usb: serial: ftdi_sio.c: For the FT232H FTDI_SIO_SET_BAUDRATE_REQUEST, index needs to be shifted too

the recent addition of the FT232H showed that baudrate was set wrong. See
gmane.linux.usb.general: "[ftdi_sio] FT232H support".  With the old code,
the MSB of the 4 encoded fractional divider bits and more important the
clock predivider bits got lost. Adding the FT232H to the code patch were
these bits are shifted solves the problem. I verified baud rates with a
scope now.

I suspect, that the BM device probably needs these bits shifted too. But
there is no predivider bit, so this is not obvious, and a missing MSB of the
encoded fractional divider only shifts the resulting baudrate minimal.
The AM has only 3 bits of encoded fractional divider, so it is not impacted.

I have no BM device to test, so I only added a comment and left the code for
the BM untouched.

Signed-off-by: Uwe Bonnes <bon@elektron.ikp.physik.tu-darmstadt.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 9afb36143738..7d42f61bd7ad 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1205,7 +1205,10 @@ static int change_speed(struct tty_struct *tty, struct usb_serial_port *port)
         urb_index_value = get_ftdi_divisor(tty, port);
         urb_value = (__u16)urb_index_value;
         urb_index = (__u16)(urb_index_value >> 16);
-        if (priv->interface) {  /* FT2232C */
+        if ((priv->chip_type == FT2232C) || (priv->chip_type == FT2232H) ||
+                (priv->chip_type == FT4232H) || (priv->chip_type == FT232H)) {
+                /* Probably the BM type needs the MSB of the encoded fractional
+                 * divider also moved like for the chips above. Any infos? */
                 urb_index = (__u16)((urb_index << 8) | priv->interface);
         }