4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Shevchenko <andriy.shevche...@linux.intel.com>

commit 47b34d2ef266e2c283b514d65c8963c2ccd42474 upstream.

Since the commit c1a67b48f6a5 ("serial: 8250_pci: replace switch-case by
formula for Intel MID"), the 8250 driver crashes in the byt_set_termios()
function with a divide error. This is caused by the fact that a baud rate of 0
(B0) is not handled properly. Fix it by falling back to B9600 in this case.

Reported-by: "Mendez Salinas, Fernando" <fernando.mendez.sali...@intel.com>
Fixes: c1a67b48f6a5 ("serial: 8250_pci: replace switch-case by formula for 
Intel MID")
Signed-off-by: Andy Shevchenko <andriy.shevche...@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/tty/serial/8250/8250_mid.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/tty/serial/8250/8250_mid.c
+++ b/drivers/tty/serial/8250/8250_mid.c
@@ -149,6 +149,9 @@ static void mid8250_set_termios(struct u
        unsigned long w = BIT(24) - 1;
        unsigned long mul, div;
 
+       /* Gracefully handle the B0 case: fall back to B9600 */
+       fuart = fuart ? fuart : 9600 * 16;
+
        if (mid->board->freq < fuart) {
                /* Find prescaler value that satisfies Fuart < Fref */
                if (mid->board->freq > baud)


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