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DMA transfer may end prematurely due to the DMA Rx timeout even during an active transfer because a constant timeout does not accurately simulate an EOP (End Of Package) event. This patch uses a timer to simulate the hardware EOP event. The timer should only complete a DMA transfer once the idle period satisfies a specified interval which is baud rate dependent. The problem has been observed with low baud rates but could occur also with high baud rates. Make the DMA Rx timeout baud rate dependent and check the DMA residue count before copying data to the TTY buffer. If the residue count remains unchanged since the last interrupt, that indicates no new data was received. In this case, the DMA should complete as an EOP event. Otherwise, new data was received during the interval and the EOP condition is not met so restart the DMA Rx timeout Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://lore.kernel.org/r/20230510203359.1353469-1-shenwei.wang@nxp.com 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.
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.