Hi Nuno, Thanks for reporting this and the patch.
On 11/01/18 13:38, Nuno Goncalves wrote: > When target_rate is big enough and not permitted in hardware, > then i is looped to UART_DIV_MAX (0xFFFF), and i * max_rate will overflow > (32b signed). > > A fix is to quit the loop early enough, as soon as rate < i * min_rate as it > means the rate is not permitted. 'rate < i * min_rate' does not mean the rate is not permitted. clk_round_rate() gives the nearest achievable rate to the one requested, which may be lower than i * min_rate. This is not an error and in this case we want to continue the loop searching for an acceptable rate. > > This avoids arbitraty rates to be applied. Still in my hardware the max > allowed rate (1500000) is aplied when a higher is requested. This seems a > artifact of clk_round_rate which is not understood by me and independent of > this fix. Might or might not be another bug. > > Signed-off-by: Nuno Goncalves <[email protected]> > --- > drivers/tty/serial/8250/8250_dw.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/8250/8250_dw.c > b/drivers/tty/serial/8250/8250_dw.c > index 5bb0c42c88dd..a27ea916abbf 100644 > --- a/drivers/tty/serial/8250/8250_dw.c > +++ b/drivers/tty/serial/8250/8250_dw.c > @@ -267,7 +267,13 @@ static void dw8250_set_termios(struct uart_port *p, > struct ktermios *termios, > > for (i = 1; i <= UART_DIV_MAX; i++) { > rate = clk_round_rate(d->clk, i * target_rate); > - if (rate >= i * min_rate && rate <= i * max_rate) > + > + if (rate < i * min_rate) { > + i = UART_DIV_MAX + 1; > + break; > + } > + > + if (rate <= i * max_rate) > break; > } > if (i <= UART_DIV_MAX) { -- Ed
