Re: [PATCH v6 0/3] Add logic to consolidate TRBs for Synopsys xHC

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 23.11.2020 18.37, Tejas Joglekar wrote:
> 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(-)
> 

Dropped last version and picked first two patches from this series.

-Mathias