serial: 8250_dw: Honor clk_round_rate errors in dw8250_set_termios

clk_round_rate returns a signed long and may possibly return errors
in it, for example if there is no possible rate.

Till now dw8250_set_termios ignored any error, the signednes and would
just use the value as input to clk_set_rate. This of course falls apart
if there is an actual error, so check for errors and only try to set
a rate if the value is actually valid.

This turned up on some Rockchip platforms after commit
6a171b299379 ("serial: 8250_dw: Allow hardware flow control to be used")
enabled set_termios callback in all cases, not only ACPI.

Fixes: 6a171b299379 ("serial: 8250_dw: Allow hardware flow control to be used")
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 6ee55a2..223ac23 100644 (file)
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -257,7 +257,7 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
 {
        unsigned int baud = tty_termios_baud_rate(termios);
        struct dw8250_data *d = p->private_data;
-       unsigned int rate;
+       long rate;
        int ret;
 
        if (IS_ERR(d->clk) || !old)
@@ -265,7 +265,10 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
 
        clk_disable_unprepare(d->clk);
        rate = clk_round_rate(d->clk, baud * 16);
-       ret = clk_set_rate(d->clk, rate);
+       if (rate < 0)
+               ret = rate;
+       else
+               ret = clk_set_rate(d->clk, rate);
        clk_prepare_enable(d->clk);
 
        if (!ret)