From 74365bc138ab03bdac205047aac02f8db0a479fa Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Fri, 15 Oct 2021 13:14:22 +0200 Subject: serial: 8250_dw: drop bogus uartclk optimisation 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. Tested-by: Serge Semin Reviewed-by: Serge Semin Acked-by: Andy Shevchenko Signed-off-by: Johan Hovold Link: https://lore.kernel.org/r/20211015111422.1027-4-johan@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_dw.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) (limited to 'drivers/tty') diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index 5a2ff843ec5d..53f57c3b9f42 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) { /* - * Preliminary 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); -- cgit v1.2.3