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When using half-duplex mode (which disables receiver during txing) the RTS signal cannot be driven low during transmission when using i.MX UART RTS/CTS control. This seems to be a limitation of the i.MX UART IP: The RTS (CTS_B) signal is controlled by the receiver. When the receiver is disabled, the signal stays in UART logic idle state which is high... If SER_RS485_RTS_ON_SEND is used, RTS needs to be high active during transmission. Since this is the default state of the RTS (CTS_B) signal when the receiver is off, half-duplex mode in this configuration works fine. However, a low-active RTS signal (flag SER_RS485_RTS_ON_SEND not set) cannot be generated when the receiver is turned off. Print an error if the user selects this unsupported configuration (both SER_RS485_RTS_ON_SEND and SER_RS485_RX_DURING_TX unset) and configure the closest working configuration (set the SER_RS485_RX_DURING_TX flag). Signed-off-by: Stefan Agner <stefan@agner.ch> Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> 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 Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
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.