Re: [PATCH v3 0/4] Add logic to consolidate TRBs for Synopsys xHC

[Jun Li <lijun.kernel@gmail.com>]

Tejas Joglekar <Tejas.Joglekar@synopsys.com> 于2020年5月27日周三 下午7:54写道：
>
> 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.

Hi Tejas Joglekar

I am debugging  a similar issue on Synipsys XHC, it's not the same case
but I am wondering if it also linked to this HW limitation.

My Synopsys XHC based host enable UAS, when enumerates a UAS
HDD, one BULK-IN EP with stream enabled will not generate event for
trb(with stream ID 1) after a 16/4096 bytes(with stream ID 2) finished in
previous trb.

If I change the last OK urb/trb's buffer length from 4096 to 512, the issue
will gone.

following is the sequence of the question EP-IN:

<idle>-0     [000] d.h1   154.961710: xhci_urb_giveback: ep3in-bulk:
urb ffff0001775f6f00 pipe 3221324672 slot 1 length 36/36 sgs 1/1
stream 1 flags 00040200
<idle>-0     [000] d.h1   154.962023: xhci_urb_giveback: ep3in-bulk:
urb ffff000177d00400 pipe 3221324672 slot 1 length 96/96 sgs 1/1
stream 1 flags 00040200
<idle>-0     [000] d.h1   154.970395: xhci_urb_giveback: ep3in-bulk:
urb ffff000177d00400 pipe 3221324672 slot 1 length 11/255 sgs 1/1
stream 1 flags 00040200
<idle>-0     [000] d.h1   154.970562: xhci_urb_giveback: ep3in-bulk:
urb ffff000177d00400 pipe 3221324672 slot 1 length 20/255 sgs 1/1
stream 1 flags 00040200
<idle>-0     [000] d.h1   154.970786: xhci_urb_giveback: ep3in-bulk:
urb ffff000177d00400 pipe 3221324672 slot 1 length 60/255 sgs 1/1
stream 1 flags 00040200
<idle>-0     [000] d.h1   155.851600: xhci_urb_giveback: ep3in-bulk:
urb ffff000177d00200 pipe 3221324672 slot 1 length 16/4096 sgs 1/1
stream 2 flags 00040200

/* then the next ep3-in trb will not generate event and stopped, so
driver timeout in the end */
kworker/u8:2-349   [003] d..3   155.851987: xhci_urb_enqueue:
ep3in-bulk: urb ffff000170492400 pipe 3221324672 slot 1 length 0/32
sgs 1/1 stream 1 flags 00040200
kworker/u8:2-349   [003] d..4   155.851989: xhci_queue_trb: STREAM:
Buffer 00000000c19cf000 length 32 TD size 0 intr 0 type 'Normal' flags
b:i:I:c:s:I:e:c
kworker/u8:2-349   [003] d..4   155.851991: xhci_inc_enq: STREAM
ffff000177f86f80: enq 0x00000000be0eb060(0x00000000be0eb000) deq
0x00000000be0eb050(0x00000000be0eb000) segs 2 stream 1 free_trbs 508
bounce 1024 cycle 1

Do you have any ideas?

thanks
Li Jun
>
> 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 v2:
>  - Modified the xhci_unmap_temp_buffer function to unmap dma and clear
>    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 (4):
>   dt-bindings: usb: Add documentation for SG trb cache size quirk
>   usb: xhci: Set quirk for XHCI_SG_TRB_CACHE_SIZE_QUIRK
>   usb: dwc3: Add device property sgl-trb-cache-size-quirk
>   usb: xhci: Use temporary buffer to consolidate SG
>
>  Documentation/devicetree/bindings/usb/dwc3.txt     |   4 +
>  Documentation/devicetree/bindings/usb/usb-xhci.txt |   3 +
>  drivers/usb/dwc3/core.c                            |   2 +
>  drivers/usb/dwc3/core.h                            |   2 +
>  drivers/usb/dwc3/dwc3-haps.c                       |   1 +
>  drivers/usb/dwc3/host.c                            |   6 +-
>  drivers/usb/host/xhci-pci.c                        |   3 +
>  drivers/usb/host/xhci-plat.c                       |   4 +
>  drivers/usb/host/xhci-ring.c                       |   2 +-
>  drivers/usb/host/xhci.c                            | 135 +++++++++++++++++++++
>  drivers/usb/host/xhci.h                            |   5 +
>  11 files changed, 165 insertions(+), 2 deletions(-)
>
> --
> 2.11.0
>