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commit 1af2156e58f3af1216ce2f0456b3b8949faa5c7e upstream. If a process is killed while writing to a /dev/ttymxc* device in RS485 mode, we observe that the RTS signal is left high, thus making it impossible for other devices to transmit anything. Moreover, the ->tx_state variable is left in state SEND, which means that when one next opens the device and configures baud rate etc., the initialization code in imx_uart_set_termios dutifully ensures the RTS pin is pulled down, but since ->tx_state is already SEND, the logic in imx_uart_start_tx() does not in fact pull the pin high before transmitting, so nothing actually gets on the wire on the other side of the transceiver. Only when that transmission is allowed to complete is the state machine then back in a consistent state. This is completely reproducible by doing something as simple as seq 10000 > /dev/ttymxc0 and hitting ctrl-C, and watching with a logic analyzer. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: stable <stable@kernel.org> Reviewed-by: Marek Vasut <marex@denx.de> Link: https://lore.kernel.org/r/20240625184206.508837-1-linux@rasmusvillemoes.dk Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.