Add logic to consolidate TRBs for Synopsys xHC

The Synopsys xHC has an internal TRB cache of size TRB_CACHE_SIZE for each endpoint. The default value for TRB_CACHE_SIZE is 16 for SS and 8 for HS. The controller loads and updates the TRB cache from the transfer ring in system memory whenever the driver issues a start transfer or update transfer command.

For chained TRBs, the Synopsys xHC requires that the total amount of bytes for all TRBs loaded in the TRB cache be greater than or equal to 1 MPS. Or the chain ends within the TRB cache (with a last TRB).

If this requirement is not met, the controller will not be able to send or receive a packet and it will hang causing a driver timeout and error.

This patch set adds logic to the XHCI driver to detect and prevent this from happening along with the quirk to enable this logic for Synopsys HAPS platform.

Based on Mathias's feedback on previous implementation where consolidation was done in TRB cache, with this patch series the implementation is done during mapping of the URB by consolidating the SG list into a temporary buffer if the SG list buffer sizes within TRB_CACHE_SIZE is less than MPS.

Changes since v5:
- Update the quirk macro to have next number [Patch 1/3]
- Fixed the issues reported by kernel test robot [Patch 2/3]

Changes since v4:
- Updated [Patch 3/3] platform data structure initialization
- Trivial changes in commit wordings

Changes since v3:
- Removed the dt-binding patch
- Added new patch to pass the quirk as platform data
- Modified the patch to set the quirk

Changes since v2:
- Modified the xhci_unmap_temp_buffer function to unmap dma and c the dma flag
- Removed RFC tag

Changes since v1:
- Comments from Greg are addressed on [PATCH 4/4] and [PATCH 1/4]
- Renamed the property and quirk as in other patches based on [PATCH 1/4]

Tejas Joglekar (3):
usb: xhci: Set quirk for XHCI_SG_TRB_CACHE_SIZE_QUIRK
usb: xhci: Use temporary buffer to consolidate SG
usb: dwc3: Pass quirk as platform data

 drivers/usb/dwc3/host.c      |  10 +++
 drivers/usb/host/xhci-plat.c |   3 +
 drivers/usb/host/xhci-ring.c |   2 +-
 drivers/usb/host/xhci.c      | 129 ++++++++++++++++++++++++++++++++++-
 drivers/usb/host/xhci.h      |   5 ++
 5 files changed, 147 insertions(+), 2 deletions(-)

2.28.0