_t baud_base;
        struct work_struct lsr_work;
        struct work_struct interrupt_work;
        struct usb_serial_port *port;
 };
 
-static int calc_baud_divisor(speed_t baudrate)
+static u32 const baudrate_table[] = { 115200, 921600, 1152000, 1500000 };
+static u8 const clock_table[] = { F81232_CLK_1_846_MHZ, F81232_CLK_14_77_MHZ,
+                               F81232_CLK_18_46_MHZ, F81232_CLK_24_MHZ };
+
+static int calc_baud_divisor(speed_t baudrate, speed_t clockrate)
 {
-       return DIV_ROUND_CLOSEST(F81232_MAX_BAUDRATE, baudrate);
+       if (!baudrate)
+               return 0;
+
+       return DIV_ROUND_CLOSEST(clockrate, baudrate);
 }
 
 static int f81232_get_register(struct usb_serial_port *port, u16 reg, u8 *val)
@@ -129,6 +154,21 @@ static int f81232_set_register(struct usb_serial_port 
*port, u16 reg, u8 val)
        return status;
 }
 
+static int f81232_set_mask_register(struct usb_serial_port *port, u16 reg,
+                                       u8 mask, u8 val)
+{
+       int status;
+       u8 tmp;
+
+       status = f81232_get_register(port, reg, &tmp);
+       if (status)
+               return status;
+
+       tmp = (tmp & ~mask) | (val & mask);
+
+       return f81232_set_register(port, reg, tmp);
+}
+
 static void f81232_read_msr(struct usb_serial_port *port)
 {
        int status;
@@ -346,13 +386,53 @@ static void f81232_break_ctl(struct tty_struct *tty, int 
break_state)
         */
 }
 
-static void f81232_set_baudrate(struct usb_serial_port *port, speed_t baudrate)
+static int f81232_find_clk(speed_t 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 void f81232_set_baudrate(struct tty_struct *tty,
+                               struct usb_serial_port *port, speed_t baudrate,
+                               speed_t old_baudrate)
 {
+       struct f81232_private *priv = usb_get_serial_port_data(port);
        u8 lcr;
        int divisor;
        int status = 0;
+       int i;
+       int idx;
+       speed_t baud_list[] = {baudrate, old_baudrate, F81232_DEF_BAUDRATE};
+
+       for (i = 0; i < ARRAY_SIZE(baud_list); ++i) {
+               idx = f81232_find_clk(baud_list[i]);
+               if (idx >= 0) {
+                       baudrate = baud_list[i];
+                       tty_encode_baud_rate(tty, baudrate, baudrate);
+                       break;
+               }
+       }
 
-       divisor = calc_baud_divisor(baudrate);
+       if (idx < 0)
+               return;
+
+       priv->baud_base = baudrate_table[idx];
+       divisor = calc_baud_divisor(baudrate, priv->baud_base);
+
+       status = f81232_set_mask_register(port, F81232_CLK_REGISTER,
+                       F81232_CLK_MASK, clock_table[idx]);
+       if (status) {
+               dev_err(&port->dev, "%s failed to set CLK_REG: %d\n",
+                       __func__, status);
+               return;
+       }
 
        status = f81232_get_register(port, LINE_CONTROL_REGISTER,
                         &lcr); /* get LCR */
@@ -442,6 +522,7 @@ static void f81232_set_termios(struct tty_struct *tty,
        u8 new_lcr = 0;
        int status = 0;
        speed_t baudrate;
+       speed_t old_baud;
 
        /* Don't change anything if nothing has changed */
        if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios))
@@ -454,11 +535,12 @@ static void f81232_set_termios(struct tty_struct *tty,
 
        baudrate = tty_get_baud_rate(tty);
        if (baudrate > 0) {
-               if (baudrate > F81232_MAX_BAUDRATE) {
-                       baudrate = F81232_MAX_BAUDRATE;
-                       tty_encode_baud_rate(tty, baudrate, baudrate);
-               }
-               f81232_set_baudrate(port, baudrate);
+               if (old_termios)
+                       old_baud = tty_termios_baud_rate(old_termios);
+               else
+                       old_baud = F81232_DEF_BAUDRATE;
+
+               f81232_set_baudrate(tty, port, baudrate, old_baud);
        }
 
        if (C_PARENB(tty)) {
@@ -590,6 +672,7 @@ static int f81232_carrier_raised(struct usb_serial_port 
*port)
 static int f81232_get_serial_info(struct usb_serial_port *port,
                unsigned long arg)
 {
+       struct f81232_private *priv = usb_get_serial_port_data(port);
        struct serial_struct ser;
 
        memset(&ser, 0, sizeof(ser));
@@ -597,7 +680,7 @@ static int f81232_get_serial_info(struct usb_serial_port 
*port,
        ser.type = PORT_16550A;
        ser.line = port->minor;
        ser.port = port->port_number;
-       ser.baud_base = F81232_MAX_BAUDRATE;
+       ser.baud_base = priv->baud_base;
 
        if (copy_to_user((void __user *)arg, &ser, sizeof(ser)))
                return -EFAULT;
-- 
2.7.4

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