usb: pl2303: do not round to the next nearest standard baud rate for the divisor...

In opposition to the direct baud rate encoding method, the divisor
based method is not limited to a fixed set of standard baud rates.
Hence, there is no need to round to the next nearest standard value.

Reported-by: Mastro Gippo <gipmad@gmail.com>
Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Reinhard Max <max@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c
index b93b3b3..04390df 100644 (file)
--- a/drivers/usb/serial/pl2303.c
+++ b/drivers/usb/serial/pl2303.c
@@ -273,44 +273,46 @@ static void pl2303_encode_baudrate(struct tty_struct *tty,
                                        struct usb_serial_port *port,
                                        u8 buf[4])
 {
-       const int baud_sup[] = { 75, 150, 300, 600, 1200, 1800, 2400, 3600,
-                                4800, 7200, 9600, 14400, 19200, 28800, 38400,
-                                57600, 115200, 230400, 460800, 500000, 614400,
-                                921600, 1228800, 2457600, 3000000, 6000000 };
-
        struct usb_serial *serial = port->serial;
        struct pl2303_serial_private *spriv = usb_get_serial_data(serial);
        int baud;
-       int i;
 
-       /*
-        * 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)
-        */
        baud = tty_get_baud_rate(tty);
        dev_dbg(&port->dev, "baud requested = %d\n", baud);
        if (!baud)
                return;
 
-       /* Set baudrate to nearest supported value */
-       for (i = 0; i < ARRAY_SIZE(baud_sup); ++i) {
-               if (baud_sup[i] > baud)
-                       break;
-       }
+       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, 500000, 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];
+               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);
+               /* type_0, type_1 only support up to 1228800 baud */
+               if (spriv->type != HX)
+                       baud = min_t(int, baud, 1228800);
 
-       if (spriv->type != HX || baud <= 115200) {
                /* Direct (standard) baud rate encoding method */
                put_unaligned_le32(baud, buf);
        } else {
@@ -331,10 +333,17 @@ static void pl2303_encode_baudrate(struct tty_struct *tty,
                 * => 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 */
-               unsigned int A = 0;
-               unsigned int B = 12000000 * 32 / baud;  /* 12MHz */
+               A = 0;
+               B = 12000000 * 32 / baud;  /* 12MHz */
                B <<= 1; /* Add one bit for rounding */
                while (B > (512 << 1) && A <= 14) {
                        A += 2;