| Message ID | CAEXMXLR=wuxgPJHGmn0bTUC5_8kZ-mc1u3FmAGyAs9HmV_FNig@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | 8250_dw bug | expand |
On Thu, Jan 11, 2018 at 01:47:31PM +0100, Nuno Gonçalves wrote: > Dear Ed and Greg, > > There is a small bug on de9e33bdfa22e607a88494ff21e9196d00bf4550, at > least on 32bit devices. > > Line 274 if (rate >= i * min_rate && rate <= i * max_rate) > > This will overflow when min_rate/max_rate is large and can not be > achieved in the hardware. > > Eg. > > stty -F /dev/ttyS2 raw 3500000 (not achievable on my board). > > target_rate=56000000 (for 3500000baud) > min_rate=55125000 > max_rate=56875000 > rate=24000000 (clk_round_rate for my board) > > Since my board can only do 1500000baud, this loop will keep > incrementing i until i=77*56875000 will overflow, and there are > unexpected results. > > I suggest this patch: > > --- 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; > + break; > + } > + > + if (rate <= i * max_rate) > break; > } > if (i <= UART_DIV_MAX) { > > > Let me know if you want me to submit the formal patch. Why wouldn't you submit a "formal patch", that way we could apply it if it is correct :) also cc: the linux-serial mailing list when you do so, thanks. greg k-h
--- 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; + break; + } + + if (rate <= i * max_rate) break; }
Dear Ed and Greg, There is a small bug on de9e33bdfa22e607a88494ff21e9196d00bf4550, at least on 32bit devices. Line 274 if (rate >= i * min_rate && rate <= i * max_rate) This will overflow when min_rate/max_rate is large and can not be achieved in the hardware. Eg. stty -F /dev/ttyS2 raw 3500000 (not achievable on my board). target_rate=56000000 (for 3500000baud) min_rate=55125000 max_rate=56875000 rate=24000000 (clk_round_rate for my board) Since my board can only do 1500000baud, this loop will keep incrementing i until i=77*56875000 will overflow, and there are unexpected results. I suggest this patch: if (i <= UART_DIV_MAX) { Let me know if you want me to submit the formal patch. Thanks, Nuno