usb: dwc3: gadget: Handle streams

Overview of stream transfer requirement:
* A transfer will have a set of TRBs of the same stream ID.
* A transfer is started with a stream ID in START_TRANSFER command.
* A new stream will only start when the previous completes.

Overview of stream events:
* A "prime" from host indicates that its endpoints are active (buffers prepared and ready to receive/transmit data). The controller automatically initiates stream if it sees this.
* A "NoStream" rejection event indicates that the host isn't ready. Host will put the endpoint back to idle state. Device may need to reinitiate the stream to start transfer again.
* A Stream Found event means host accepted device initiated stream. Nothing needs to be done from driver.

To initiate a stream, the driver will issue START_TRANSFER command with a stream ID. To reinitiate the stream, the driver must issue END_TRANSFER and restart the transfer with START_TRANSFER command with the same stream ID.

This implementation handles device-initated streams (e.g. UASP driver). It also handles some hosts' quirky behavior where they only prime each endpoint once.

Prerequisite:
This series requires DWC_usb32 patch series
https://patchwork.kernel.org/project/linux-usb/list/?series=269641

[PATCH 1/2] usb: dwc3: Add support for DWC_usb32 IP [PATCH 2/2] usb: dwc3: Get MDWIDTH for DWC_usb32

Changes in v2:
- Update cover letter
- Split handling of stream and of transfer completion into smaller patches
- Reword usb_request->is_last to strictly use for streams
- Enforce transfer completion handling to only for stream capable endpoints

Thinh Nguyen (11):
usb: gadget: Introduce usb_request->is_last
usb: gadget: f_tcm: Inform last stream request
usb: dwc3: gadget: Continue to process pending requests
usb: dwc3: gadget: Check for in-progress END_TRANSFER
usb: dwc3: gadget: Refactor TRB completion handler
usb: dwc3: gadget: Enable XferComplete event
usb: dwc3: gadget: Handle XferComplete for streams
usb: dwc3: gadget: Wait for transfer completion
usb: dwc3: gadget: Don't prepare beyond a transfer
usb: dwc3: gadget: Handle stream transfers
usb: dwc3: gadget: Use SET_EP_PRIME for NoStream

 drivers/usb/dwc3/core.h             |  12 ++
 drivers/usb/dwc3/debug.h            |   2 +
 drivers/usb/dwc3/gadget.c           | 225 +++++++++++++++++++++++++++++++-----
 drivers/usb/gadget/function/f_tcm.c |   3 +
 include/linux/usb/gadget.h          |   3 +
 5 files changed, 215 insertions(+), 30 deletions(-)

2.11.0