The driver was updating the port uartclk before setting the new rate in
an attempt to avoid having the clock notifier redundantly update the
divisors.
The set_termios() callback is however called under the termios semaphore
and tty-port mutex so the worker scheduled by the clock notifier will
block in serial8250_update_uartclk() until the uartclk and divisors have
been updated anyway.
Drop the unnecessary swaps and incorrect comment and simply update the
uartclk field if the clock-rate change was successful.
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
---
drivers/tty/serial/8250/8250_dw.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index a3a0154da567..52e03dd0eb3b 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -338,15 +338,12 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
rate = clk_round_rate(d->clk, newrate);
if (rate > 0) {
/*
- * Premilinary set the uartclk to the new clock rate so the
- * clock update event handler caused by the clk_set_rate()
- * calling wouldn't actually update the UART divisor since
- * we about to do this anyway.
+ * Note that any clock-notifer worker will block in
+ * serial8250_update_uartclk() until we are done.
*/
- swap(p->uartclk, rate);
ret = clk_set_rate(d->clk, newrate);
- if (ret)
- swap(p->uartclk, rate);
+ if (!ret)
+ p->uartclk = rate;
}
clk_prepare_enable(d->clk);
--
2.32.0
