Re: [PATCH v2 2/2] serial: 8250_mid: wait for LSR tx empty before setting termios

[Jiri Slaby <jirislaby@kernel.org>]

On 28. 08. 26, 19:57, Tate Whiteberg wrote:
> If mid8250_set_termios() is called while data is still in transmission,
> the corresponding register updates will corrupt the transmission.
> 
> Fix this by locking the port and and waiting for the transmitter to
> empty before performing updates. It is necessary to wait for both
> UART_LSR_THRE and UART_LSR_TEMT to ensure the final character is sent.
> 
> Fixes: d9eda9bab237 ("serial: 8250_pci: Intel MID UART support to its own driver")
> Signed-off-by: Tate Whiteberg <whiteberg@arista.com>
> ---
> Changes in v2:
>    - Separate changes to 8250.h and 8250_port.c into prerequisite patch,
>      as recommended by andriy.shevchenko@intel.com
>    - Apply feedback from andriy.shevchenko@intel.com to 8250_mid.c
> 
>   drivers/tty/serial/8250/8250_mid.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/tty/serial/8250/8250_mid.c b/drivers/tty/serial/8250/8250_mid.c
> index 82656645b8a6..ce792888acfe 100644
> --- a/drivers/tty/serial/8250/8250_mid.c
> +++ b/drivers/tty/serial/8250/8250_mid.c
> @@ -209,6 +209,7 @@ static void mid8250_set_termios(struct uart_port *p, struct ktermios *termios,
>   				const struct ktermios *old)
>   {
>   	unsigned int baud = tty_termios_baud_rate(termios);
> +	struct uart_8250_port *up = up_to_u8250p(p);
>   	struct mid8250 *mid = p->private_data;
>   	unsigned short ps = 16;
>   	unsigned long fuart = baud * ps;
> @@ -231,12 +232,18 @@ static void mid8250_set_termios(struct uart_port *p, struct ktermios *termios,
>   	}
>   
>   	rational_best_approximation(fuart, mid->board->freq, w, w, &mul, &div);
> +
> +	uart_port_lock_irq(p);

Use scoped_guard(), please.

-- 
js
suse labs