Re: [PATCH] serial: imx: fix tx statemachine deadlock

From: Greg KH <gregkh@linuxfoundation.org>
To: Paul Geurts <paul_geurts@live.nl>
Cc: jirislaby@kernel.org, shawnguo@kernel.org,
	s.hauer@pengutronix.de, kernel@pengutronix.de,
	festevam@gmail.com, linux-imx@nxp.com,
	linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] serial: imx: fix tx statemachine deadlock
Date: Wed, 4 Oct 2023 14:13:01 +0200	[thread overview]
Message-ID: <2023100450-charger-disregard-9683@gregkh> (raw)
In-Reply-To: <AM0PR09MB26750E782F81CD447058FE7D95CBA@AM0PR09MB2675.eurprd09.prod.outlook.com>

On Wed, Oct 04, 2023 at 11:57:22AM +0200, Paul Geurts wrote:
> When using the serial port as RS485 port, the tx statemachine is used to
> control the RTS pin to drive the RS485 transceiver TX_EN pin. When the
> TTY port is closed in the middle of a transmission (for instance during
> userland application crash), imx_uart_shutdown disables the interface
> and disables the Transmission Complete interrupt. afer that,
> imx_uart_stop_tx bails on an incomplete transmission, to be retriggered
> by the TC interrupt. This interrupt is disabled and therefore the tx
> statemachine never transitions out of SEND. The statemachine is in
> deadlock now, and the TX_EN remains low, making the interface useless.
> 
> imx_uart_stop_tx now checks for incomplete transmission AND whether TC
> interrupts are enabled before bailing to be retriggered. This makes sure
> the state machine handling is reached, and is properly set to
> WAIT_AFTER_SEND.
> 
> Signed-off-by: Paul Geurts <paul_geurts@live.nl>
> ---
>  drivers/tty/serial/imx.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

What commit id does this fix?

thanks,

greg k-h

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel