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From: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
To: Wander Lairson Costa <wander@redhat.com>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Jiri Slaby" <jirislaby@kernel.org>,
	"Johan Hovold" <johan@kernel.org>,
	"Maciej W. Rozycki" <macro@orcam.me.uk>,
	"Serge Semin" <fancer.lancer@gmail.com>,
	"Lukas Wunner" <lukas@wunner.de>, "Pali Rohár" <pali@kernel.org>,
	"open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
	"open list" <linux-kernel@vger.kernel.org>,
	rostedt@goodmis.org, senozhatsky@chromium.org,
	andre.goddard@gmail.com, sudipm.mukherjee@gmail.com,
	andy.shevchenko@gmail.com, David.Laight@aculab.com,
	jonathanh@nvidia.com, phil@raspberrypi.com
Subject: Re: [PATCH v4 5/5] serial/8250: Only use fifo after the port is initialized in console_write
Date: Thu, 17 Mar 2022 10:43:11 +0200 (EET)	[thread overview]
Message-ID: <2f3d386-b82a-9ae1-eaba-f2123b1346f8@linux.intel.com> (raw)
In-Reply-To: <20220316143646.13301-6-wander@redhat.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.


  parent reply	other threads:[~2022-03-17  8:43 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-16 14:36 [PATCH v4 0/5] tty/8250: Use fifo in 8250 console driver Wander Lairson Costa
2022-03-16 14:36 ` [PATCH v4 1/5] serial/8250: " Wander Lairson Costa
2022-03-16 15:27   ` David Laight
2022-03-17 12:27     ` Wander Costa
2022-03-16 14:36 ` [PATCH v4 2/5] serial/8250: Use the cache value of the FCR register Wander Lairson Costa
2022-03-17  8:29   ` Ilpo Järvinen
2022-03-17 12:03     ` Wander Costa
2022-03-16 14:36 ` [PATCH v4 3/5] serial/8250: Use tx_loadsz as the transmitter fifo size Wander Lairson Costa
2022-03-16 14:36 ` [PATCH v4 4/5] serial/8250: exclude BCM283x from console_fifo_write Wander Lairson Costa
2022-03-16 14:36 ` [PATCH v4 5/5] serial/8250: Only use fifo after the port is initialized in console_write Wander Lairson Costa
2022-03-17  7:06   ` Jiri Slaby
2022-03-17 12:22     ` Wander Costa
2022-03-17  8:43   ` Ilpo Järvinen [this message]
2022-03-17 12:23     ` Wander Costa
2022-03-16 16:13 ` [PATCH v4 0/5] tty/8250: Use fifo in 8250 console driver Andy Shevchenko
2022-03-16 16:14   ` Andy Shevchenko
2022-03-16 16:37   ` Wander Costa
2022-03-17 15:47 ` Steven Rostedt

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