Commit 2a1c4639 authored May 18, 2023 by Frank Li Committed by Greg Kroah-Hartman May 29, 2023

usb: cdns3: improve handling of unaligned address case



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>

parent bfb46b42

drivers/usb/cdns3/cdns3-gadget.c

+7 −4

Original line number	Diff line number	Diff line
		@@ -800,6 +800,7 @@ void cdns3_gadget_giveback(struct cdns3_endpoint *priv_ep,
		if (request->status == -EINPROGRESS)
		request->status = status;

		if (likely(!(priv_req->flags & REQUEST_UNALIGNED)))
		usb_gadget_unmap_request_by_dev(priv_dev->sysdev, request,
		priv_ep->dir);

		@@ -2530,10 +2531,12 @@ static int __cdns3_gadget_ep_queue(struct usb_ep *ep,
		if (ret < 0)
		return ret;

		if (likely(!(priv_req->flags & REQUEST_UNALIGNED))) {
		ret = usb_gadget_map_request_by_dev(priv_dev->sysdev, request,
		usb_endpoint_dir_in(ep->desc));
		if (ret)
		return ret;
		}

		list_add_tail(&request->list, &priv_ep->deferred_req_list);