serial: 8250_mid: fix divide error bug if baud rate is 0

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.salinas@intel.com>
Fixes: c1a67b48f6a5 ("serial: 8250_pci: replace switch-case by formula for Intel MID")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_mid.c b/drivers/tty/serial/8250/8250_mid.c
index ed489880e62b3ec4bd988dc833885afc68d7d367..83b3988eb6b20297b9a304fb97c2c2dffaec2848 100644 (file)
--- 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 uart_port *p,
        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)