85a64208b3
[ Upstream commit 477b8383100023ea0769979cff67e9be3a720397 ] At this moment, TXEMPTY is checked before sending data on RS485 and ISO7816 modes. However, TXEMPTY is risen when FIFO (if used) or the Transmit Shift Register are empty, even though TXRDY might be up and controller is able to receive data. Since the controller sends data only when TXEMPTY is ready, on RS485, when DMA is not used, the RTS pin is driven low after each byte. With this patch, the characters will be transmitted when TXRDY is up and so, RTS pin will remain high between bytes. The performance improvement on RS485 is about 8% with a baudrate of 300. Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com> Acked-by: Richard Genoud <richard.genoud@gmail.com> Link: https://lore.kernel.org/r/20200107111656.26308-1-codrin.ciubotariu@microchip.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Stable-dep-of: 692a8ebcfc24 ("tty: serial: atmel: Preserve previous USART mode if RS485 disabled") 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.