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[ Upstream commitc47527cbcc] The stm32_usart_transmit_chars() may be called with empty or stopped transmit queue, and no XON/OFF character pending. This can happen at the end of transmission, where this last call is used to either handle the XON/XOFF x_char, or disable TX interrupt if queue is empty or stopped. If that occurs, do not assert the RS485 RTS/DE GPIO anymore, as the GPIO would remain asserted past the end of transmission and that would block the RS485 bus after the transmission. Only assert the RS485 RTS/DE GPIO if there is either pending XON/XOFF x_char, or at least one character in running transmit queue. Fixes:d7c7671616("serial: stm32: Use TC interrupt to deassert GPIO RTS in RS485 mode") Signed-off-by: Marek Vasut <marex@denx.de> Link: https://lore.kernel.org/r/20230223042252.95480-2-marex@denx.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.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.
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.