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

Tejas Joglekar [off-list ref] 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(-)

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2.11.0