usb: cdns3: improve handling of unaligned address case

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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>

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Frank Li 2023-05-18 16:49:45 -04:00 • committed by Greg Kroah-Hartman

parent bfb46b4246

commit 2a1c4639d6

1 changed files with 7 additions and 4 deletions

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drivers/usb/cdns3/cdns3-gadget.c

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