Re: [PATCH v4 5/5] serial/8250: Only use fifo after the port is initialized in console_write

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

On Wed, 16 Mar 2022, Wander Lairson Costa wrote:

> The serial driver set the value of uart_8250_port.fcr in the function
> serial8250_config_port, but only writes the value to the controller
> register later in the initalization code.
> 
> That opens a small window in which is not safe to use the fifo for
> console write.
> 
> Make sure the port is initialized correctly before reading the FCR
> cached value.
> 
> Unfortunately, I lost track of who originally reported the issue. If
> s/he is reading this, please speak up so I can give you the due credit.
> 
> Signed-off-by: Wander Lairson Costa <wander@redhat.com>
> ---
>  drivers/tty/serial/8250/8250_port.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 4acf620be241..7e2227161555 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -3416,6 +3416,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
>  		!(up->capabilities & UART_CAP_MINI) &&
>  		up->tx_loadsz > 1 &&
>  		(up->fcr & UART_FCR_ENABLE_FIFO) &&
> +		test_bit(TTY_PORT_INITIALIZED, &port->state->port.iflags) &&
>  		/*
>  		 * After we put a data in the fifo, the controller will send
>  		 * it regardless of the CTS state. Therefore, only use fifo

So it looks like 2-5 just contain your development history and should all 
be merged to 1/5 (perhaps with Co-developed-by: tags where appropriate).

And please don't just merge them "silently" there w/o describing in the 
message _why_ you ended up doing the things the way you did in the end.
The messages you've written for patches 2-5 will serve you as great source 
material (with small mods, obviously).


-- 
 i.