Messages in this thread Patch in this message |  | | From | Nuno Gonçalves <> | | Date | Thu, 11 Jan 2018 13:47:31 +0100 | | Subject | 8250_dw bug |
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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.
Thanks, Nuno
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