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

commit 6f210c18c1c0f016772c8cd51ae12a02bfb9e7ef upstream.

Since commit 21947ba654a6 ("serial: 8250_pci: replace switch-case by
formula"), 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.

Signed-off-by: David Müller <d.mueller@elsoft.ch>
Fixes: 21947ba654a6 ("serial: 8250_pci: replace switch-case by formula")
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-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_pci.c b/drivers/tty/serial/8250/8250_pci.c
index 7cd6f9a9054212d905e808bcfba2d76d676aaae2..c1d4a8fa9be889fd839a02ed576511b3c28919cb 100644 (file)
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1401,6 +1401,9 @@ byt_set_termios(struct uart_port *p, struct ktermios *termios,
        unsigned long m, n;
        u32 reg;
 
+       /* Gracefully handle the B0 case: fall back to B9600 */
+       fuart = fuart ? fuart : 9600 * 16;
+
        /* Get Fuart closer to Fref */
        fuart *= rounddown_pow_of_two(fref / fuart);