usb: pl2303: move the two baud rate encoding methods to separate functions

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c
index a0ea92e..693ed7e 100644 (file)
--- a/drivers/usb/serial/pl2303.c
+++ b/drivers/usb/serial/pl2303.c
@@ -269,115 +269,128 @@ static int pl2303_set_control_lines(struct usb_serial_port *port, u8 value)
        return retval;
 }
 
+static int pl2303_baudrate_encode_direct(int baud, enum pl2303_type type,
+                                                                     u8 buf[4])
+{
+       /*
+        * NOTE: Only the values defined in baud_sup are supported !
+        *       => if unsupported values are set, the PL2303 seems to
+        *          use 9600 baud (at least my PL2303X always does)
+        */
+       const int baud_sup[] = { 75, 150, 300, 600, 1200, 1800, 2400, 3600,
+                                4800, 7200, 9600, 14400, 19200, 28800, 38400,
+                                57600, 115200, 230400, 460800, 614400, 921600,
+                                1228800, 2457600, 3000000, 6000000 };
+       int i;
+
+       /* Set baudrate to nearest supported value */
+       for (i = 0; i < ARRAY_SIZE(baud_sup); ++i) {
+               if (baud_sup[i] > baud)
+                       break;
+       }
+       if (i == ARRAY_SIZE(baud_sup))
+               baud = baud_sup[i - 1];
+       else if (i > 0 && (baud_sup[i] - baud) > (baud - baud_sup[i - 1]))
+               baud = baud_sup[i - 1];
+       else
+               baud = baud_sup[i];
+       /* type_0, type_1 only support up to 1228800 baud */
+       if (type != HX)
+               baud = min_t(int, baud, 1228800);
+       /* Direct (standard) baud rate encoding method */
+       put_unaligned_le32(baud, buf);
+
+       return baud;
+}
+
+static int pl2303_baudrate_encode_divisor(int baud, enum pl2303_type type,
+                                                                     u8 buf[4])
+{
+       /*
+        * Divisor based baud rate encoding method
+        *
+        * NOTE: it's not clear if the type_0/1 chips support this method
+        *
+        * divisor = 12MHz * 32 / baudrate = 2^A * B
+        *
+        * with
+        *
+        * A = buf[1] & 0x0e
+        * B = buf[0]  +  (buf[1] & 0x01) << 8
+        *
+        * Special cases:
+        * => 8 < B < 16: device seems to work not properly
+        * => B <= 8: device uses the max. value B = 512 instead
+        */
+       unsigned int A, B;
+
+       /* Respect the specified baud rate limits */
+       baud = max_t(int, baud, 75);
+       if (type == HX)
+               baud = min_t(int, baud, 6000000);
+       else
+               baud = min_t(int, baud, 1228800);
+       /* Determine factors A and B */
+       A = 0;
+       B = 12000000 * 32 / baud;  /* 12MHz */
+       B <<= 1; /* Add one bit for rounding */
+       while (B > (512 << 1) && A <= 14) {
+               A += 2;
+               B >>= 2;
+       }
+       if (A > 14) { /* max. divisor = min. baudrate reached */
+               A = 14;
+               B = 512;
+               /* => ~45.78 baud */
+       } else {
+               B = (B + 1) >> 1; /* Round the last bit */
+       }
+       /* Handle special cases */
+       if (B == 512)
+               B = 0; /* also: 1 to 8 */
+       else if (B < 16)
+               /*
+                * NOTE: With the current algorithm this happens
+                * only for A=0 and means that the min. divisor
+                * (respectively: the max. baudrate) is reached.
+                */
+               B = 16;         /* => 24 MBaud */
+       /* Encode the baud rate */
+       buf[3] = 0x80;     /* Select divisor encoding method */
+       buf[2] = 0;
+       buf[1] = (A & 0x0e);            /* A */
+       buf[1] |= ((B & 0x100) >> 8);   /* MSB of B */
+       buf[0] = B & 0xff;              /* 8 LSBs of B */
+       /* Calculate the actual/resulting baud rate */
+       if (B <= 8)
+               B = 512;
+       baud = 12000000 * 32 / ((1 << A) * B);
+
+       return baud;
+}
+
 static void pl2303_encode_baudrate(struct tty_struct *tty,
                                        struct usb_serial_port *port,
+                                       enum pl2303_type type,
                                        u8 buf[4])
 {
-       struct usb_serial *serial = port->serial;
-       struct pl2303_serial_private *spriv = usb_get_serial_data(serial);
        int baud;
 
        baud = tty_get_baud_rate(tty);
        dev_dbg(&port->dev, "baud requested = %d\n", baud);
        if (!baud)
                return;
-
-       if (spriv->type != HX || baud <= 115200) {
-               /*
-                * NOTE: Only the values defined in baud_sup are supported !
-                *       => if unsupported values are set, the PL2303 seems to
-                *          use 9600 baud (at least my PL2303X always does)
-                */
-               const int baud_sup[] = { 75, 150, 300, 600, 1200, 1800, 2400,
-                                        3600, 4800, 7200, 9600, 14400, 19200,
-                                        28800, 38400, 57600, 115200, 230400,
-                                        460800, 614400, 921600, 1228800,
-                                        2457600, 3000000, 6000000 };
-               int i;
-
-               /* Set baudrate to nearest supported value */
-               for (i = 0; i < ARRAY_SIZE(baud_sup); ++i) {
-                       if (baud_sup[i] > baud)
-                               break;
-               }
-
-               if (i == ARRAY_SIZE(baud_sup))
-                       baud = baud_sup[i - 1];
-               else if (i > 0
-                            && (baud_sup[i] - baud) > (baud - baud_sup[i - 1]))
-                       baud = baud_sup[i - 1];
-               else
-                       baud = baud_sup[i];
-
-               /* type_0, type_1 only support up to 1228800 baud */
-               if (spriv->type != HX)
-                       baud = min_t(int, baud, 1228800);
-
-               /* Direct (standard) baud rate encoding method */
-               put_unaligned_le32(baud, buf);
-       } else {
-               /*
-                * Divisor based baud rate encoding method
-                *
-                * NOTE: it's not clear if the type_0/1 chips
-                * support this method
-                *
-                * divisor = 12MHz * 32 / baudrate = 2^A * B
-                *
-                * with
-                *
-                * A = buf[1] & 0x0e
-                * B = buf[0]  +  (buf[1] & 0x01) << 8
-                *
-                * Special cases:
-                * => 8 < B < 16: device seems to work not properly
-                * => B <= 8: device uses the max. value B = 512 instead
-                */
-               unsigned int A, B;
-
-               /* Respect the specified baud rate limits */
-               baud = max_t(int, baud, 75);
-               if (spriv->type == HX)
-                       baud = min_t(int, baud, 6000000);
-               else
-                       baud = min_t(int, baud, 1228800);
-               /* Determine factors A and B */
-               A = 0;
-               B = 12000000 * 32 / baud;  /* 12MHz */
-               B <<= 1; /* Add one bit for rounding */
-               while (B > (512 << 1) && A <= 14) {
-                       A += 2;
-                       B >>= 2;
-               }
-               if (A > 14) { /* max. divisor = min. baudrate reached */
-                       A = 14;
-                       B = 512;
-                       /* => ~45.78 baud */
-               } else {
-                       B = (B + 1) >> 1; /* Round the last bit */
-               }
-               /* Handle special cases */
-               if (B == 512)
-                       B = 0; /* also: 1 to 8 */
-               else if (B < 16)
-                       /*
-                        * NOTE: With the current algorithm this happens
-                        * only for A=0 and means that the min. divisor
-                        * (respectively: the max. baudrate) is reached.
-                        */
-                       B = 16;         /* => 24 MBaud */
-               /* Encode the baud rate */
-               buf[3] = 0x80;     /* Select divisor encoding method */
-               buf[2] = 0;
-               buf[1] = (A & 0x0e);            /* A */
-               buf[1] |= ((B & 0x100) >> 8);   /* MSB of B */
-               buf[0] = B & 0xff;              /* 8 LSBs of B */
-               /* Calculate the actual/resulting baud rate */
-               if (B <= 8)
-                       B = 512;
-               baud = 12000000 * 32 / ((1 << A) * B);
-       }
-
+       /*
+        * There are two methods for setting/encoding the baud rate
+        * 1) Direct method: encodes the baud rate value directly
+        *    => supported by all chip types
+        * 2) Divisor based method: encodes a divisor to a base value (12MHz*32)
+        *    => supported by HX chips (and likely not by type_0/1 chips)
+        */
+       if (type != HX || baud <= 115200)
+               baud = pl2303_baudrate_encode_direct(baud, type, buf);
+       else
+               baud = pl2303_baudrate_encode_divisor(baud, type, buf);
        /* Save resulting baud rate */
        tty_encode_baud_rate(tty, baud, baud);
        dev_dbg(&port->dev, "baud set = %d\n", baud);
@@ -434,8 +447,8 @@ static void pl2303_set_termios(struct tty_struct *tty,
                dev_dbg(&port->dev, "data bits = %d\n", buf[6]);
        }
 
-       /* For reference buf[0]:buf[3] baud rate value */
-       pl2303_encode_baudrate(tty, port, &buf[0]);
+       /* For reference:   buf[0]:buf[3] baud rate value */
+       pl2303_encode_baudrate(tty, port, spriv->type, buf);
 
        /* For reference buf[4]=0 is 1 stop bits */
        /* For reference buf[4]=1 is 1.5 stop bits */