[PATCH 0/1] Add version check for setting ForceRM

Hi Thinh,
 
We are observing an issue on DWC_usb31 v2.00a and v2.10a controllers where
a transfer aborted through the ep_dequeue() path continues to generate
writes even after EndTransfer has completed. In our testing, the issue was
reproduced on an OUT bulk endpoint.
 
The stale writes are not observed immediately following EndTransfer.
Instead, they are triggered when a subsequent StartTransfer is issued on
the same endpoint. Since the transfer buffer is freed as part of the
EndTransfer command-completion cleanup, these delayed writes result in an
SMMU fault when the controller accesses the already-unmapped buffer.
 
We found that issuing EndTransfer with ForceRM=0 eliminates the issue.
 
While investigating the issue, I reviewed the DWC_usb31 programming guides.
Starting with version 2.00a, section 3.2.2.7 (End Transfer) specifies that
EndTransfer should be issued with ForceRM cleared, whereas older revisions
specified ForceRM=1.
 
This appears to align with our observations, where using ForceRM=0
prevents the stale writes observed after a transfer has been aborted
through the dequeue path.
 
Based on this guidance, the patch clears ForceRM for DWC_usb31 controllers
starting from version 2.00a, while retaining the existing behavior for
older revisions where the programming guide specified ForceRM=1.
 
Since I only have access to the DWC_usb31 programming guides, I have
currently restricted the change to DWC_usb31 IP revisions. Please let me
know if this is not the right approach or if the change should also be
extended to other DWC3 IPs, and I will update the patch accordingly.
 
Thanks,
Elson

Elson Serrao (1):
  usb: dwc3: gadget: add version check for setting ForceRM

 drivers/usb/dwc3/gadget.c | 7 +++++++
 1 file changed, 7 insertions(+)

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2.34.1