linux-kernel - Re: [PATCH V7 5/6] tty: serial: meson: The system stuck when you run the stty command on the console to change the baud rate

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Date:   Mon, 28 Feb 2022 11:58:30 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Yu Tu <yu.tu@...ogic.com>, linux-serial@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: Re: [PATCH V7 5/6] tty: serial: meson: The system stuck when you
 run the stty command on the console to change the baud rate


On Fri 25 Feb 2022 at 15:39, Yu Tu <yu.tu@...ogic.com> wrote:

> Start the console and run the following commands in turn:
> stty -F /dev/ttyAML0 115200 and stty -F /dev/ttyAML0 921600. The
> system will stuck.
>
> Signed-off-by: Yu Tu <yu.tu@...ogic.com>
> ---
>  drivers/tty/serial/meson_uart.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
> index ba8dc203b9cb..d19349ead738 100644
> --- a/drivers/tty/serial/meson_uart.c
> +++ b/drivers/tty/serial/meson_uart.c
> @@ -365,8 +365,13 @@ static void meson_uart_set_termios(struct uart_port *port,
>  	writel(val, port->membase + AML_UART_CONTROL);
>  
>  	baud = uart_get_baud_rate(port, termios, old, 50, 4000000);
> +
> +	spin_unlock_irqrestore(&port->lock, flags);
> +
>  	meson_uart_change_speed(port, baud);
>  
> +	spin_lock_irqsave(&port->lock, flags);

Already told you before, you can make meson_change_speed()
clk_set_rate() uses mutex and may sleep.

> +
>  	port->read_status_mask = AML_UART_TX_FIFO_WERR;
>  	if (iflags & INPCK)
>  		port->read_status_mask |= AML_UART_PARITY_ERR |