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When the address of a request was not aligned with an 8-byte boundary, the USB DMA was unable to process it, necessitating the use of an internal bounce buffer. In these cases, the request->buf had to be copied to/from this bounce buffer. However, if this unaligned address scenario arises, it is unnecessary to perform heavy cache maintenance operations like usb_gadget_map(unmap)_request_by_dev() on the request->buf, as the DMA does not utilize it at all. it can be skipped at this case. iperf3 tests on the rndis case: Transmit speed (TX): Improved from 299Mbps to 440Mbps Receive speed (RX): Improved from 290Mbps to 500Mbps Signed-off-by: Frank Li <Frank.Li@nxp.com> Link: https://lore.kernel.org/r/20230518204947.3770236-1-Frank.Li@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.