From 1d6ba284dff546baca58e78546da46be3b48462a Mon Sep 17 00:00:00 2001 From: Maxime COQUELIN Date: Thu, 24 Jul 2014 14:02:56 +0200 Subject: [PATCH] serial: st-asc: Fix overflow in baudrate calculation In the current calculation, if the required baud rate is above 262143, we get an overflow. This patch uses a 64bits variable to do the maths. Also, we remove the '+1' to avoid a divide by zero if the input clock rate is something unexpected. Indeed, if the input clock rate is zero, it is preferable to be notified, since the UART won't work anyway. Signed-off-by: Maxime Coquelin Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/st-asc.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/tty/serial/st-asc.c b/drivers/tty/serial/st-asc.c index 4e9f4f2..8b2d735 100644 --- a/drivers/tty/serial/st-asc.c +++ b/drivers/tty/serial/st-asc.c @@ -527,12 +527,12 @@ static void asc_set_termios(struct uart_port *port, struct ktermios *termios, * ASCBaudRate = ------------------------ * inputclock * - * However to keep the maths inside 32bits we divide top and - * bottom by 64. The +1 is to avoid a divide by zero if the - * input clock rate is something unexpected. + * To keep maths inside 64bits, we divide inputclock by 16. */ - u32 counter = (baud * 16384) / ((port->uartclk / 64) + 1); - asc_out(port, ASC_BAUDRATE, counter); + u64 dividend = (u64)baud * (1 << 16); + + do_div(dividend, port->uartclk / 16); + asc_out(port, ASC_BAUDRATE, dividend); ctrl_val |= ASC_CTL_BAUDMODE; } -- 2.7.4